cmd/gc: another special (%hhS) case for method names.

Fixes #2877

R=rsc
CC=golang-dev
https://golang.org/cl/5637047

src/cmd/gc/fmt.c

@@ -1097,6 +1097,16 @@ exprfmt(Fmt *f, Node *n, int prec)
 		return fmtprint(f, "%V", &n->val);
 
 	case ONAME:
+		// Special case: explicit name of func (*T) method(...) is turned into pkg.(*T).method,
+		// but for export, this should be rendered as (*pkg.T).meth.
+		// These nodes have the special property that they are names with a left OTYPE and a right ONAME.
+		if(fmtmode == FExp && n->left && n->left->op == OTYPE && n->right && n->right->op == ONAME) {
+			if(isptr[n->left->type->etype])
+				return fmtprint(f, "(%T).%hhS", n->left->type, n->right->sym);
+			else
+				return fmtprint(f, "%T.%hhS", n->left->type, n->right->sym);
+		}
+		//fallthrough
 	case OPACK:
 	case ONONAME:
 		return fmtprint(f, "%S", n->sym);

test/fixedbugs/bug407.dir/one.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 one
+
+// Issue 2877
+type T struct {
+	f func(t *T, arg int)
+	g func(t T, arg int)
+}
+
+func (t *T) foo(arg int) {}
+func (t T) goo(arg int) {}
+
+func (t *T) F() { t.f = (*T).foo }
+func (t *T) G() { t.g = T.goo }
+
+
+

test/fixedbugs/bug407.dir/two.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.
+
+// Use the functions in one.go so that the inlined
+// forms get type-checked.
+
+package two
+
+import "./one"
+
+func use() {
+	var r one.T
+	r.F()
+}

test/fixedbugs/bug407.go

+// $G $D/$F.dir/one.go && $G $D/$F.dir/two.go
+
+// Copyright 2011 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 ignored