added vendor

vendor/golang.org/x/tools/AUTHORS

@@ -0,0 +1,3 @@
+# This source code refers to The Go Authors for copyright purposes.
+# The master list of authors is in the main Go distribution,
+# visible at http://tip.golang.org/AUTHORS.

vendor/golang.org/x/tools/CONTRIBUTORS

@@ -0,0 +1,3 @@
+# This source code was written by the Go contributors.
+# The master list of contributors is in the main Go distribution,
+# visible at http://tip.golang.org/CONTRIBUTORS.

vendor/golang.org/x/tools/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/golang.org/x/tools/PATENTS

@@ -0,0 +1,22 @@
+Additional IP Rights Grant (Patents)
+
+"This implementation" means the copyrightable works distributed by
+Google as part of the Go project.
+
+Google hereby grants to You a perpetual, worldwide, non-exclusive,
+no-charge, royalty-free, irrevocable (except as stated in this section)
+patent license to make, have made, use, offer to sell, sell, import,
+transfer and otherwise run, modify and propagate the contents of this
+implementation of Go, where such license applies only to those patent
+claims, both currently owned or controlled by Google and acquired in
+the future, licensable by Google that are necessarily infringed by this
+implementation of Go.  This grant does not include claims that would be
+infringed only as a consequence of further modification of this
+implementation.  If you or your agent or exclusive licensee institute or
+order or agree to the institution of patent litigation against any
+entity (including a cross-claim or counterclaim in a lawsuit) alleging
+that this implementation of Go or any code incorporated within this
+implementation of Go constitutes direct or contributory patent
+infringement, or inducement of patent infringement, then any patent
+rights granted to you under this License for this implementation of Go
+shall terminate as of the date such litigation is filed.

vendor/golang.org/x/tools/go/ast/astutil/enclosing.go

@@ -0,0 +1,627 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+// This file defines utilities for working with source positions.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"sort"
+)
+
+// PathEnclosingInterval returns the node that encloses the source
+// interval [start, end), and all its ancestors up to the AST root.
+//
+// The definition of "enclosing" used by this function considers
+// additional whitespace abutting a node to be enclosed by it.
+// In this example:
+//
+//              z := x + y // add them
+//                   <-A->
+//                  <----B----->
+//
+// the ast.BinaryExpr(+) node is considered to enclose interval B
+// even though its [Pos()..End()) is actually only interval A.
+// This behaviour makes user interfaces more tolerant of imperfect
+// input.
+//
+// This function treats tokens as nodes, though they are not included
+// in the result. e.g. PathEnclosingInterval("+") returns the
+// enclosing ast.BinaryExpr("x + y").
+//
+// If start==end, the 1-char interval following start is used instead.
+//
+// The 'exact' result is true if the interval contains only path[0]
+// and perhaps some adjacent whitespace.  It is false if the interval
+// overlaps multiple children of path[0], or if it contains only
+// interior whitespace of path[0].
+// In this example:
+//
+//              z := x + y // add them
+//                <--C-->     <---E-->
+//                  ^
+//                  D
+//
+// intervals C, D and E are inexact.  C is contained by the
+// z-assignment statement, because it spans three of its children (:=,
+// x, +).  So too is the 1-char interval D, because it contains only
+// interior whitespace of the assignment.  E is considered interior
+// whitespace of the BlockStmt containing the assignment.
+//
+// Precondition: [start, end) both lie within the same file as root.
+// TODO(adonovan): return (nil, false) in this case and remove precond.
+// Requires FileSet; see loader.tokenFileContainsPos.
+//
+// Postcondition: path is never nil; it always contains at least 'root'.
+//
+func PathEnclosingInterval(root *ast.File, start, end token.Pos) (path []ast.Node, exact bool) {
+	// fmt.Printf("EnclosingInterval %d %d\n", start, end) // debugging
+
+	// Precondition: node.[Pos..End) and adjoining whitespace contain [start, end).
+	var visit func(node ast.Node) bool
+	visit = func(node ast.Node) bool {
+		path = append(path, node)
+
+		nodePos := node.Pos()
+		nodeEnd := node.End()
+
+		// fmt.Printf("visit(%T, %d, %d)\n", node, nodePos, nodeEnd) // debugging
+
+		// Intersect [start, end) with interval of node.
+		if start < nodePos {
+			start = nodePos
+		}
+		if end > nodeEnd {
+			end = nodeEnd
+		}
+
+		// Find sole child that contains [start, end).
+		children := childrenOf(node)
+		l := len(children)
+		for i, child := range children {
+			// [childPos, childEnd) is unaugmented interval of child.
+			childPos := child.Pos()
+			childEnd := child.End()
+
+			// [augPos, augEnd) is whitespace-augmented interval of child.
+			augPos := childPos
+			augEnd := childEnd
+			if i > 0 {
+				augPos = children[i-1].End() // start of preceding whitespace
+			}
+			if i < l-1 {
+				nextChildPos := children[i+1].Pos()
+				// Does [start, end) lie between child and next child?
+				if start >= augEnd && end <= nextChildPos {
+					return false // inexact match
+				}
+				augEnd = nextChildPos // end of following whitespace
+			}
+
+			// fmt.Printf("\tchild %d: [%d..%d)\tcontains interval [%d..%d)?\n",
+			// 	i, augPos, augEnd, start, end) // debugging
+
+			// Does augmented child strictly contain [start, end)?
+			if augPos <= start && end <= augEnd {
+				_, isToken := child.(tokenNode)
+				return isToken || visit(child)
+			}
+
+			// Does [start, end) overlap multiple children?
+			// i.e. left-augmented child contains start
+			// but LR-augmented child does not contain end.
+			if start < childEnd && end > augEnd {
+				break
+			}
+		}
+
+		// No single child contained [start, end),
+		// so node is the result.  Is it exact?
+
+		// (It's tempting to put this condition before the
+		// child loop, but it gives the wrong result in the
+		// case where a node (e.g. ExprStmt) and its sole
+		// child have equal intervals.)
+		if start == nodePos && end == nodeEnd {
+			return true // exact match
+		}
+
+		return false // inexact: overlaps multiple children
+	}
+
+	if start > end {
+		start, end = end, start
+	}
+
+	if start < root.End() && end > root.Pos() {
+		if start == end {
+			end = start + 1 // empty interval => interval of size 1
+		}
+		exact = visit(root)
+
+		// Reverse the path:
+		for i, l := 0, len(path); i < l/2; i++ {
+			path[i], path[l-1-i] = path[l-1-i], path[i]
+		}
+	} else {
+		// Selection lies within whitespace preceding the
+		// first (or following the last) declaration in the file.
+		// The result nonetheless always includes the ast.File.
+		path = append(path, root)
+	}
+
+	return
+}
+
+// tokenNode is a dummy implementation of ast.Node for a single token.
+// They are used transiently by PathEnclosingInterval but never escape
+// this package.
+//
+type tokenNode struct {
+	pos token.Pos
+	end token.Pos
+}
+
+func (n tokenNode) Pos() token.Pos {
+	return n.pos
+}
+
+func (n tokenNode) End() token.Pos {
+	return n.end
+}
+
+func tok(pos token.Pos, len int) ast.Node {
+	return tokenNode{pos, pos + token.Pos(len)}
+}
+
+// childrenOf returns the direct non-nil children of ast.Node n.
+// It may include fake ast.Node implementations for bare tokens.
+// it is not safe to call (e.g.) ast.Walk on such nodes.
+//
+func childrenOf(n ast.Node) []ast.Node {
+	var children []ast.Node
+
+	// First add nodes for all true subtrees.
+	ast.Inspect(n, func(node ast.Node) bool {
+		if node == n { // push n
+			return true // recur
+		}
+		if node != nil { // push child
+			children = append(children, node)
+		}
+		return false // no recursion
+	})
+
+	// Then add fake Nodes for bare tokens.
+	switch n := n.(type) {
+	case *ast.ArrayType:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Elt.End(), len("]")))
+
+	case *ast.AssignStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.BasicLit:
+		children = append(children,
+			tok(n.ValuePos, len(n.Value)))
+
+	case *ast.BinaryExpr:
+		children = append(children, tok(n.OpPos, len(n.Op.String())))
+
+	case *ast.BlockStmt:
+		children = append(children,
+			tok(n.Lbrace, len("{")),
+			tok(n.Rbrace, len("}")))
+
+	case *ast.BranchStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.CallExpr:
+		children = append(children,
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+		if n.Ellipsis != 0 {
+			children = append(children, tok(n.Ellipsis, len("...")))
+		}
+
+	case *ast.CaseClause:
+		if n.List == nil {
+			children = append(children,
+				tok(n.Case, len("default")))
+		} else {
+			children = append(children,
+				tok(n.Case, len("case")))
+		}
+		children = append(children, tok(n.Colon, len(":")))
+
+	case *ast.ChanType:
+		switch n.Dir {
+		case ast.RECV:
+			children = append(children, tok(n.Begin, len("<-chan")))
+		case ast.SEND:
+			children = append(children, tok(n.Begin, len("chan<-")))
+		case ast.RECV | ast.SEND:
+			children = append(children, tok(n.Begin, len("chan")))
+		}
+
+	case *ast.CommClause:
+		if n.Comm == nil {
+			children = append(children,
+				tok(n.Case, len("default")))
+		} else {
+			children = append(children,
+				tok(n.Case, len("case")))
+		}
+		children = append(children, tok(n.Colon, len(":")))
+
+	case *ast.Comment:
+		// nop
+
+	case *ast.CommentGroup:
+		// nop
+
+	case *ast.CompositeLit:
+		children = append(children,
+			tok(n.Lbrace, len("{")),
+			tok(n.Rbrace, len("{")))
+
+	case *ast.DeclStmt:
+		// nop
+
+	case *ast.DeferStmt:
+		children = append(children,
+			tok(n.Defer, len("defer")))
+
+	case *ast.Ellipsis:
+		children = append(children,
+			tok(n.Ellipsis, len("...")))
+
+	case *ast.EmptyStmt:
+		// nop
+
+	case *ast.ExprStmt:
+		// nop
+
+	case *ast.Field:
+		// TODO(adonovan): Field.{Doc,Comment,Tag}?
+
+	case *ast.FieldList:
+		children = append(children,
+			tok(n.Opening, len("(")),
+			tok(n.Closing, len(")")))
+
+	case *ast.File:
+		// TODO test: Doc
+		children = append(children,
+			tok(n.Package, len("package")))
+
+	case *ast.ForStmt:
+		children = append(children,
+			tok(n.For, len("for")))
+
+	case *ast.FuncDecl:
+		// TODO(adonovan): FuncDecl.Comment?
+
+		// Uniquely, FuncDecl breaks the invariant that
+		// preorder traversal yields tokens in lexical order:
+		// in fact, FuncDecl.Recv precedes FuncDecl.Type.Func.
+		//
+		// As a workaround, we inline the case for FuncType
+		// here and order things correctly.
+		//
+		children = nil // discard ast.Walk(FuncDecl) info subtrees
+		children = append(children, tok(n.Type.Func, len("func")))
+		if n.Recv != nil {
+			children = append(children, n.Recv)
+		}
+		children = append(children, n.Name)
+		if n.Type.Params != nil {
+			children = append(children, n.Type.Params)
+		}
+		if n.Type.Results != nil {
+			children = append(children, n.Type.Results)
+		}
+		if n.Body != nil {
+			children = append(children, n.Body)
+		}
+
+	case *ast.FuncLit:
+		// nop
+
+	case *ast.FuncType:
+		if n.Func != 0 {
+			children = append(children,
+				tok(n.Func, len("func")))
+		}
+
+	case *ast.GenDecl:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+		if n.Lparen != 0 {
+			children = append(children,
+				tok(n.Lparen, len("(")),
+				tok(n.Rparen, len(")")))
+		}
+
+	case *ast.GoStmt:
+		children = append(children,
+			tok(n.Go, len("go")))
+
+	case *ast.Ident:
+		children = append(children,
+			tok(n.NamePos, len(n.Name)))
+
+	case *ast.IfStmt:
+		children = append(children,
+			tok(n.If, len("if")))
+
+	case *ast.ImportSpec:
+		// TODO(adonovan): ImportSpec.{Doc,EndPos}?
+
+	case *ast.IncDecStmt:
+		children = append(children,
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.IndexExpr:
+		children = append(children,
+			tok(n.Lbrack, len("{")),
+			tok(n.Rbrack, len("}")))
+
+	case *ast.InterfaceType:
+		children = append(children,
+			tok(n.Interface, len("interface")))
+
+	case *ast.KeyValueExpr:
+		children = append(children,
+			tok(n.Colon, len(":")))
+
+	case *ast.LabeledStmt:
+		children = append(children,
+			tok(n.Colon, len(":")))
+
+	case *ast.MapType:
+		children = append(children,
+			tok(n.Map, len("map")))
+
+	case *ast.ParenExpr:
+		children = append(children,
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+
+	case *ast.RangeStmt:
+		children = append(children,
+			tok(n.For, len("for")),
+			tok(n.TokPos, len(n.Tok.String())))
+
+	case *ast.ReturnStmt:
+		children = append(children,
+			tok(n.Return, len("return")))
+
+	case *ast.SelectStmt:
+		children = append(children,
+			tok(n.Select, len("select")))
+
+	case *ast.SelectorExpr:
+		// nop
+
+	case *ast.SendStmt:
+		children = append(children,
+			tok(n.Arrow, len("<-")))
+
+	case *ast.SliceExpr:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
+
+	case *ast.StarExpr:
+		children = append(children, tok(n.Star, len("*")))
+
+	case *ast.StructType:
+		children = append(children, tok(n.Struct, len("struct")))
+
+	case *ast.SwitchStmt:
+		children = append(children, tok(n.Switch, len("switch")))
+
+	case *ast.TypeAssertExpr:
+		children = append(children,
+			tok(n.Lparen-1, len(".")),
+			tok(n.Lparen, len("(")),
+			tok(n.Rparen, len(")")))
+
+	case *ast.TypeSpec:
+		// TODO(adonovan): TypeSpec.{Doc,Comment}?
+
+	case *ast.TypeSwitchStmt:
+		children = append(children, tok(n.Switch, len("switch")))
+
+	case *ast.UnaryExpr:
+		children = append(children, tok(n.OpPos, len(n.Op.String())))
+
+	case *ast.ValueSpec:
+		// TODO(adonovan): ValueSpec.{Doc,Comment}?
+
+	case *ast.BadDecl, *ast.BadExpr, *ast.BadStmt:
+		// nop
+	}
+
+	// TODO(adonovan): opt: merge the logic of ast.Inspect() into
+	// the switch above so we can make interleaved callbacks for
+	// both Nodes and Tokens in the right order and avoid the need
+	// to sort.
+	sort.Sort(byPos(children))
+
+	return children
+}
+
+type byPos []ast.Node
+
+func (sl byPos) Len() int {
+	return len(sl)
+}
+func (sl byPos) Less(i, j int) bool {
+	return sl[i].Pos() < sl[j].Pos()
+}
+func (sl byPos) Swap(i, j int) {
+	sl[i], sl[j] = sl[j], sl[i]
+}
+
+// NodeDescription returns a description of the concrete type of n suitable
+// for a user interface.
+//
+// TODO(adonovan): in some cases (e.g. Field, FieldList, Ident,
+// StarExpr) we could be much more specific given the path to the AST
+// root.  Perhaps we should do that.
+//
+func NodeDescription(n ast.Node) string {
+	switch n := n.(type) {
+	case *ast.ArrayType:
+		return "array type"
+	case *ast.AssignStmt:
+		return "assignment"
+	case *ast.BadDecl:
+		return "bad declaration"
+	case *ast.BadExpr:
+		return "bad expression"
+	case *ast.BadStmt:
+		return "bad statement"
+	case *ast.BasicLit:
+		return "basic literal"
+	case *ast.BinaryExpr:
+		return fmt.Sprintf("binary %s operation", n.Op)
+	case *ast.BlockStmt:
+		return "block"
+	case *ast.BranchStmt:
+		switch n.Tok {
+		case token.BREAK:
+			return "break statement"
+		case token.CONTINUE:
+			return "continue statement"
+		case token.GOTO:
+			return "goto statement"
+		case token.FALLTHROUGH:
+			return "fall-through statement"
+		}
+	case *ast.CallExpr:
+		if len(n.Args) == 1 && !n.Ellipsis.IsValid() {
+			return "function call (or conversion)"
+		}
+		return "function call"
+	case *ast.CaseClause:
+		return "case clause"
+	case *ast.ChanType:
+		return "channel type"
+	case *ast.CommClause:
+		return "communication clause"
+	case *ast.Comment:
+		return "comment"
+	case *ast.CommentGroup:
+		return "comment group"
+	case *ast.CompositeLit:
+		return "composite literal"
+	case *ast.DeclStmt:
+		return NodeDescription(n.Decl) + " statement"
+	case *ast.DeferStmt:
+		return "defer statement"
+	case *ast.Ellipsis:
+		return "ellipsis"
+	case *ast.EmptyStmt:
+		return "empty statement"
+	case *ast.ExprStmt:
+		return "expression statement"
+	case *ast.Field:
+		// Can be any of these:
+		// struct {x, y int}  -- struct field(s)
+		// struct {T}         -- anon struct field
+		// interface {I}      -- interface embedding
+		// interface {f()}    -- interface method
+		// func (A) func(B) C -- receiver, param(s), result(s)
+		return "field/method/parameter"
+	case *ast.FieldList:
+		return "field/method/parameter list"
+	case *ast.File:
+		return "source file"
+	case *ast.ForStmt:
+		return "for loop"
+	case *ast.FuncDecl:
+		return "function declaration"
+	case *ast.FuncLit:
+		return "function literal"
+	case *ast.FuncType:
+		return "function type"
+	case *ast.GenDecl:
+		switch n.Tok {
+		case token.IMPORT:
+			return "import declaration"
+		case token.CONST:
+			return "constant declaration"
+		case token.TYPE:
+			return "type declaration"
+		case token.VAR:
+			return "variable declaration"
+		}
+	case *ast.GoStmt:
+		return "go statement"
+	case *ast.Ident:
+		return "identifier"
+	case *ast.IfStmt:
+		return "if statement"
+	case *ast.ImportSpec:
+		return "import specification"
+	case *ast.IncDecStmt:
+		if n.Tok == token.INC {
+			return "increment statement"
+		}
+		return "decrement statement"
+	case *ast.IndexExpr:
+		return "index expression"
+	case *ast.InterfaceType:
+		return "interface type"
+	case *ast.KeyValueExpr:
+		return "key/value association"
+	case *ast.LabeledStmt:
+		return "statement label"
+	case *ast.MapType:
+		return "map type"
+	case *ast.Package:
+		return "package"
+	case *ast.ParenExpr:
+		return "parenthesized " + NodeDescription(n.X)
+	case *ast.RangeStmt:
+		return "range loop"
+	case *ast.ReturnStmt:
+		return "return statement"
+	case *ast.SelectStmt:
+		return "select statement"
+	case *ast.SelectorExpr:
+		return "selector"
+	case *ast.SendStmt:
+		return "channel send"
+	case *ast.SliceExpr:
+		return "slice expression"
+	case *ast.StarExpr:
+		return "*-operation" // load/store expr or pointer type
+	case *ast.StructType:
+		return "struct type"
+	case *ast.SwitchStmt:
+		return "switch statement"
+	case *ast.TypeAssertExpr:
+		return "type assertion"
+	case *ast.TypeSpec:
+		return "type specification"
+	case *ast.TypeSwitchStmt:
+		return "type switch"
+	case *ast.UnaryExpr:
+		return fmt.Sprintf("unary %s operation", n.Op)
+	case *ast.ValueSpec:
+		return "value specification"
+
+	}
+	panic(fmt.Sprintf("unexpected node type: %T", n))
+}

