undo CL 66510044 / 6c0339d94123

Broke other things - see issue 7522.

Fixes #7522.
Reopens issue 7363.

««« original CL description
cmd/gc: make embedded, unexported fields read-only.

Fixes #7363.

LGTM=gri
R=gri, rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/66510044
»»»

LGTM=r, mpvl
R=golang-codereviews, r
CC=golang-codereviews, iant, mpvl
https://golang.org/cl/85580046

src/cmd/gc/reflect.c

@@ -1138,8 +1138,7 @@ ok:
 					ot = dgopkgpath(s, ot, t1->sym->pkg);
 			} else {
 				ot = dgostringptr(s, ot, nil);
-				if(t1->type->sym != S &&
-				   (t1->type->sym->pkg == builtinpkg || !exportname(t1->type->sym->name)))
+				if(t1->type->sym != S && t1->type->sym->pkg == builtinpkg)
 					ot = dgopkgpath(s, ot, localpkg);
 				else
 					ot = dgostringptr(s, ot, nil);

test/fixedbugs/issue7363.go

-// run
-
-// Copyright 2014 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 7363: CanSet must return false for unexported embedded struct fields.
-
-package main
-
-import "reflect"
-
-type a struct {
-}
-
-type B struct {
-	a
-}
-
-func main() {
-	b := &B{}
-	v := reflect.ValueOf(b).Elem().Field(0)
-	if v.CanSet() {
-		panic("B.a is an unexported embedded struct field")
-	}
-}