Implement type checks for switch expression

Implement type checks for switch expression

If the switch expression is not compatible with the case clause
constants, we must report a runtime error. Implement this by annotating
the temporary variable holding the switch expression with the correct
type.

Issue 7274

R=regis@google.com

Committed: https://code.google.com/p/dart/source/detail?r=29126

[regis, 2013-10-22 23:17:19]

LGTM with one question.

https://codereview.chromium.org/34413007/diff/50001/runtime/vm/scopes.h
File runtime/vm/scopes.h (right):

https://codereview.chromium.org/34413007/diff/50001/runtime/vm/scopes.h#newco...
runtime/vm/scopes.h:30: type_(&type),
Why change this now? We usually do not store a pointer in scope, ast, graph,
etc...

[hausner, 2013-10-22 23:22:17]

https://codereview.chromium.org/34413007/diff/50001/runtime/vm/scopes.h
File runtime/vm/scopes.h (right):

https://codereview.chromium.org/34413007/diff/50001/runtime/vm/scopes.h#newco...
runtime/vm/scopes.h:30: type_(&type),
On 2013/10/22 23:17:20, regis wrote:
> Why change this now? We usually do not store a pointer in scope, ast, graph,
> etc...

Because I have to change the type of a variable after it's created. I don't know
the type of the temporary variable holding the evaluated switch expression until
the case clauses have been parsed. Do you have a better idea how to add the type
check to the internal variable retroactively?

[regis, 2013-10-22 23:32:11]

On 2013/10/22 23:22:17, hausner wrote:
> https://codereview.chromium.org/34413007/diff/50001/runtime/vm/scopes.h
> File runtime/vm/scopes.h (right):
> 
>
https://codereview.chromium.org/34413007/diff/50001/runtime/vm/scopes.h#newco...
> runtime/vm/scopes.h:30: type_(&type),
> On 2013/10/22 23:17:20, regis wrote:
> > Why change this now? We usually do not store a pointer in scope, ast, graph,
> > etc...
> 
> Because I have to change the type of a variable after it's created. I don't
know
> the type of the temporary variable holding the evaluated switch expression
until
> the case clauses have been parsed. Do you have a better idea how to add the
type
> check to the internal variable retroactively?

We do exactly that for the signature type of a function variable, which is only
known after the signature is parsed, but the variable must be entered in the
scope before parsing the signature. We know it is a Type, so we patch its
type_class and arguments fields. See parser.cc, lines 5470 (dummy
initialization) and 5565 (patching).

[hausner, 2013-10-23 18:32:03]

PTAL

[regis, 2013-10-23 18:55:42]

LGTM

[hausner, 2013-10-23 21:15:30]

Committed patchset #3 manually as r29126 (presubmit successful).