vendor/golang.org/x/tools/go/ast/astutil/imports.go

@@ -0,0 +1,471 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package astutil contains common utilities for working with the Go AST.
+package astutil // import "golang.org/x/tools/go/ast/astutil"
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"strconv"
+	"strings"
+)
+
+// AddImport adds the import path to the file f, if absent.
+func AddImport(fset *token.FileSet, f *ast.File, ipath string) (added bool) {
+	return AddNamedImport(fset, f, "", ipath)
+}
+
+// AddNamedImport adds the import path to the file f, if absent.
+// If name is not empty, it is used to rename the import.
+//
+// For example, calling
+//	AddNamedImport(fset, f, "pathpkg", "path")
+// adds
+//	import pathpkg "path"
+func AddNamedImport(fset *token.FileSet, f *ast.File, name, ipath string) (added bool) {
+	if imports(f, ipath) {
+		return false
+	}
+
+	newImport := &ast.ImportSpec{
+		Path: &ast.BasicLit{
+			Kind:  token.STRING,
+			Value: strconv.Quote(ipath),
+		},
+	}
+	if name != "" {
+		newImport.Name = &ast.Ident{Name: name}
+	}
+
+	// Find an import decl to add to.
+	// The goal is to find an existing import
+	// whose import path has the longest shared
+	// prefix with ipath.
+	var (
+		bestMatch  = -1         // length of longest shared prefix
+		lastImport = -1         // index in f.Decls of the file's final import decl
+		impDecl    *ast.GenDecl // import decl containing the best match
+		impIndex   = -1         // spec index in impDecl containing the best match
+
+		isThirdPartyPath = isThirdParty(ipath)
+	)
+	for i, decl := range f.Decls {
+		gen, ok := decl.(*ast.GenDecl)
+		if ok && gen.Tok == token.IMPORT {
+			lastImport = i
+			// Do not add to import "C", to avoid disrupting the
+			// association with its doc comment, breaking cgo.
+			if declImports(gen, "C") {
+				continue
+			}
+
+			// Match an empty import decl if that's all that is available.
+			if len(gen.Specs) == 0 && bestMatch == -1 {
+				impDecl = gen
+			}
+
+			// Compute longest shared prefix with imports in this group and find best
+			// matched import spec.
+			// 1. Always prefer import spec with longest shared prefix.
+			// 2. While match length is 0,
+			// - for stdlib package: prefer first import spec.
+			// - for third party package: prefer first third party import spec.
+			// We cannot use last import spec as best match for third party package
+			// because grouped imports are usually placed last by goimports -local
+			// flag.
+			// See issue #19190.
+			seenAnyThirdParty := false
+			for j, spec := range gen.Specs {
+				impspec := spec.(*ast.ImportSpec)
+				p := importPath(impspec)
+				n := matchLen(p, ipath)
+				if n > bestMatch || (bestMatch == 0 && !seenAnyThirdParty && isThirdPartyPath) {
+					bestMatch = n
+					impDecl = gen
+					impIndex = j
+				}
+				seenAnyThirdParty = seenAnyThirdParty || isThirdParty(p)
+			}
+		}
+	}
+
+	// If no import decl found, add one after the last import.
+	if impDecl == nil {
+		impDecl = &ast.GenDecl{
+			Tok: token.IMPORT,
+		}
+		if lastImport >= 0 {
+			impDecl.TokPos = f.Decls[lastImport].End()
+		} else {
+			// There are no existing imports.
+			// Our new import, preceded by a blank line,  goes after the package declaration
+			// and after the comment, if any, that starts on the same line as the
+			// package declaration.
+			impDecl.TokPos = f.Package
+
+			file := fset.File(f.Package)
+			pkgLine := file.Line(f.Package)
+			for _, c := range f.Comments {
+				if file.Line(c.Pos()) > pkgLine {
+					break
+				}
+				// +2 for a blank line
+				impDecl.TokPos = c.End() + 2
+			}
+		}
+		f.Decls = append(f.Decls, nil)
+		copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
+		f.Decls[lastImport+1] = impDecl
+	}
+
+	// Insert new import at insertAt.
+	insertAt := 0
+	if impIndex >= 0 {
+		// insert after the found import
+		insertAt = impIndex + 1
+	}
+	impDecl.Specs = append(impDecl.Specs, nil)
+	copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
+	impDecl.Specs[insertAt] = newImport
+	pos := impDecl.Pos()
+	if insertAt > 0 {
+		// If there is a comment after an existing import, preserve the comment
+		// position by adding the new import after the comment.
+		if spec, ok := impDecl.Specs[insertAt-1].(*ast.ImportSpec); ok && spec.Comment != nil {
+			pos = spec.Comment.End()
+		} else {
+			// Assign same position as the previous import,
+			// so that the sorter sees it as being in the same block.
+			pos = impDecl.Specs[insertAt-1].Pos()
+		}
+	}
+	if newImport.Name != nil {
+		newImport.Name.NamePos = pos
+	}
+	newImport.Path.ValuePos = pos
+	newImport.EndPos = pos
+
+	// Clean up parens. impDecl contains at least one spec.
+	if len(impDecl.Specs) == 1 {
+		// Remove unneeded parens.
+		impDecl.Lparen = token.NoPos
+	} else if !impDecl.Lparen.IsValid() {
+		// impDecl needs parens added.
+		impDecl.Lparen = impDecl.Specs[0].Pos()
+	}
+
+	f.Imports = append(f.Imports, newImport)
+
+	if len(f.Decls) <= 1 {
+		return true
+	}
+
+	// Merge all the import declarations into the first one.
+	var first *ast.GenDecl
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT || declImports(gen, "C") {
+			continue
+		}
+		if first == nil {
+			first = gen
+			continue // Don't touch the first one.
+		}
+		// We now know there is more than one package in this import
+		// declaration. Ensure that it ends up parenthesized.
+		first.Lparen = first.Pos()
+		// Move the imports of the other import declaration to the first one.
+		for _, spec := range gen.Specs {
+			spec.(*ast.ImportSpec).Path.ValuePos = first.Pos()
+			first.Specs = append(first.Specs, spec)
+		}
+		f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		i--
+	}
+
+	return true
+}
+
+func isThirdParty(importPath string) bool {
+	// Third party package import path usually contains "." (".com", ".org", ...)
+	// This logic is taken from golang.org/x/tools/imports package.
+	return strings.Contains(importPath, ".")
+}
+
+// DeleteImport deletes the import path from the file f, if present.
+func DeleteImport(fset *token.FileSet, f *ast.File, path string) (deleted bool) {
+	return DeleteNamedImport(fset, f, "", path)
+}
+
+// DeleteNamedImport deletes the import with the given name and path from the file f, if present.
+func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (deleted bool) {
+	var delspecs []*ast.ImportSpec
+	var delcomments []*ast.CommentGroup
+
+	// Find the import nodes that import path, if any.
+	for i := 0; i < len(f.Decls); i++ {
+		decl := f.Decls[i]
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT {
+			continue
+		}
+		for j := 0; j < len(gen.Specs); j++ {
+			spec := gen.Specs[j]
+			impspec := spec.(*ast.ImportSpec)
+			if impspec.Name == nil && name != "" {
+				continue
+			}
+			if impspec.Name != nil && impspec.Name.Name != name {
+				continue
+			}
+			if importPath(impspec) != path {
+				continue
+			}
+
+			// We found an import spec that imports path.
+			// Delete it.
+			delspecs = append(delspecs, impspec)
+			deleted = true
+			copy(gen.Specs[j:], gen.Specs[j+1:])
+			gen.Specs = gen.Specs[:len(gen.Specs)-1]
+
+			// If this was the last import spec in this decl,
+			// delete the decl, too.
+			if len(gen.Specs) == 0 {
+				copy(f.Decls[i:], f.Decls[i+1:])
+				f.Decls = f.Decls[:len(f.Decls)-1]
+				i--
+				break
+			} else if len(gen.Specs) == 1 {
+				if impspec.Doc != nil {
+					delcomments = append(delcomments, impspec.Doc)
+				}
+				if impspec.Comment != nil {
+					delcomments = append(delcomments, impspec.Comment)
+				}
+				for _, cg := range f.Comments {
+					// Found comment on the same line as the import spec.
+					if cg.End() < impspec.Pos() && fset.Position(cg.End()).Line == fset.Position(impspec.Pos()).Line {
+						delcomments = append(delcomments, cg)
+						break
+					}
+				}
+
+				spec := gen.Specs[0].(*ast.ImportSpec)
+
+				// Move the documentation right after the import decl.
+				if spec.Doc != nil {
+					for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Doc.Pos()).Line {
+						fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
+					}
+				}
+				for _, cg := range f.Comments {
+					if cg.End() < spec.Pos() && fset.Position(cg.End()).Line == fset.Position(spec.Pos()).Line {
+						for fset.Position(gen.TokPos).Line+1 < fset.Position(spec.Pos()).Line {
+							fset.File(gen.TokPos).MergeLine(fset.Position(gen.TokPos).Line)
+						}
+						break
+					}
+				}
+			}
+			if j > 0 {
+				lastImpspec := gen.Specs[j-1].(*ast.ImportSpec)
+				lastLine := fset.Position(lastImpspec.Path.ValuePos).Line
+				line := fset.Position(impspec.Path.ValuePos).Line
+
+				// We deleted an entry but now there may be
+				// a blank line-sized hole where the import was.
+				if line-lastLine > 1 {
+					// There was a blank line immediately preceding the deleted import,
+					// so there's no need to close the hole.
+					// Do nothing.
+				} else if line != fset.File(gen.Rparen).LineCount() {
+					// There was no blank line. Close the hole.
+					fset.File(gen.Rparen).MergeLine(line)
+				}
+			}
+			j--
+		}
+	}
+
+	// Delete imports from f.Imports.
+	for i := 0; i < len(f.Imports); i++ {
+		imp := f.Imports[i]
+		for j, del := range delspecs {
+			if imp == del {
+				copy(f.Imports[i:], f.Imports[i+1:])
+				f.Imports = f.Imports[:len(f.Imports)-1]
+				copy(delspecs[j:], delspecs[j+1:])
+				delspecs = delspecs[:len(delspecs)-1]
+				i--
+				break
+			}
+		}
+	}
+
+	// Delete comments from f.Comments.
+	for i := 0; i < len(f.Comments); i++ {
+		cg := f.Comments[i]
+		for j, del := range delcomments {
+			if cg == del {
+				copy(f.Comments[i:], f.Comments[i+1:])
+				f.Comments = f.Comments[:len(f.Comments)-1]
+				copy(delcomments[j:], delcomments[j+1:])
+				delcomments = delcomments[:len(delcomments)-1]
+				i--
+				break
+			}
+		}
+	}
+
+	if len(delspecs) > 0 {
+		panic(fmt.Sprintf("deleted specs from Decls but not Imports: %v", delspecs))
+	}
+
+	return
+}
+
+// RewriteImport rewrites any import of path oldPath to path newPath.
+func RewriteImport(fset *token.FileSet, f *ast.File, oldPath, newPath string) (rewrote bool) {
+	for _, imp := range f.Imports {
+		if importPath(imp) == oldPath {
+			rewrote = true
+			// record old End, because the default is to compute
+			// it using the length of imp.Path.Value.
+			imp.EndPos = imp.End()
+			imp.Path.Value = strconv.Quote(newPath)
+		}
+	}
+	return
+}
+
+// UsesImport reports whether a given import is used.
+func UsesImport(f *ast.File, path string) (used bool) {
+	spec := importSpec(f, path)
+	if spec == nil {
+		return
+	}
+
+	name := spec.Name.String()
+	switch name {
+	case "<nil>":
+		// If the package name is not explicitly specified,
+		// make an educated guess. This is not guaranteed to be correct.
+		lastSlash := strings.LastIndex(path, "/")
+		if lastSlash == -1 {
+			name = path
+		} else {
+			name = path[lastSlash+1:]
+		}
+	case "_", ".":
+		// Not sure if this import is used - err on the side of caution.
+		return true
+	}
+
+	ast.Walk(visitFn(func(n ast.Node) {
+		sel, ok := n.(*ast.SelectorExpr)
+		if ok && isTopName(sel.X, name) {
+			used = true
+		}
+	}), f)
+
+	return
+}
+
+type visitFn func(node ast.Node)
+
+func (fn visitFn) Visit(node ast.Node) ast.Visitor {
+	fn(node)
+	return fn
+}
+
+// imports returns true if f imports path.
+func imports(f *ast.File, path string) bool {
+	return importSpec(f, path) != nil
+}
+
+// importSpec returns the import spec if f imports path,
+// or nil otherwise.
+func importSpec(f *ast.File, path string) *ast.ImportSpec {
+	for _, s := range f.Imports {
+		if importPath(s) == path {
+			return s
+		}
+	}
+	return nil
+}
+
+// importPath returns the unquoted import path of s,
+// or "" if the path is not properly quoted.
+func importPath(s *ast.ImportSpec) string {
+	t, err := strconv.Unquote(s.Path.Value)
+	if err == nil {
+		return t
+	}
+	return ""
+}
+
+// declImports reports whether gen contains an import of path.
+func declImports(gen *ast.GenDecl, path string) bool {
+	if gen.Tok != token.IMPORT {
+		return false
+	}
+	for _, spec := range gen.Specs {
+		impspec := spec.(*ast.ImportSpec)
+		if importPath(impspec) == path {
+			return true
+		}
+	}
+	return false
+}
+
+// matchLen returns the length of the longest path segment prefix shared by x and y.
+func matchLen(x, y string) int {
+	n := 0
+	for i := 0; i < len(x) && i < len(y) && x[i] == y[i]; i++ {
+		if x[i] == '/' {
+			n++
+		}
+	}
+	return n
+}
+
+// isTopName returns true if n is a top-level unresolved identifier with the given name.
+func isTopName(n ast.Expr, name string) bool {
+	id, ok := n.(*ast.Ident)
+	return ok && id.Name == name && id.Obj == nil
+}
+
+// Imports returns the file imports grouped by paragraph.
+func Imports(fset *token.FileSet, f *ast.File) [][]*ast.ImportSpec {
+	var groups [][]*ast.ImportSpec
+
+	for _, decl := range f.Decls {
+		genDecl, ok := decl.(*ast.GenDecl)
+		if !ok || genDecl.Tok != token.IMPORT {
+			break
+		}
+
+		group := []*ast.ImportSpec{}
+
+		var lastLine int
+		for _, spec := range genDecl.Specs {
+			importSpec := spec.(*ast.ImportSpec)
+			pos := importSpec.Path.ValuePos
+			line := fset.Position(pos).Line
+			if lastLine > 0 && pos > 0 && line-lastLine > 1 {
+				groups = append(groups, group)
+				group = []*ast.ImportSpec{}
+			}
+			group = append(group, importSpec)
+			lastLine = line
+		}
+		groups = append(groups, group)
+	}
+
+	return groups
+}

vendor/golang.org/x/tools/go/ast/astutil/rewrite.go

@@ -0,0 +1,477 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package astutil
+
+import (
+	"fmt"
+	"go/ast"
+	"reflect"
+	"sort"
+)
+
+// An ApplyFunc is invoked by Apply for each node n, even if n is nil,
+// before and/or after the node's children, using a Cursor describing
+// the current node and providing operations on it.
+//
+// The return value of ApplyFunc controls the syntax tree traversal.
+// See Apply for details.
+type ApplyFunc func(*Cursor) bool
+
+// Apply traverses a syntax tree recursively, starting with root,
+// and calling pre and post for each node as described below.
+// Apply returns the syntax tree, possibly modified.
+//
+// If pre is not nil, it is called for each node before the node's
+// children are traversed (pre-order). If pre returns false, no
+// children are traversed, and post is not called for that node.
+//
+// If post is not nil, and a prior call of pre didn't return false,
+// post is called for each node after its children are traversed
+// (post-order). If post returns false, traversal is terminated and
+// Apply returns immediately.
+//
+// Only fields that refer to AST nodes are considered children;
+// i.e., token.Pos, Scopes, Objects, and fields of basic types
+// (strings, etc.) are ignored.
+//
+// Children are traversed in the order in which they appear in the
+// respective node's struct definition. A package's files are
+// traversed in the filenames' alphabetical order.
+//
+func Apply(root ast.Node, pre, post ApplyFunc) (result ast.Node) {
+	parent := &struct{ ast.Node }{root}
+	defer func() {
+		if r := recover(); r != nil && r != abort {
+			panic(r)
+		}
+		result = parent.Node
+	}()
+	a := &application{pre: pre, post: post}
+	a.apply(parent, "Node", nil, root)
+	return
+}
+
+var abort = new(int) // singleton, to signal termination of Apply
+
+// A Cursor describes a node encountered during Apply.
+// Information about the node and its parent is available
+// from the Node, Parent, Name, and Index methods.
+//
+// If p is a variable of type and value of the current parent node
+// c.Parent(), and f is the field identifier with name c.Name(),
+// the following invariants hold:
+//
+//   p.f            == c.Node()  if c.Index() <  0
+//   p.f[c.Index()] == c.Node()  if c.Index() >= 0
+//
+// The methods Replace, Delete, InsertBefore, and InsertAfter
+// can be used to change the AST without disrupting Apply.
+type Cursor struct {
+	parent ast.Node
+	name   string
+	iter   *iterator // valid if non-nil
+	node   ast.Node
+}
+
+// Node returns the current Node.
+func (c *Cursor) Node() ast.Node { return c.node }
+
+// Parent returns the parent of the current Node.
+func (c *Cursor) Parent() ast.Node { return c.parent }
+
+// Name returns the name of the parent Node field that contains the current Node.
+// If the parent is a *ast.Package and the current Node is a *ast.File, Name returns
+// the filename for the current Node.
+func (c *Cursor) Name() string { return c.name }
+
+// Index reports the index >= 0 of the current Node in the slice of Nodes that
+// contains it, or a value < 0 if the current Node is not part of a slice.
+// The index of the current node changes if InsertBefore is called while
+// processing the current node.
+func (c *Cursor) Index() int {
+	if c.iter != nil {
+		return c.iter.index
+	}
+	return -1
+}
+
+// field returns the current node's parent field value.
+func (c *Cursor) field() reflect.Value {
+	return reflect.Indirect(reflect.ValueOf(c.parent)).FieldByName(c.name)
+}
+
+// Replace replaces the current Node with n.
+// The replacement node is not walked by Apply.
+func (c *Cursor) Replace(n ast.Node) {
+	if _, ok := c.node.(*ast.File); ok {
+		file, ok := n.(*ast.File)
+		if !ok {
+			panic("attempt to replace *ast.File with non-*ast.File")
+		}
+		c.parent.(*ast.Package).Files[c.name] = file
+		return
+	}
+
+	v := c.field()
+	if i := c.Index(); i >= 0 {
+		v = v.Index(i)
+	}
+	v.Set(reflect.ValueOf(n))
+}
+
+// Delete deletes the current Node from its containing slice.
+// If the current Node is not part of a slice, Delete panics.
+// As a special case, if the current node is a package file,
+// Delete removes it from the package's Files map.
+func (c *Cursor) Delete() {
+	if _, ok := c.node.(*ast.File); ok {
+		delete(c.parent.(*ast.Package).Files, c.name)
+		return
+	}
+
+	i := c.Index()
+	if i < 0 {
+		panic("Delete node not contained in slice")
+	}
+	v := c.field()
+	l := v.Len()
+	reflect.Copy(v.Slice(i, l), v.Slice(i+1, l))
+	v.Index(l - 1).Set(reflect.Zero(v.Type().Elem()))
+	v.SetLen(l - 1)
+	c.iter.step--
+}
+
+// InsertAfter inserts n after the current Node in its containing slice.
+// If the current Node is not part of a slice, InsertAfter panics.
+// Apply does not walk n.
+func (c *Cursor) InsertAfter(n ast.Node) {
+	i := c.Index()
+	if i < 0 {
+		panic("InsertAfter node not contained in slice")
+	}
+	v := c.field()
+	v.Set(reflect.Append(v, reflect.Zero(v.Type().Elem())))
+	l := v.Len()
+	reflect.Copy(v.Slice(i+2, l), v.Slice(i+1, l))
+	v.Index(i + 1).Set(reflect.ValueOf(n))
+	c.iter.step++
+}
+
+// InsertBefore inserts n before the current Node in its containing slice.
+// If the current Node is not part of a slice, InsertBefore panics.
+// Apply will not walk n.
+func (c *Cursor) InsertBefore(n ast.Node) {
+	i := c.Index()
+	if i < 0 {
+		panic("InsertBefore node not contained in slice")
+	}
+	v := c.field()
+	v.Set(reflect.Append(v, reflect.Zero(v.Type().Elem())))
+	l := v.Len()
+	reflect.Copy(v.Slice(i+1, l), v.Slice(i, l))
+	v.Index(i).Set(reflect.ValueOf(n))
+	c.iter.index++
+}
+
+// application carries all the shared data so we can pass it around cheaply.
+type application struct {
+	pre, post ApplyFunc
+	cursor    Cursor
+	iter      iterator
+}
+
+func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.Node) {
+	// convert typed nil into untyped nil
+	if v := reflect.ValueOf(n); v.Kind() == reflect.Ptr && v.IsNil() {
+		n = nil
+	}
+
+	// avoid heap-allocating a new cursor for each apply call; reuse a.cursor instead
+	saved := a.cursor
+	a.cursor.parent = parent
+	a.cursor.name = name
+	a.cursor.iter = iter
+	a.cursor.node = n
+
+	if a.pre != nil && !a.pre(&a.cursor) {
+		a.cursor = saved
+		return
+	}
+
+	// walk children
+	// (the order of the cases matches the order of the corresponding node types in go/ast)
+	switch n := n.(type) {
+	case nil:
+		// nothing to do
+
+	// Comments and fields
+	case *ast.Comment:
+		// nothing to do
+
+	case *ast.CommentGroup:
+		if n != nil {
+			a.applyList(n, "List")
+		}
+
+	case *ast.Field:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Names")
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Tag", nil, n.Tag)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.FieldList:
+		a.applyList(n, "List")
+
+	// Expressions
+	case *ast.BadExpr, *ast.Ident, *ast.BasicLit:
+		// nothing to do
+
+	case *ast.Ellipsis:
+		a.apply(n, "Elt", nil, n.Elt)
+
+	case *ast.FuncLit:
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.CompositeLit:
+		a.apply(n, "Type", nil, n.Type)
+		a.applyList(n, "Elts")
+
+	case *ast.ParenExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.SelectorExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Sel", nil, n.Sel)
+
+	case *ast.IndexExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Index", nil, n.Index)
+
+	case *ast.SliceExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Low", nil, n.Low)
+		a.apply(n, "High", nil, n.High)
+		a.apply(n, "Max", nil, n.Max)
+
+	case *ast.TypeAssertExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Type", nil, n.Type)
+
+	case *ast.CallExpr:
+		a.apply(n, "Fun", nil, n.Fun)
+		a.applyList(n, "Args")
+
+	case *ast.StarExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.UnaryExpr:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.BinaryExpr:
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Y", nil, n.Y)
+
+	case *ast.KeyValueExpr:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+
+	// Types
+	case *ast.ArrayType:
+		a.apply(n, "Len", nil, n.Len)
+		a.apply(n, "Elt", nil, n.Elt)
+
+	case *ast.StructType:
+		a.apply(n, "Fields", nil, n.Fields)
+
+	case *ast.FuncType:
+		a.apply(n, "Params", nil, n.Params)
+		a.apply(n, "Results", nil, n.Results)
+
+	case *ast.InterfaceType:
+		a.apply(n, "Methods", nil, n.Methods)
+
+	case *ast.MapType:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+
+	case *ast.ChanType:
+		a.apply(n, "Value", nil, n.Value)
+
+	// Statements
+	case *ast.BadStmt:
+		// nothing to do
+
+	case *ast.DeclStmt:
+		a.apply(n, "Decl", nil, n.Decl)
+
+	case *ast.EmptyStmt:
+		// nothing to do
+
+	case *ast.LabeledStmt:
+		a.apply(n, "Label", nil, n.Label)
+		a.apply(n, "Stmt", nil, n.Stmt)
+
+	case *ast.ExprStmt:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.SendStmt:
+		a.apply(n, "Chan", nil, n.Chan)
+		a.apply(n, "Value", nil, n.Value)
+
+	case *ast.IncDecStmt:
+		a.apply(n, "X", nil, n.X)
+
+	case *ast.AssignStmt:
+		a.applyList(n, "Lhs")
+		a.applyList(n, "Rhs")
+
+	case *ast.GoStmt:
+		a.apply(n, "Call", nil, n.Call)
+
+	case *ast.DeferStmt:
+		a.apply(n, "Call", nil, n.Call)
+
+	case *ast.ReturnStmt:
+		a.applyList(n, "Results")
+
+	case *ast.BranchStmt:
+		a.apply(n, "Label", nil, n.Label)
+
+	case *ast.BlockStmt:
+		a.applyList(n, "List")
+
+	case *ast.IfStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Cond", nil, n.Cond)
+		a.apply(n, "Body", nil, n.Body)
+		a.apply(n, "Else", nil, n.Else)
+
+	case *ast.CaseClause:
+		a.applyList(n, "List")
+		a.applyList(n, "Body")
+
+	case *ast.SwitchStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Tag", nil, n.Tag)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.TypeSwitchStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Assign", nil, n.Assign)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.CommClause:
+		a.apply(n, "Comm", nil, n.Comm)
+		a.applyList(n, "Body")
+
+	case *ast.SelectStmt:
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.ForStmt:
+		a.apply(n, "Init", nil, n.Init)
+		a.apply(n, "Cond", nil, n.Cond)
+		a.apply(n, "Post", nil, n.Post)
+		a.apply(n, "Body", nil, n.Body)
+
+	case *ast.RangeStmt:
+		a.apply(n, "Key", nil, n.Key)
+		a.apply(n, "Value", nil, n.Value)
+		a.apply(n, "X", nil, n.X)
+		a.apply(n, "Body", nil, n.Body)
+
+	// Declarations
+	case *ast.ImportSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Path", nil, n.Path)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.ValueSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Names")
+		a.apply(n, "Type", nil, n.Type)
+		a.applyList(n, "Values")
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.TypeSpec:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Comment", nil, n.Comment)
+
+	case *ast.BadDecl:
+		// nothing to do
+
+	case *ast.GenDecl:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.applyList(n, "Specs")
+
+	case *ast.FuncDecl:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Recv", nil, n.Recv)
+		a.apply(n, "Name", nil, n.Name)
+		a.apply(n, "Type", nil, n.Type)
+		a.apply(n, "Body", nil, n.Body)
+
+	// Files and packages
+	case *ast.File:
+		a.apply(n, "Doc", nil, n.Doc)
+		a.apply(n, "Name", nil, n.Name)
+		a.applyList(n, "Decls")
+		// Don't walk n.Comments; they have either been walked already if
+		// they are Doc comments, or they can be easily walked explicitly.
+
+	case *ast.Package:
+		// collect and sort names for reproducible behavior
+		var names []string
+		for name := range n.Files {
+			names = append(names, name)
+		}
+		sort.Strings(names)
+		for _, name := range names {
+			a.apply(n, name, nil, n.Files[name])
+		}
+
+	default:
+		panic(fmt.Sprintf("Apply: unexpected node type %T", n))
+	}
+
+	if a.post != nil && !a.post(&a.cursor) {
+		panic(abort)
+	}
+
+	a.cursor = saved
+}
+
+// An iterator controls iteration over a slice of nodes.
+type iterator struct {
+	index, step int
+}
+
+func (a *application) applyList(parent ast.Node, name string) {
+	// avoid heap-allocating a new iterator for each applyList call; reuse a.iter instead
+	saved := a.iter
+	a.iter.index = 0
+	for {
+		// must reload parent.name each time, since cursor modifications might change it
+		v := reflect.Indirect(reflect.ValueOf(parent)).FieldByName(name)
+		if a.iter.index >= v.Len() {
+			break
+		}
+
+		// element x may be nil in a bad AST - be cautious
+		var x ast.Node
+		if e := v.Index(a.iter.index); e.IsValid() {
+			x = e.Interface().(ast.Node)
+		}
+
+		a.iter.step = 1
+		a.apply(parent, name, &a.iter, x)
+		a.iter.index += a.iter.step
+	}
+	a.iter = saved
+}

vendor/golang.org/x/tools/go/ast/astutil/util.go

@@ -0,0 +1,14 @@
+package astutil
+
+import "go/ast"
+
+// Unparen returns e with any enclosing parentheses stripped.
+func Unparen(e ast.Expr) ast.Expr {
+	for {
+		p, ok := e.(*ast.ParenExpr)
+		if !ok {
+			return e
+		}
+		e = p.X
+	}
+}

vendor/golang.org/x/tools/go/buildutil/allpackages.go

@@ -0,0 +1,198 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package buildutil provides utilities related to the go/build
+// package in the standard library.
+//
+// All I/O is done via the build.Context file system interface, which must
+// be concurrency-safe.
+package buildutil // import "golang.org/x/tools/go/buildutil"
+
+import (
+	"go/build"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+)
+
+// AllPackages returns the package path of each Go package in any source
+// directory of the specified build context (e.g. $GOROOT or an element
+// of $GOPATH).  Errors are ignored.  The results are sorted.
+// All package paths are canonical, and thus may contain "/vendor/".
+//
+// The result may include import paths for directories that contain no
+// *.go files, such as "archive" (in $GOROOT/src).
+//
+// All I/O is done via the build.Context file system interface,
+// which must be concurrency-safe.
+//
+func AllPackages(ctxt *build.Context) []string {
+	var list []string
+	ForEachPackage(ctxt, func(pkg string, _ error) {
+		list = append(list, pkg)
+	})
+	sort.Strings(list)
+	return list
+}
+
+// ForEachPackage calls the found function with the package path of
+// each Go package it finds in any source directory of the specified
+// build context (e.g. $GOROOT or an element of $GOPATH).
+// All package paths are canonical, and thus may contain "/vendor/".
+//
+// If the package directory exists but could not be read, the second
+// argument to the found function provides the error.
+//
+// All I/O is done via the build.Context file system interface,
+// which must be concurrency-safe.
+//
+func ForEachPackage(ctxt *build.Context, found func(importPath string, err error)) {
+	ch := make(chan item)
+
+	var wg sync.WaitGroup
+	for _, root := range ctxt.SrcDirs() {
+		root := root
+		wg.Add(1)
+		go func() {
+			allPackages(ctxt, root, ch)
+			wg.Done()
+		}()
+	}
+	go func() {
+		wg.Wait()
+		close(ch)
+	}()
+
+	// All calls to found occur in the caller's goroutine.
+	for i := range ch {
+		found(i.importPath, i.err)
+	}
+}
+
+type item struct {
+	importPath string
+	err        error // (optional)
+}
+
+// We use a process-wide counting semaphore to limit
+// the number of parallel calls to ReadDir.
+var ioLimit = make(chan bool, 20)
+
+func allPackages(ctxt *build.Context, root string, ch chan<- item) {
+	root = filepath.Clean(root) + string(os.PathSeparator)
+
+	var wg sync.WaitGroup
+
+	var walkDir func(dir string)
+	walkDir = func(dir string) {
+		// Avoid .foo, _foo, and testdata directory trees.
+		base := filepath.Base(dir)
+		if base == "" || base[0] == '.' || base[0] == '_' || base == "testdata" {
+			return
+		}
+
+		pkg := filepath.ToSlash(strings.TrimPrefix(dir, root))
+
+		// Prune search if we encounter any of these import paths.
+		switch pkg {
+		case "builtin":
+			return
+		}
+
+		ioLimit <- true
+		files, err := ReadDir(ctxt, dir)
+		<-ioLimit
+		if pkg != "" || err != nil {
+			ch <- item{pkg, err}
+		}
+		for _, fi := range files {
+			fi := fi
+			if fi.IsDir() {
+				wg.Add(1)
+				go func() {
+					walkDir(filepath.Join(dir, fi.Name()))
+					wg.Done()
+				}()
+			}
+		}
+	}
+
+	walkDir(root)
+	wg.Wait()
+}
+
+// ExpandPatterns returns the set of packages matched by patterns,
+// which may have the following forms:
+//
+//		golang.org/x/tools/cmd/guru     # a single package
+//		golang.org/x/tools/...          # all packages beneath dir
+//		...                             # the entire workspace.
+//
+// Order is significant: a pattern preceded by '-' removes matching
+// packages from the set.  For example, these patterns match all encoding
+// packages except encoding/xml:
+//
+// 	encoding/... -encoding/xml
+//
+// A trailing slash in a pattern is ignored.  (Path components of Go
+// package names are separated by slash, not the platform's path separator.)
+//
+func ExpandPatterns(ctxt *build.Context, patterns []string) map[string]bool {
+	// TODO(adonovan): support other features of 'go list':
+	// - "std"/"cmd"/"all" meta-packages
+	// - "..." not at the end of a pattern
+	// - relative patterns using "./" or "../" prefix
+
+	pkgs := make(map[string]bool)
+	doPkg := func(pkg string, neg bool) {
+		if neg {
+			delete(pkgs, pkg)
+		} else {
+			pkgs[pkg] = true
+		}
+	}
+
+	// Scan entire workspace if wildcards are present.
+	// TODO(adonovan): opt: scan only the necessary subtrees of the workspace.
+	var all []string
+	for _, arg := range patterns {
+		if strings.HasSuffix(arg, "...") {
+			all = AllPackages(ctxt)
+			break
+		}
+	}
+
+	for _, arg := range patterns {
+		if arg == "" {
+			continue
+		}
+
+		neg := arg[0] == '-'
+		if neg {
+			arg = arg[1:]
+		}
+
+		if arg == "..." {
+			// ... matches all packages
+			for _, pkg := range all {
+				doPkg(pkg, neg)
+			}
+		} else if dir := strings.TrimSuffix(arg, "/..."); dir != arg {
+			// dir/... matches all packages beneath dir
+			for _, pkg := range all {
+				if strings.HasPrefix(pkg, dir) &&
+					(len(pkg) == len(dir) || pkg[len(dir)] == '/') {
+					doPkg(pkg, neg)
+				}
+			}
+		} else {
+			// single package
+			doPkg(strings.TrimSuffix(arg, "/"), neg)
+		}
+	}
+
+	return pkgs
+}

