cmd/gc: disable inlining of method values

They caused internal compiler errors and they're expensive enough that inlining them doesn't make sense.

Fixes #5259.

R=golang-dev, r, iant, remyoudompheng
CC=golang-dev
https://golang.org/cl/8636043

src/cmd/gc/inl.c

@@ -188,6 +188,7 @@ ishairy(Node *n, int *budget)
 		break;
 
 	case OCLOSURE:
+	case OCALLPART:
 	case ORANGE:
 	case OFOR:
 	case OSELECT:

test/fixedbugs/issue5259.dir/bug.go

+// 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.
+
+package bug
+
+type S struct {
+	F func()
+}
+
+type X interface {
+	Bar()
+}
+
+func Foo(x X) *S {
+	return &S{F: x.Bar}
+}

test/fixedbugs/issue5259.dir/main.go

+// 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.
+
+package main
+
+import "./bug"
+
+type foo int
+
+func (f *foo) Bar() {
+}
+
+func main() {
+	bug.Foo(new(foo))
+}

test/fixedbugs/issue5259.go

+// compiledir
+
+// 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.
+
+// Issue 5259: Inlining of method value causes internal compiler error
+
+package ignored