[CI] Add more checks (#43)

vendor/honnef.co/go/tools/internal/sharedcheck/lint.go

@@ -0,0 +1,68 @@
+package sharedcheck
+
+import (
+	"go/ast"
+	"go/types"
+
+	"honnef.co/go/tools/lint"
+	. "honnef.co/go/tools/lint/lintdsl"
+	"honnef.co/go/tools/ssa"
+)
+
+func CheckRangeStringRunes(j *lint.Job) {
+	for _, ssafn := range j.Program.InitialFunctions {
+		fn := func(node ast.Node) bool {
+			rng, ok := node.(*ast.RangeStmt)
+			if !ok || !IsBlank(rng.Key) {
+				return true
+			}
+
+			v, _ := ssafn.ValueForExpr(rng.X)
+
+			// Check that we're converting from string to []rune
+			val, _ := v.(*ssa.Convert)
+			if val == nil {
+				return true
+			}
+			Tsrc, ok := val.X.Type().(*types.Basic)
+			if !ok || Tsrc.Kind() != types.String {
+				return true
+			}
+			Tdst, ok := val.Type().(*types.Slice)
+			if !ok {
+				return true
+			}
+			TdstElem, ok := Tdst.Elem().(*types.Basic)
+			if !ok || TdstElem.Kind() != types.Int32 {
+				return true
+			}
+
+			// Check that the result of the conversion is only used to
+			// range over
+			refs := val.Referrers()
+			if refs == nil {
+				return true
+			}
+
+			// Expect two refs: one for obtaining the length of the slice,
+			// one for accessing the elements
+			if len(FilterDebug(*refs)) != 2 {
+				// TODO(dh): right now, we check that only one place
+				// refers to our slice. This will miss cases such as
+				// ranging over the slice twice. Ideally, we'd ensure that
+				// the slice is only used for ranging over (without
+				// accessing the key), but that is harder to do because in
+				// SSA form, ranging over a slice looks like an ordinary
+				// loop with index increments and slice accesses. We'd
+				// have to look at the associated AST node to check that
+				// it's a range statement.
+				return true
+			}
+
+			j.Errorf(rng, "should range over string, not []rune(string)")
+
+			return true
+		}
+		Inspect(ssafn.Syntax(), fn)
+	}
+}