vendor/golang.org/x/tools/go/buildutil/fakecontext.go

@@ -0,0 +1,109 @@
+package buildutil
+
+import (
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+	"time"
+)
+
+// FakeContext returns a build.Context for the fake file tree specified
+// by pkgs, which maps package import paths to a mapping from file base
+// names to contents.
+//
+// The fake Context has a GOROOT of "/go" and no GOPATH, and overrides
+// the necessary file access methods to read from memory instead of the
+// real file system.
+//
+// Unlike a real file tree, the fake one has only two levels---packages
+// and files---so ReadDir("/go/src/") returns all packages under
+// /go/src/ including, for instance, "math" and "math/big".
+// ReadDir("/go/src/math/big") would return all the files in the
+// "math/big" package.
+//
+func FakeContext(pkgs map[string]map[string]string) *build.Context {
+	clean := func(filename string) string {
+		f := path.Clean(filepath.ToSlash(filename))
+		// Removing "/go/src" while respecting segment
+		// boundaries has this unfortunate corner case:
+		if f == "/go/src" {
+			return ""
+		}
+		return strings.TrimPrefix(f, "/go/src/")
+	}
+
+	ctxt := build.Default // copy
+	ctxt.GOROOT = "/go"
+	ctxt.GOPATH = ""
+	ctxt.Compiler = "gc"
+	ctxt.IsDir = func(dir string) bool {
+		dir = clean(dir)
+		if dir == "" {
+			return true // needed by (*build.Context).SrcDirs
+		}
+		return pkgs[dir] != nil
+	}
+	ctxt.ReadDir = func(dir string) ([]os.FileInfo, error) {
+		dir = clean(dir)
+		var fis []os.FileInfo
+		if dir == "" {
+			// enumerate packages
+			for importPath := range pkgs {
+				fis = append(fis, fakeDirInfo(importPath))
+			}
+		} else {
+			// enumerate files of package
+			for basename := range pkgs[dir] {
+				fis = append(fis, fakeFileInfo(basename))
+			}
+		}
+		sort.Sort(byName(fis))
+		return fis, nil
+	}
+	ctxt.OpenFile = func(filename string) (io.ReadCloser, error) {
+		filename = clean(filename)
+		dir, base := path.Split(filename)
+		content, ok := pkgs[path.Clean(dir)][base]
+		if !ok {
+			return nil, fmt.Errorf("file not found: %s", filename)
+		}
+		return ioutil.NopCloser(strings.NewReader(content)), nil
+	}
+	ctxt.IsAbsPath = func(path string) bool {
+		path = filepath.ToSlash(path)
+		// Don't rely on the default (filepath.Path) since on
+		// Windows, it reports virtual paths as non-absolute.
+		return strings.HasPrefix(path, "/")
+	}
+	return &ctxt
+}
+
+type byName []os.FileInfo
+
+func (s byName) Len() int           { return len(s) }
+func (s byName) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+func (s byName) Less(i, j int) bool { return s[i].Name() < s[j].Name() }
+
+type fakeFileInfo string
+
+func (fi fakeFileInfo) Name() string    { return string(fi) }
+func (fakeFileInfo) Sys() interface{}   { return nil }
+func (fakeFileInfo) ModTime() time.Time { return time.Time{} }
+func (fakeFileInfo) IsDir() bool        { return false }
+func (fakeFileInfo) Size() int64        { return 0 }
+func (fakeFileInfo) Mode() os.FileMode  { return 0644 }
+
+type fakeDirInfo string
+
+func (fd fakeDirInfo) Name() string    { return string(fd) }
+func (fakeDirInfo) Sys() interface{}   { return nil }
+func (fakeDirInfo) ModTime() time.Time { return time.Time{} }
+func (fakeDirInfo) IsDir() bool        { return true }
+func (fakeDirInfo) Size() int64        { return 0 }
+func (fakeDirInfo) Mode() os.FileMode  { return 0755 }

vendor/golang.org/x/tools/go/buildutil/overlay.go

@@ -0,0 +1,103 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// OverlayContext overlays a build.Context with additional files from
+// a map. Files in the map take precedence over other files.
+//
+// In addition to plain string comparison, two file names are
+// considered equal if their base names match and their directory
+// components point at the same directory on the file system. That is,
+// symbolic links are followed for directories, but not files.
+//
+// A common use case for OverlayContext is to allow editors to pass in
+// a set of unsaved, modified files.
+//
+// Currently, only the Context.OpenFile function will respect the
+// overlay. This may change in the future.
+func OverlayContext(orig *build.Context, overlay map[string][]byte) *build.Context {
+	// TODO(dominikh): Implement IsDir, HasSubdir and ReadDir
+
+	rc := func(data []byte) (io.ReadCloser, error) {
+		return ioutil.NopCloser(bytes.NewBuffer(data)), nil
+	}
+
+	copy := *orig // make a copy
+	ctxt := &copy
+	ctxt.OpenFile = func(path string) (io.ReadCloser, error) {
+		// Fast path: names match exactly.
+		if content, ok := overlay[path]; ok {
+			return rc(content)
+		}
+
+		// Slow path: check for same file under a different
+		// alias, perhaps due to a symbolic link.
+		for filename, content := range overlay {
+			if sameFile(path, filename) {
+				return rc(content)
+			}
+		}
+
+		return OpenFile(orig, path)
+	}
+	return ctxt
+}
+
+// ParseOverlayArchive parses an archive containing Go files and their
+// contents. The result is intended to be used with OverlayContext.
+//
+//
+// Archive format
+//
+// The archive consists of a series of files. Each file consists of a
+// name, a decimal file size and the file contents, separated by
+// newlinews. No newline follows after the file contents.
+func ParseOverlayArchive(archive io.Reader) (map[string][]byte, error) {
+	overlay := make(map[string][]byte)
+	r := bufio.NewReader(archive)
+	for {
+		// Read file name.
+		filename, err := r.ReadString('\n')
+		if err != nil {
+			if err == io.EOF {
+				break // OK
+			}
+			return nil, fmt.Errorf("reading archive file name: %v", err)
+		}
+		filename = filepath.Clean(strings.TrimSpace(filename))
+
+		// Read file size.
+		sz, err := r.ReadString('\n')
+		if err != nil {
+			return nil, fmt.Errorf("reading size of archive file %s: %v", filename, err)
+		}
+		sz = strings.TrimSpace(sz)
+		size, err := strconv.ParseUint(sz, 10, 32)
+		if err != nil {
+			return nil, fmt.Errorf("parsing size of archive file %s: %v", filename, err)
+		}
+
+		// Read file content.
+		content := make([]byte, size)
+		if _, err := io.ReadFull(r, content); err != nil {
+			return nil, fmt.Errorf("reading archive file %s: %v", filename, err)
+		}
+		overlay[filename] = content
+	}
+
+	return overlay, nil
+}

vendor/golang.org/x/tools/go/buildutil/tags.go

@@ -0,0 +1,75 @@
+package buildutil
+
+// This logic was copied from stringsFlag from $GOROOT/src/cmd/go/build.go.
+
+import "fmt"
+
+const TagsFlagDoc = "a list of `build tags` to consider satisfied during the build. " +
+	"For more information about build tags, see the description of " +
+	"build constraints in the documentation for the go/build package"
+
+// TagsFlag is an implementation of the flag.Value and flag.Getter interfaces that parses
+// a flag value in the same manner as go build's -tags flag and
+// populates a []string slice.
+//
+// See $GOROOT/src/go/build/doc.go for description of build tags.
+// See $GOROOT/src/cmd/go/doc.go for description of 'go build -tags' flag.
+//
+// Example:
+// 	flag.Var((*buildutil.TagsFlag)(&build.Default.BuildTags), "tags", buildutil.TagsFlagDoc)
+type TagsFlag []string
+
+func (v *TagsFlag) Set(s string) error {
+	var err error
+	*v, err = splitQuotedFields(s)
+	if *v == nil {
+		*v = []string{}
+	}
+	return err
+}
+
+func (v *TagsFlag) Get() interface{} { return *v }
+
+func splitQuotedFields(s string) ([]string, error) {
+	// Split fields allowing '' or "" around elements.
+	// Quotes further inside the string do not count.
+	var f []string
+	for len(s) > 0 {
+		for len(s) > 0 && isSpaceByte(s[0]) {
+			s = s[1:]
+		}
+		if len(s) == 0 {
+			break
+		}
+		// Accepted quoted string. No unescaping inside.
+		if s[0] == '"' || s[0] == '\'' {
+			quote := s[0]
+			s = s[1:]
+			i := 0
+			for i < len(s) && s[i] != quote {
+				i++
+			}
+			if i >= len(s) {
+				return nil, fmt.Errorf("unterminated %c string", quote)
+			}
+			f = append(f, s[:i])
+			s = s[i+1:]
+			continue
+		}
+		i := 0
+		for i < len(s) && !isSpaceByte(s[i]) {
+			i++
+		}
+		f = append(f, s[:i])
+		s = s[i:]
+	}
+	return f, nil
+}
+
+func (v *TagsFlag) String() string {
+	return "<tagsFlag>"
+}
+
+func isSpaceByte(c byte) bool {
+	return c == ' ' || c == '\t' || c == '\n' || c == '\r'
+}

vendor/golang.org/x/tools/go/buildutil/util.go

@@ -0,0 +1,212 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package buildutil
+
+import (
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+// ParseFile behaves like parser.ParseFile,
+// but uses the build context's file system interface, if any.
+//
+// If file is not absolute (as defined by IsAbsPath), the (dir, file)
+// components are joined using JoinPath; dir must be absolute.
+//
+// The displayPath function, if provided, is used to transform the
+// filename that will be attached to the ASTs.
+//
+// TODO(adonovan): call this from go/loader.parseFiles when the tree thaws.
+//
+func ParseFile(fset *token.FileSet, ctxt *build.Context, displayPath func(string) string, dir string, file string, mode parser.Mode) (*ast.File, error) {
+	if !IsAbsPath(ctxt, file) {
+		file = JoinPath(ctxt, dir, file)
+	}
+	rd, err := OpenFile(ctxt, file)
+	if err != nil {
+		return nil, err
+	}
+	defer rd.Close() // ignore error
+	if displayPath != nil {
+		file = displayPath(file)
+	}
+	return parser.ParseFile(fset, file, rd, mode)
+}
+
+// ContainingPackage returns the package containing filename.
+//
+// If filename is not absolute, it is interpreted relative to working directory dir.
+// All I/O is via the build context's file system interface, if any.
+//
+// The '...Files []string' fields of the resulting build.Package are not
+// populated (build.FindOnly mode).
+//
+func ContainingPackage(ctxt *build.Context, dir, filename string) (*build.Package, error) {
+	if !IsAbsPath(ctxt, filename) {
+		filename = JoinPath(ctxt, dir, filename)
+	}
+
+	// We must not assume the file tree uses
+	// "/" always,
+	// `\` always,
+	// or os.PathSeparator (which varies by platform),
+	// but to make any progress, we are forced to assume that
+	// paths will not use `\` unless the PathSeparator
+	// is also `\`, thus we can rely on filepath.ToSlash for some sanity.
+
+	dirSlash := path.Dir(filepath.ToSlash(filename)) + "/"
+
+	// We assume that no source root (GOPATH[i] or GOROOT) contains any other.
+	for _, srcdir := range ctxt.SrcDirs() {
+		srcdirSlash := filepath.ToSlash(srcdir) + "/"
+		if importPath, ok := HasSubdir(ctxt, srcdirSlash, dirSlash); ok {
+			return ctxt.Import(importPath, dir, build.FindOnly)
+		}
+	}
+
+	return nil, fmt.Errorf("can't find package containing %s", filename)
+}
+
+// -- Effective methods of file system interface -------------------------
+
+// (go/build.Context defines these as methods, but does not export them.)
+
+// hasSubdir calls ctxt.HasSubdir (if not nil) or else uses
+// the local file system to answer the question.
+func HasSubdir(ctxt *build.Context, root, dir string) (rel string, ok bool) {
+	if f := ctxt.HasSubdir; f != nil {
+		return f(root, dir)
+	}
+
+	// Try using paths we received.
+	if rel, ok = hasSubdir(root, dir); ok {
+		return
+	}
+
+	// Try expanding symlinks and comparing
+	// expanded against unexpanded and
+	// expanded against expanded.
+	rootSym, _ := filepath.EvalSymlinks(root)
+	dirSym, _ := filepath.EvalSymlinks(dir)
+
+	if rel, ok = hasSubdir(rootSym, dir); ok {
+		return
+	}
+	if rel, ok = hasSubdir(root, dirSym); ok {
+		return
+	}
+	return hasSubdir(rootSym, dirSym)
+}
+
+func hasSubdir(root, dir string) (rel string, ok bool) {
+	const sep = string(filepath.Separator)
+	root = filepath.Clean(root)
+	if !strings.HasSuffix(root, sep) {
+		root += sep
+	}
+
+	dir = filepath.Clean(dir)
+	if !strings.HasPrefix(dir, root) {
+		return "", false
+	}
+
+	return filepath.ToSlash(dir[len(root):]), true
+}
+
+// FileExists returns true if the specified file exists,
+// using the build context's file system interface.
+func FileExists(ctxt *build.Context, path string) bool {
+	if ctxt.OpenFile != nil {
+		r, err := ctxt.OpenFile(path)
+		if err != nil {
+			return false
+		}
+		r.Close() // ignore error
+		return true
+	}
+	_, err := os.Stat(path)
+	return err == nil
+}
+
+// OpenFile behaves like os.Open,
+// but uses the build context's file system interface, if any.
+func OpenFile(ctxt *build.Context, path string) (io.ReadCloser, error) {
+	if ctxt.OpenFile != nil {
+		return ctxt.OpenFile(path)
+	}
+	return os.Open(path)
+}
+
+// IsAbsPath behaves like filepath.IsAbs,
+// but uses the build context's file system interface, if any.
+func IsAbsPath(ctxt *build.Context, path string) bool {
+	if ctxt.IsAbsPath != nil {
+		return ctxt.IsAbsPath(path)
+	}
+	return filepath.IsAbs(path)
+}
+
+// JoinPath behaves like filepath.Join,
+// but uses the build context's file system interface, if any.
+func JoinPath(ctxt *build.Context, path ...string) string {
+	if ctxt.JoinPath != nil {
+		return ctxt.JoinPath(path...)
+	}
+	return filepath.Join(path...)
+}
+
+// IsDir behaves like os.Stat plus IsDir,
+// but uses the build context's file system interface, if any.
+func IsDir(ctxt *build.Context, path string) bool {
+	if ctxt.IsDir != nil {
+		return ctxt.IsDir(path)
+	}
+	fi, err := os.Stat(path)
+	return err == nil && fi.IsDir()
+}
+
+// ReadDir behaves like ioutil.ReadDir,
+// but uses the build context's file system interface, if any.
+func ReadDir(ctxt *build.Context, path string) ([]os.FileInfo, error) {
+	if ctxt.ReadDir != nil {
+		return ctxt.ReadDir(path)
+	}
+	return ioutil.ReadDir(path)
+}
+
+// SplitPathList behaves like filepath.SplitList,
+// but uses the build context's file system interface, if any.
+func SplitPathList(ctxt *build.Context, s string) []string {
+	if ctxt.SplitPathList != nil {
+		return ctxt.SplitPathList(s)
+	}
+	return filepath.SplitList(s)
+}
+
+// sameFile returns true if x and y have the same basename and denote
+// the same file.
+//
+func sameFile(x, y string) bool {
+	if path.Clean(x) == path.Clean(y) {
+		return true
+	}
+	if filepath.Base(x) == filepath.Base(y) { // (optimisation)
+		if xi, err := os.Stat(x); err == nil {
+			if yi, err := os.Stat(y); err == nil {
+				return os.SameFile(xi, yi)
+			}
+		}
+	}
+	return false
+}

vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go

@@ -0,0 +1,109 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gcexportdata provides functions for locating, reading, and
+// writing export data files containing type information produced by the
+// gc compiler.  This package supports go1.7 export data format and all
+// later versions.
+//
+// Although it might seem convenient for this package to live alongside
+// go/types in the standard library, this would cause version skew
+// problems for developer tools that use it, since they must be able to
+// consume the outputs of the gc compiler both before and after a Go
+// update such as from Go 1.7 to Go 1.8.  Because this package lives in
+// golang.org/x/tools, sites can update their version of this repo some
+// time before the Go 1.8 release and rebuild and redeploy their
+// developer tools, which will then be able to consume both Go 1.7 and
+// Go 1.8 export data files, so they will work before and after the
+// Go update. (See discussion at https://github.com/golang/go/issues/15651.)
+//
+package gcexportdata // import "golang.org/x/tools/go/gcexportdata"
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/token"
+	"go/types"
+	"io"
+	"io/ioutil"
+
+	"golang.org/x/tools/go/internal/gcimporter"
+)
+
+// Find returns the name of an object (.o) or archive (.a) file
+// containing type information for the specified import path,
+// using the workspace layout conventions of go/build.
+// If no file was found, an empty filename is returned.
+//
+// A relative srcDir is interpreted relative to the current working directory.
+//
+// Find also returns the package's resolved (canonical) import path,
+// reflecting the effects of srcDir and vendoring on importPath.
+func Find(importPath, srcDir string) (filename, path string) {
+	return gcimporter.FindPkg(importPath, srcDir)
+}
+
+// NewReader returns a reader for the export data section of an object
+// (.o) or archive (.a) file read from r.  The new reader may provide
+// additional trailing data beyond the end of the export data.
+func NewReader(r io.Reader) (io.Reader, error) {
+	buf := bufio.NewReader(r)
+	_, err := gcimporter.FindExportData(buf)
+	// If we ever switch to a zip-like archive format with the ToC
+	// at the end, we can return the correct portion of export data,
+	// but for now we must return the entire rest of the file.
+	return buf, err
+}
+
+// Read reads export data from in, decodes it, and returns type
+// information for the package.
+// The package name is specified by path.
+// File position information is added to fset.
+//
+// Read may inspect and add to the imports map to ensure that references
+// within the export data to other packages are consistent.  The caller
+// must ensure that imports[path] does not exist, or exists but is
+// incomplete (see types.Package.Complete), and Read inserts the
+// resulting package into this map entry.
+//
+// On return, the state of the reader is undefined.
+func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package, path string) (*types.Package, error) {
+	data, err := ioutil.ReadAll(in)
+	if err != nil {
+		return nil, fmt.Errorf("reading export data for %q: %v", path, err)
+	}
+
+	if bytes.HasPrefix(data, []byte("!<arch>")) {
+		return nil, fmt.Errorf("can't read export data for %q directly from an archive file (call gcexportdata.NewReader first to extract export data)", path)
+	}
+
+	// The App Engine Go runtime v1.6 uses the old export data format.
+	// TODO(adonovan): delete once v1.7 has been around for a while.
+	if bytes.HasPrefix(data, []byte("package ")) {
+		return gcimporter.ImportData(imports, path, path, bytes.NewReader(data))
+	}
+
+	// The indexed export format starts with an 'i'; the older
+	// binary export format starts with a 'c', 'd', or 'v'
+	// (from "version"). Select appropriate importer.
+	if len(data) > 0 && data[0] == 'i' {
+		_, pkg, err := gcimporter.IImportData(fset, imports, data[1:], path)
+		return pkg, err
+	}
+
+	_, pkg, err := gcimporter.BImportData(fset, imports, data, path)
+	return pkg, err
+}
+
+// Write writes encoded type information for the specified package to out.
+// The FileSet provides file position information for named objects.
+func Write(out io.Writer, fset *token.FileSet, pkg *types.Package) error {
+	b, err := gcimporter.BExportData(fset, pkg)
+	if err != nil {
+		return err
+	}
+	_, err = out.Write(b)
+	return err
+}

vendor/golang.org/x/tools/go/gcexportdata/importer.go

@@ -0,0 +1,73 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gcexportdata
+
+import (
+	"fmt"
+	"go/token"
+	"go/types"
+	"os"
+)
+
+// NewImporter returns a new instance of the types.Importer interface
+// that reads type information from export data files written by gc.
+// The Importer also satisfies types.ImporterFrom.
+//
+// Export data files are located using "go build" workspace conventions
+// and the build.Default context.
+//
+// Use this importer instead of go/importer.For("gc", ...) to avoid the
+// version-skew problems described in the documentation of this package,
+// or to control the FileSet or access the imports map populated during
+// package loading.
+//
+func NewImporter(fset *token.FileSet, imports map[string]*types.Package) types.ImporterFrom {
+	return importer{fset, imports}
+}
+
+type importer struct {
+	fset    *token.FileSet
+	imports map[string]*types.Package
+}
+
+func (imp importer) Import(importPath string) (*types.Package, error) {
+	return imp.ImportFrom(importPath, "", 0)
+}
+
+func (imp importer) ImportFrom(importPath, srcDir string, mode types.ImportMode) (_ *types.Package, err error) {
+	filename, path := Find(importPath, srcDir)
+	if filename == "" {
+		if importPath == "unsafe" {
+			// Even for unsafe, call Find first in case
+			// the package was vendored.
+			return types.Unsafe, nil
+		}
+		return nil, fmt.Errorf("can't find import: %s", importPath)
+	}
+
+	if pkg, ok := imp.imports[path]; ok && pkg.Complete() {
+		return pkg, nil // cache hit
+	}
+
+	// open file
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		f.Close()
+		if err != nil {
+			// add file name to error
+			err = fmt.Errorf("reading export data: %s: %v", filename, err)
+		}
+	}()
+
+	r, err := NewReader(f)
+	if err != nil {
+		return nil, err
+	}
+
+	return Read(r, imp.fset, imp.imports, path)
+}

vendor/golang.org/x/tools/go/gcexportdata/main.go

@@ -0,0 +1,99 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+// The gcexportdata command is a diagnostic tool that displays the
+// contents of gc export data files.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"go/token"
+	"go/types"
+	"log"
+	"os"
+
+	"golang.org/x/tools/go/gcexportdata"
+	"golang.org/x/tools/go/types/typeutil"
+)
+
+var packageFlag = flag.String("package", "", "alternative package to print")
+
+func main() {
+	log.SetPrefix("gcexportdata: ")
+	log.SetFlags(0)
+	flag.Usage = func() {
+		fmt.Fprintln(os.Stderr, "usage: gcexportdata [-package path] file.a")
+	}
+	flag.Parse()
+	if flag.NArg() != 1 {
+		flag.Usage()
+		os.Exit(2)
+	}
+	filename := flag.Args()[0]
+
+	f, err := os.Open(filename)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	r, err := gcexportdata.NewReader(f)
+	if err != nil {
+		log.Fatalf("%s: %s", filename, err)
+	}
+
+	// Decode the package.
+	const primary = "<primary>"
+	imports := make(map[string]*types.Package)
+	fset := token.NewFileSet()
+	pkg, err := gcexportdata.Read(r, fset, imports, primary)
+	if err != nil {
+		log.Fatalf("%s: %s", filename, err)
+	}
+
+	// Optionally select an indirectly mentioned package.
+	if *packageFlag != "" {
+		pkg = imports[*packageFlag]
+		if pkg == nil {
+			fmt.Fprintf(os.Stderr, "export data file %s does not mention %s; has:\n",
+				filename, *packageFlag)
+			for p := range imports {
+				if p != primary {
+					fmt.Fprintf(os.Stderr, "\t%s\n", p)
+				}
+			}
+			os.Exit(1)
+		}
+	}
+
+	// Print all package-level declarations, including non-exported ones.
+	fmt.Printf("package %s\n", pkg.Name())
+	for _, imp := range pkg.Imports() {
+		fmt.Printf("import %q\n", imp.Path())
+	}
+	qual := func(p *types.Package) string {
+		if pkg == p {
+			return ""
+		}
+		return p.Name()
+	}
+	scope := pkg.Scope()
+	for _, name := range scope.Names() {
+		obj := scope.Lookup(name)
+		fmt.Printf("%s: %s\n",
+			fset.Position(obj.Pos()),
+			types.ObjectString(obj, qual))
+
+		// For types, print each method.
+		if _, ok := obj.(*types.TypeName); ok {
+			for _, method := range typeutil.IntuitiveMethodSet(obj.Type(), nil) {
+				fmt.Printf("%s: %s\n",
+					fset.Position(method.Obj().Pos()),
+					types.SelectionString(method, qual))
+			}
+		}
+	}
+}

