Support `void` as generic argument.

Support `void` as generic argument.

Also allows `void` in other positions (like parameter positions).

See https://docs.google.com/a/google.com/document/d/1HU7jRFqzRih4JpyHtiiVfitgtSKjN4Axi4HRAYurrSU for more context.

Tests are (for now) in this CL: https://codereview.chromium.org/2707933002

BUG= TBD.

[floitsch, 2017-02-17 17:05:37]

floitsch@google.com changed reviewers:
+ johnniwinther@google.com, sigmund@google.com

[floitsch, 2017-02-17 17:05:38]

First incomplete implementation.

I would like to know if you are ok with this approach. If you have some feedback
on the TODOs, I would be happy, too.

Note: I couldn't get the `Void` class included, and had to do the hack of `new
Void().runtimeType`. I thought I just needed to change the impact, but that
wasn't enough.

[floitsch, 2017-02-22 19:44:26]

Description was changed from

==========
Support `void` as generic argument.

Also allows `void` in other positions (like parameter positions).

See
https://docs.google.com/a/google.com/document/d/1HU7jRFqzRih4JpyHtiiVfitgtSKj...
for more context.

BUG= TBD.
==========

to

==========
Support `void` as generic argument.

Also allows `void` in other positions (like parameter positions).

See
https://docs.google.com/a/google.com/document/d/1HU7jRFqzRih4JpyHtiiVfitgtSKj...
for more context.

Tests are (for now) in this CL: https://codereview.chromium.org/2707933002

BUG= TBD.
==========

[floitsch, 2017-02-22 19:44:57]

Changed it, to keep the void-type. Probably now need to adjust some inference,
...

[Siggi Cherem (dart-lang), 2017-03-13 22:50:58]

Overall changes lgtm. Adding ahe@ to make sure he takes a quick look at the
changes to the parser.

small nit about the error message/suggestions.

I understand new tests are in the other CL, aren't there any other tests or test
expectations that need to be updated with your changes?

https://codereview.chromium.org/2699073003/diff/180001/pkg/compiler/lib/src/d...
File pkg/compiler/lib/src/diagnostics/messages.dart (right):

https://codereview.chromium.org/2699073003/diff/180001/pkg/compiler/lib/src/d...
pkg/compiler/lib/src/diagnostics/messages.dart:529: howToFix: "Try casting the
iterable.",
can a cast succeed? Doesn't this error imply that there is no way to read the
elements of the collection?

https://codereview.chromium.org/2699073003/diff/180001/pkg/compiler/lib/src/d...
pkg/compiler/lib/src/diagnostics/messages.dart:561: howToFix: "Try casting the
stream.",
same

[floitsch, 2017-03-14 13:30:49]

I added the tests.
I will need to update the status files for the implementations that don't
correctly deal with them yet.

https://codereview.chromium.org/2699073003/diff/180001/pkg/compiler/lib/src/d...
File pkg/compiler/lib/src/diagnostics/messages.dart (right):

https://codereview.chromium.org/2699073003/diff/180001/pkg/compiler/lib/src/d...
pkg/compiler/lib/src/diagnostics/messages.dart:529: howToFix: "Try casting the
iterable.",
On 2017/03/13 22:50:58, Siggi Cherem (dart-lang) wrote:
> can a cast succeed? Doesn't this error imply that there is no way to read the
> elements of the collection?

Removed the "howToFix". There doesn't seem to be a good suggestion.

https://codereview.chromium.org/2699073003/diff/180001/pkg/compiler/lib/src/d...
pkg/compiler/lib/src/diagnostics/messages.dart:561: howToFix: "Try casting the
stream.",
On 2017/03/13 22:50:58, Siggi Cherem (dart-lang) wrote:
> same

ditto.

[floitsch, 2017-05-08 14:48:35]

After rebase I don't have access to the rtiEncoder from the
TypeRepresentationGenerator.
Do you have any suggestion on how I could make this work again?  (I could, of
course, just keep them separate, but that feels dirty and brittle).

https://codereview.chromium.org/2699073003/diff/220001/pkg/compiler/lib/src/j...
File pkg/compiler/lib/src/js_backend/runtime_types.dart (right):

https://codereview.chromium.org/2699073003/diff/220001/pkg/compiler/lib/src/j...
pkg/compiler/lib/src/js_backend/runtime_types.dart:1072: // TODO(floitsch): this
should use the `voidRti` field from the rti encoder.
@johnni or @siggi: how should I get from here to the rtiEncoder?

[Johnni Winther, 2017-05-09 07:50:40]

https://codereview.chromium.org/2699073003/diff/220001/pkg/compiler/lib/src/j...
File pkg/compiler/lib/src/js_backend/runtime_types.dart (right):

https://codereview.chromium.org/2699073003/diff/220001/pkg/compiler/lib/src/j...
pkg/compiler/lib/src/js_backend/runtime_types.dart:1072: // TODO(floitsch): this
should use the `voidRti` field from the rti encoder.
On 2017/05/08 14:48:35, floitsch wrote:
> @johnni or @siggi: how should I get from here to the rtiEncoder?

Putt the `voidRti` getter on TypeRepresentationGenerator and access it from here
and through `_representationGenerator.voidRti` in _RuntimeTypesEncoder.

[floitsch, 2017-05-09 09:48:25]

Also made the type-representation generator private (as discussed in person).

https://codereview.chromium.org/2699073003/diff/220001/pkg/compiler/lib/src/j...
File pkg/compiler/lib/src/js_backend/runtime_types.dart (right):

https://codereview.chromium.org/2699073003/diff/220001/pkg/compiler/lib/src/j...
pkg/compiler/lib/src/js_backend/runtime_types.dart:1072: // TODO(floitsch): this
should use the `voidRti` field from the rti encoder.
On 2017/05/09 07:50:40, Johnni Winther wrote:
> On 2017/05/08 14:48:35, floitsch wrote:
> > @johnni or @siggi: how should I get from here to the rtiEncoder?
> 
> Putt the `voidRti` getter on TypeRepresentationGenerator and access it from
here
> and through `_representationGenerator.voidRti` in _RuntimeTypesEncoder.

As discussed in person: made a static in the encoder.

[Johnni Winther, 2017-05-09 10:20:08]

lgtm

[floitsch, 2017-05-09 11:08:04]

Note: this currently breaks the warning for `Cannot return value from void
function.'

As in:

```
void foo() => 42;
```