gc: fix type switch error message for invalid cases.

Fixes #1606.

R=rsc
CC=golang-dev
https://golang.org/cl/4532045

diff --git a/src/cmd/gc/swt.c b/src/cmd/gc/swt.c
index 6e8436c3c52760347908e20b5cdbbc7c8ccafab0..c2968c44bcf9f5e34b968f71077a477a2a7befbb 100644 (file)
--- a/src/cmd/gc/swt.c
+++ b/src/cmd/gc/swt.c
@@ -867,8 +867,11 @@ typecheckswitch(Node *n)
                                case Etype:     // type switch
                                        if(ll->n->op == OLITERAL && istype(ll->n->type, TNIL))
                                                ;
-                                       else if(ll->n->op != OTYPE && ll->n->type != T)
+                                       else if(ll->n->op != OTYPE && ll->n->type != T) {
                                                yyerror("%#N is not a type", ll->n);
+                                               // reset to original type
+                                               ll->n = n->ntest->right;
+                                       }
                                        break;
                                }
                        }

diff --git a/test/fixedbugs/bug340.go b/test/fixedbugs/bug340.go
new file mode 100644 (file)
index 0000000..461cc6c
--- /dev/null
+++ b/test/fixedbugs/bug340.go
@@ -0,0 +1,17 @@
+// errchk $G $D/$F.go
+
+// Copyright 2011 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 1606.
+
+package main
+
+func main() {
+       var x interface{}
+       switch t := x.(type) { // ERROR "0 is not a type"
+       case 0:
+               t.x = 1 // ERROR "type interface \{ \}"
+       }
+}