vendor/golang.org/x/tools/go/internal/cgo/cgo.go

@@ -0,0 +1,220 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cgo
+
+// This file handles cgo preprocessing of files containing `import "C"`.
+//
+// DESIGN
+//
+// The approach taken is to run the cgo processor on the package's
+// CgoFiles and parse the output, faking the filenames of the
+// resulting ASTs so that the synthetic file containing the C types is
+// called "C" (e.g. "~/go/src/net/C") and the preprocessed files
+// have their original names (e.g. "~/go/src/net/cgo_unix.go"),
+// not the names of the actual temporary files.
+//
+// The advantage of this approach is its fidelity to 'go build'.  The
+// downside is that the token.Position.Offset for each AST node is
+// incorrect, being an offset within the temporary file.  Line numbers
+// should still be correct because of the //line comments.
+//
+// The logic of this file is mostly plundered from the 'go build'
+// tool, which also invokes the cgo preprocessor.
+//
+//
+// REJECTED ALTERNATIVE
+//
+// An alternative approach that we explored is to extend go/types'
+// Importer mechanism to provide the identity of the importing package
+// so that each time `import "C"` appears it resolves to a different
+// synthetic package containing just the objects needed in that case.
+// The loader would invoke cgo but parse only the cgo_types.go file
+// defining the package-level objects, discarding the other files
+// resulting from preprocessing.
+//
+// The benefit of this approach would have been that source-level
+// syntax information would correspond exactly to the original cgo
+// file, with no preprocessing involved, making source tools like
+// godoc, guru, and eg happy.  However, the approach was rejected
+// due to the additional complexity it would impose on go/types.  (It
+// made for a beautiful demo, though.)
+//
+// cgo files, despite their *.go extension, are not legal Go source
+// files per the specification since they may refer to unexported
+// members of package "C" such as C.int.  Also, a function such as
+// C.getpwent has in effect two types, one matching its C type and one
+// which additionally returns (errno C.int).  The cgo preprocessor
+// uses name mangling to distinguish these two functions in the
+// processed code, but go/types would need to duplicate this logic in
+// its handling of function calls, analogous to the treatment of map
+// lookups in which y=m[k] and y,ok=m[k] are both legal.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+// ProcessFiles invokes the cgo preprocessor on bp.CgoFiles, parses
+// the output and returns the resulting ASTs.
+//
+func ProcessFiles(bp *build.Package, fset *token.FileSet, DisplayPath func(path string) string, mode parser.Mode) ([]*ast.File, error) {
+	tmpdir, err := ioutil.TempDir("", strings.Replace(bp.ImportPath, "/", "_", -1)+"_C")
+	if err != nil {
+		return nil, err
+	}
+	defer os.RemoveAll(tmpdir)
+
+	pkgdir := bp.Dir
+	if DisplayPath != nil {
+		pkgdir = DisplayPath(pkgdir)
+	}
+
+	cgoFiles, cgoDisplayFiles, err := Run(bp, pkgdir, tmpdir, false)
+	if err != nil {
+		return nil, err
+	}
+	var files []*ast.File
+	for i := range cgoFiles {
+		rd, err := os.Open(cgoFiles[i])
+		if err != nil {
+			return nil, err
+		}
+		display := filepath.Join(bp.Dir, cgoDisplayFiles[i])
+		f, err := parser.ParseFile(fset, display, rd, mode)
+		rd.Close()
+		if err != nil {
+			return nil, err
+		}
+		files = append(files, f)
+	}
+	return files, nil
+}
+
+var cgoRe = regexp.MustCompile(`[/\\:]`)
+
+// Run invokes the cgo preprocessor on bp.CgoFiles and returns two
+// lists of files: the resulting processed files (in temporary
+// directory tmpdir) and the corresponding names of the unprocessed files.
+//
+// Run is adapted from (*builder).cgo in
+// $GOROOT/src/cmd/go/build.go, but these features are unsupported:
+// Objective C, CGOPKGPATH, CGO_FLAGS.
+//
+// If useabs is set to true, absolute paths of the bp.CgoFiles will be passed in
+// to the cgo preprocessor. This in turn will set the // line comments
+// referring to those files to use absolute paths. This is needed for
+// go/packages using the legacy go list support so it is able to find
+// the original files.
+func Run(bp *build.Package, pkgdir, tmpdir string, useabs bool) (files, displayFiles []string, err error) {
+	cgoCPPFLAGS, _, _, _ := cflags(bp, true)
+	_, cgoexeCFLAGS, _, _ := cflags(bp, false)
+
+	if len(bp.CgoPkgConfig) > 0 {
+		pcCFLAGS, err := pkgConfigFlags(bp)
+		if err != nil {
+			return nil, nil, err
+		}
+		cgoCPPFLAGS = append(cgoCPPFLAGS, pcCFLAGS...)
+	}
+
+	// Allows including _cgo_export.h from .[ch] files in the package.
+	cgoCPPFLAGS = append(cgoCPPFLAGS, "-I", tmpdir)
+
+	// _cgo_gotypes.go (displayed "C") contains the type definitions.
+	files = append(files, filepath.Join(tmpdir, "_cgo_gotypes.go"))
+	displayFiles = append(displayFiles, "C")
+	for _, fn := range bp.CgoFiles {
+		// "foo.cgo1.go" (displayed "foo.go") is the processed Go source.
+		f := cgoRe.ReplaceAllString(fn[:len(fn)-len("go")], "_")
+		files = append(files, filepath.Join(tmpdir, f+"cgo1.go"))
+		displayFiles = append(displayFiles, fn)
+	}
+
+	var cgoflags []string
+	if bp.Goroot && bp.ImportPath == "runtime/cgo" {
+		cgoflags = append(cgoflags, "-import_runtime_cgo=false")
+	}
+	if bp.Goroot && bp.ImportPath == "runtime/race" || bp.ImportPath == "runtime/cgo" {
+		cgoflags = append(cgoflags, "-import_syscall=false")
+	}
+
+	var cgoFiles []string = bp.CgoFiles
+	if useabs {
+		cgoFiles = make([]string, len(bp.CgoFiles))
+		for i := range cgoFiles {
+			cgoFiles[i] = filepath.Join(pkgdir, bp.CgoFiles[i])
+		}
+	}
+
+	args := stringList(
+		"go", "tool", "cgo", "-objdir", tmpdir, cgoflags, "--",
+		cgoCPPFLAGS, cgoexeCFLAGS, cgoFiles,
+	)
+	if false {
+		log.Printf("Running cgo for package %q: %s (dir=%s)", bp.ImportPath, args, pkgdir)
+	}
+	cmd := exec.Command(args[0], args[1:]...)
+	cmd.Dir = pkgdir
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return nil, nil, fmt.Errorf("cgo failed: %s: %s", args, err)
+	}
+
+	return files, displayFiles, nil
+}
+
+// -- unmodified from 'go build' ---------------------------------------
+
+// Return the flags to use when invoking the C or C++ compilers, or cgo.
+func cflags(p *build.Package, def bool) (cppflags, cflags, cxxflags, ldflags []string) {
+	var defaults string
+	if def {
+		defaults = "-g -O2"
+	}
+
+	cppflags = stringList(envList("CGO_CPPFLAGS", ""), p.CgoCPPFLAGS)
+	cflags = stringList(envList("CGO_CFLAGS", defaults), p.CgoCFLAGS)
+	cxxflags = stringList(envList("CGO_CXXFLAGS", defaults), p.CgoCXXFLAGS)
+	ldflags = stringList(envList("CGO_LDFLAGS", defaults), p.CgoLDFLAGS)
+	return
+}
+
+// envList returns the value of the given environment variable broken
+// into fields, using the default value when the variable is empty.
+func envList(key, def string) []string {
+	v := os.Getenv(key)
+	if v == "" {
+		v = def
+	}
+	return strings.Fields(v)
+}
+
+// stringList's arguments should be a sequence of string or []string values.
+// stringList flattens them into a single []string.
+func stringList(args ...interface{}) []string {
+	var x []string
+	for _, arg := range args {
+		switch arg := arg.(type) {
+		case []string:
+			x = append(x, arg...)
+		case string:
+			x = append(x, arg)
+		default:
+			panic("stringList: invalid argument")
+		}
+	}
+	return x
+}

vendor/golang.org/x/tools/go/internal/cgo/cgo_pkgconfig.go

@@ -0,0 +1,39 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cgo
+
+import (
+	"errors"
+	"fmt"
+	"go/build"
+	"os/exec"
+	"strings"
+)
+
+// pkgConfig runs pkg-config with the specified arguments and returns the flags it prints.
+func pkgConfig(mode string, pkgs []string) (flags []string, err error) {
+	cmd := exec.Command("pkg-config", append([]string{mode}, pkgs...)...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		s := fmt.Sprintf("%s failed: %v", strings.Join(cmd.Args, " "), err)
+		if len(out) > 0 {
+			s = fmt.Sprintf("%s: %s", s, out)
+		}
+		return nil, errors.New(s)
+	}
+	if len(out) > 0 {
+		flags = strings.Fields(string(out))
+	}
+	return
+}
+
+// pkgConfigFlags calls pkg-config if needed and returns the cflags
+// needed to build the package.
+func pkgConfigFlags(p *build.Package) (cflags []string, err error) {
+	if len(p.CgoPkgConfig) == 0 {
+		return nil, nil
+	}
+	return pkgConfig("--cflags", p.CgoPkgConfig)
+}

vendor/golang.org/x/tools/go/internal/gcimporter/bexport.go

@@ -0,0 +1,852 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Binary package export.
+// This file was derived from $GOROOT/src/cmd/compile/internal/gc/bexport.go;
+// see that file for specification of the format.
+
+package gcimporter
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"math"
+	"math/big"
+	"sort"
+	"strings"
+)
+
+// If debugFormat is set, each integer and string value is preceded by a marker
+// and position information in the encoding. This mechanism permits an importer
+// to recognize immediately when it is out of sync. The importer recognizes this
+// mode automatically (i.e., it can import export data produced with debugging
+// support even if debugFormat is not set at the time of import). This mode will
+// lead to massively larger export data (by a factor of 2 to 3) and should only
+// be enabled during development and debugging.
+//
+// NOTE: This flag is the first flag to enable if importing dies because of
+// (suspected) format errors, and whenever a change is made to the format.
+const debugFormat = false // default: false
+
+// If trace is set, debugging output is printed to std out.
+const trace = false // default: false
+
+// Current export format version. Increase with each format change.
+// Note: The latest binary (non-indexed) export format is at version 6.
+//       This exporter is still at level 4, but it doesn't matter since
+//       the binary importer can handle older versions just fine.
+// 6: package height (CL 105038) -- NOT IMPLEMENTED HERE
+// 5: improved position encoding efficiency (issue 20080, CL 41619) -- NOT IMPLEMEMTED HERE
+// 4: type name objects support type aliases, uses aliasTag
+// 3: Go1.8 encoding (same as version 2, aliasTag defined but never used)
+// 2: removed unused bool in ODCL export (compiler only)
+// 1: header format change (more regular), export package for _ struct fields
+// 0: Go1.7 encoding
+const exportVersion = 4
+
+// trackAllTypes enables cycle tracking for all types, not just named
+// types. The existing compiler invariants assume that unnamed types
+// that are not completely set up are not used, or else there are spurious
+// errors.
+// If disabled, only named types are tracked, possibly leading to slightly
+// less efficient encoding in rare cases. It also prevents the export of
+// some corner-case type declarations (but those are not handled correctly
+// with with the textual export format either).
+// TODO(gri) enable and remove once issues caused by it are fixed
+const trackAllTypes = false
+
+type exporter struct {
+	fset *token.FileSet
+	out  bytes.Buffer
+
+	// object -> index maps, indexed in order of serialization
+	strIndex map[string]int
+	pkgIndex map[*types.Package]int
+	typIndex map[types.Type]int
+
+	// position encoding
+	posInfoFormat bool
+	prevFile      string
+	prevLine      int
+
+	// debugging support
+	written int // bytes written
+	indent  int // for trace
+}
+
+// internalError represents an error generated inside this package.
+type internalError string
+
+func (e internalError) Error() string { return "gcimporter: " + string(e) }
+
+func internalErrorf(format string, args ...interface{}) error {
+	return internalError(fmt.Sprintf(format, args...))
+}
+
+// BExportData returns binary export data for pkg.
+// If no file set is provided, position info will be missing.
+func BExportData(fset *token.FileSet, pkg *types.Package) (b []byte, err error) {
+	defer func() {
+		if e := recover(); e != nil {
+			if ierr, ok := e.(internalError); ok {
+				err = ierr
+				return
+			}
+			// Not an internal error; panic again.
+			panic(e)
+		}
+	}()
+
+	p := exporter{
+		fset:          fset,
+		strIndex:      map[string]int{"": 0}, // empty string is mapped to 0
+		pkgIndex:      make(map[*types.Package]int),
+		typIndex:      make(map[types.Type]int),
+		posInfoFormat: true, // TODO(gri) might become a flag, eventually
+	}
+
+	// write version info
+	// The version string must start with "version %d" where %d is the version
+	// number. Additional debugging information may follow after a blank; that
+	// text is ignored by the importer.
+	p.rawStringln(fmt.Sprintf("version %d", exportVersion))
+	var debug string
+	if debugFormat {
+		debug = "debug"
+	}
+	p.rawStringln(debug) // cannot use p.bool since it's affected by debugFormat; also want to see this clearly
+	p.bool(trackAllTypes)
+	p.bool(p.posInfoFormat)
+
+	// --- generic export data ---
+
+	// populate type map with predeclared "known" types
+	for index, typ := range predeclared {
+		p.typIndex[typ] = index
+	}
+	if len(p.typIndex) != len(predeclared) {
+		return nil, internalError("duplicate entries in type map?")
+	}
+
+	// write package data
+	p.pkg(pkg, true)
+	if trace {
+		p.tracef("\n")
+	}
+
+	// write objects
+	objcount := 0
+	scope := pkg.Scope()
+	for _, name := range scope.Names() {
+		if !ast.IsExported(name) {
+			continue
+		}
+		if trace {
+			p.tracef("\n")
+		}
+		p.obj(scope.Lookup(name))
+		objcount++
+	}
+
+	// indicate end of list
+	if trace {
+		p.tracef("\n")
+	}
+	p.tag(endTag)
+
+	// for self-verification only (redundant)
+	p.int(objcount)
+
+	if trace {
+		p.tracef("\n")
+	}
+
+	// --- end of export data ---
+
+	return p.out.Bytes(), nil
+}
+
+func (p *exporter) pkg(pkg *types.Package, emptypath bool) {
+	if pkg == nil {
+		panic(internalError("unexpected nil pkg"))
+	}
+
+	// if we saw the package before, write its index (>= 0)
+	if i, ok := p.pkgIndex[pkg]; ok {
+		p.index('P', i)
+		return
+	}
+
+	// otherwise, remember the package, write the package tag (< 0) and package data
+	if trace {
+		p.tracef("P%d = { ", len(p.pkgIndex))
+		defer p.tracef("} ")
+	}
+	p.pkgIndex[pkg] = len(p.pkgIndex)
+
+	p.tag(packageTag)
+	p.string(pkg.Name())
+	if emptypath {
+		p.string("")
+	} else {
+		p.string(pkg.Path())
+	}
+}
+
+func (p *exporter) obj(obj types.Object) {
+	switch obj := obj.(type) {
+	case *types.Const:
+		p.tag(constTag)
+		p.pos(obj)
+		p.qualifiedName(obj)
+		p.typ(obj.Type())
+		p.value(obj.Val())
+
+	case *types.TypeName:
+		if obj.IsAlias() {
+			p.tag(aliasTag)
+			p.pos(obj)
+			p.qualifiedName(obj)
+		} else {
+			p.tag(typeTag)
+		}
+		p.typ(obj.Type())
+
+	case *types.Var:
+		p.tag(varTag)
+		p.pos(obj)
+		p.qualifiedName(obj)
+		p.typ(obj.Type())
+
+	case *types.Func:
+		p.tag(funcTag)
+		p.pos(obj)
+		p.qualifiedName(obj)
+		sig := obj.Type().(*types.Signature)
+		p.paramList(sig.Params(), sig.Variadic())
+		p.paramList(sig.Results(), false)
+
+	default:
+		panic(internalErrorf("unexpected object %v (%T)", obj, obj))
+	}
+}
+
+func (p *exporter) pos(obj types.Object) {
+	if !p.posInfoFormat {
+		return
+	}
+
+	file, line := p.fileLine(obj)
+	if file == p.prevFile {
+		// common case: write line delta
+		// delta == 0 means different file or no line change
+		delta := line - p.prevLine
+		p.int(delta)
+		if delta == 0 {
+			p.int(-1) // -1 means no file change
+		}
+	} else {
+		// different file
+		p.int(0)
+		// Encode filename as length of common prefix with previous
+		// filename, followed by (possibly empty) suffix. Filenames
+		// frequently share path prefixes, so this can save a lot
+		// of space and make export data size less dependent on file
+		// path length. The suffix is unlikely to be empty because
+		// file names tend to end in ".go".
+		n := commonPrefixLen(p.prevFile, file)
+		p.int(n)           // n >= 0
+		p.string(file[n:]) // write suffix only
+		p.prevFile = file
+		p.int(line)
+	}
+	p.prevLine = line
+}
+
+func (p *exporter) fileLine(obj types.Object) (file string, line int) {
+	if p.fset != nil {
+		pos := p.fset.Position(obj.Pos())
+		file = pos.Filename
+		line = pos.Line
+	}
+	return
+}
+
+func commonPrefixLen(a, b string) int {
+	if len(a) > len(b) {
+		a, b = b, a
+	}
+	// len(a) <= len(b)
+	i := 0
+	for i < len(a) && a[i] == b[i] {
+		i++
+	}
+	return i
+}
+
+func (p *exporter) qualifiedName(obj types.Object) {
+	p.string(obj.Name())
+	p.pkg(obj.Pkg(), false)
+}
+
+func (p *exporter) typ(t types.Type) {
+	if t == nil {
+		panic(internalError("nil type"))
+	}
+
+	// Possible optimization: Anonymous pointer types *T where
+	// T is a named type are common. We could canonicalize all
+	// such types *T to a single type PT = *T. This would lead
+	// to at most one *T entry in typIndex, and all future *T's
+	// would be encoded as the respective index directly. Would
+	// save 1 byte (pointerTag) per *T and reduce the typIndex
+	// size (at the cost of a canonicalization map). We can do
+	// this later, without encoding format change.
+
+	// if we saw the type before, write its index (>= 0)
+	if i, ok := p.typIndex[t]; ok {
+		p.index('T', i)
+		return
+	}
+
+	// otherwise, remember the type, write the type tag (< 0) and type data
+	if trackAllTypes {
+		if trace {
+			p.tracef("T%d = {>\n", len(p.typIndex))
+			defer p.tracef("<\n} ")
+		}
+		p.typIndex[t] = len(p.typIndex)
+	}
+
+	switch t := t.(type) {
+	case *types.Named:
+		if !trackAllTypes {
+			// if we don't track all types, track named types now
+			p.typIndex[t] = len(p.typIndex)
+		}
+
+		p.tag(namedTag)
+		p.pos(t.Obj())
+		p.qualifiedName(t.Obj())
+		p.typ(t.Underlying())
+		if !types.IsInterface(t) {
+			p.assocMethods(t)
+		}
+
+	case *types.Array:
+		p.tag(arrayTag)
+		p.int64(t.Len())
+		p.typ(t.Elem())
+
+	case *types.Slice:
+		p.tag(sliceTag)
+		p.typ(t.Elem())
+
+	case *dddSlice:
+		p.tag(dddTag)
+		p.typ(t.elem)
+
+	case *types.Struct:
+		p.tag(structTag)
+		p.fieldList(t)
+
+	case *types.Pointer:
+		p.tag(pointerTag)
+		p.typ(t.Elem())
+
+	case *types.Signature:
+		p.tag(signatureTag)
+		p.paramList(t.Params(), t.Variadic())
+		p.paramList(t.Results(), false)
+
+	case *types.Interface:
+		p.tag(interfaceTag)
+		p.iface(t)
+
+	case *types.Map:
+		p.tag(mapTag)
+		p.typ(t.Key())
+		p.typ(t.Elem())
+
+	case *types.Chan:
+		p.tag(chanTag)
+		p.int(int(3 - t.Dir())) // hack
+		p.typ(t.Elem())
+
+	default:
+		panic(internalErrorf("unexpected type %T: %s", t, t))
+	}
+}
+
+func (p *exporter) assocMethods(named *types.Named) {
+	// Sort methods (for determinism).
+	var methods []*types.Func
+	for i := 0; i < named.NumMethods(); i++ {
+		methods = append(methods, named.Method(i))
+	}
+	sort.Sort(methodsByName(methods))
+
+	p.int(len(methods))
+
+	if trace && methods != nil {
+		p.tracef("associated methods {>\n")
+	}
+
+	for i, m := range methods {
+		if trace && i > 0 {
+			p.tracef("\n")
+		}
+
+		p.pos(m)
+		name := m.Name()
+		p.string(name)
+		if !exported(name) {
+			p.pkg(m.Pkg(), false)
+		}
+
+		sig := m.Type().(*types.Signature)
+		p.paramList(types.NewTuple(sig.Recv()), false)
+		p.paramList(sig.Params(), sig.Variadic())
+		p.paramList(sig.Results(), false)
+		p.int(0) // dummy value for go:nointerface pragma - ignored by importer
+	}
+
+	if trace && methods != nil {
+		p.tracef("<\n} ")
+	}
+}
+
+type methodsByName []*types.Func
+
+func (x methodsByName) Len() int           { return len(x) }
+func (x methodsByName) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
+func (x methodsByName) Less(i, j int) bool { return x[i].Name() < x[j].Name() }
+
+func (p *exporter) fieldList(t *types.Struct) {
+	if trace && t.NumFields() > 0 {
+		p.tracef("fields {>\n")
+		defer p.tracef("<\n} ")
+	}
+
+	p.int(t.NumFields())
+	for i := 0; i < t.NumFields(); i++ {
+		if trace && i > 0 {
+			p.tracef("\n")
+		}
+		p.field(t.Field(i))
+		p.string(t.Tag(i))
+	}
+}
+
+func (p *exporter) field(f *types.Var) {
+	if !f.IsField() {
+		panic(internalError("field expected"))
+	}
+
+	p.pos(f)
+	p.fieldName(f)
+	p.typ(f.Type())
+}
+
+func (p *exporter) iface(t *types.Interface) {
+	// TODO(gri): enable importer to load embedded interfaces,
+	// then emit Embeddeds and ExplicitMethods separately here.
+	p.int(0)
+
+	n := t.NumMethods()
+	if trace && n > 0 {
+		p.tracef("methods {>\n")
+		defer p.tracef("<\n} ")
+	}
+	p.int(n)
+	for i := 0; i < n; i++ {
+		if trace && i > 0 {
+			p.tracef("\n")
+		}
+		p.method(t.Method(i))
+	}
+}
+
+func (p *exporter) method(m *types.Func) {
+	sig := m.Type().(*types.Signature)
+	if sig.Recv() == nil {
+		panic(internalError("method expected"))
+	}
+
+	p.pos(m)
+	p.string(m.Name())
+	if m.Name() != "_" && !ast.IsExported(m.Name()) {
+		p.pkg(m.Pkg(), false)
+	}
+
+	// interface method; no need to encode receiver.
+	p.paramList(sig.Params(), sig.Variadic())
+	p.paramList(sig.Results(), false)
+}
+
+func (p *exporter) fieldName(f *types.Var) {
+	name := f.Name()
+
+	if f.Anonymous() {
+		// anonymous field - we distinguish between 3 cases:
+		// 1) field name matches base type name and is exported
+		// 2) field name matches base type name and is not exported
+		// 3) field name doesn't match base type name (alias name)
+		bname := basetypeName(f.Type())
+		if name == bname {
+			if ast.IsExported(name) {
+				name = "" // 1) we don't need to know the field name or package
+			} else {
+				name = "?" // 2) use unexported name "?" to force package export
+			}
+		} else {
+			// 3) indicate alias and export name as is
+			// (this requires an extra "@" but this is a rare case)
+			p.string("@")
+		}
+	}
+
+	p.string(name)
+	if name != "" && !ast.IsExported(name) {
+		p.pkg(f.Pkg(), false)
+	}
+}
+
+func basetypeName(typ types.Type) string {
+	switch typ := deref(typ).(type) {
+	case *types.Basic:
+		return typ.Name()
+	case *types.Named:
+		return typ.Obj().Name()
+	default:
+		return "" // unnamed type
+	}
+}
+
+func (p *exporter) paramList(params *types.Tuple, variadic bool) {
+	// use negative length to indicate unnamed parameters
+	// (look at the first parameter only since either all
+	// names are present or all are absent)
+	n := params.Len()
+	if n > 0 && params.At(0).Name() == "" {
+		n = -n
+	}
+	p.int(n)
+	for i := 0; i < params.Len(); i++ {
+		q := params.At(i)
+		t := q.Type()
+		if variadic && i == params.Len()-1 {
+			t = &dddSlice{t.(*types.Slice).Elem()}
+		}
+		p.typ(t)
+		if n > 0 {
+			name := q.Name()
+			p.string(name)
+			if name != "_" {
+				p.pkg(q.Pkg(), false)
+			}
+		}
+		p.string("") // no compiler-specific info
+	}
+}
+
+func (p *exporter) value(x constant.Value) {
+	if trace {
+		p.tracef("= ")
+	}
+
+	switch x.Kind() {
+	case constant.Bool:
+		tag := falseTag
+		if constant.BoolVal(x) {
+			tag = trueTag
+		}
+		p.tag(tag)
+
+	case constant.Int:
+		if v, exact := constant.Int64Val(x); exact {
+			// common case: x fits into an int64 - use compact encoding
+			p.tag(int64Tag)
+			p.int64(v)
+			return
+		}
+		// uncommon case: large x - use float encoding
+		// (powers of 2 will be encoded efficiently with exponent)
+		p.tag(floatTag)
+		p.float(constant.ToFloat(x))
+
+	case constant.Float:
+		p.tag(floatTag)
+		p.float(x)
+
+	case constant.Complex:
+		p.tag(complexTag)
+		p.float(constant.Real(x))
+		p.float(constant.Imag(x))
+
+	case constant.String:
+		p.tag(stringTag)
+		p.string(constant.StringVal(x))
+
+	case constant.Unknown:
+		// package contains type errors
+		p.tag(unknownTag)
+
+	default:
+		panic(internalErrorf("unexpected value %v (%T)", x, x))
+	}
+}
+
+func (p *exporter) float(x constant.Value) {
+	if x.Kind() != constant.Float {
+		panic(internalErrorf("unexpected constant %v, want float", x))
+	}
+	// extract sign (there is no -0)
+	sign := constant.Sign(x)
+	if sign == 0 {
+		// x == 0
+		p.int(0)
+		return
+	}
+	// x != 0
+
+	var f big.Float
+	if v, exact := constant.Float64Val(x); exact {
+		// float64
+		f.SetFloat64(v)
+	} else if num, denom := constant.Num(x), constant.Denom(x); num.Kind() == constant.Int {
+		// TODO(gri): add big.Rat accessor to constant.Value.
+		r := valueToRat(num)
+		f.SetRat(r.Quo(r, valueToRat(denom)))
+	} else {
+		// Value too large to represent as a fraction => inaccessible.
+		// TODO(gri): add big.Float accessor to constant.Value.
+		f.SetFloat64(math.MaxFloat64) // FIXME
+	}
+
+	// extract exponent such that 0.5 <= m < 1.0
+	var m big.Float
+	exp := f.MantExp(&m)
+
+	// extract mantissa as *big.Int
+	// - set exponent large enough so mant satisfies mant.IsInt()
+	// - get *big.Int from mant
+	m.SetMantExp(&m, int(m.MinPrec()))
+	mant, acc := m.Int(nil)
+	if acc != big.Exact {
+		panic(internalError("internal error"))
+	}
+
+	p.int(sign)
+	p.int(exp)
+	p.string(string(mant.Bytes()))
+}
+
+func valueToRat(x constant.Value) *big.Rat {
+	// Convert little-endian to big-endian.
+	// I can't believe this is necessary.
+	bytes := constant.Bytes(x)
+	for i := 0; i < len(bytes)/2; i++ {
+		bytes[i], bytes[len(bytes)-1-i] = bytes[len(bytes)-1-i], bytes[i]
+	}
+	return new(big.Rat).SetInt(new(big.Int).SetBytes(bytes))
+}
+
+func (p *exporter) bool(b bool) bool {
+	if trace {
+		p.tracef("[")
+		defer p.tracef("= %v] ", b)
+	}
+
+	x := 0
+	if b {
+		x = 1
+	}
+	p.int(x)
+	return b
+}
+
+// ----------------------------------------------------------------------------
+// Low-level encoders
+
+func (p *exporter) index(marker byte, index int) {
+	if index < 0 {
+		panic(internalError("invalid index < 0"))
+	}
+	if debugFormat {
+		p.marker('t')
+	}
+	if trace {
+		p.tracef("%c%d ", marker, index)
+	}
+	p.rawInt64(int64(index))
+}
+
+func (p *exporter) tag(tag int) {
+	if tag >= 0 {
+		panic(internalError("invalid tag >= 0"))
+	}
+	if debugFormat {
+		p.marker('t')
+	}
+	if trace {
+		p.tracef("%s ", tagString[-tag])
+	}
+	p.rawInt64(int64(tag))
+}
+
+func (p *exporter) int(x int) {
+	p.int64(int64(x))
+}
+
+func (p *exporter) int64(x int64) {
+	if debugFormat {
+		p.marker('i')
+	}
+	if trace {
+		p.tracef("%d ", x)
+	}
+	p.rawInt64(x)
+}
+
+func (p *exporter) string(s string) {
+	if debugFormat {
+		p.marker('s')
+	}
+	if trace {
+		p.tracef("%q ", s)
+	}
+	// if we saw the string before, write its index (>= 0)
+	// (the empty string is mapped to 0)
+	if i, ok := p.strIndex[s]; ok {
+		p.rawInt64(int64(i))
+		return
+	}
+	// otherwise, remember string and write its negative length and bytes
+	p.strIndex[s] = len(p.strIndex)
+	p.rawInt64(-int64(len(s)))
+	for i := 0; i < len(s); i++ {
+		p.rawByte(s[i])
+	}
+}
+
+// marker emits a marker byte and position information which makes
+// it easy for a reader to detect if it is "out of sync". Used for
+// debugFormat format only.
+func (p *exporter) marker(m byte) {
+	p.rawByte(m)
+	// Enable this for help tracking down the location
+	// of an incorrect marker when running in debugFormat.
+	if false && trace {
+		p.tracef("#%d ", p.written)
+	}
+	p.rawInt64(int64(p.written))
+}
+
+// rawInt64 should only be used by low-level encoders.
+func (p *exporter) rawInt64(x int64) {
+	var tmp [binary.MaxVarintLen64]byte
+	n := binary.PutVarint(tmp[:], x)
+	for i := 0; i < n; i++ {
+		p.rawByte(tmp[i])
+	}
+}
+
+// rawStringln should only be used to emit the initial version string.
+func (p *exporter) rawStringln(s string) {
+	for i := 0; i < len(s); i++ {
+		p.rawByte(s[i])
+	}
+	p.rawByte('\n')
+}
+
+// rawByte is the bottleneck interface to write to p.out.
+// rawByte escapes b as follows (any encoding does that
+// hides '$'):
+//
+//	'$'  => '|' 'S'
+//	'|'  => '|' '|'
+//
+// Necessary so other tools can find the end of the
+// export data by searching for "$$".
+// rawByte should only be used by low-level encoders.
+func (p *exporter) rawByte(b byte) {
+	switch b {
+	case '$':
+		// write '$' as '|' 'S'
+		b = 'S'
+		fallthrough
+	case '|':
+		// write '|' as '|' '|'
+		p.out.WriteByte('|')
+		p.written++
+	}
+	p.out.WriteByte(b)
+	p.written++
+}
+
+// tracef is like fmt.Printf but it rewrites the format string
+// to take care of indentation.
+func (p *exporter) tracef(format string, args ...interface{}) {
+	if strings.ContainsAny(format, "<>\n") {
+		var buf bytes.Buffer
+		for i := 0; i < len(format); i++ {
+			// no need to deal with runes
+			ch := format[i]
+			switch ch {
+			case '>':
+				p.indent++
+				continue
+			case '<':
+				p.indent--
+				continue
+			}
+			buf.WriteByte(ch)
+			if ch == '\n' {
+				for j := p.indent; j > 0; j-- {
+					buf.WriteString(".  ")
+				}
+			}
+		}
+		format = buf.String()
+	}
+	fmt.Printf(format, args...)
+}
+
+// Debugging support.
+// (tagString is only used when tracing is enabled)
+var tagString = [...]string{
+	// Packages
+	-packageTag: "package",
+
+	// Types
+	-namedTag:     "named type",
+	-arrayTag:     "array",
+	-sliceTag:     "slice",
+	-dddTag:       "ddd",
+	-structTag:    "struct",
+	-pointerTag:   "pointer",
+	-signatureTag: "signature",
+	-interfaceTag: "interface",
+	-mapTag:       "map",
+	-chanTag:      "chan",
+
+	// Values
+	-falseTag:    "false",
+	-trueTag:     "true",
+	-int64Tag:    "int64",
+	-floatTag:    "float",
+	-fractionTag: "fraction",
+	-complexTag:  "complex",
+	-stringTag:   "string",
+	-unknownTag:  "unknown",
+
+	// Type aliases
+	-aliasTag: "alias",
+}

