gc: fix handling of types inside function bodies

Fixes #849.
Fixes #920.

R=ken2
CC=golang-dev
https://golang.org/cl/1841042

test/fixedbugs/bug286.go

@@ -0,0 +1,94 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug286 failed
+
+// Copyright 2010 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 issue 849.
+
+package main
+
+type I interface {
+	f()
+}
+
+
+var callee string
+var error bool
+
+type T int
+
+func (t *T) f() { callee = "f" }
+func (i *T) g() { callee = "g" }
+
+
+// test1 and test2 are the same except that in the interface J
+// the entries are swapped. test2 and test3 are the same except
+// that in test3 the interface J is declared outside the function.
+//
+// Error: test2 calls g instead of f
+
+func test1(x I) {
+	type J interface {
+		I
+		g()
+	}
+	x.(J).f()
+	if callee != "f" {
+		println("test1 called", callee)
+		error = true
+	}
+}
+
+
+func test2(x I) {
+	type J interface {
+		g()
+		I
+	}
+	x.(J).f()
+	if callee != "f" {
+		println("test2 called", callee)
+		error = true
+	}
+}
+
+
+type J interface {
+	g()
+	I
+}
+
+func test3(x I) {
+	x.(J).f()
+	if callee != "f" {
+		println("test3 called", callee)
+		error = true
+	}
+}
+
+func main() {
+	x := new(T)
+	test1(x)
+	test2(x)
+	test3(x)
+	if error {
+		panic("wrong method called")
+	}
+}
+
+/*
+6g bug286.go && 6l bug286.6 && 6.out
+test2 called g
+panic: wrong method called
+
+panic PC=0x24e040
+runtime.panic+0x7c /home/gri/go1/src/pkg/runtime/proc.c:1012
+	runtime.panic(0x0, 0x24e0a0)
+main.main+0xef /home/gri/go1/test/bugs/bug286.go:76
+	main.main()
+mainstart+0xf /home/gri/go1/src/pkg/runtime/amd64/asm.s:60
+	mainstart()
+goexit /home/gri/go1/src/pkg/runtime/proc.c:145
+	goexit()
+*/

test/fixedbugs/bug290.go

@@ -0,0 +1,15 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2010 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.
+
+// http://code.google.com/p/go/issues/detail?id=920
+
+package main
+
+type X struct { x []X }
+
+func main() {
+	type Y struct { x []Y }	// used to get invalid recursive type
+}