cmd/gc: do not confuse unexported methods of same name

Fixes #3146.

R=ken2
CC=golang-dev
https://golang.org/cl/5756074

src/cmd/gc/dcl.c

@@ -1195,10 +1195,17 @@ methodsym(Sym *nsym, Type *t0, int iface)
 		if(t0->width < types[tptr]->width)
 			suffix = "·i";
 	}
-	if(t0->sym == S && isptr[t0->etype])
-		p = smprint("(%-hT).%s%s", t0, nsym->name, suffix);
-	else
-		p = smprint("%-hT.%s%s", t0, nsym->name, suffix);
+	if(nsym->pkg != s->pkg && !exportname(nsym->name)) {
+		if(t0->sym == S && isptr[t0->etype])
+			p = smprint("(%-hT).%s.%s%s", t0, nsym->pkg->prefix, nsym->name, suffix);
+		else
+			p = smprint("%-hT.%s.%s%s", t0, nsym->pkg->prefix, nsym->name, suffix);
+	} else {
+		if(t0->sym == S && isptr[t0->etype])
+			p = smprint("(%-hT).%s%s", t0, nsym->name, suffix);
+		else
+			p = smprint("%-hT.%s%s", t0, nsym->name, suffix);
+	}
 	s = pkglookup(p, s->pkg);
 	free(p);
 	return s;

test/bugs/424.go

-// $G $D/$F.dir/lib.go && $G $D/$F.dir/main.go && $L main.$A && $A.out
-
-// 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.
-
-// Test case for embedded method invocation.
-
-ignored

test/bugs/424.dir/main.go → test/fixedbugs/bug424.go

+// run
+
 // 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.
@@ -9,7 +11,9 @@
 
 package main
 
-import "./lib"
+import "./bug424.dir"
+import "reflect"
+import "fmt"
 
 type localI interface {
 	m() string
@@ -53,9 +57,19 @@ func main() {
 		println("BUG: myT2:", i.m(), "called")
 	}
 
+	t3 := new(myT3)
+	if t3.m() != "main.localT.m" {
+		println("BUG: t3:", t3.m(), "called")
+	}
+	
 	i = new(myT3)
 	if i.m() != "main.localT.m" {
+		t := reflect.TypeOf(i)
+		n := t.NumMethod()
+		for j := 0; j < n; j++ {
+			m := t.Method(j)
+			fmt.Printf("#%d: %s.%s %s\n", j, m.PkgPath, m.Name, m.Type)
+		}
 		println("BUG: myT3:", i.m(), "called")
 	}
-
 }