vendor/golang.org/x/tools/go/internal/gcimporter/exportdata.go

@@ -0,0 +1,93 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is a copy of $GOROOT/src/go/internal/gcimporter/exportdata.go.
+
+// This file implements FindExportData.
+
+package gcimporter
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
+	// See $GOROOT/include/ar.h.
+	hdr := make([]byte, 16+12+6+6+8+10+2)
+	_, err = io.ReadFull(r, hdr)
+	if err != nil {
+		return
+	}
+	// leave for debugging
+	if false {
+		fmt.Printf("header: %s", hdr)
+	}
+	s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10]))
+	size, err = strconv.Atoi(s)
+	if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
+		err = fmt.Errorf("invalid archive header")
+		return
+	}
+	name = strings.TrimSpace(string(hdr[:16]))
+	return
+}
+
+// FindExportData positions the reader r at the beginning of the
+// export data section of an underlying GC-created object/archive
+// file by reading from it. The reader must be positioned at the
+// start of the file before calling this function. The hdr result
+// is the string before the export data, either "$$" or "$$B".
+//
+func FindExportData(r *bufio.Reader) (hdr string, err error) {
+	// Read first line to make sure this is an object file.
+	line, err := r.ReadSlice('\n')
+	if err != nil {
+		err = fmt.Errorf("can't find export data (%v)", err)
+		return
+	}
+
+	if string(line) == "!<arch>\n" {
+		// Archive file. Scan to __.PKGDEF.
+		var name string
+		if name, _, err = readGopackHeader(r); err != nil {
+			return
+		}
+
+		// First entry should be __.PKGDEF.
+		if name != "__.PKGDEF" {
+			err = fmt.Errorf("go archive is missing __.PKGDEF")
+			return
+		}
+
+		// Read first line of __.PKGDEF data, so that line
+		// is once again the first line of the input.
+		if line, err = r.ReadSlice('\n'); err != nil {
+			err = fmt.Errorf("can't find export data (%v)", err)
+			return
+		}
+	}
+
+	// Now at __.PKGDEF in archive or still at beginning of file.
+	// Either way, line should begin with "go object ".
+	if !strings.HasPrefix(string(line), "go object ") {
+		err = fmt.Errorf("not a Go object file")
+		return
+	}
+
+	// Skip over object header to export data.
+	// Begins after first line starting with $$.
+	for line[0] != '$' {
+		if line, err = r.ReadSlice('\n'); err != nil {
+			err = fmt.Errorf("can't find export data (%v)", err)
+			return
+		}
+	}
+	hdr = string(line)
+
+	return
+}

vendor/golang.org/x/tools/go/internal/gcimporter/iimport.go

@@ -0,0 +1,598 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Indexed package import.
+// See cmd/compile/internal/gc/iexport.go for the export data format.
+
+// This file is a copy of $GOROOT/src/go/internal/gcimporter/iimport.go.
+
+package gcimporter
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"io"
+	"sort"
+)
+
+type intReader struct {
+	*bytes.Reader
+	path string
+}
+
+func (r *intReader) int64() int64 {
+	i, err := binary.ReadVarint(r.Reader)
+	if err != nil {
+		errorf("import %q: read varint error: %v", r.path, err)
+	}
+	return i
+}
+
+func (r *intReader) uint64() uint64 {
+	i, err := binary.ReadUvarint(r.Reader)
+	if err != nil {
+		errorf("import %q: read varint error: %v", r.path, err)
+	}
+	return i
+}
+
+const predeclReserved = 32
+
+type itag uint64
+
+const (
+	// Types
+	definedType itag = iota
+	pointerType
+	sliceType
+	arrayType
+	chanType
+	mapType
+	signatureType
+	structType
+	interfaceType
+)
+
+// IImportData imports a package from the serialized package data
+// and returns the number of bytes consumed and a reference to the package.
+// If the export data version is not recognized or the format is otherwise
+// compromised, an error is returned.
+func IImportData(fset *token.FileSet, imports map[string]*types.Package, data []byte, path string) (_ int, pkg *types.Package, err error) {
+	const currentVersion = 0
+	version := -1
+	defer func() {
+		if e := recover(); e != nil {
+			if version > currentVersion {
+				err = fmt.Errorf("cannot import %q (%v), export data is newer version - update tool", path, e)
+			} else {
+				err = fmt.Errorf("cannot import %q (%v), possibly version skew - reinstall package", path, e)
+			}
+		}
+	}()
+
+	r := &intReader{bytes.NewReader(data), path}
+
+	version = int(r.uint64())
+	switch version {
+	case currentVersion:
+	default:
+		errorf("unknown iexport format version %d", version)
+	}
+
+	sLen := int64(r.uint64())
+	dLen := int64(r.uint64())
+
+	whence, _ := r.Seek(0, io.SeekCurrent)
+	stringData := data[whence : whence+sLen]
+	declData := data[whence+sLen : whence+sLen+dLen]
+	r.Seek(sLen+dLen, io.SeekCurrent)
+
+	p := iimporter{
+		ipath: path,
+
+		stringData:  stringData,
+		stringCache: make(map[uint64]string),
+		pkgCache:    make(map[uint64]*types.Package),
+
+		declData: declData,
+		pkgIndex: make(map[*types.Package]map[string]uint64),
+		typCache: make(map[uint64]types.Type),
+
+		fake: fakeFileSet{
+			fset:  fset,
+			files: make(map[string]*token.File),
+		},
+	}
+
+	for i, pt := range predeclared {
+		p.typCache[uint64(i)] = pt
+	}
+
+	pkgList := make([]*types.Package, r.uint64())
+	for i := range pkgList {
+		pkgPathOff := r.uint64()
+		pkgPath := p.stringAt(pkgPathOff)
+		pkgName := p.stringAt(r.uint64())
+		_ = r.uint64() // package height; unused by go/types
+
+		if pkgPath == "" {
+			pkgPath = path
+		}
+		pkg := imports[pkgPath]
+		if pkg == nil {
+			pkg = types.NewPackage(pkgPath, pkgName)
+			imports[pkgPath] = pkg
+		} else if pkg.Name() != pkgName {
+			errorf("conflicting names %s and %s for package %q", pkg.Name(), pkgName, path)
+		}
+
+		p.pkgCache[pkgPathOff] = pkg
+
+		nameIndex := make(map[string]uint64)
+		for nSyms := r.uint64(); nSyms > 0; nSyms-- {
+			name := p.stringAt(r.uint64())
+			nameIndex[name] = r.uint64()
+		}
+
+		p.pkgIndex[pkg] = nameIndex
+		pkgList[i] = pkg
+	}
+
+	localpkg := pkgList[0]
+
+	names := make([]string, 0, len(p.pkgIndex[localpkg]))
+	for name := range p.pkgIndex[localpkg] {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	for _, name := range names {
+		p.doDecl(localpkg, name)
+	}
+
+	for _, typ := range p.interfaceList {
+		typ.Complete()
+	}
+
+	// record all referenced packages as imports
+	list := append(([]*types.Package)(nil), pkgList[1:]...)
+	sort.Sort(byPath(list))
+	localpkg.SetImports(list)
+
+	// package was imported completely and without errors
+	localpkg.MarkComplete()
+
+	consumed, _ := r.Seek(0, io.SeekCurrent)
+	return int(consumed), localpkg, nil
+}
+
+type iimporter struct {
+	ipath string
+
+	stringData  []byte
+	stringCache map[uint64]string
+	pkgCache    map[uint64]*types.Package
+
+	declData []byte
+	pkgIndex map[*types.Package]map[string]uint64
+	typCache map[uint64]types.Type
+
+	fake          fakeFileSet
+	interfaceList []*types.Interface
+}
+
+func (p *iimporter) doDecl(pkg *types.Package, name string) {
+	// See if we've already imported this declaration.
+	if obj := pkg.Scope().Lookup(name); obj != nil {
+		return
+	}
+
+	off, ok := p.pkgIndex[pkg][name]
+	if !ok {
+		errorf("%v.%v not in index", pkg, name)
+	}
+
+	r := &importReader{p: p, currPkg: pkg}
+	r.declReader.Reset(p.declData[off:])
+
+	r.obj(name)
+}
+
+func (p *iimporter) stringAt(off uint64) string {
+	if s, ok := p.stringCache[off]; ok {
+		return s
+	}
+
+	slen, n := binary.Uvarint(p.stringData[off:])
+	if n <= 0 {
+		errorf("varint failed")
+	}
+	spos := off + uint64(n)
+	s := string(p.stringData[spos : spos+slen])
+	p.stringCache[off] = s
+	return s
+}
+
+func (p *iimporter) pkgAt(off uint64) *types.Package {
+	if pkg, ok := p.pkgCache[off]; ok {
+		return pkg
+	}
+	path := p.stringAt(off)
+	errorf("missing package %q in %q", path, p.ipath)
+	return nil
+}
+
+func (p *iimporter) typAt(off uint64, base *types.Named) types.Type {
+	if t, ok := p.typCache[off]; ok && (base == nil || !isInterface(t)) {
+		return t
+	}
+
+	if off < predeclReserved {
+		errorf("predeclared type missing from cache: %v", off)
+	}
+
+	r := &importReader{p: p}
+	r.declReader.Reset(p.declData[off-predeclReserved:])
+	t := r.doType(base)
+
+	if base == nil || !isInterface(t) {
+		p.typCache[off] = t
+	}
+	return t
+}
+
+type importReader struct {
+	p          *iimporter
+	declReader bytes.Reader
+	currPkg    *types.Package
+	prevFile   string
+	prevLine   int64
+}
+
+func (r *importReader) obj(name string) {
+	tag := r.byte()
+	pos := r.pos()
+
+	switch tag {
+	case 'A':
+		typ := r.typ()
+
+		r.declare(types.NewTypeName(pos, r.currPkg, name, typ))
+
+	case 'C':
+		typ, val := r.value()
+
+		r.declare(types.NewConst(pos, r.currPkg, name, typ, val))
+
+	case 'F':
+		sig := r.signature(nil)
+
+		r.declare(types.NewFunc(pos, r.currPkg, name, sig))
+
+	case 'T':
+		// Types can be recursive. We need to setup a stub
+		// declaration before recursing.
+		obj := types.NewTypeName(pos, r.currPkg, name, nil)
+		named := types.NewNamed(obj, nil, nil)
+		r.declare(obj)
+
+		underlying := r.p.typAt(r.uint64(), named).Underlying()
+		named.SetUnderlying(underlying)
+
+		if !isInterface(underlying) {
+			for n := r.uint64(); n > 0; n-- {
+				mpos := r.pos()
+				mname := r.ident()
+				recv := r.param()
+				msig := r.signature(recv)
+
+				named.AddMethod(types.NewFunc(mpos, r.currPkg, mname, msig))
+			}
+		}
+
+	case 'V':
+		typ := r.typ()
+
+		r.declare(types.NewVar(pos, r.currPkg, name, typ))
+
+	default:
+		errorf("unexpected tag: %v", tag)
+	}
+}
+
+func (r *importReader) declare(obj types.Object) {
+	obj.Pkg().Scope().Insert(obj)
+}
+
+func (r *importReader) value() (typ types.Type, val constant.Value) {
+	typ = r.typ()
+
+	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
+	case types.IsBoolean:
+		val = constant.MakeBool(r.bool())
+
+	case types.IsString:
+		val = constant.MakeString(r.string())
+
+	case types.IsInteger:
+		val = r.mpint(b)
+
+	case types.IsFloat:
+		val = r.mpfloat(b)
+
+	case types.IsComplex:
+		re := r.mpfloat(b)
+		im := r.mpfloat(b)
+		val = constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
+
+	default:
+		errorf("unexpected type %v", typ) // panics
+		panic("unreachable")
+	}
+
+	return
+}
+
+func intSize(b *types.Basic) (signed bool, maxBytes uint) {
+	if (b.Info() & types.IsUntyped) != 0 {
+		return true, 64
+	}
+
+	switch b.Kind() {
+	case types.Float32, types.Complex64:
+		return true, 3
+	case types.Float64, types.Complex128:
+		return true, 7
+	}
+
+	signed = (b.Info() & types.IsUnsigned) == 0
+	switch b.Kind() {
+	case types.Int8, types.Uint8:
+		maxBytes = 1
+	case types.Int16, types.Uint16:
+		maxBytes = 2
+	case types.Int32, types.Uint32:
+		maxBytes = 4
+	default:
+		maxBytes = 8
+	}
+
+	return
+}
+
+func (r *importReader) mpint(b *types.Basic) constant.Value {
+	signed, maxBytes := intSize(b)
+
+	maxSmall := 256 - maxBytes
+	if signed {
+		maxSmall = 256 - 2*maxBytes
+	}
+	if maxBytes == 1 {
+		maxSmall = 256
+	}
+
+	n, _ := r.declReader.ReadByte()
+	if uint(n) < maxSmall {
+		v := int64(n)
+		if signed {
+			v >>= 1
+			if n&1 != 0 {
+				v = ^v
+			}
+		}
+		return constant.MakeInt64(v)
+	}
+
+	v := -n
+	if signed {
+		v = -(n &^ 1) >> 1
+	}
+	if v < 1 || uint(v) > maxBytes {
+		errorf("weird decoding: %v, %v => %v", n, signed, v)
+	}
+
+	buf := make([]byte, v)
+	io.ReadFull(&r.declReader, buf)
+
+	// convert to little endian
+	// TODO(gri) go/constant should have a more direct conversion function
+	//           (e.g., once it supports a big.Float based implementation)
+	for i, j := 0, len(buf)-1; i < j; i, j = i+1, j-1 {
+		buf[i], buf[j] = buf[j], buf[i]
+	}
+
+	x := constant.MakeFromBytes(buf)
+	if signed && n&1 != 0 {
+		x = constant.UnaryOp(token.SUB, x, 0)
+	}
+	return x
+}
+
+func (r *importReader) mpfloat(b *types.Basic) constant.Value {
+	x := r.mpint(b)
+	if constant.Sign(x) == 0 {
+		return x
+	}
+
+	exp := r.int64()
+	switch {
+	case exp > 0:
+		x = constant.Shift(x, token.SHL, uint(exp))
+	case exp < 0:
+		d := constant.Shift(constant.MakeInt64(1), token.SHL, uint(-exp))
+		x = constant.BinaryOp(x, token.QUO, d)
+	}
+	return x
+}
+
+func (r *importReader) ident() string {
+	return r.string()
+}
+
+func (r *importReader) qualifiedIdent() (*types.Package, string) {
+	name := r.string()
+	pkg := r.pkg()
+	return pkg, name
+}
+
+func (r *importReader) pos() token.Pos {
+	delta := r.int64()
+	if delta != deltaNewFile {
+		r.prevLine += delta
+	} else if l := r.int64(); l == -1 {
+		r.prevLine += deltaNewFile
+	} else {
+		r.prevFile = r.string()
+		r.prevLine = l
+	}
+
+	if r.prevFile == "" && r.prevLine == 0 {
+		return token.NoPos
+	}
+
+	return r.p.fake.pos(r.prevFile, int(r.prevLine))
+}
+
+func (r *importReader) typ() types.Type {
+	return r.p.typAt(r.uint64(), nil)
+}
+
+func isInterface(t types.Type) bool {
+	_, ok := t.(*types.Interface)
+	return ok
+}
+
+func (r *importReader) pkg() *types.Package { return r.p.pkgAt(r.uint64()) }
+func (r *importReader) string() string      { return r.p.stringAt(r.uint64()) }
+
+func (r *importReader) doType(base *types.Named) types.Type {
+	switch k := r.kind(); k {
+	default:
+		errorf("unexpected kind tag in %q: %v", r.p.ipath, k)
+		return nil
+
+	case definedType:
+		pkg, name := r.qualifiedIdent()
+		r.p.doDecl(pkg, name)
+		return pkg.Scope().Lookup(name).(*types.TypeName).Type()
+	case pointerType:
+		return types.NewPointer(r.typ())
+	case sliceType:
+		return types.NewSlice(r.typ())
+	case arrayType:
+		n := r.uint64()
+		return types.NewArray(r.typ(), int64(n))
+	case chanType:
+		dir := chanDir(int(r.uint64()))
+		return types.NewChan(dir, r.typ())
+	case mapType:
+		return types.NewMap(r.typ(), r.typ())
+	case signatureType:
+		r.currPkg = r.pkg()
+		return r.signature(nil)
+
+	case structType:
+		r.currPkg = r.pkg()
+
+		fields := make([]*types.Var, r.uint64())
+		tags := make([]string, len(fields))
+		for i := range fields {
+			fpos := r.pos()
+			fname := r.ident()
+			ftyp := r.typ()
+			emb := r.bool()
+			tag := r.string()
+
+			fields[i] = types.NewField(fpos, r.currPkg, fname, ftyp, emb)
+			tags[i] = tag
+		}
+		return types.NewStruct(fields, tags)
+
+	case interfaceType:
+		r.currPkg = r.pkg()
+
+		embeddeds := make([]types.Type, r.uint64())
+		for i := range embeddeds {
+			_ = r.pos()
+			embeddeds[i] = r.typ()
+		}
+
+		methods := make([]*types.Func, r.uint64())
+		for i := range methods {
+			mpos := r.pos()
+			mname := r.ident()
+
+			// TODO(mdempsky): Matches bimport.go, but I
+			// don't agree with this.
+			var recv *types.Var
+			if base != nil {
+				recv = types.NewVar(token.NoPos, r.currPkg, "", base)
+			}
+
+			msig := r.signature(recv)
+			methods[i] = types.NewFunc(mpos, r.currPkg, mname, msig)
+		}
+
+		typ := newInterface(methods, embeddeds)
+		r.p.interfaceList = append(r.p.interfaceList, typ)
+		return typ
+	}
+}
+
+func (r *importReader) kind() itag {
+	return itag(r.uint64())
+}
+
+func (r *importReader) signature(recv *types.Var) *types.Signature {
+	params := r.paramList()
+	results := r.paramList()
+	variadic := params.Len() > 0 && r.bool()
+	return types.NewSignature(recv, params, results, variadic)
+}
+
+func (r *importReader) paramList() *types.Tuple {
+	xs := make([]*types.Var, r.uint64())
+	for i := range xs {
+		xs[i] = r.param()
+	}
+	return types.NewTuple(xs...)
+}
+
+func (r *importReader) param() *types.Var {
+	pos := r.pos()
+	name := r.ident()
+	typ := r.typ()
+	return types.NewParam(pos, r.currPkg, name, typ)
+}
+
+func (r *importReader) bool() bool {
+	return r.uint64() != 0
+}
+
+func (r *importReader) int64() int64 {
+	n, err := binary.ReadVarint(&r.declReader)
+	if err != nil {
+		errorf("readVarint: %v", err)
+	}
+	return n
+}
+
+func (r *importReader) uint64() uint64 {
+	n, err := binary.ReadUvarint(&r.declReader)
+	if err != nil {
+		errorf("readUvarint: %v", err)
+	}
+	return n
+}
+
+func (r *importReader) byte() byte {
+	x, err := r.declReader.ReadByte()
+	if err != nil {
+		errorf("declReader.ReadByte: %v", err)
+	}
+	return x
+}

vendor/golang.org/x/tools/go/internal/gcimporter/newInterface10.go

@@ -0,0 +1,21 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !go1.11
+
+package gcimporter
+
+import "go/types"
+
+func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interface {
+	named := make([]*types.Named, len(embeddeds))
+	for i, e := range embeddeds {
+		var ok bool
+		named[i], ok = e.(*types.Named)
+		if !ok {
+			panic("embedding of non-defined interfaces in interfaces is not supported before Go 1.11")
+		}
+	}
+	return types.NewInterface(methods, named)
+}

vendor/golang.org/x/tools/go/internal/gcimporter/newInterface11.go

@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.11
+
+package gcimporter
+
+import "go/types"
+
+func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interface {
+	return types.NewInterfaceType(methods, embeddeds)
+}

