gc: bug fixes.

* better error for lookup of unexported field
  * do not assign "ideal string" type to typed string literal
  * do not confuse methods and fields during interface check

Fixes #410.
Fixes #411.
Fixes #426.

R=ken2
https://golang.org/cl/179069

src/cmd/gc/subr.c

@@ -320,7 +320,7 @@ Sym*
 restrictlookup(char *name, char *pkg)
 {
 	if(!exportname(name) && strcmp(pkg, package) != 0)
-		yyerror("cannot refer to %s.%s", pkg, name);
+		yyerror("cannot refer to unexported name %s.%s", pkg, name);
 	return pkglookup(name, pkg);
 }
 
@@ -2871,6 +2871,10 @@ ifacelookdot(Sym *s, Type *t, int *followptr)
 					break;
 				}
 			}
+			if(m->type->etype != TFUNC || m->type->thistuple == 0) {
+				yyerror("%T.%S is a field, not a method", t, s);
+				return T;
+			}
 			return m;
 		}
 	}

src/cmd/gc/typecheck.c

@@ -18,10 +18,10 @@
 
 static void	implicitstar(Node**);
 static int	onearg(Node*);
-static int	lookdot(Node*, Type*);
+static int	lookdot(Node*, Type*, int);
 static void	typecheckaste(int, Type*, NodeList*, char*);
 static int	exportassignok(Type*, char*);
-static Type*	lookdot1(Sym *s, Type *t, Type *f);
+static Type*	lookdot1(Sym *s, Type *t, Type *f, int);
 static int	nokeys(NodeList*);
 static void	typecheckcomplit(Node**);
 static void	addrescapes(Node*);
@@ -102,7 +102,7 @@ reswitch:
 	 */
 	case OLITERAL:
 		ok |= Erv;
-		if(n->val.ctype == CTSTR)
+		if(n->type == T && n->val.ctype == CTSTR)
 			n->type = idealstring;
 		goto ret;
 
@@ -459,8 +459,11 @@ reswitch:
 			n->op = ODOTPTR;
 			checkwidth(t);
 		}
-		if(!lookdot(n, t)) {
-			yyerror("%#N undefined (type %T has no field %S)", n, t, n->right->sym);
+		if(!lookdot(n, t, 0)) {
+			if(lookdot(n, t, 1))
+				yyerror("%#N undefined (cannot refer to unexported field %S)", n, n->right->sym);
+			else
+				yyerror("%#N undefined (type %T has no field %S)", n, t, n->right->sym);
 			goto error;
 		}
 		switch(n->op) {
@@ -1168,12 +1171,14 @@ onearg(Node *n)
 }
 
 static Type*
-lookdot1(Sym *s, Type *t, Type *f)
+lookdot1(Sym *s, Type *t, Type *f, int dostrcmp)
 {
 	Type *r;
 
 	r = T;
 	for(; f!=T; f=f->down) {
+		if(dostrcmp && strcmp(f->sym->name, s->name) == 0)
+			return f;
 		if(f->sym != s)
 			continue;
 		if(r != T) {
@@ -1186,7 +1191,7 @@ lookdot1(Sym *s, Type *t, Type *f)
 }
 
 static int
-lookdot(Node *n, Type *t)
+lookdot(Node *n, Type *t, int dostrcmp)
 {
 	Type *f1, *f2, *tt, *rcvr;
 	Sym *s;
@@ -1196,11 +1201,11 @@ lookdot(Node *n, Type *t)
 	dowidth(t);
 	f1 = T;
 	if(t->etype == TSTRUCT || t->etype == TINTER)
-		f1 = lookdot1(s, t, t->type);
+		f1 = lookdot1(s, t, t->type, dostrcmp);
 
 	f2 = methtype(n->left->type);
 	if(f2 != T)
-		f2 = lookdot1(s, f2, f2->method);
+		f2 = lookdot1(s, f2, f2->method, dostrcmp);
 
 	if(f1 != T) {
 		if(f2 != T)
@@ -1793,7 +1798,7 @@ typecheckcomplit(Node **np)
 				}
 				l->left = newname(s);
 				l->left->typecheck = 1;
-				f = lookdot1(s, t, t->type);
+				f = lookdot1(s, t, t->type, 0);
 				typecheck(&l->right, Erv);
 				if(f == nil) {
 					yyerror("unknown %T field '%s' in struct literal", t, s->name);

test/fixedbugs/bug229.go

@@ -0,0 +1,20 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2009 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 "testing"
+
+func main() {
+	var t testing.T
+	
+	// make sure error mentions that
+	// ch is unexported, not just "ch not found".
+
+	t.ch = nil	// ERROR "unexported"
+	
+	println(testing.anyLowercaseName("asdf"))	// ERROR "unexported"
+}

test/fixedbugs/bug230.go

@@ -0,0 +1,25 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 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
+
+type S string
+type I int
+type F float
+
+func (S) m() {}
+func (I) m() {}
+func (F) m() {}
+
+func main() {
+	c := make(chan interface { m() }, 10)
+	c <- I(0)
+	c <- F(1)
+	c <- S("hi")
+	<-c
+	<-c
+	<-c
+}

test/fixedbugs/bug231.go

@@ -0,0 +1,22 @@
+// errchk $G -e $D/$F.go
+
+// Copyright 2009 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
+
+type I interface { m() }
+type T struct { m func() }
+type M struct {}
+func (M) m() {}
+
+func main() {
+	var t T
+	var m M
+	var i I
+	
+	i = m
+	i = t	// ERROR "not a method"
+	_ = i
+}