cmd/gc: fix escape analysis of method values

R=ken2
CC=golang-dev
https://golang.org/cl/7518050

src/cmd/gc/closure.c

@@ -270,8 +270,9 @@ typecheckpartialcall(Node *fn, Node *sym)
 
 	// Create top-level function.
 	fn->nname = makepartialcall(fn, fn->type, sym);
+	fn->right = sym;
 	fn->op = OCALLPART;
-	fn->type = fn->right->type;
+	fn->type = fn->nname->type;
 }
 
 static Node*

src/cmd/gc/esc.c

@@ -597,6 +597,14 @@ esc(EscState *e, Node *n)
 		escassign(e, &e->theSink, n->left);
 		break;
 	
+	case OCALLPART:
+		n->esc = EscNone; // until proven otherwise
+		e->noesc = list(e->noesc, n);
+		n->escloopdepth = e->loopdepth;
+		// Contents make it to memory, lose track.
+		escassign(e, &e->theSink, n->left);
+		break;
+
 	case OMAPLIT:
 		n->esc = EscNone;  // until proven otherwise
 		e->noesc = list(e->noesc, n);
@@ -667,6 +675,7 @@ escassign(EscState *e, Node *dst, Node *src)
 	case OCONVNOP:
 	case OMAPLIT:
 	case OSTRUCTLIT:
+	case OCALLPART:
 		break;
 
 	case ONAME:
@@ -713,6 +722,7 @@ escassign(EscState *e, Node *dst, Node *src)
 	case OMAKESLICE:
 	case ONEW:
 	case OCLOSURE:
+	case OCALLPART:
 		escflows(e, dst, src);
 		break;
 
@@ -1073,6 +1083,7 @@ escwalk(EscState *e, int level, Node *dst, Node *src)
 	case OMAPLIT:
 	case ONEW:
 	case OCLOSURE:
+	case OCALLPART:
 		if(leaks) {
 			src->esc = EscHeap;
 			if(debug['m'])

src/cmd/gc/fmt.c

@@ -1022,6 +1022,7 @@ static int opprec[] = {
 	[ODOTTYPE] = 8,
 	[ODOT] = 8,
 	[OXDOT] = 8,
+	[OCALLPART] = 8,
 
 	[OPLUS] = 7,
 	[ONOT] = 7,
@@ -1269,9 +1270,10 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case ODOTPTR:
 	case ODOTINTER:
 	case ODOTMETH:
+	case OCALLPART:
 		exprfmt(f, n->left, nprec);
 		if(n->right == N || n->right->sym == S)
-			fmtstrcpy(f, ".<nil>");
+			return fmtstrcpy(f, ".<nil>");
 		return fmtprint(f, ".%hhS", n->right->sym);
 
 	case ODOTTYPE:

test/escape2.go

@@ -1303,3 +1303,25 @@ func G() {
 	var buf4 [10]byte // ERROR "moved to heap: buf4"
 	F4(buf4[:]) // ERROR "buf4 escapes to heap"
 }
+
+type Tm struct {
+	x int
+}
+
+func (t *Tm) M() { // ERROR "t does not escape"
+}
+
+func foo141() {
+	var f func()
+	
+	t := new(Tm) // ERROR "escapes to heap"
+	f = t.M // ERROR "t.M does not escape"
+	_ = f
+}
+
+var gf func()
+
+func foo142() {
+	t := new(Tm) // ERROR "escapes to heap"
+	gf = t.M // ERROR "t.M escapes to heap"
+}

test/fixedbugs/bug474.go

+// run
+
+// 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.
+
+// Bug in method values: escape analysis was off.
+
+package main
+
+import "sync"
+
+var called = false
+
+type T struct {
+	once sync.Once
+}
+
+func (t *T) M() {
+	called = true
+}
+
+func main() {
+	var t T
+	t.once.Do(t.M)
+	if !called {
+		panic("not called")
+	}
+}