vendor/golang.org/x/tools/go/loader/doc.go

@@ -0,0 +1,205 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package loader loads a complete Go program from source code, parsing
+// and type-checking the initial packages plus their transitive closure
+// of dependencies.  The ASTs and the derived facts are retained for
+// later use.
+//
+// THIS INTERFACE IS EXPERIMENTAL AND IS LIKELY TO CHANGE.
+//
+// The package defines two primary types: Config, which specifies a
+// set of initial packages to load and various other options; and
+// Program, which is the result of successfully loading the packages
+// specified by a configuration.
+//
+// The configuration can be set directly, but *Config provides various
+// convenience methods to simplify the common cases, each of which can
+// be called any number of times.  Finally, these are followed by a
+// call to Load() to actually load and type-check the program.
+//
+//      var conf loader.Config
+//
+//      // Use the command-line arguments to specify
+//      // a set of initial packages to load from source.
+//      // See FromArgsUsage for help.
+//      rest, err := conf.FromArgs(os.Args[1:], wantTests)
+//
+//      // Parse the specified files and create an ad hoc package with path "foo".
+//      // All files must have the same 'package' declaration.
+//      conf.CreateFromFilenames("foo", "foo.go", "bar.go")
+//
+//      // Create an ad hoc package with path "foo" from
+//      // the specified already-parsed files.
+//      // All ASTs must have the same 'package' declaration.
+//      conf.CreateFromFiles("foo", parsedFiles)
+//
+//      // Add "runtime" to the set of packages to be loaded.
+//      conf.Import("runtime")
+//
+//      // Adds "fmt" and "fmt_test" to the set of packages
+//      // to be loaded.  "fmt" will include *_test.go files.
+//      conf.ImportWithTests("fmt")
+//
+//      // Finally, load all the packages specified by the configuration.
+//      prog, err := conf.Load()
+//
+// See examples_test.go for examples of API usage.
+//
+//
+// CONCEPTS AND TERMINOLOGY
+//
+// The WORKSPACE is the set of packages accessible to the loader.  The
+// workspace is defined by Config.Build, a *build.Context.  The
+// default context treats subdirectories of $GOROOT and $GOPATH as
+// packages, but this behavior may be overridden.
+//
+// An AD HOC package is one specified as a set of source files on the
+// command line.  In the simplest case, it may consist of a single file
+// such as $GOROOT/src/net/http/triv.go.
+//
+// EXTERNAL TEST packages are those comprised of a set of *_test.go
+// files all with the same 'package foo_test' declaration, all in the
+// same directory.  (go/build.Package calls these files XTestFiles.)
+//
+// An IMPORTABLE package is one that can be referred to by some import
+// spec.  Every importable package is uniquely identified by its
+// PACKAGE PATH or just PATH, a string such as "fmt", "encoding/json",
+// or "cmd/vendor/golang.org/x/arch/x86/x86asm".  A package path
+// typically denotes a subdirectory of the workspace.
+//
+// An import declaration uses an IMPORT PATH to refer to a package.
+// Most import declarations use the package path as the import path.
+//
+// Due to VENDORING (https://golang.org/s/go15vendor), the
+// interpretation of an import path may depend on the directory in which
+// it appears.  To resolve an import path to a package path, go/build
+// must search the enclosing directories for a subdirectory named
+// "vendor".
+//
+// ad hoc packages and external test packages are NON-IMPORTABLE.  The
+// path of an ad hoc package is inferred from the package
+// declarations of its files and is therefore not a unique package key.
+// For example, Config.CreatePkgs may specify two initial ad hoc
+// packages, both with path "main".
+//
+// An AUGMENTED package is an importable package P plus all the
+// *_test.go files with same 'package foo' declaration as P.
+// (go/build.Package calls these files TestFiles.)
+//
+// The INITIAL packages are those specified in the configuration.  A
+// DEPENDENCY is a package loaded to satisfy an import in an initial
+// package or another dependency.
+//
+package loader
+
+// IMPLEMENTATION NOTES
+//
+// 'go test', in-package test files, and import cycles
+// ---------------------------------------------------
+//
+// An external test package may depend upon members of the augmented
+// package that are not in the unaugmented package, such as functions
+// that expose internals.  (See bufio/export_test.go for an example.)
+// So, the loader must ensure that for each external test package
+// it loads, it also augments the corresponding non-test package.
+//
+// The import graph over n unaugmented packages must be acyclic; the
+// import graph over n-1 unaugmented packages plus one augmented
+// package must also be acyclic.  ('go test' relies on this.)  But the
+// import graph over n augmented packages may contain cycles.
+//
+// First, all the (unaugmented) non-test packages and their
+// dependencies are imported in the usual way; the loader reports an
+// error if it detects an import cycle.
+//
+// Then, each package P for which testing is desired is augmented by
+// the list P' of its in-package test files, by calling
+// (*types.Checker).Files.  This arrangement ensures that P' may
+// reference definitions within P, but P may not reference definitions
+// within P'.  Furthermore, P' may import any other package, including
+// ones that depend upon P, without an import cycle error.
+//
+// Consider two packages A and B, both of which have lists of
+// in-package test files we'll call A' and B', and which have the
+// following import graph edges:
+//    B  imports A
+//    B' imports A
+//    A' imports B
+// This last edge would be expected to create an error were it not
+// for the special type-checking discipline above.
+// Cycles of size greater than two are possible.  For example:
+//   compress/bzip2/bzip2_test.go (package bzip2)  imports "io/ioutil"
+//   io/ioutil/tempfile_test.go   (package ioutil) imports "regexp"
+//   regexp/exec_test.go          (package regexp) imports "compress/bzip2"
+//
+//
+// Concurrency
+// -----------
+//
+// Let us define the import dependency graph as follows.  Each node is a
+// list of files passed to (Checker).Files at once.  Many of these lists
+// are the production code of an importable Go package, so those nodes
+// are labelled by the package's path.  The remaining nodes are
+// ad hoc packages and lists of in-package *_test.go files that augment
+// an importable package; those nodes have no label.
+//
+// The edges of the graph represent import statements appearing within a
+// file.  An edge connects a node (a list of files) to the node it
+// imports, which is importable and thus always labelled.
+//
+// Loading is controlled by this dependency graph.
+//
+// To reduce I/O latency, we start loading a package's dependencies
+// asynchronously as soon as we've parsed its files and enumerated its
+// imports (scanImports).  This performs a preorder traversal of the
+// import dependency graph.
+//
+// To exploit hardware parallelism, we type-check unrelated packages in
+// parallel, where "unrelated" means not ordered by the partial order of
+// the import dependency graph.
+//
+// We use a concurrency-safe non-blocking cache (importer.imported) to
+// record the results of type-checking, whether success or failure.  An
+// entry is created in this cache by startLoad the first time the
+// package is imported.  The first goroutine to request an entry becomes
+// responsible for completing the task and broadcasting completion to
+// subsequent requestors, which block until then.
+//
+// Type checking occurs in (parallel) postorder: we cannot type-check a
+// set of files until we have loaded and type-checked all of their
+// immediate dependencies (and thus all of their transitive
+// dependencies). If the input were guaranteed free of import cycles,
+// this would be trivial: we could simply wait for completion of the
+// dependencies and then invoke the typechecker.
+//
+// But as we saw in the 'go test' section above, some cycles in the
+// import graph over packages are actually legal, so long as the
+// cycle-forming edge originates in the in-package test files that
+// augment the package.  This explains why the nodes of the import
+// dependency graph are not packages, but lists of files: the unlabelled
+// nodes avoid the cycles.  Consider packages A and B where B imports A
+// and A's in-package tests AT import B.  The naively constructed import
+// graph over packages would contain a cycle (A+AT) --> B --> (A+AT) but
+// the graph over lists of files is AT --> B --> A, where AT is an
+// unlabelled node.
+//
+// Awaiting completion of the dependencies in a cyclic graph would
+// deadlock, so we must materialize the import dependency graph (as
+// importer.graph) and check whether each import edge forms a cycle.  If
+// x imports y, and the graph already contains a path from y to x, then
+// there is an import cycle, in which case the processing of x must not
+// wait for the completion of processing of y.
+//
+// When the type-checker makes a callback (doImport) to the loader for a
+// given import edge, there are two possible cases.  In the normal case,
+// the dependency has already been completely type-checked; doImport
+// does a cache lookup and returns it.  In the cyclic case, the entry in
+// the cache is still necessarily incomplete, indicating a cycle.  We
+// perform the cycle check again to obtain the error message, and return
+// the error.
+//
+// The result of using concurrency is about a 2.5x speedup for stdlib_test.
+
+// TODO(adonovan): overhaul the package documentation.

vendor/golang.org/x/tools/go/loader/util.go

@@ -0,0 +1,124 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package loader
+
+import (
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io"
+	"os"
+	"strconv"
+	"sync"
+
+	"golang.org/x/tools/go/buildutil"
+)
+
+// We use a counting semaphore to limit
+// the number of parallel I/O calls per process.
+var ioLimit = make(chan bool, 10)
+
+// parseFiles parses the Go source files within directory dir and
+// returns the ASTs of the ones that could be at least partially parsed,
+// along with a list of I/O and parse errors encountered.
+//
+// I/O is done via ctxt, which may specify a virtual file system.
+// displayPath is used to transform the filenames attached to the ASTs.
+//
+func parseFiles(fset *token.FileSet, ctxt *build.Context, displayPath func(string) string, dir string, files []string, mode parser.Mode) ([]*ast.File, []error) {
+	if displayPath == nil {
+		displayPath = func(path string) string { return path }
+	}
+	var wg sync.WaitGroup
+	n := len(files)
+	parsed := make([]*ast.File, n)
+	errors := make([]error, n)
+	for i, file := range files {
+		if !buildutil.IsAbsPath(ctxt, file) {
+			file = buildutil.JoinPath(ctxt, dir, file)
+		}
+		wg.Add(1)
+		go func(i int, file string) {
+			ioLimit <- true // wait
+			defer func() {
+				wg.Done()
+				<-ioLimit // signal
+			}()
+			var rd io.ReadCloser
+			var err error
+			if ctxt.OpenFile != nil {
+				rd, err = ctxt.OpenFile(file)
+			} else {
+				rd, err = os.Open(file)
+			}
+			if err != nil {
+				errors[i] = err // open failed
+				return
+			}
+
+			// ParseFile may return both an AST and an error.
+			parsed[i], errors[i] = parser.ParseFile(fset, displayPath(file), rd, mode)
+			rd.Close()
+		}(i, file)
+	}
+	wg.Wait()
+
+	// Eliminate nils, preserving order.
+	var o int
+	for _, f := range parsed {
+		if f != nil {
+			parsed[o] = f
+			o++
+		}
+	}
+	parsed = parsed[:o]
+
+	o = 0
+	for _, err := range errors {
+		if err != nil {
+			errors[o] = err
+			o++
+		}
+	}
+	errors = errors[:o]
+
+	return parsed, errors
+}
+
+// scanImports returns the set of all import paths from all
+// import specs in the specified files.
+func scanImports(files []*ast.File) map[string]bool {
+	imports := make(map[string]bool)
+	for _, f := range files {
+		for _, decl := range f.Decls {
+			if decl, ok := decl.(*ast.GenDecl); ok && decl.Tok == token.IMPORT {
+				for _, spec := range decl.Specs {
+					spec := spec.(*ast.ImportSpec)
+
+					// NB: do not assume the program is well-formed!
+					path, err := strconv.Unquote(spec.Path.Value)
+					if err != nil {
+						continue // quietly ignore the error
+					}
+					if path == "C" {
+						continue // skip pseudopackage
+					}
+					imports[path] = true
+				}
+			}
+		}
+	}
+	return imports
+}
+
+// ---------- Internal helpers ----------
+
+// TODO(adonovan): make this a method: func (*token.File) Contains(token.Pos)
+func tokenFileContainsPos(f *token.File, pos token.Pos) bool {
+	p := int(pos)
+	base := f.Base()
+	return base <= p && p < base+f.Size()
+}

vendor/golang.org/x/tools/imports/fix.go

@@ -0,0 +1,934 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package imports
+
+import (
+	"context"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/internal/gopathwalk"
+)
+
+// Debug controls verbose logging.
+var Debug = false
+
+// LocalPrefix is a comma-separated string of import path prefixes, which, if
+// set, instructs Process to sort the import paths with the given prefixes
+// into another group after 3rd-party packages.
+var LocalPrefix string
+
+func localPrefixes() []string {
+	if LocalPrefix != "" {
+		return strings.Split(LocalPrefix, ",")
+	}
+	return nil
+}
+
+// importToGroup is a list of functions which map from an import path to
+// a group number.
+var importToGroup = []func(importPath string) (num int, ok bool){
+	func(importPath string) (num int, ok bool) {
+		for _, p := range localPrefixes() {
+			if strings.HasPrefix(importPath, p) || strings.TrimSuffix(p, "/") == importPath {
+				return 3, true
+			}
+		}
+		return
+	},
+	func(importPath string) (num int, ok bool) {
+		if strings.HasPrefix(importPath, "appengine") {
+			return 2, true
+		}
+		return
+	},
+	func(importPath string) (num int, ok bool) {
+		if strings.Contains(importPath, ".") {
+			return 1, true
+		}
+		return
+	},
+}
+
+func importGroup(importPath string) int {
+	for _, fn := range importToGroup {
+		if n, ok := fn(importPath); ok {
+			return n
+		}
+	}
+	return 0
+}
+
+// importInfo is a summary of information about one import.
+type importInfo struct {
+	Path  string // full import path (e.g. "crypto/rand")
+	Alias string // import alias, if present (e.g. "crand")
+}
+
+// packageInfo is a summary of features found in a package.
+type packageInfo struct {
+	Globals map[string]bool       // symbol => true
+	Imports map[string]importInfo // pkg base name or alias => info
+	// refs are a set of package references currently satisfied by imports.
+	// first key: either base package (e.g. "fmt") or renamed package
+	// second key: referenced package symbol (e.g. "Println")
+	Refs map[string]map[string]bool
+}
+
+// dirPackageInfo exposes the dirPackageInfoFile function so that it can be overridden.
+var dirPackageInfo = dirPackageInfoFile
+
+// dirPackageInfoFile gets information from other files in the package.
+func dirPackageInfoFile(pkgName, srcDir, filename string) (*packageInfo, error) {
+	considerTests := strings.HasSuffix(filename, "_test.go")
+
+	fileBase := filepath.Base(filename)
+	packageFileInfos, err := ioutil.ReadDir(srcDir)
+	if err != nil {
+		return nil, err
+	}
+
+	info := &packageInfo{
+		Globals: make(map[string]bool),
+		Imports: make(map[string]importInfo),
+		Refs:    make(map[string]map[string]bool),
+	}
+
+	visitor := collectReferences(info.Refs)
+	for _, fi := range packageFileInfos {
+		if fi.Name() == fileBase || !strings.HasSuffix(fi.Name(), ".go") {
+			continue
+		}
+		if !considerTests && strings.HasSuffix(fi.Name(), "_test.go") {
+			continue
+		}
+
+		fileSet := token.NewFileSet()
+		root, err := parser.ParseFile(fileSet, filepath.Join(srcDir, fi.Name()), nil, 0)
+		if err != nil {
+			continue
+		}
+
+		for _, decl := range root.Decls {
+			genDecl, ok := decl.(*ast.GenDecl)
+			if !ok {
+				continue
+			}
+
+			for _, spec := range genDecl.Specs {
+				valueSpec, ok := spec.(*ast.ValueSpec)
+				if !ok {
+					continue
+				}
+				info.Globals[valueSpec.Names[0].Name] = true
+			}
+		}
+
+		for _, imp := range root.Imports {
+			impInfo := importInfo{Path: strings.Trim(imp.Path.Value, `"`)}
+			name := path.Base(impInfo.Path)
+			if imp.Name != nil {
+				name = strings.Trim(imp.Name.Name, `"`)
+				impInfo.Alias = name
+			}
+			info.Imports[name] = impInfo
+		}
+
+		ast.Walk(visitor, root)
+	}
+	return info, nil
+}
+
+// collectReferences returns a visitor that collects all exported package
+// references
+func collectReferences(refs map[string]map[string]bool) visitFn {
+	var visitor visitFn
+	visitor = func(node ast.Node) ast.Visitor {
+		if node == nil {
+			return visitor
+		}
+		switch v := node.(type) {
+		case *ast.SelectorExpr:
+			xident, ok := v.X.(*ast.Ident)
+			if !ok {
+				break
+			}
+			if xident.Obj != nil {
+				// if the parser can resolve it, it's not a package ref
+				break
+			}
+			pkgName := xident.Name
+			r := refs[pkgName]
+			if r == nil {
+				r = make(map[string]bool)
+				refs[pkgName] = r
+			}
+			if ast.IsExported(v.Sel.Name) {
+				r[v.Sel.Name] = true
+			}
+		}
+		return visitor
+	}
+	return visitor
+}
+
+func fixImports(fset *token.FileSet, f *ast.File, filename string) (added []string, err error) {
+	// refs are a set of possible package references currently unsatisfied by imports.
+	// first key: either base package (e.g. "fmt") or renamed package
+	// second key: referenced package symbol (e.g. "Println")
+	refs := make(map[string]map[string]bool)
+
+	// decls are the current package imports. key is base package or renamed package.
+	decls := make(map[string]*ast.ImportSpec)
+
+	abs, err := filepath.Abs(filename)
+	if err != nil {
+		return nil, err
+	}
+	srcDir := filepath.Dir(abs)
+	if Debug {
+		log.Printf("fixImports(filename=%q), abs=%q, srcDir=%q ...", filename, abs, srcDir)
+	}
+
+	var packageInfo *packageInfo
+	var loadedPackageInfo bool
+
+	// collect potential uses of packages.
+	var visitor visitFn
+	visitor = visitFn(func(node ast.Node) ast.Visitor {
+		if node == nil {
+			return visitor
+		}
+		switch v := node.(type) {
+		case *ast.ImportSpec:
+			if v.Name != nil {
+				decls[v.Name.Name] = v
+				break
+			}
+			ipath := strings.Trim(v.Path.Value, `"`)
+			if ipath == "C" {
+				break
+			}
+			local := importPathToName(ipath, srcDir)
+			decls[local] = v
+		case *ast.SelectorExpr:
+			xident, ok := v.X.(*ast.Ident)
+			if !ok {
+				break
+			}
+			if xident.Obj != nil {
+				// if the parser can resolve it, it's not a package ref
+				break
+			}
+			pkgName := xident.Name
+			if refs[pkgName] == nil {
+				refs[pkgName] = make(map[string]bool)
+			}
+			if !loadedPackageInfo {
+				loadedPackageInfo = true
+				packageInfo, _ = dirPackageInfo(f.Name.Name, srcDir, filename)
+			}
+			if decls[pkgName] == nil && (packageInfo == nil || !packageInfo.Globals[pkgName]) {
+				refs[pkgName][v.Sel.Name] = true
+			}
+		}
+		return visitor
+	})
+	ast.Walk(visitor, f)
+
+	// Nil out any unused ImportSpecs, to be removed in following passes
+	unusedImport := map[string]string{}
+	for pkg, is := range decls {
+		if refs[pkg] == nil && pkg != "_" && pkg != "." {
+			name := ""
+			if is.Name != nil {
+				name = is.Name.Name
+			}
+			unusedImport[strings.Trim(is.Path.Value, `"`)] = name
+		}
+	}
+	for ipath, name := range unusedImport {
+		if ipath == "C" {
+			// Don't remove cgo stuff.
+			continue
+		}
+		astutil.DeleteNamedImport(fset, f, name, ipath)
+	}
+
+	for pkgName, symbols := range refs {
+		if len(symbols) == 0 {
+			// skip over packages already imported
+			delete(refs, pkgName)
+		}
+	}
+
+	// Fast path, all references already imported.
+	if len(refs) == 0 {
+		return nil, nil
+	}
+
+	// Can assume this will be necessary in all cases now.
+	if !loadedPackageInfo {
+		packageInfo, _ = dirPackageInfo(f.Name.Name, srcDir, filename)
+	}
+
+	// Search for imports matching potential package references.
+	type result struct {
+		ipath string // import path
+		name  string // optional name to rename import as
+	}
+	results := make(chan result, len(refs))
+
+	ctx, cancel := context.WithCancel(context.TODO())
+	var wg sync.WaitGroup
+	defer func() {
+		cancel()
+		wg.Wait()
+	}()
+	var (
+		firstErr     error
+		firstErrOnce sync.Once
+	)
+	for pkgName, symbols := range refs {
+		wg.Add(1)
+		go func(pkgName string, symbols map[string]bool) {
+			defer wg.Done()
+
+			if packageInfo != nil {
+				sibling := packageInfo.Imports[pkgName]
+				if sibling.Path != "" {
+					refs := packageInfo.Refs[pkgName]
+					for symbol := range symbols {
+						if refs[symbol] {
+							results <- result{ipath: sibling.Path, name: sibling.Alias}
+							return
+						}
+					}
+				}
+			}
+
+			ipath, rename, err := findImport(ctx, pkgName, symbols, filename)
+			if err != nil {
+				firstErrOnce.Do(func() {
+					firstErr = err
+					cancel()
+				})
+				return
+			}
+
+			if ipath == "" {
+				return // No matching package.
+			}
+
+			r := result{ipath: ipath}
+			if rename {
+				r.name = pkgName
+			}
+			results <- r
+			return
+		}(pkgName, symbols)
+	}
+	go func() {
+		wg.Wait()
+		close(results)
+	}()
+
+	for result := range results {
+		if result.name != "" {
+			astutil.AddNamedImport(fset, f, result.name, result.ipath)
+		} else {
+			astutil.AddImport(fset, f, result.ipath)
+		}
+		added = append(added, result.ipath)
+	}
+
+	if firstErr != nil {
+		return nil, firstErr
+	}
+	return added, nil
+}
+
+// importPathToName returns the package name for the given import path.
+var importPathToName func(importPath, srcDir string) (packageName string) = importPathToNameGoPath
+
+// importPathToNameBasic assumes the package name is the base of import path,
+// except that if the path ends in foo/vN, it assumes the package name is foo.
+func importPathToNameBasic(importPath, srcDir string) (packageName string) {
+	base := path.Base(importPath)
+	if strings.HasPrefix(base, "v") {
+		if _, err := strconv.Atoi(base[1:]); err == nil {
+			dir := path.Dir(importPath)
+			if dir != "." {
+				return path.Base(dir)
+			}
+		}
+	}
+	return base
+}
+
+// importPathToNameGoPath finds out the actual package name, as declared in its .go files.
+// If there's a problem, it falls back to using importPathToNameBasic.
+func importPathToNameGoPath(importPath, srcDir string) (packageName string) {
+	// Fast path for standard library without going to disk.
+	if pkg, ok := stdImportPackage[importPath]; ok {
+		return pkg
+	}
+
+	pkgName, err := importPathToNameGoPathParse(importPath, srcDir)
+	if Debug {
+		log.Printf("importPathToNameGoPathParse(%q, srcDir=%q) = %q, %v", importPath, srcDir, pkgName, err)
+	}
+	if err == nil {
+		return pkgName
+	}
+	return importPathToNameBasic(importPath, srcDir)
+}
+
+// importPathToNameGoPathParse is a faster version of build.Import if
+// the only thing desired is the package name. It uses build.FindOnly
+// to find the directory and then only parses one file in the package,
+// trusting that the files in the directory are consistent.
+func importPathToNameGoPathParse(importPath, srcDir string) (packageName string, err error) {
+	buildPkg, err := build.Import(importPath, srcDir, build.FindOnly)
+	if err != nil {
+		return "", err
+	}
+	d, err := os.Open(buildPkg.Dir)
+	if err != nil {
+		return "", err
+	}
+	names, err := d.Readdirnames(-1)
+	d.Close()
+	if err != nil {
+		return "", err
+	}
+	sort.Strings(names) // to have predictable behavior
+	var lastErr error
+	var nfile int
+	for _, name := range names {
+		if !strings.HasSuffix(name, ".go") {
+			continue
+		}
+		if strings.HasSuffix(name, "_test.go") {
+			continue
+		}
+		nfile++
+		fullFile := filepath.Join(buildPkg.Dir, name)
+
+		fset := token.NewFileSet()
+		f, err := parser.ParseFile(fset, fullFile, nil, parser.PackageClauseOnly)
+		if err != nil {
+			lastErr = err
+			continue
+		}
+		pkgName := f.Name.Name
+		if pkgName == "documentation" {
+			// Special case from go/build.ImportDir, not
+			// handled by ctx.MatchFile.
+			continue
+		}
+		if pkgName == "main" {
+			// Also skip package main, assuming it's a +build ignore generator or example.
+			// Since you can't import a package main anyway, there's no harm here.
+			continue
+		}
+		return pkgName, nil
+	}
+	if lastErr != nil {
+		return "", lastErr
+	}
+	return "", fmt.Errorf("no importable package found in %d Go files", nfile)
+}
+
+var stdImportPackage = map[string]string{} // "net/http" => "http"
+
+func init() {
+	// Nothing in the standard library has a package name not
+	// matching its import base name.
+	for _, pkg := range stdlib {
+		if _, ok := stdImportPackage[pkg]; !ok {
+			stdImportPackage[pkg] = path.Base(pkg)
+		}
+	}
+}
+
+// Directory-scanning state.
+var (
+	// scanOnce guards calling scanGoDirs and assigning dirScan
+	scanOnce sync.Once
+	dirScan  map[string]*pkg // abs dir path => *pkg
+)
+
+type pkg struct {
+	dir             string // absolute file path to pkg directory ("/usr/lib/go/src/net/http")
+	importPath      string // full pkg import path ("net/http", "foo/bar/vendor/a/b")
+	importPathShort string // vendorless import path ("net/http", "a/b")
+}
+
+type pkgDistance struct {
+	pkg      *pkg
+	distance int // relative distance to target
+}
+
+// byDistanceOrImportPathShortLength sorts by relative distance breaking ties
+// on the short import path length and then the import string itself.
+type byDistanceOrImportPathShortLength []pkgDistance
+
+func (s byDistanceOrImportPathShortLength) Len() int { return len(s) }
+func (s byDistanceOrImportPathShortLength) Less(i, j int) bool {
+	di, dj := s[i].distance, s[j].distance
+	if di == -1 {
+		return false
+	}
+	if dj == -1 {
+		return true
+	}
+	if di != dj {
+		return di < dj
+	}
+
+	vi, vj := s[i].pkg.importPathShort, s[j].pkg.importPathShort
+	if len(vi) != len(vj) {
+		return len(vi) < len(vj)
+	}
+	return vi < vj
+}
+func (s byDistanceOrImportPathShortLength) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+func distance(basepath, targetpath string) int {
+	p, err := filepath.Rel(basepath, targetpath)
+	if err != nil {
+		return -1
+	}
+	if p == "." {
+		return 0
+	}
+	return strings.Count(p, string(filepath.Separator)) + 1
+}
+
+// scanGoDirs populates the dirScan map for GOPATH and GOROOT.
+func scanGoDirs() map[string]*pkg {
+	result := make(map[string]*pkg)
+	var mu sync.Mutex
+
+	add := func(root gopathwalk.Root, dir string) {
+		mu.Lock()
+		defer mu.Unlock()
+
+		if _, dup := result[dir]; dup {
+			return
+		}
+		importpath := filepath.ToSlash(dir[len(root.Path)+len("/"):])
+		result[dir] = &pkg{
+			importPath:      importpath,
+			importPathShort: VendorlessPath(importpath),
+			dir:             dir,
+		}
+	}
+	gopathwalk.Walk(gopathwalk.SrcDirsRoots(), add, gopathwalk.Options{Debug: Debug, ModulesEnabled: false})
+	return result
+}
+
+// VendorlessPath returns the devendorized version of the import path ipath.
+// For example, VendorlessPath("foo/bar/vendor/a/b") returns "a/b".
+func VendorlessPath(ipath string) string {
+	// Devendorize for use in import statement.
+	if i := strings.LastIndex(ipath, "/vendor/"); i >= 0 {
+		return ipath[i+len("/vendor/"):]
+	}
+	if strings.HasPrefix(ipath, "vendor/") {
+		return ipath[len("vendor/"):]
+	}
+	return ipath
+}
+
+// loadExports returns the set of exported symbols in the package at dir.
+// It returns nil on error or if the package name in dir does not match expectPackage.
+var loadExports func(ctx context.Context, expectPackage, dir string) (map[string]bool, error) = loadExportsGoPath
+
+func loadExportsGoPath(ctx context.Context, expectPackage, dir string) (map[string]bool, error) {
+	if Debug {
+		log.Printf("loading exports in dir %s (seeking package %s)", dir, expectPackage)
+	}
+	exports := make(map[string]bool)
+
+	buildCtx := build.Default
+
+	// ReadDir is like ioutil.ReadDir, but only returns *.go files
+	// and filters out _test.go files since they're not relevant
+	// and only slow things down.
+	buildCtx.ReadDir = func(dir string) (notTests []os.FileInfo, err error) {
+		all, err := ioutil.ReadDir(dir)
+		if err != nil {
+			return nil, err
+		}
+		notTests = all[:0]
+		for _, fi := range all {
+			name := fi.Name()
+			if strings.HasSuffix(name, ".go") && !strings.HasSuffix(name, "_test.go") {
+				notTests = append(notTests, fi)
+			}
+		}
+		return notTests, nil
+	}
+
+	files, err := buildCtx.ReadDir(dir)
+	if err != nil {
+		log.Print(err)
+		return nil, err
+	}
+
+	fset := token.NewFileSet()
+
+	for _, fi := range files {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+
+		match, err := buildCtx.MatchFile(dir, fi.Name())
+		if err != nil || !match {
+			continue
+		}
+		fullFile := filepath.Join(dir, fi.Name())
+		f, err := parser.ParseFile(fset, fullFile, nil, 0)
+		if err != nil {
+			if Debug {
+				log.Printf("Parsing %s: %v", fullFile, err)
+			}
+			return nil, err
+		}
+		pkgName := f.Name.Name
+		if pkgName == "documentation" {
+			// Special case from go/build.ImportDir, not
+			// handled by buildCtx.MatchFile.
+			continue
+		}
+		if pkgName != expectPackage {
+			err := fmt.Errorf("scan of dir %v is not expected package %v (actually %v)", dir, expectPackage, pkgName)
+			if Debug {
+				log.Print(err)
+			}
+			return nil, err
+		}
+		for name := range f.Scope.Objects {
+			if ast.IsExported(name) {
+				exports[name] = true
+			}
+		}
+	}
+
+	if Debug {
+		exportList := make([]string, 0, len(exports))
+		for k := range exports {
+			exportList = append(exportList, k)
+		}
+		sort.Strings(exportList)
+		log.Printf("loaded exports in dir %v (package %v): %v", dir, expectPackage, strings.Join(exportList, ", "))
+	}
+	return exports, nil
+}
+
+// findImport searches for a package with the given symbols.
+// If no package is found, findImport returns ("", false, nil)
+//
+// This is declared as a variable rather than a function so goimports
+// can be easily extended by adding a file with an init function.
+//
+// The rename value tells goimports whether to use the package name as
+// a local qualifier in an import. For example, if findImports("pkg",
+// "X") returns ("foo/bar", rename=true), then goimports adds the
+// import line:
+// 	import pkg "foo/bar"
+// to satisfy uses of pkg.X in the file.
+var findImport func(ctx context.Context, pkgName string, symbols map[string]bool, filename string) (foundPkg string, rename bool, err error) = findImportGoPath
+
+// findImportGoPath is the normal implementation of findImport.
+// (Some companies have their own internally.)
+func findImportGoPath(ctx context.Context, pkgName string, symbols map[string]bool, filename string) (foundPkg string, rename bool, err error) {
+	pkgDir, err := filepath.Abs(filename)
+	if err != nil {
+		return "", false, err
+	}
+	pkgDir = filepath.Dir(pkgDir)
+
+	// Fast path for the standard library.
+	// In the common case we hopefully never have to scan the GOPATH, which can
+	// be slow with moving disks.
+	if pkg, ok := findImportStdlib(pkgName, symbols); ok {
+		return pkg, false, nil
+	}
+	if pkgName == "rand" && symbols["Read"] {
+		// Special-case rand.Read.
+		//
+		// If findImportStdlib didn't find it above, don't go
+		// searching for it, lest it find and pick math/rand
+		// in GOROOT (new as of Go 1.6)
+		//
+		// crypto/rand is the safer choice.
+		return "", false, nil
+	}
+
+	// TODO(sameer): look at the import lines for other Go files in the
+	// local directory, since the user is likely to import the same packages
+	// in the current Go file.  Return rename=true when the other Go files
+	// use a renamed package that's also used in the current file.
+
+	// Scan $GOROOT and each $GOPATH.
+	scanOnce.Do(func() { dirScan = scanGoDirs() })
+
+	// Find candidate packages, looking only at their directory names first.
+	var candidates []pkgDistance
+	for _, pkg := range dirScan {
+		if pkgIsCandidate(filename, pkgName, pkg) {
+			candidates = append(candidates, pkgDistance{
+				pkg:      pkg,
+				distance: distance(pkgDir, pkg.dir),
+			})
+		}
+	}
+
+	// Sort the candidates by their import package length,
+	// assuming that shorter package names are better than long
+	// ones.  Note that this sorts by the de-vendored name, so
+	// there's no "penalty" for vendoring.
+	sort.Sort(byDistanceOrImportPathShortLength(candidates))
+	if Debug {
+		for i, c := range candidates {
+			log.Printf("%s candidate %d/%d: %v in %v", pkgName, i+1, len(candidates), c.pkg.importPathShort, c.pkg.dir)
+		}
+	}
+
+	// Collect exports for packages with matching names.
+
+	rescv := make([]chan *pkg, len(candidates))
+	for i := range candidates {
+		rescv[i] = make(chan *pkg, 1)
+	}
+	const maxConcurrentPackageImport = 4
+	loadExportsSem := make(chan struct{}, maxConcurrentPackageImport)
+
+	ctx, cancel := context.WithCancel(ctx)
+	var wg sync.WaitGroup
+	defer func() {
+		cancel()
+		wg.Wait()
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for i, c := range candidates {
+			select {
+			case loadExportsSem <- struct{}{}:
+			case <-ctx.Done():
+				return
+			}
+
+			wg.Add(1)
+			go func(c pkgDistance, resc chan<- *pkg) {
+				defer func() {
+					<-loadExportsSem
+					wg.Done()
+				}()
+
+				exports, err := loadExports(ctx, pkgName, c.pkg.dir)
+				if err != nil {
+					resc <- nil
+					return
+				}
+
+				// If it doesn't have the right
+				// symbols, send nil to mean no match.
+				for symbol := range symbols {
+					if !exports[symbol] {
+						resc <- nil
+						return
+					}
+				}
+				resc <- c.pkg
+			}(c, rescv[i])
+		}
+	}()
+
+	for _, resc := range rescv {
+		pkg := <-resc
+		if pkg == nil {
+			continue
+		}
+		// If the package name in the source doesn't match the import path's base,
+		// return true so the rewriter adds a name (import foo "github.com/bar/go-foo")
+		needsRename := path.Base(pkg.importPath) != pkgName
+		return pkg.importPathShort, needsRename, nil
+	}
+	return "", false, nil
+}
+
+// pkgIsCandidate reports whether pkg is a candidate for satisfying the
+// finding which package pkgIdent in the file named by filename is trying
+// to refer to.
+//
+// This check is purely lexical and is meant to be as fast as possible
+// because it's run over all $GOPATH directories to filter out poor
+// candidates in order to limit the CPU and I/O later parsing the
+// exports in candidate packages.
+//
+// filename is the file being formatted.
+// pkgIdent is the package being searched for, like "client" (if
+// searching for "client.New")
+func pkgIsCandidate(filename, pkgIdent string, pkg *pkg) bool {
+	// Check "internal" and "vendor" visibility:
+	if !canUse(filename, pkg.dir) {
+		return false
+	}
+
+	// Speed optimization to minimize disk I/O:
+	// the last two components on disk must contain the
+	// package name somewhere.
+	//
+	// This permits mismatch naming like directory
+	// "go-foo" being package "foo", or "pkg.v3" being "pkg",
+	// or directory "google.golang.org/api/cloudbilling/v1"
+	// being package "cloudbilling", but doesn't
+	// permit a directory "foo" to be package
+	// "bar", which is strongly discouraged
+	// anyway. There's no reason goimports needs
+	// to be slow just to accommodate that.
+	lastTwo := lastTwoComponents(pkg.importPathShort)
+	if strings.Contains(lastTwo, pkgIdent) {
+		return true
+	}
+	if hasHyphenOrUpperASCII(lastTwo) && !hasHyphenOrUpperASCII(pkgIdent) {
+		lastTwo = lowerASCIIAndRemoveHyphen(lastTwo)
+		if strings.Contains(lastTwo, pkgIdent) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func hasHyphenOrUpperASCII(s string) bool {
+	for i := 0; i < len(s); i++ {
+		b := s[i]
+		if b == '-' || ('A' <= b && b <= 'Z') {
+			return true
+		}
+	}
+	return false
+}
+
+func lowerASCIIAndRemoveHyphen(s string) (ret string) {
+	buf := make([]byte, 0, len(s))
+	for i := 0; i < len(s); i++ {
+		b := s[i]
+		switch {
+		case b == '-':
+			continue
+		case 'A' <= b && b <= 'Z':
+			buf = append(buf, b+('a'-'A'))
+		default:
+			buf = append(buf, b)
+		}
+	}
+	return string(buf)
+}
+
+// canUse reports whether the package in dir is usable from filename,
+// respecting the Go "internal" and "vendor" visibility rules.
+func canUse(filename, dir string) bool {
+	// Fast path check, before any allocations. If it doesn't contain vendor
+	// or internal, it's not tricky:
+	// Note that this can false-negative on directories like "notinternal",
+	// but we check it correctly below. This is just a fast path.
+	if !strings.Contains(dir, "vendor") && !strings.Contains(dir, "internal") {
+		return true
+	}
+
+	dirSlash := filepath.ToSlash(dir)
+	if !strings.Contains(dirSlash, "/vendor/") && !strings.Contains(dirSlash, "/internal/") && !strings.HasSuffix(dirSlash, "/internal") {
+		return true
+	}
+	// Vendor or internal directory only visible from children of parent.
+	// That means the path from the current directory to the target directory
+	// can contain ../vendor or ../internal but not ../foo/vendor or ../foo/internal
+	// or bar/vendor or bar/internal.
+	// After stripping all the leading ../, the only okay place to see vendor or internal
+	// is at the very beginning of the path.
+	absfile, err := filepath.Abs(filename)
+	if err != nil {
+		return false
+	}
+	absdir, err := filepath.Abs(dir)
+	if err != nil {
+		return false
+	}
+	rel, err := filepath.Rel(absfile, absdir)
+	if err != nil {
+		return false
+	}
+	relSlash := filepath.ToSlash(rel)
+	if i := strings.LastIndex(relSlash, "../"); i >= 0 {
+		relSlash = relSlash[i+len("../"):]
+	}
+	return !strings.Contains(relSlash, "/vendor/") && !strings.Contains(relSlash, "/internal/") && !strings.HasSuffix(relSlash, "/internal")
+}
+
+// lastTwoComponents returns at most the last two path components
+// of v, using either / or \ as the path separator.
+func lastTwoComponents(v string) string {
+	nslash := 0
+	for i := len(v) - 1; i >= 0; i-- {
+		if v[i] == '/' || v[i] == '\\' {
+			nslash++
+			if nslash == 2 {
+				return v[i:]
+			}
+		}
+	}
+	return v
+}
+
+type visitFn func(node ast.Node) ast.Visitor
+
+func (fn visitFn) Visit(node ast.Node) ast.Visitor {
+	return fn(node)
+}
+
+func findImportStdlib(shortPkg string, symbols map[string]bool) (importPath string, ok bool) {
+	for symbol := range symbols {
+		key := shortPkg + "." + symbol
+		path := stdlib[key]
+		if path == "" {
+			if key == "rand.Read" {
+				continue
+			}
+			return "", false
+		}
+		if importPath != "" && importPath != path {
+			// Ambiguous. Symbols pointed to different things.
+			return "", false
+		}
+		importPath = path
+	}
+	if importPath == "" && shortPkg == "rand" && symbols["Read"] {
+		return "crypto/rand", true
+	}
+	return importPath, importPath != ""
+}

