cmd/gc: fix inlining bug for composite literals in if statements.

Fixes #4230.

R=golang-dev, rsc
CC=golang-dev, remy
https://golang.org/cl/6640056

src/cmd/gc/fmt.c

@@ -1161,7 +1161,7 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OCOMPLIT:
 		if(fmtmode == FErr)
 			return fmtstrcpy(f, "composite literal");
-		return fmtprint(f, "%N{ %,H }", n->right, n->list);
+		return fmtprint(f, "(%N{ %,H })", n->right, n->list);
 
 	case OPTRLIT:
 		if(fmtmode == FExp && n->left->implicit)
@@ -1172,8 +1172,8 @@ exprfmt(Fmt *f, Node *n, int prec)
 		if(fmtmode == FExp) {   // requires special handling of field names
 			if(n->implicit)
 				fmtstrcpy(f, "{");
-			else 
-				fmtprint(f, "%T{", n->type);
+			else
+				fmtprint(f, "(%T{", n->type);
 			for(l=n->list; l; l=l->next) {
 				// another special case: if n->left is an embedded field of builtin type,
 				// it needs to be non-qualified.  Can't figure that out in %S, so do it here
@@ -1190,6 +1190,8 @@ exprfmt(Fmt *f, Node *n, int prec)
 				else
 					fmtstrcpy(f, " ");
 			}
+			if(!n->implicit)
+				return fmtstrcpy(f, "})");
 			return fmtstrcpy(f, "}");
 		}
 		// fallthrough
@@ -1200,7 +1202,7 @@ exprfmt(Fmt *f, Node *n, int prec)
 			return fmtprint(f, "%T literal", n->type);
 		if(fmtmode == FExp && n->implicit)
 			return fmtprint(f, "{ %,H }", n->list);
-		return fmtprint(f, "%T{ %,H }", n->type, n->list);
+		return fmtprint(f, "(%T{ %,H })", n->type, n->list);
 
 	case OKEY:
 		if(n->left && n->right)

test/fixedbugs/bug465.dir/a.go

+// Copyright 2012 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 a
+
+type T struct{ A, B int }
+
+type A []int
+
+type M map[int]int
+
+func F1() int {
+	if (T{1, 2}) == (T{3, 4}) {
+		return 1
+	}
+	return 0
+}
+
+func F2() int {
+	if (M{1: 2}) == nil {
+		return 1
+	}
+	return 0
+}
+
+func F3() int {
+	if nil == (A{}) {
+		return 1
+	}
+	return 0
+}
+
+func F4() int {
+	if a := (A{}); a == nil {
+		return 1
+	}
+	return 0
+}
+
+func F5() int {
+	for k, v := range (M{1: 2}) {
+		return v - k
+	}
+	return 0
+}
+
+func F6() int {
+	switch a := (T{1, 1}); a == (T{1, 2}) {
+	default:
+		return 1
+	}
+	return 0
+}
+
+func F7() int {
+	for m := (M{}); len(m) < (T{1, 2}).A; m[1] = (A{1})[0] {
+		return 1
+	}
+	return 0
+}

test/fixedbugs/bug465.dir/b.go

+// Copyright 2012 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 main
+
+import "./a"
+
+func main() {
+	for _, f := range []func() int{
+		a.F1, a.F2, a.F3, a.F4,
+		a.F5, a.F6, a.F7} {
+		if f() > 1 {
+			panic("f() > 1")
+		}
+	}
+}

test/fixedbugs/bug465.go

+// rundir
+
+// Copyright 2012 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.
+
+// Issue 4230: inlining bug for composite literal in
+// if, for, switch statements.
+
+package ignored