gc: various bugs

Fixes #1016.
Fixes #1152.
Fixes #1153.

R=ken2
CC=golang-dev
https://golang.org/cl/2344042

src/cmd/gc/go.h

@@ -403,7 +403,6 @@ enum
 	ORETURN,
 	OSELECT,
 	OSWITCH,
-	OTYPECASE,
 	OTYPESW,	// l = r.(type)
 
 	// types

src/cmd/gc/go.y

@@ -673,11 +673,13 @@ select_stmt:
 	LSELECT
 	{
 		markdcl();
+		typesw = nod(OXXX, typesw, N);
 	}
 	switch_body
 	{
 		$$ = nod(OSELECT, N, N);
 		$$->list = $3;
+		typesw = typesw->left;
 		popdcl();
 	}
 

src/cmd/gc/print.c

@@ -106,6 +106,11 @@ exprfmt(Fmt *f, Node *n, int prec)
 	case OOROR:
 		nprec = 1;
 		break;
+	
+	case OTYPE:
+		if(n->sym != S)
+			nprec = 7;
+		break;
 	}
 
 	if(prec > nprec)

src/cmd/gc/typecheck.c

@@ -1186,11 +1186,6 @@ reswitch:
 		typecheckrange(n);
 		goto ret;
 
-	case OTYPECASE:
-		ok |= Etop | Erv;
-		typecheck(&n->left, Erv);
-		goto ret;
-
 	case OTYPESW:
 		yyerror("use of .(type) outside type switch");
 		goto error;
@@ -1415,6 +1410,8 @@ looktypedot(Node *n, Type *t, int dostrcmp)
 
 	expandmeth(f2->sym, f2);
 	f2 = lookdot1(s, f2, f2->xmethod, dostrcmp);
+	if(f2 == T)
+		return 0;
 
 	// disallow T.m if m requires *T receiver
 	if(isptr[getthisx(f2->type)->type->type->etype]
@@ -1531,13 +1528,16 @@ typecheckaste(int op, int isddd, Type *tstruct, NodeList *nl, char *desc)
 		tn = n->type->type;
 		for(tl=tstruct->type; tl; tl=tl->down) {
 			if(tl->isddd) {
-				for(; tn; tn=tn->down)
+				for(; tn; tn=tn->down) {
+					exportassignok(tn->type, desc);
 					if(assignop(tn->type, tl->type->type, &why) == 0)
 						yyerror("cannot use %T as type %T in %s%s", tn->type, tl->type->type, desc, why);
+				}
 				goto out;
 			}
 			if(tn == T)
 				goto notenough;
+			exportassignok(tn->type, desc);
 			if(assignop(tn->type, tl->type, &why) == 0)
 				yyerror("cannot use %T as type %T in %s%s", tn->type, tl->type, desc, why);
 			tn = tn->down;
@@ -1560,15 +1560,17 @@ typecheckaste(int op, int isddd, Type *tstruct, NodeList *nl, char *desc)
 					goto notenough;
 				if(nl->next != nil)
 					goto toomany;
-				if(assignop(nl->n->type, t, &why) == 0)
-					yyerror("ddd cannot use %+N as type %T in %s%s", nl->n, t, desc, why);
+				n = nl->n;
+				setlineno(n);
+				if(n->type != T)
+					nl->n = assignconv(n, t, desc);
 				goto out;
 			}
 			for(; nl; nl=nl->next) {
+				n = nl->n;
 				setlineno(nl->n);
-				defaultlit(&nl->n, t->type);
-				if(assignop(nl->n->type, t->type, &why) == 0)
-					yyerror("cannot use %+N as type %T in %s%s", nl->n, t->type, desc, why);
+				if(n->type != T)
+					nl->n = assignconv(n, t->type, desc);
 			}
 			goto out;
 		}

test/fixedbugs/bug309.go

+// $G $D/$F.go
+
+// 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.
+
+// issue 1016
+
+package main
+
+func foo(t interface{}, c chan int) {
+	switch v := t.(type) {
+	case int:
+		select {
+		case <-c:
+			// bug was: internal compiler error: var without type, init: v
+		}
+	}
+}

test/fixedbugs/bug310.go

+// errchk $G $D/$F.go
+
+// 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.
+
+package p
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type t int
+
+func main() {
+	_ = t.bar	// ERROR "no method"
+	var b bytes.Buffer
+	fmt.Print(b)	// ERROR "implicit assignment"
+}