vendor/golang.org/x/tools/imports/imports.go

@@ -0,0 +1,310 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:generate go run mkstdlib.go
+
+// Package imports implements a Go pretty-printer (like package "go/format")
+// that also adds or removes import statements as necessary.
+package imports // import "golang.org/x/tools/imports"
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/go/ast/astutil"
+)
+
+// Options specifies options for processing files.
+type Options struct {
+	Fragment  bool // Accept fragment of a source file (no package statement)
+	AllErrors bool // Report all errors (not just the first 10 on different lines)
+
+	Comments  bool // Print comments (true if nil *Options provided)
+	TabIndent bool // Use tabs for indent (true if nil *Options provided)
+	TabWidth  int  // Tab width (8 if nil *Options provided)
+
+	FormatOnly bool // Disable the insertion and deletion of imports
+}
+
+// Process formats and adjusts imports for the provided file.
+// If opt is nil the defaults are used.
+//
+// Note that filename's directory influences which imports can be chosen,
+// so it is important that filename be accurate.
+// To process data ``as if'' it were in filename, pass the data as a non-nil src.
+func Process(filename string, src []byte, opt *Options) ([]byte, error) {
+	if opt == nil {
+		opt = &Options{Comments: true, TabIndent: true, TabWidth: 8}
+	}
+	if src == nil {
+		b, err := ioutil.ReadFile(filename)
+		if err != nil {
+			return nil, err
+		}
+		src = b
+	}
+
+	fileSet := token.NewFileSet()
+	file, adjust, err := parse(fileSet, filename, src, opt)
+	if err != nil {
+		return nil, err
+	}
+
+	if !opt.FormatOnly {
+		_, err = fixImports(fileSet, file, filename)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	sortImports(fileSet, file)
+	imps := astutil.Imports(fileSet, file)
+	var spacesBefore []string // import paths we need spaces before
+	for _, impSection := range imps {
+		// Within each block of contiguous imports, see if any
+		// import lines are in different group numbers. If so,
+		// we'll need to put a space between them so it's
+		// compatible with gofmt.
+		lastGroup := -1
+		for _, importSpec := range impSection {
+			importPath, _ := strconv.Unquote(importSpec.Path.Value)
+			groupNum := importGroup(importPath)
+			if groupNum != lastGroup && lastGroup != -1 {
+				spacesBefore = append(spacesBefore, importPath)
+			}
+			lastGroup = groupNum
+		}
+
+	}
+
+	printerMode := printer.UseSpaces
+	if opt.TabIndent {
+		printerMode |= printer.TabIndent
+	}
+	printConfig := &printer.Config{Mode: printerMode, Tabwidth: opt.TabWidth}
+
+	var buf bytes.Buffer
+	err = printConfig.Fprint(&buf, fileSet, file)
+	if err != nil {
+		return nil, err
+	}
+	out := buf.Bytes()
+	if adjust != nil {
+		out = adjust(src, out)
+	}
+	if len(spacesBefore) > 0 {
+		out, err = addImportSpaces(bytes.NewReader(out), spacesBefore)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	out, err = format.Source(out)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
+// parse parses src, which was read from filename,
+// as a Go source file or statement list.
+func parse(fset *token.FileSet, filename string, src []byte, opt *Options) (*ast.File, func(orig, src []byte) []byte, error) {
+	parserMode := parser.Mode(0)
+	if opt.Comments {
+		parserMode |= parser.ParseComments
+	}
+	if opt.AllErrors {
+		parserMode |= parser.AllErrors
+	}
+
+	// Try as whole source file.
+	file, err := parser.ParseFile(fset, filename, src, parserMode)
+	if err == nil {
+		return file, nil, nil
+	}
+	// If the error is that the source file didn't begin with a
+	// package line and we accept fragmented input, fall through to
+	// try as a source fragment.  Stop and return on any other error.
+	if !opt.Fragment || !strings.Contains(err.Error(), "expected 'package'") {
+		return nil, nil, err
+	}
+
+	// If this is a declaration list, make it a source file
+	// by inserting a package clause.
+	// Insert using a ;, not a newline, so that parse errors are on
+	// the correct line.
+	const prefix = "package main;"
+	psrc := append([]byte(prefix), src...)
+	file, err = parser.ParseFile(fset, filename, psrc, parserMode)
+	if err == nil {
+		// Gofmt will turn the ; into a \n.
+		// Do that ourselves now and update the file contents,
+		// so that positions and line numbers are correct going forward.
+		psrc[len(prefix)-1] = '\n'
+		fset.File(file.Package).SetLinesForContent(psrc)
+
+		// If a main function exists, we will assume this is a main
+		// package and leave the file.
+		if containsMainFunc(file) {
+			return file, nil, nil
+		}
+
+		adjust := func(orig, src []byte) []byte {
+			// Remove the package clause.
+			src = src[len(prefix):]
+			return matchSpace(orig, src)
+		}
+		return file, adjust, nil
+	}
+	// If the error is that the source file didn't begin with a
+	// declaration, fall through to try as a statement list.
+	// Stop and return on any other error.
+	if !strings.Contains(err.Error(), "expected declaration") {
+		return nil, nil, err
+	}
+
+	// If this is a statement list, make it a source file
+	// by inserting a package clause and turning the list
+	// into a function body.  This handles expressions too.
+	// Insert using a ;, not a newline, so that the line numbers
+	// in fsrc match the ones in src.
+	fsrc := append(append([]byte("package p; func _() {"), src...), '}')
+	file, err = parser.ParseFile(fset, filename, fsrc, parserMode)
+	if err == nil {
+		adjust := func(orig, src []byte) []byte {
+			// Remove the wrapping.
+			// Gofmt has turned the ; into a \n\n.
+			src = src[len("package p\n\nfunc _() {"):]
+			src = src[:len(src)-len("}\n")]
+			// Gofmt has also indented the function body one level.
+			// Remove that indent.
+			src = bytes.Replace(src, []byte("\n\t"), []byte("\n"), -1)
+			return matchSpace(orig, src)
+		}
+		return file, adjust, nil
+	}
+
+	// Failed, and out of options.
+	return nil, nil, err
+}
+
+// containsMainFunc checks if a file contains a function declaration with the
+// function signature 'func main()'
+func containsMainFunc(file *ast.File) bool {
+	for _, decl := range file.Decls {
+		if f, ok := decl.(*ast.FuncDecl); ok {
+			if f.Name.Name != "main" {
+				continue
+			}
+
+			if len(f.Type.Params.List) != 0 {
+				continue
+			}
+
+			if f.Type.Results != nil && len(f.Type.Results.List) != 0 {
+				continue
+			}
+
+			return true
+		}
+	}
+
+	return false
+}
+
+func cutSpace(b []byte) (before, middle, after []byte) {
+	i := 0
+	for i < len(b) && (b[i] == ' ' || b[i] == '\t' || b[i] == '\n') {
+		i++
+	}
+	j := len(b)
+	for j > 0 && (b[j-1] == ' ' || b[j-1] == '\t' || b[j-1] == '\n') {
+		j--
+	}
+	if i <= j {
+		return b[:i], b[i:j], b[j:]
+	}
+	return nil, nil, b[j:]
+}
+
+// matchSpace reformats src to use the same space context as orig.
+// 1) If orig begins with blank lines, matchSpace inserts them at the beginning of src.
+// 2) matchSpace copies the indentation of the first non-blank line in orig
+//    to every non-blank line in src.
+// 3) matchSpace copies the trailing space from orig and uses it in place
+//   of src's trailing space.
+func matchSpace(orig []byte, src []byte) []byte {
+	before, _, after := cutSpace(orig)
+	i := bytes.LastIndex(before, []byte{'\n'})
+	before, indent := before[:i+1], before[i+1:]
+
+	_, src, _ = cutSpace(src)
+
+	var b bytes.Buffer
+	b.Write(before)
+	for len(src) > 0 {
+		line := src
+		if i := bytes.IndexByte(line, '\n'); i >= 0 {
+			line, src = line[:i+1], line[i+1:]
+		} else {
+			src = nil
+		}
+		if len(line) > 0 && line[0] != '\n' { // not blank
+			b.Write(indent)
+		}
+		b.Write(line)
+	}
+	b.Write(after)
+	return b.Bytes()
+}
+
+var impLine = regexp.MustCompile(`^\s+(?:[\w\.]+\s+)?"(.+)"`)
+
+func addImportSpaces(r io.Reader, breaks []string) ([]byte, error) {
+	var out bytes.Buffer
+	in := bufio.NewReader(r)
+	inImports := false
+	done := false
+	for {
+		s, err := in.ReadString('\n')
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+
+		if !inImports && !done && strings.HasPrefix(s, "import") {
+			inImports = true
+		}
+		if inImports && (strings.HasPrefix(s, "var") ||
+			strings.HasPrefix(s, "func") ||
+			strings.HasPrefix(s, "const") ||
+			strings.HasPrefix(s, "type")) {
+			done = true
+			inImports = false
+		}
+		if inImports && len(breaks) > 0 {
+			if m := impLine.FindStringSubmatch(s); m != nil {
+				if m[1] == breaks[0] {
+					out.WriteByte('\n')
+					breaks = breaks[1:]
+				}
+			}
+		}
+
+		fmt.Fprint(&out, s)
+	}
+	return out.Bytes(), nil
+}

vendor/golang.org/x/tools/imports/mkindex.go

@@ -0,0 +1,173 @@
+// +build ignore
+
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Command mkindex creates the file "pkgindex.go" containing an index of the Go
+// standard library. The file is intended to be built as part of the imports
+// package, so that the package may be used in environments where a GOROOT is
+// not available (such as App Engine).
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+var (
+	pkgIndex = make(map[string][]pkg)
+	exports  = make(map[string]map[string]bool)
+)
+
+func main() {
+	// Don't use GOPATH.
+	ctx := build.Default
+	ctx.GOPATH = ""
+
+	// Populate pkgIndex global from GOROOT.
+	for _, path := range ctx.SrcDirs() {
+		f, err := os.Open(path)
+		if err != nil {
+			log.Print(err)
+			continue
+		}
+		children, err := f.Readdir(-1)
+		f.Close()
+		if err != nil {
+			log.Print(err)
+			continue
+		}
+		for _, child := range children {
+			if child.IsDir() {
+				loadPkg(path, child.Name())
+			}
+		}
+	}
+	// Populate exports global.
+	for _, ps := range pkgIndex {
+		for _, p := range ps {
+			e := loadExports(p.dir)
+			if e != nil {
+				exports[p.dir] = e
+			}
+		}
+	}
+
+	// Construct source file.
+	var buf bytes.Buffer
+	fmt.Fprint(&buf, pkgIndexHead)
+	fmt.Fprintf(&buf, "var pkgIndexMaster = %#v\n", pkgIndex)
+	fmt.Fprintf(&buf, "var exportsMaster = %#v\n", exports)
+	src := buf.Bytes()
+
+	// Replace main.pkg type name with pkg.
+	src = bytes.Replace(src, []byte("main.pkg"), []byte("pkg"), -1)
+	// Replace actual GOROOT with "/go".
+	src = bytes.Replace(src, []byte(ctx.GOROOT), []byte("/go"), -1)
+	// Add some line wrapping.
+	src = bytes.Replace(src, []byte("}, "), []byte("},\n"), -1)
+	src = bytes.Replace(src, []byte("true, "), []byte("true,\n"), -1)
+
+	var err error
+	src, err = format.Source(src)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Write out source file.
+	err = ioutil.WriteFile("pkgindex.go", src, 0644)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+const pkgIndexHead = `package imports
+
+func init() {
+	pkgIndexOnce.Do(func() {
+		pkgIndex.m = pkgIndexMaster
+	})
+	loadExports = func(dir string) map[string]bool {
+		return exportsMaster[dir]
+	}
+}
+`
+
+type pkg struct {
+	importpath string // full pkg import path, e.g. "net/http"
+	dir        string // absolute file path to pkg directory e.g. "/usr/lib/go/src/fmt"
+}
+
+var fset = token.NewFileSet()
+
+func loadPkg(root, importpath string) {
+	shortName := path.Base(importpath)
+	if shortName == "testdata" {
+		return
+	}
+
+	dir := filepath.Join(root, importpath)
+	pkgIndex[shortName] = append(pkgIndex[shortName], pkg{
+		importpath: importpath,
+		dir:        dir,
+	})
+
+	pkgDir, err := os.Open(dir)
+	if err != nil {
+		return
+	}
+	children, err := pkgDir.Readdir(-1)
+	pkgDir.Close()
+	if err != nil {
+		return
+	}
+	for _, child := range children {
+		name := child.Name()
+		if name == "" {
+			continue
+		}
+		if c := name[0]; c == '.' || ('0' <= c && c <= '9') {
+			continue
+		}
+		if child.IsDir() {
+			loadPkg(root, filepath.Join(importpath, name))
+		}
+	}
+}
+
+func loadExports(dir string) map[string]bool {
+	exports := make(map[string]bool)
+	buildPkg, err := build.ImportDir(dir, 0)
+	if err != nil {
+		if strings.Contains(err.Error(), "no buildable Go source files in") {
+			return nil
+		}
+		log.Printf("could not import %q: %v", dir, err)
+		return nil
+	}
+	for _, file := range buildPkg.GoFiles {
+		f, err := parser.ParseFile(fset, filepath.Join(dir, file), nil, 0)
+		if err != nil {
+			log.Printf("could not parse %q: %v", file, err)
+			continue
+		}
+		for name := range f.Scope.Objects {
+			if ast.IsExported(name) {
+				exports[name] = true
+			}
+		}
+	}
+	return exports
+}

vendor/golang.org/x/tools/imports/mkstdlib.go

@@ -0,0 +1,108 @@
+// +build ignore
+
+// mkstdlib generates the zstdlib.go file, containing the Go standard
+// library API symbols. It's baked into the binary to avoid scanning
+// GOPATH in the common case.
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/format"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"sort"
+	"strings"
+)
+
+func mustOpen(name string) io.Reader {
+	f, err := os.Open(name)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return f
+}
+
+func api(base string) string {
+	return filepath.Join(runtime.GOROOT(), "api", base)
+}
+
+var sym = regexp.MustCompile(`^pkg (\S+).*?, (?:var|func|type|const) ([A-Z]\w*)`)
+
+func main() {
+	var buf bytes.Buffer
+	outf := func(format string, args ...interface{}) {
+		fmt.Fprintf(&buf, format, args...)
+	}
+	outf("// Code generated by mkstdlib.go. DO NOT EDIT.\n\n")
+	outf("package imports\n")
+	outf("var stdlib = map[string]string{\n")
+	f := io.MultiReader(
+		mustOpen(api("go1.txt")),
+		mustOpen(api("go1.1.txt")),
+		mustOpen(api("go1.2.txt")),
+		mustOpen(api("go1.3.txt")),
+		mustOpen(api("go1.4.txt")),
+		mustOpen(api("go1.5.txt")),
+		mustOpen(api("go1.6.txt")),
+		mustOpen(api("go1.7.txt")),
+		mustOpen(api("go1.8.txt")),
+		mustOpen(api("go1.9.txt")),
+		mustOpen(api("go1.10.txt")),
+		mustOpen(api("go1.11.txt")),
+	)
+	sc := bufio.NewScanner(f)
+	fullImport := map[string]string{} // "zip.NewReader" => "archive/zip"
+	ambiguous := map[string]bool{}
+	var keys []string
+	for sc.Scan() {
+		l := sc.Text()
+		has := func(v string) bool { return strings.Contains(l, v) }
+		if has("struct, ") || has("interface, ") || has(", method (") {
+			continue
+		}
+		if m := sym.FindStringSubmatch(l); m != nil {
+			full := m[1]
+			key := path.Base(full) + "." + m[2]
+			if exist, ok := fullImport[key]; ok {
+				if exist != full {
+					ambiguous[key] = true
+				}
+			} else {
+				fullImport[key] = full
+				keys = append(keys, key)
+			}
+		}
+	}
+	if err := sc.Err(); err != nil {
+		log.Fatal(err)
+	}
+	sort.Strings(keys)
+	for _, key := range keys {
+		if ambiguous[key] {
+			outf("\t// %q is ambiguous\n", key)
+		} else {
+			outf("\t%q: %q,\n", key, fullImport[key])
+		}
+	}
+	outf("\n")
+	for _, sym := range [...]string{"Alignof", "ArbitraryType", "Offsetof", "Pointer", "Sizeof"} {
+		outf("\t%q: %q,\n", "unsafe."+sym, "unsafe")
+	}
+	outf("}\n")
+	fmtbuf, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = ioutil.WriteFile("zstdlib.go", fmtbuf, 0666)
+	if err != nil {
+		log.Fatal(err)
+	}
+}

