Add labels to tasks (#45)

vendor/honnef.co/go/tools/functions/concrete.go

@@ -0,0 +1,56 @@
+package functions
+
+import (
+	"go/token"
+	"go/types"
+
+	"honnef.co/go/tools/ssa"
+)
+
+func concreteReturnTypes(fn *ssa.Function) []*types.Tuple {
+	res := fn.Signature.Results()
+	if res == nil {
+		return nil
+	}
+	ifaces := make([]bool, res.Len())
+	any := false
+	for i := 0; i < res.Len(); i++ {
+		_, ifaces[i] = res.At(i).Type().Underlying().(*types.Interface)
+		any = any || ifaces[i]
+	}
+	if !any {
+		return []*types.Tuple{res}
+	}
+	var out []*types.Tuple
+	for _, block := range fn.Blocks {
+		if len(block.Instrs) == 0 {
+			continue
+		}
+		ret, ok := block.Instrs[len(block.Instrs)-1].(*ssa.Return)
+		if !ok {
+			continue
+		}
+		vars := make([]*types.Var, res.Len())
+		for i, v := range ret.Results {
+			var typ types.Type
+			if !ifaces[i] {
+				typ = res.At(i).Type()
+			} else if mi, ok := v.(*ssa.MakeInterface); ok {
+				// TODO(dh): if mi.X is a function call that returns
+				// an interface, call concreteReturnTypes on that
+				// function (or, really, go through Descriptions,
+				// avoid infinite recursion etc, just like nil error
+				// detection)
+
+				// TODO(dh): support Phi nodes
+				typ = mi.X.Type()
+			} else {
+				typ = res.At(i).Type()
+			}
+			vars[i] = types.NewParam(token.NoPos, nil, "", typ)
+		}
+		out = append(out, types.NewTuple(vars...))
+	}
+	// TODO(dh): deduplicate out
+	return out
+}

