cmd/gc: Don't export embedded builtins

Fixes #4124.

R=golang-dev, dave, minux.ma, remyoudompheng, rsc
CC=golang-dev
https://golang.org/cl/6543057

src/cmd/gc/align.c

@@ -607,7 +607,7 @@ typeinit(void)
 			fatal("typeinit: %s already defined", s->name);
 
 		t = typ(etype);
-		t->sym = s;
+		t->sym = s1;
 
 		dowidth(t);
 		types[etype] = t;

src/cmd/gc/dcl.c

@@ -982,7 +982,7 @@ embedded(Sym *s)
 		*utfrune(name, CenterDot) = 0;
 	}
 
-	if(exportname(name) || s->pkg == builtinpkg)  // old behaviour, tests pass, but is it correct?
+	if(exportname(name))
 		n = newname(lookup(name));
 	else
 		n = newname(pkglookup(name, s->pkg));

src/cmd/gc/fmt.c

@@ -1181,7 +1181,7 @@ exprfmt(Fmt *f, Node *n, int prec)
 					t = l->n->left->type->type;
 					if(t->sym == S)
 						t = t->type;
-					fmtprint(f, " %T:%N", t, l->n->right);
+					fmtprint(f, " %hhS:%N", t->sym, l->n->right);
 				} else
 					fmtprint(f, " %hhS:%N", l->n->left->sym, l->n->right);
 

src/cmd/gc/lex.c

@@ -1831,16 +1831,16 @@ lexinit(void)
 		if(etype != Txxx) {
 			if(etype < 0 || etype >= nelem(types))
 				fatal("lexinit: %s bad etype", s->name);
+			s1 = pkglookup(syms[i].name, builtinpkg);
 			t = types[etype];
 			if(t == T) {
 				t = typ(etype);
-				t->sym = s;
+				t->sym = s1;
 
 				if(etype != TANY && etype != TSTRING)
 					dowidth(t);
 				types[etype] = t;
 			}
-			s1 = pkglookup(syms[i].name, builtinpkg);
 			s1->lexical = LNAME;
 			s1->def = typenod(t);
 			continue;

src/cmd/gc/reflect.c

@@ -866,7 +866,10 @@ ok:
 					ot = dgopkgpath(s, ot, t1->sym->pkg);
 			} else {
 				ot = dgostringptr(s, ot, nil);
-				ot = dgostringptr(s, ot, nil);
+				if(t1->type->sym != S && t1->type->sym->pkg == builtinpkg)
+					ot = dgopkgpath(s, ot, localpkg);
+				else
+					ot = dgostringptr(s, ot, nil);
 			}
 			ot = dsymptr(s, ot, dtypesym(t1->type), 0);
 			ot = dgostrlitptr(s, ot, t1->note);

test/fixedbugs/bug460.dir/a.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 a
+
+type Foo struct {
+	int
+}

test/fixedbugs/bug460.dir/b.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 b
+
+import "./a"
+
+var x a.Foo
+
+func main() {
+	x.int = 20 // ERROR "unexported field"
+}
+

test/fixedbugs/bug460.go

+// errorcheckdir
+
+// 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.
+
+// part one of issue 4124. Make sure that the compiler rejects access attempts.
+
+package ignored
+

test/fixedbugs/bug461.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.
+
+// part two of issue 4124. Make sure reflect doesn't mark the field as exported.
+
+package main
+
+import "reflect"
+
+var T struct {
+	int
+}
+
+func main() {
+	v := reflect.ValueOf(&T)
+	v = v.Elem().Field(0)
+	if v.CanSet() {
+		panic("int should be unexported")
+	}
+}