vendor/golang.org/x/tools/imports/sortimports.go

@@ -0,0 +1,230 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Hacked up copy of go/ast/import.go
+
+package imports
+
+import (
+	"go/ast"
+	"go/token"
+	"sort"
+	"strconv"
+)
+
+// sortImports sorts runs of consecutive import lines in import blocks in f.
+// It also removes duplicate imports when it is possible to do so without data loss.
+func sortImports(fset *token.FileSet, f *ast.File) {
+	for i, d := range f.Decls {
+		d, ok := d.(*ast.GenDecl)
+		if !ok || d.Tok != token.IMPORT {
+			// Not an import declaration, so we're done.
+			// Imports are always first.
+			break
+		}
+
+		if len(d.Specs) == 0 {
+			// Empty import block, remove it.
+			f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
+		}
+
+		if !d.Lparen.IsValid() {
+			// Not a block: sorted by default.
+			continue
+		}
+
+		// Identify and sort runs of specs on successive lines.
+		i := 0
+		specs := d.Specs[:0]
+		for j, s := range d.Specs {
+			if j > i && fset.Position(s.Pos()).Line > 1+fset.Position(d.Specs[j-1].End()).Line {
+				// j begins a new run.  End this one.
+				specs = append(specs, sortSpecs(fset, f, d.Specs[i:j])...)
+				i = j
+			}
+		}
+		specs = append(specs, sortSpecs(fset, f, d.Specs[i:])...)
+		d.Specs = specs
+
+		// Deduping can leave a blank line before the rparen; clean that up.
+		if len(d.Specs) > 0 {
+			lastSpec := d.Specs[len(d.Specs)-1]
+			lastLine := fset.Position(lastSpec.Pos()).Line
+			if rParenLine := fset.Position(d.Rparen).Line; rParenLine > lastLine+1 {
+				fset.File(d.Rparen).MergeLine(rParenLine - 1)
+			}
+		}
+	}
+}
+
+func importPath(s ast.Spec) string {
+	t, err := strconv.Unquote(s.(*ast.ImportSpec).Path.Value)
+	if err == nil {
+		return t
+	}
+	return ""
+}
+
+func importName(s ast.Spec) string {
+	n := s.(*ast.ImportSpec).Name
+	if n == nil {
+		return ""
+	}
+	return n.Name
+}
+
+func importComment(s ast.Spec) string {
+	c := s.(*ast.ImportSpec).Comment
+	if c == nil {
+		return ""
+	}
+	return c.Text()
+}
+
+// collapse indicates whether prev may be removed, leaving only next.
+func collapse(prev, next ast.Spec) bool {
+	if importPath(next) != importPath(prev) || importName(next) != importName(prev) {
+		return false
+	}
+	return prev.(*ast.ImportSpec).Comment == nil
+}
+
+type posSpan struct {
+	Start token.Pos
+	End   token.Pos
+}
+
+func sortSpecs(fset *token.FileSet, f *ast.File, specs []ast.Spec) []ast.Spec {
+	// Can't short-circuit here even if specs are already sorted,
+	// since they might yet need deduplication.
+	// A lone import, however, may be safely ignored.
+	if len(specs) <= 1 {
+		return specs
+	}
+
+	// Record positions for specs.
+	pos := make([]posSpan, len(specs))
+	for i, s := range specs {
+		pos[i] = posSpan{s.Pos(), s.End()}
+	}
+
+	// Identify comments in this range.
+	// Any comment from pos[0].Start to the final line counts.
+	lastLine := fset.Position(pos[len(pos)-1].End).Line
+	cstart := len(f.Comments)
+	cend := len(f.Comments)
+	for i, g := range f.Comments {
+		if g.Pos() < pos[0].Start {
+			continue
+		}
+		if i < cstart {
+			cstart = i
+		}
+		if fset.Position(g.End()).Line > lastLine {
+			cend = i
+			break
+		}
+	}
+	comments := f.Comments[cstart:cend]
+
+	// Assign each comment to the import spec preceding it.
+	importComment := map[*ast.ImportSpec][]*ast.CommentGroup{}
+	specIndex := 0
+	for _, g := range comments {
+		for specIndex+1 < len(specs) && pos[specIndex+1].Start <= g.Pos() {
+			specIndex++
+		}
+		s := specs[specIndex].(*ast.ImportSpec)
+		importComment[s] = append(importComment[s], g)
+	}
+
+	// Sort the import specs by import path.
+	// Remove duplicates, when possible without data loss.
+	// Reassign the import paths to have the same position sequence.
+	// Reassign each comment to abut the end of its spec.
+	// Sort the comments by new position.
+	sort.Sort(byImportSpec(specs))
+
+	// Dedup. Thanks to our sorting, we can just consider
+	// adjacent pairs of imports.
+	deduped := specs[:0]
+	for i, s := range specs {
+		if i == len(specs)-1 || !collapse(s, specs[i+1]) {
+			deduped = append(deduped, s)
+		} else {
+			p := s.Pos()
+			fset.File(p).MergeLine(fset.Position(p).Line)
+		}
+	}
+	specs = deduped
+
+	// Fix up comment positions
+	for i, s := range specs {
+		s := s.(*ast.ImportSpec)
+		if s.Name != nil {
+			s.Name.NamePos = pos[i].Start
+		}
+		s.Path.ValuePos = pos[i].Start
+		s.EndPos = pos[i].End
+		nextSpecPos := pos[i].End
+
+		for _, g := range importComment[s] {
+			for _, c := range g.List {
+				c.Slash = pos[i].End
+				nextSpecPos = c.End()
+			}
+		}
+		if i < len(specs)-1 {
+			pos[i+1].Start = nextSpecPos
+			pos[i+1].End = nextSpecPos
+		}
+	}
+
+	sort.Sort(byCommentPos(comments))
+
+	// Fixup comments can insert blank lines, because import specs are on different lines.
+	// We remove those blank lines here by merging import spec to the first import spec line.
+	firstSpecLine := fset.Position(specs[0].Pos()).Line
+	for _, s := range specs[1:] {
+		p := s.Pos()
+		line := fset.File(p).Line(p)
+		for previousLine := line - 1; previousLine >= firstSpecLine; {
+			fset.File(p).MergeLine(previousLine)
+			previousLine--
+		}
+	}
+	return specs
+}
+
+type byImportSpec []ast.Spec // slice of *ast.ImportSpec
+
+func (x byImportSpec) Len() int      { return len(x) }
+func (x byImportSpec) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+func (x byImportSpec) Less(i, j int) bool {
+	ipath := importPath(x[i])
+	jpath := importPath(x[j])
+
+	igroup := importGroup(ipath)
+	jgroup := importGroup(jpath)
+	if igroup != jgroup {
+		return igroup < jgroup
+	}
+
+	if ipath != jpath {
+		return ipath < jpath
+	}
+	iname := importName(x[i])
+	jname := importName(x[j])
+
+	if iname != jname {
+		return iname < jname
+	}
+	return importComment(x[i]) < importComment(x[j])
+}
+
+type byCommentPos []*ast.CommentGroup
+
+func (x byCommentPos) Len() int           { return len(x) }
+func (x byCommentPos) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
+func (x byCommentPos) Less(i, j int) bool { return x[i].Pos() < x[j].Pos() }

vendor/golang.org/x/tools/internal/fastwalk/fastwalk.go

@@ -0,0 +1,196 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package fastwalk provides a faster version of filepath.Walk for file system
+// scanning tools.
+package fastwalk
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sync"
+)
+
+// TraverseLink is used as a return value from WalkFuncs to indicate that the
+// symlink named in the call may be traversed.
+var TraverseLink = errors.New("fastwalk: traverse symlink, assuming target is a directory")
+
+// SkipFiles is a used as a return value from WalkFuncs to indicate that the
+// callback should not be called for any other files in the current directory.
+// Child directories will still be traversed.
+var SkipFiles = errors.New("fastwalk: skip remaining files in directory")
+
+// Walk is a faster implementation of filepath.Walk.
+//
+// filepath.Walk's design necessarily calls os.Lstat on each file,
+// even if the caller needs less info.
+// Many tools need only the type of each file.
+// On some platforms, this information is provided directly by the readdir
+// system call, avoiding the need to stat each file individually.
+// fastwalk_unix.go contains a fork of the syscall routines.
+//
+// See golang.org/issue/16399
+//
+// Walk walks the file tree rooted at root, calling walkFn for
+// each file or directory in the tree, including root.
+//
+// If fastWalk returns filepath.SkipDir, the directory is skipped.
+//
+// Unlike filepath.Walk:
+//   * file stat calls must be done by the user.
+//     The only provided metadata is the file type, which does not include
+//     any permission bits.
+//   * multiple goroutines stat the filesystem concurrently. The provided
+//     walkFn must be safe for concurrent use.
+//   * fastWalk can follow symlinks if walkFn returns the TraverseLink
+//     sentinel error. It is the walkFn's responsibility to prevent
+//     fastWalk from going into symlink cycles.
+func Walk(root string, walkFn func(path string, typ os.FileMode) error) error {
+	// TODO(bradfitz): make numWorkers configurable? We used a
+	// minimum of 4 to give the kernel more info about multiple
+	// things we want, in hopes its I/O scheduling can take
+	// advantage of that. Hopefully most are in cache. Maybe 4 is
+	// even too low of a minimum. Profile more.
+	numWorkers := 4
+	if n := runtime.NumCPU(); n > numWorkers {
+		numWorkers = n
+	}
+
+	// Make sure to wait for all workers to finish, otherwise
+	// walkFn could still be called after returning. This Wait call
+	// runs after close(e.donec) below.
+	var wg sync.WaitGroup
+	defer wg.Wait()
+
+	w := &walker{
+		fn:       walkFn,
+		enqueuec: make(chan walkItem, numWorkers), // buffered for performance
+		workc:    make(chan walkItem, numWorkers), // buffered for performance
+		donec:    make(chan struct{}),
+
+		// buffered for correctness & not leaking goroutines:
+		resc: make(chan error, numWorkers),
+	}
+	defer close(w.donec)
+
+	for i := 0; i < numWorkers; i++ {
+		wg.Add(1)
+		go w.doWork(&wg)
+	}
+	todo := []walkItem{{dir: root}}
+	out := 0
+	for {
+		workc := w.workc
+		var workItem walkItem
+		if len(todo) == 0 {
+			workc = nil
+		} else {
+			workItem = todo[len(todo)-1]
+		}
+		select {
+		case workc <- workItem:
+			todo = todo[:len(todo)-1]
+			out++
+		case it := <-w.enqueuec:
+			todo = append(todo, it)
+		case err := <-w.resc:
+			out--
+			if err != nil {
+				return err
+			}
+			if out == 0 && len(todo) == 0 {
+				// It's safe to quit here, as long as the buffered
+				// enqueue channel isn't also readable, which might
+				// happen if the worker sends both another unit of
+				// work and its result before the other select was
+				// scheduled and both w.resc and w.enqueuec were
+				// readable.
+				select {
+				case it := <-w.enqueuec:
+					todo = append(todo, it)
+				default:
+					return nil
+				}
+			}
+		}
+	}
+}
+
+// doWork reads directories as instructed (via workc) and runs the
+// user's callback function.
+func (w *walker) doWork(wg *sync.WaitGroup) {
+	defer wg.Done()
+	for {
+		select {
+		case <-w.donec:
+			return
+		case it := <-w.workc:
+			select {
+			case <-w.donec:
+				return
+			case w.resc <- w.walk(it.dir, !it.callbackDone):
+			}
+		}
+	}
+}
+
+type walker struct {
+	fn func(path string, typ os.FileMode) error
+
+	donec    chan struct{} // closed on fastWalk's return
+	workc    chan walkItem // to workers
+	enqueuec chan walkItem // from workers
+	resc     chan error    // from workers
+}
+
+type walkItem struct {
+	dir          string
+	callbackDone bool // callback already called; don't do it again
+}
+
+func (w *walker) enqueue(it walkItem) {
+	select {
+	case w.enqueuec <- it:
+	case <-w.donec:
+	}
+}
+
+func (w *walker) onDirEnt(dirName, baseName string, typ os.FileMode) error {
+	joined := dirName + string(os.PathSeparator) + baseName
+	if typ == os.ModeDir {
+		w.enqueue(walkItem{dir: joined})
+		return nil
+	}
+
+	err := w.fn(joined, typ)
+	if typ == os.ModeSymlink {
+		if err == TraverseLink {
+			// Set callbackDone so we don't call it twice for both the
+			// symlink-as-symlink and the symlink-as-directory later:
+			w.enqueue(walkItem{dir: joined, callbackDone: true})
+			return nil
+		}
+		if err == filepath.SkipDir {
+			// Permit SkipDir on symlinks too.
+			return nil
+		}
+	}
+	return err
+}
+
+func (w *walker) walk(root string, runUserCallback bool) error {
+	if runUserCallback {
+		err := w.fn(root, os.ModeDir)
+		if err == filepath.SkipDir {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+	}
+
+	return readDir(root, w.onDirEnt)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_fileno.go

@@ -0,0 +1,13 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build freebsd openbsd netbsd
+
+package fastwalk
+
+import "syscall"
+
+func direntInode(dirent *syscall.Dirent) uint64 {
+	return uint64(dirent.Fileno)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_ino.go

@@ -0,0 +1,14 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux darwin
+// +build !appengine
+
+package fastwalk
+
+import "syscall"
+
+func direntInode(dirent *syscall.Dirent) uint64 {
+	return uint64(dirent.Ino)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_namlen_bsd.go

@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin freebsd openbsd netbsd
+
+package fastwalk
+
+import "syscall"
+
+func direntNamlen(dirent *syscall.Dirent) uint64 {
+	return uint64(dirent.Namlen)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_dirent_namlen_linux.go

@@ -0,0 +1,24 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux
+// +build !appengine
+
+package fastwalk
+
+import (
+	"bytes"
+	"syscall"
+	"unsafe"
+)
+
+func direntNamlen(dirent *syscall.Dirent) uint64 {
+	const fixedHdr = uint16(unsafe.Offsetof(syscall.Dirent{}.Name))
+	nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
+	nameLen := bytes.IndexByte(nameBuf[:dirent.Reclen-fixedHdr], 0)
+	if nameLen < 0 {
+		panic("failed to find terminating 0 byte in dirent")
+	}
+	return uint64(nameLen)
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_portable.go

@@ -0,0 +1,37 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build appengine !linux,!darwin,!freebsd,!openbsd,!netbsd
+
+package fastwalk
+
+import (
+	"io/ioutil"
+	"os"
+)
+
+// readDir calls fn for each directory entry in dirName.
+// It does not descend into directories or follow symlinks.
+// If fn returns a non-nil error, readDir returns with that error
+// immediately.
+func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error {
+	fis, err := ioutil.ReadDir(dirName)
+	if err != nil {
+		return err
+	}
+	skipFiles := false
+	for _, fi := range fis {
+		if fi.Mode().IsRegular() && skipFiles {
+			continue
+		}
+		if err := fn(dirName, fi.Name(), fi.Mode()&os.ModeType); err != nil {
+			if err == SkipFiles {
+				skipFiles = true
+				continue
+			}
+			return err
+		}
+	}
+	return nil
+}

vendor/golang.org/x/tools/internal/fastwalk/fastwalk_unix.go

@@ -0,0 +1,127 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux darwin freebsd openbsd netbsd
+// +build !appengine
+
+package fastwalk
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+const blockSize = 8 << 10
+
+// unknownFileMode is a sentinel (and bogus) os.FileMode
+// value used to represent a syscall.DT_UNKNOWN Dirent.Type.
+const unknownFileMode os.FileMode = os.ModeNamedPipe | os.ModeSocket | os.ModeDevice
+
+func readDir(dirName string, fn func(dirName, entName string, typ os.FileMode) error) error {
+	fd, err := syscall.Open(dirName, 0, 0)
+	if err != nil {
+		return &os.PathError{Op: "open", Path: dirName, Err: err}
+	}
+	defer syscall.Close(fd)
+
+	// The buffer must be at least a block long.
+	buf := make([]byte, blockSize) // stack-allocated; doesn't escape
+	bufp := 0                      // starting read position in buf
+	nbuf := 0                      // end valid data in buf
+	skipFiles := false
+	for {
+		if bufp >= nbuf {
+			bufp = 0
+			nbuf, err = syscall.ReadDirent(fd, buf)
+			if err != nil {
+				return os.NewSyscallError("readdirent", err)
+			}
+			if nbuf <= 0 {
+				return nil
+			}
+		}
+		consumed, name, typ := parseDirEnt(buf[bufp:nbuf])
+		bufp += consumed
+		if name == "" || name == "." || name == ".." {
+			continue
+		}
+		// Fallback for filesystems (like old XFS) that don't
+		// support Dirent.Type and have DT_UNKNOWN (0) there
+		// instead.
+		if typ == unknownFileMode {
+			fi, err := os.Lstat(dirName + "/" + name)
+			if err != nil {
+				// It got deleted in the meantime.
+				if os.IsNotExist(err) {
+					continue
+				}
+				return err
+			}
+			typ = fi.Mode() & os.ModeType
+		}
+		if skipFiles && typ.IsRegular() {
+			continue
+		}
+		if err := fn(dirName, name, typ); err != nil {
+			if err == SkipFiles {
+				skipFiles = true
+				continue
+			}
+			return err
+		}
+	}
+}
+
+func parseDirEnt(buf []byte) (consumed int, name string, typ os.FileMode) {
+	// golang.org/issue/15653
+	dirent := (*syscall.Dirent)(unsafe.Pointer(&buf[0]))
+	if v := unsafe.Offsetof(dirent.Reclen) + unsafe.Sizeof(dirent.Reclen); uintptr(len(buf)) < v {
+		panic(fmt.Sprintf("buf size of %d smaller than dirent header size %d", len(buf), v))
+	}
+	if len(buf) < int(dirent.Reclen) {
+		panic(fmt.Sprintf("buf size %d < record length %d", len(buf), dirent.Reclen))
+	}
+	consumed = int(dirent.Reclen)
+	if direntInode(dirent) == 0 { // File absent in directory.
+		return
+	}
+	switch dirent.Type {
+	case syscall.DT_REG:
+		typ = 0
+	case syscall.DT_DIR:
+		typ = os.ModeDir
+	case syscall.DT_LNK:
+		typ = os.ModeSymlink
+	case syscall.DT_BLK:
+		typ = os.ModeDevice
+	case syscall.DT_FIFO:
+		typ = os.ModeNamedPipe
+	case syscall.DT_SOCK:
+		typ = os.ModeSocket
+	case syscall.DT_UNKNOWN:
+		typ = unknownFileMode
+	default:
+		// Skip weird things.
+		// It's probably a DT_WHT (http://lwn.net/Articles/325369/)
+		// or something. Revisit if/when this package is moved outside
+		// of goimports. goimports only cares about regular files,
+		// symlinks, and directories.
+		return
+	}
+
+	nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
+	nameLen := direntNamlen(dirent)
+
+	// Special cases for common things:
+	if nameLen == 1 && nameBuf[0] == '.' {
+		name = "."
+	} else if nameLen == 2 && nameBuf[0] == '.' && nameBuf[1] == '.' {
+		name = ".."
+	} else {
+		name = string(nameBuf[:nameLen])
+	}
+	return
+}

vendor/golang.org/x/tools/internal/gopathwalk/walk.go

@@ -0,0 +1,246 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gopathwalk is like filepath.Walk but specialized for finding Go
+// packages, particularly in $GOPATH and $GOROOT.
+package gopathwalk
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"go/build"
+	"golang.org/x/tools/internal/fastwalk"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Options controls the behavior of a Walk call.
+type Options struct {
+	Debug          bool // Enable debug logging
+	ModulesEnabled bool // Search module caches. Also disables legacy goimports ignore rules.
+}
+
+// RootType indicates the type of a Root.
+type RootType int
+
+const (
+	RootUnknown RootType = iota
+	RootGOROOT
+	RootGOPATH
+	RootCurrentModule
+	RootModuleCache
+)
+
+// A Root is a starting point for a Walk.
+type Root struct {
+	Path string
+	Type RootType
+}
+
+// SrcDirsRoots returns the roots from build.Default.SrcDirs(). Not modules-compatible.
+func SrcDirsRoots() []Root {
+	var roots []Root
+	roots = append(roots, Root{filepath.Join(build.Default.GOROOT, "src"), RootGOROOT})
+	for _, p := range filepath.SplitList(build.Default.GOPATH) {
+		roots = append(roots, Root{filepath.Join(p, "src"), RootGOPATH})
+	}
+	return roots
+}
+
+// Walk walks Go source directories ($GOROOT, $GOPATH, etc) to find packages.
+// For each package found, add will be called (concurrently) with the absolute
+// paths of the containing source directory and the package directory.
+// add will be called concurrently.
+func Walk(roots []Root, add func(root Root, dir string), opts Options) {
+	for _, root := range roots {
+		walkDir(root, add, opts)
+	}
+}
+
+func walkDir(root Root, add func(Root, string), opts Options) {
+	if _, err := os.Stat(root.Path); os.IsNotExist(err) {
+		if opts.Debug {
+			log.Printf("skipping nonexistant directory: %v", root.Path)
+		}
+		return
+	}
+	if opts.Debug {
+		log.Printf("scanning %s", root.Path)
+	}
+	w := &walker{
+		root: root,
+		add:  add,
+		opts: opts,
+	}
+	w.init()
+	if err := fastwalk.Walk(root.Path, w.walk); err != nil {
+		log.Printf("gopathwalk: scanning directory %v: %v", root.Path, err)
+	}
+
+	if opts.Debug {
+		log.Printf("scanned %s", root.Path)
+	}
+}
+
+// walker is the callback for fastwalk.Walk.
+type walker struct {
+	root Root               // The source directory to scan.
+	add  func(Root, string) // The callback that will be invoked for every possible Go package dir.
+	opts Options            // Options passed to Walk by the user.
+
+	ignoredDirs []os.FileInfo // The ignored directories, loaded from .goimportsignore files.
+}
+
+// init initializes the walker based on its Options.
+func (w *walker) init() {
+	var ignoredPaths []string
+	if w.root.Type == RootModuleCache {
+		ignoredPaths = []string{"cache"}
+	}
+	if !w.opts.ModulesEnabled && w.root.Type == RootGOPATH {
+		ignoredPaths = w.getIgnoredDirs(w.root.Path)
+		ignoredPaths = append(ignoredPaths, "v", "mod")
+	}
+
+	for _, p := range ignoredPaths {
+		full := filepath.Join(w.root.Path, p)
+		if fi, err := os.Stat(full); err == nil {
+			w.ignoredDirs = append(w.ignoredDirs, fi)
+			if w.opts.Debug {
+				log.Printf("Directory added to ignore list: %s", full)
+			}
+		} else if w.opts.Debug {
+			log.Printf("Error statting ignored directory: %v", err)
+		}
+	}
+}
+
+// getIgnoredDirs reads an optional config file at <path>/.goimportsignore
+// of relative directories to ignore when scanning for go files.
+// The provided path is one of the $GOPATH entries with "src" appended.
+func (w *walker) getIgnoredDirs(path string) []string {
+	file := filepath.Join(path, ".goimportsignore")
+	slurp, err := ioutil.ReadFile(file)
+	if w.opts.Debug {
+		if err != nil {
+			log.Print(err)
+		} else {
+			log.Printf("Read %s", file)
+		}
+	}
+	if err != nil {
+		return nil
+	}
+
+	var ignoredDirs []string
+	bs := bufio.NewScanner(bytes.NewReader(slurp))
+	for bs.Scan() {
+		line := strings.TrimSpace(bs.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		ignoredDirs = append(ignoredDirs, line)
+	}
+	return ignoredDirs
+}
+
+func (w *walker) shouldSkipDir(fi os.FileInfo) bool {
+	for _, ignoredDir := range w.ignoredDirs {
+		if os.SameFile(fi, ignoredDir) {
+			return true
+		}
+	}
+	return false
+}
+
+func (w *walker) walk(path string, typ os.FileMode) error {
+	dir := filepath.Dir(path)
+	if typ.IsRegular() {
+		if dir == w.root.Path {
+			// Doesn't make sense to have regular files
+			// directly in your $GOPATH/src or $GOROOT/src.
+			return fastwalk.SkipFiles
+		}
+		if !strings.HasSuffix(path, ".go") {
+			return nil
+		}
+
+		w.add(w.root, dir)
+		return fastwalk.SkipFiles
+	}
+	if typ == os.ModeDir {
+		base := filepath.Base(path)
+		if base == "" || base[0] == '.' || base[0] == '_' ||
+			base == "testdata" || (!w.opts.ModulesEnabled && base == "node_modules") {
+			return filepath.SkipDir
+		}
+		fi, err := os.Lstat(path)
+		if err == nil && w.shouldSkipDir(fi) {
+			return filepath.SkipDir
+		}
+		return nil
+	}
+	if typ == os.ModeSymlink {
+		base := filepath.Base(path)
+		if strings.HasPrefix(base, ".#") {
+			// Emacs noise.
+			return nil
+		}
+		fi, err := os.Lstat(path)
+		if err != nil {
+			// Just ignore it.
+			return nil
+		}
+		if w.shouldTraverse(dir, fi) {
+			return fastwalk.TraverseLink
+		}
+	}
+	return nil
+}
+
+// shouldTraverse reports whether the symlink fi, found in dir,
+// should be followed.  It makes sure symlinks were never visited
+// before to avoid symlink loops.
+func (w *walker) shouldTraverse(dir string, fi os.FileInfo) bool {
+	path := filepath.Join(dir, fi.Name())
+	target, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		return false
+	}
+	ts, err := os.Stat(target)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return false
+	}
+	if !ts.IsDir() {
+		return false
+	}
+	if w.shouldSkipDir(ts) {
+		return false
+	}
+	// Check for symlink loops by statting each directory component
+	// and seeing if any are the same file as ts.
+	for {
+		parent := filepath.Dir(path)
+		if parent == path {
+			// Made it to the root without seeing a cycle.
+			// Use this symlink.
+			return true
+		}
+		parentInfo, err := os.Stat(parent)
+		if err != nil {
+			return false
+		}
+		if os.SameFile(ts, parentInfo) {
+			// Cycle. Don't traverse.
+			return false
+		}
+		path = parent
+	}
+
+}