vendor/honnef.co/go/tools/functions/functions.go

@@ -0,0 +1,150 @@
+package functions
+
+import (
+	"go/types"
+	"sync"
+
+	"honnef.co/go/tools/callgraph"
+	"honnef.co/go/tools/callgraph/static"
+	"honnef.co/go/tools/ssa"
+	"honnef.co/go/tools/staticcheck/vrp"
+)
+
+var stdlibDescs = map[string]Description{
+	"errors.New": {Pure: true},
+
+	"fmt.Errorf":  {Pure: true},
+	"fmt.Sprintf": {Pure: true},
+	"fmt.Sprint":  {Pure: true},
+
+	"sort.Reverse": {Pure: true},
+
+	"strings.Map":            {Pure: true},
+	"strings.Repeat":         {Pure: true},
+	"strings.Replace":        {Pure: true},
+	"strings.Title":          {Pure: true},
+	"strings.ToLower":        {Pure: true},
+	"strings.ToLowerSpecial": {Pure: true},
+	"strings.ToTitle":        {Pure: true},
+	"strings.ToTitleSpecial": {Pure: true},
+	"strings.ToUpper":        {Pure: true},
+	"strings.ToUpperSpecial": {Pure: true},
+	"strings.Trim":           {Pure: true},
+	"strings.TrimFunc":       {Pure: true},
+	"strings.TrimLeft":       {Pure: true},
+	"strings.TrimLeftFunc":   {Pure: true},
+	"strings.TrimPrefix":     {Pure: true},
+	"strings.TrimRight":      {Pure: true},
+	"strings.TrimRightFunc":  {Pure: true},
+	"strings.TrimSpace":      {Pure: true},
+	"strings.TrimSuffix":     {Pure: true},
+
+	"(*net/http.Request).WithContext": {Pure: true},
+
+	"math/rand.Read":         {NilError: true},
+	"(*math/rand.Rand).Read": {NilError: true},
+}
+
+type Description struct {
+	// The function is known to be pure
+	Pure bool
+	// The function is known to be a stub
+	Stub bool
+	// The function is known to never return (panics notwithstanding)
+	Infinite bool
+	// Variable ranges
+	Ranges vrp.Ranges
+	Loops  []Loop
+	// Function returns an error as its last argument, but it is
+	// always nil
+	NilError            bool
+	ConcreteReturnTypes []*types.Tuple
+}
+
+type descriptionEntry struct {
+	ready  chan struct{}
+	result Description
+}
+
+type Descriptions struct {
+	CallGraph *callgraph.Graph
+	mu        sync.Mutex
+	cache     map[*ssa.Function]*descriptionEntry
+}
+
+func NewDescriptions(prog *ssa.Program) *Descriptions {
+	return &Descriptions{
+		CallGraph: static.CallGraph(prog),
+		cache:     map[*ssa.Function]*descriptionEntry{},
+	}
+}
+
+func (d *Descriptions) Get(fn *ssa.Function) Description {
+	d.mu.Lock()
+	fd := d.cache[fn]
+	if fd == nil {
+		fd = &descriptionEntry{
+			ready: make(chan struct{}),
+		}
+		d.cache[fn] = fd
+		d.mu.Unlock()
+
+		{
+			fd.result = stdlibDescs[fn.RelString(nil)]
+			fd.result.Pure = fd.result.Pure || d.IsPure(fn)
+			fd.result.Stub = fd.result.Stub || d.IsStub(fn)
+			fd.result.Infinite = fd.result.Infinite || !terminates(fn)
+			fd.result.Ranges = vrp.BuildGraph(fn).Solve()
+			fd.result.Loops = findLoops(fn)
+			fd.result.NilError = fd.result.NilError || IsNilError(fn)
+			fd.result.ConcreteReturnTypes = concreteReturnTypes(fn)
+		}
+
+		close(fd.ready)
+	} else {
+		d.mu.Unlock()
+		<-fd.ready
+	}
+	return fd.result
+}
+
+func IsNilError(fn *ssa.Function) bool {
+	// TODO(dh): This is very simplistic, as we only look for constant
+	// nil returns. A more advanced approach would work transitively.
+	// An even more advanced approach would be context-aware and
+	// determine nil errors based on inputs (e.g. io.WriteString to a
+	// bytes.Buffer will always return nil, but an io.WriteString to
+	// an os.File might not). Similarly, an os.File opened for reading
+	// won't error on Close, but other files will.
+	res := fn.Signature.Results()
+	if res.Len() == 0 {
+		return false
+	}
+	last := res.At(res.Len() - 1)
+	if types.TypeString(last.Type(), nil) != "error" {
+		return false
+	}
+
+	if fn.Blocks == nil {
+		return false
+	}
+	for _, block := range fn.Blocks {
+		if len(block.Instrs) == 0 {
+			continue
+		}
+		ins := block.Instrs[len(block.Instrs)-1]
+		ret, ok := ins.(*ssa.Return)
+		if !ok {
+			continue
+		}
+		v := ret.Results[len(ret.Results)-1]
+		c, ok := v.(*ssa.Const)
+		if !ok {
+			return false
+		}
+		if !c.IsNil() {
+			return false
+		}
+	}
+	return true
+}

vendor/honnef.co/go/tools/functions/loops.go

@@ -0,0 +1,50 @@
+package functions
+
+import "honnef.co/go/tools/ssa"
+
+type Loop map[*ssa.BasicBlock]bool
+
+func findLoops(fn *ssa.Function) []Loop {
+	if fn.Blocks == nil {
+		return nil
+	}
+	tree := fn.DomPreorder()
+	var sets []Loop
+	for _, h := range tree {
+		for _, n := range h.Preds {
+			if !h.Dominates(n) {
+				continue
+			}
+			// n is a back-edge to h
+			// h is the loop header
+			if n == h {
+				sets = append(sets, Loop{n: true})
+				continue
+			}
+			set := Loop{h: true, n: true}
+			for _, b := range allPredsBut(n, h, nil) {
+				set[b] = true
+			}
+			sets = append(sets, set)
+		}
+	}
+	return sets
+}
+
+func allPredsBut(b, but *ssa.BasicBlock, list []*ssa.BasicBlock) []*ssa.BasicBlock {
+outer:
+	for _, pred := range b.Preds {
+		if pred == but {
+			continue
+		}
+		for _, p := range list {
+			// TODO improve big-o complexity of this function
+			if pred == p {
+				continue outer
+			}
+		}
+		list = append(list, pred)
+		list = allPredsBut(pred, but, list)
+	}
+	return list
+}

