1 files changed, 186 insertions, 0 deletions
diff --git a/libgo/go/cmd/vet/bool.go b/libgo/go/cmd/vet/bool.go
new file mode 100644
index 0000000..07c2a93
--- /dev/null
+++ b/libgo/go/cmd/vet/bool.go
@@ -0,0 +1,186 @@
+// 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.
+
+// This file contains boolean condition tests.
+
+package main
+
+import (
+	"go/ast"
+	"go/token"
+)
+
+func init() {
+	register("bool",
+		"check for mistakes involving boolean operators",
+		checkBool,
+		binaryExpr)
+}
+
+func checkBool(f *File, n ast.Node) {
+	e := n.(*ast.BinaryExpr)
+
+	var op boolOp
+	switch e.Op {
+	case token.LOR:
+		op = or
+	case token.LAND:
+		op = and
+	default:
+		return
+	}
+
+	comm := op.commutativeSets(e)
+	for _, exprs := range comm {
+		op.checkRedundant(f, exprs)
+		op.checkSuspect(f, exprs)
+	}
+}
+
+type boolOp struct {
+	name  string
+	tok   token.Token // token corresponding to this operator
+	badEq token.Token // token corresponding to the equality test that should not be used with this operator
+}
+
+var (
+	or  = boolOp{"or", token.LOR, token.NEQ}
+	and = boolOp{"and", token.LAND, token.EQL}
+)
+
+// commutativeSets returns all side effect free sets of
+// expressions in e that are connected by op.
+// For example, given 'a || b || f() || c || d' with the or op,
+// commutativeSets returns {{b, a}, {d, c}}.
+func (op boolOp) commutativeSets(e *ast.BinaryExpr) [][]ast.Expr {
+	exprs := op.split(e)
+
+	// Partition the slice of expressions into commutative sets.
+	i := 0
+	var sets [][]ast.Expr
+	for j := 0; j <= len(exprs); j++ {
+		if j == len(exprs) || hasSideEffects(exprs[j]) {
+			if i < j {
+				sets = append(sets, exprs[i:j])
+			}
+			i = j + 1
+		}
+	}
+
+	return sets
+}
+
+// checkRedundant checks for expressions of the form
+//   e && e
+//   e || e
+// Exprs must contain only side effect free expressions.
+func (op boolOp) checkRedundant(f *File, exprs []ast.Expr) {
+	seen := make(map[string]bool)
+	for _, e := range exprs {
+		efmt := f.gofmt(e)
+		if seen[efmt] {
+			f.Badf(e.Pos(), "redundant %s: %s %s %s", op.name, efmt, op.tok, efmt)
+		} else {
+			seen[efmt] = true
+		}
+	}
+}
+
+// checkSuspect checks for expressions of the form
+//   x != c1 || x != c2
+//   x == c1 && x == c2
+// where c1 and c2 are constant expressions.
+// If c1 and c2 are the same then it's redundant;
+// if c1 and c2 are different then it's always true or always false.
+// Exprs must contain only side effect free expressions.
+func (op boolOp) checkSuspect(f *File, exprs []ast.Expr) {
+	// seen maps from expressions 'x' to equality expressions 'x != c'.
+	seen := make(map[string]string)
+
+	for _, e := range exprs {
+		bin, ok := e.(*ast.BinaryExpr)
+		if !ok || bin.Op != op.badEq {
+			continue
+		}
+
+		// In order to avoid false positives, restrict to cases
+		// in which one of the operands is constant. We're then
+		// interested in the other operand.
+		// In the rare case in which both operands are constant
+		// (e.g. runtime.GOOS and "windows"), we'll only catch
+		// mistakes if the LHS is repeated, which is how most
+		// code is written.
+		var x ast.Expr
+		switch {
+		case f.pkg.types[bin.Y].Value != nil:
+			x = bin.X
+		case f.pkg.types[bin.X].Value != nil:
+			x = bin.Y
+		default:
+			continue
+		}
+
+		// e is of the form 'x != c' or 'x == c'.
+		xfmt := f.gofmt(x)
+		efmt := f.gofmt(e)
+		if prev, found := seen[xfmt]; found {
+			// checkRedundant handles the case in which efmt == prev.
+			if efmt != prev {
+				f.Badf(e.Pos(), "suspect %s: %s %s %s", op.name, efmt, op.tok, prev)
+			}
+		} else {
+			seen[xfmt] = efmt
+		}
+	}
+}
+
+// hasSideEffects reports whether evaluation of e has side effects.
+func hasSideEffects(e ast.Expr) bool {
+	safe := true
+	ast.Inspect(e, func(node ast.Node) bool {
+		switch n := node.(type) {
+		// Using CallExpr here will catch conversions
+		// as well as function and method invocations.
+		// We'll live with the false negatives for now.
+		case *ast.CallExpr:
+			safe = false
+			return false
+		case *ast.UnaryExpr:
+			if n.Op == token.ARROW {
+				safe = false
+				return false
+			}
+		}
+		return true
+	})
+	return !safe
+}
+
+// split returns a slice of all subexpressions in e that are connected by op.
+// For example, given 'a || (b || c) || d' with the or op,
+// split returns []{d, c, b, a}.
+func (op boolOp) split(e ast.Expr) (exprs []ast.Expr) {
+	for {
+		e = unparen(e)
+		if b, ok := e.(*ast.BinaryExpr); ok && b.Op == op.tok {
+			exprs = append(exprs, op.split(b.Y)...)
+			e = b.X
+		} else {
+			exprs = append(exprs, e)
+			break
+		}
+	}
+	return
+}
+
+// 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
+	}
+}