code review 5574046: gc: static implements check on typeswitches only applie...

gc: static implements check on typeswitches only applies to concrete case types.

Fixes issue 2700.

[lvd, 2012-01-23 14:43:57]

Hello rsc@golang.org (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[lvd, 2012-01-23 14:47:46]

maybe i should add bug400.go below to typeswitch3.go

On Mon, Jan 23, 2012 at 15:43,  <lvd@google.com> wrote:
> Reviewers: rsc,
>
> Message:
> Hello rsc@golang.org (cc: golang-dev@googlegroups.com),
>
> I'd like you to review this change to
> https://go.googlecode.com/hg/
>
>
> Description:
> gc: static implements check on typeswitches only applies to concrete
> case types.
>
> Fixes issue 2700.
>
> Please review this at http://codereview.appspot.com/5574046/
>
> Affected files:
>  M src/cmd/gc/swt.c
>  A test/fixedbugs/bug400.go
>
>
> Index: src/cmd/gc/swt.c
> ===================================================================
> --- a/src/cmd/gc/swt.c
> +++ b/src/cmd/gc/swt.c
> @@ -889,7 +889,7 @@
>                                                yyerror("%lN is not a type",
> ll->n);
>                                                // reset to original type
>                                                ll->n = n->ntest->right;
> -                                       } else if(!implements(ll->n->type,
> t, &missing, &have, &ptr)) {
> +                                       } else if(ll->n->type->etype !=
> TINTER && !implements(ll->n->type, t, &missing, &have, &ptr)) {
>                                                if(have && !missing->broke &&
> !have->broke)
>                                                        yyerror("impossible
> type switch case: %lN cannot have dynamic type %T"
>                                                                " (wrong type
> for %S method)\n\thave %S%hT\n\twant %S%hT",
> Index: test/fixedbugs/bug400.go
> ===================================================================
> new file mode 100644
> --- /dev/null
> +++ b/test/fixedbugs/bug400.go
> @@ -0,0 +1,27 @@
> +// $G $D/$F.go || echo "Bug400"
> +
> +// 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 2700
> +
> +package main
> +
> +import (
> +       "io"
> +)
> +
> +func main() {
> +
> +   var r io.Reader
> +
> +   _, _ = r.(io.Writer)
> +
> +   switch r.(type) {
> +   case io.Writer:
> +   }
> +}
> +
> +
> +
>
>

[rsc, 2012-01-23 17:24:45]

LGTM

Adding to typeswtich3.go makes sense to me.
In general I try to put things that feel like spec
verification tests into named test files, leaving 
the bugs files for true bugs.

[lvd, 2012-01-24 12:53:05]

*** Submitted as http://code.google.com/p/go/source/detail?r=10b075a7a9b7 ***

gc: static implements check on typeswitches only applies to concrete case types.

Fixes issue 2700.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5574046