vendor/honnef.co/go/tools/functions/pure.go

@@ -0,0 +1,123 @@
+package functions
+
+import (
+	"go/token"
+	"go/types"
+
+	"honnef.co/go/tools/callgraph"
+	"honnef.co/go/tools/lint/lintdsl"
+	"honnef.co/go/tools/ssa"
+)
+
+// IsStub reports whether a function is a stub. A function is
+// considered a stub if it has no instructions or exactly one
+// instruction, which must be either returning only constant values or
+// a panic.
+func (d *Descriptions) IsStub(fn *ssa.Function) bool {
+	if len(fn.Blocks) == 0 {
+		return true
+	}
+	if len(fn.Blocks) > 1 {
+		return false
+	}
+	instrs := lintdsl.FilterDebug(fn.Blocks[0].Instrs)
+	if len(instrs) != 1 {
+		return false
+	}
+
+	switch instrs[0].(type) {
+	case *ssa.Return:
+		// Since this is the only instruction, the return value must
+		// be a constant. We consider all constants as stubs, not just
+		// the zero value. This does not, unfortunately, cover zero
+		// initialised structs, as these cause additional
+		// instructions.
+		return true
+	case *ssa.Panic:
+		return true
+	default:
+		return false
+	}
+}
+
+func (d *Descriptions) IsPure(fn *ssa.Function) bool {
+	if fn.Signature.Results().Len() == 0 {
+		// A function with no return values is empty or is doing some
+		// work we cannot see (for example because of build tags);
+		// don't consider it pure.
+		return false
+	}
+
+	for _, param := range fn.Params {
+		if _, ok := param.Type().Underlying().(*types.Basic); !ok {
+			return false
+		}
+	}
+
+	if fn.Blocks == nil {
+		return false
+	}
+	checkCall := func(common *ssa.CallCommon) bool {
+		if common.IsInvoke() {
+			return false
+		}
+		builtin, ok := common.Value.(*ssa.Builtin)
+		if !ok {
+			if common.StaticCallee() != fn {
+				if common.StaticCallee() == nil {
+					return false
+				}
+				// TODO(dh): ideally, IsPure wouldn't be responsible
+				// for avoiding infinite recursion, but
+				// FunctionDescriptions would be.
+				node := d.CallGraph.CreateNode(common.StaticCallee())
+				if callgraph.PathSearch(node, func(other *callgraph.Node) bool {
+					return other.Func == fn
+				}) != nil {
+					return false
+				}
+				if !d.Get(common.StaticCallee()).Pure {
+					return false
+				}
+			}
+		} else {
+			switch builtin.Name() {
+			case "len", "cap", "make", "new":
+			default:
+				return false
+			}
+		}
+		return true
+	}
+	for _, b := range fn.Blocks {
+		for _, ins := range b.Instrs {
+			switch ins := ins.(type) {
+			case *ssa.Call:
+				if !checkCall(ins.Common()) {
+					return false
+				}
+			case *ssa.Defer:
+				if !checkCall(&ins.Call) {
+					return false
+				}
+			case *ssa.Select:
+				return false
+			case *ssa.Send:
+				return false
+			case *ssa.Go:
+				return false
+			case *ssa.Panic:
+				return false
+			case *ssa.Store:
+				return false
+			case *ssa.FieldAddr:
+				return false
+			case *ssa.UnOp:
+				if ins.Op == token.MUL || ins.Op == token.AND {
+					return false
+				}
+			}
+		}
+	}
+	return true
+}

vendor/honnef.co/go/tools/functions/terminates.go

@@ -0,0 +1,24 @@
+package functions
+
+import "honnef.co/go/tools/ssa"
+
+// terminates reports whether fn is supposed to return, that is if it
+// has at least one theoretic path that returns from the function.
+// Explicit panics do not count as terminating.
+func terminates(fn *ssa.Function) bool {
+	if fn.Blocks == nil {
+		// assuming that a function terminates is the conservative
+		// choice
+		return true
+	}
+
+	for _, block := range fn.Blocks {
+		if len(block.Instrs) == 0 {
+			continue
+		}
+		if _, ok := block.Instrs[len(block.Instrs)-1].(*ssa.Return); ok {
+			return true
+		}
+	}
+	return false
+}