Add APIs for asserting the types of transformers.

Add APIs for asserting the types of transformers.

I thought about adding these to Delegating*Transformer classes, but
those delegates don't really make any sense at all on their own, so I
found other places instead.

R=lrn@google.com

Committed: https://github.com/dart-lang/async/commit/a4e67957e6807916526a76120852a69f28fc2ac6

[nweiz, 2016-05-09 19:12:09]

Friendly ping!

[Lasse Reichstein Nielsen, 2016-05-09 19:20:12]

lgtm

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
File lib/src/stream_sink_transformer.dart (right):

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
lib/src/stream_sink_transformer.dart:61: : new
TypeSafeStreamSinkTransformer(transformer);
I still want <S, T> on this constructor call so the class also works in spec
mode.
The purpose of the class is to add extra type checks, so if it doesn't do that
at all in spec mode, it's just not useful. That differs from cases where the
extra type parameter is just used for validation and the class still works
without them - here the purpose of the class is the validation.

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
File lib/src/stream_sink_transformer/typed.dart (right):

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
lib/src/stream_sink_transformer/typed.dart:11: /// transformer.
"coerces" isn't specific enough. At least say what it is coerced to.

https://codereview.chromium.org/1947923003/diff/1/lib/src/typed_stream_transf...
File lib/src/typed_stream_transformer.dart (right):

https://codereview.chromium.org/1947923003/diff/1/lib/src/typed_stream_transf...
lib/src/typed_stream_transformer.dart:14: /// provided. If they're not, the
stream throws a [CastError].
Also say that t expects the argument to bind to be a Stream<S> (but it doesn't
actually check that the events are S instances).

[nweiz, 2016-05-09 19:31:17]

Code review changes

[nweiz, 2016-05-09 19:31:48]

Description was changed from

==========
Add APIs for asserting the types of transformers.

I thought about adding these to Delegating*Transformer classes, but
those delegates don't really make any sense at all on their own, so I
found other places instead.

R=lrn@google.com
==========

to

==========
Add APIs for asserting the types of transformers.

I thought about adding these to Delegating*Transformer classes, but
those delegates don't really make any sense at all on their own, so I
found other places instead.

R=lrn@google.com

Committed:
https://github.com/dart-lang/async/commit/a4e67957e6807916526a76120852a69f28f...
==========

[nweiz, 2016-05-09 19:31:50]

Committed patchset #2 (id:20001) manually as
a4e67957e6807916526a76120852a69f28fc2ac6 (presubmit successful).

[nweiz, 2016-05-09 19:31:51]

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
File lib/src/stream_sink_transformer.dart (right):

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
lib/src/stream_sink_transformer.dart:61: : new
TypeSafeStreamSinkTransformer(transformer);
On 2016/05/09 19:20:12, Lasse Reichstein Nielsen wrote:
> I still want <S, T> on this constructor call so the class also works in spec
> mode.
> The purpose of the class is to add extra type checks, so if it doesn't do that
> at all in spec mode, it's just not useful. That differs from cases where the
> extra type parameter is just used for validation and the class still works
> without them - here the purpose of the class is the validation.

This clause can't be reached in spec mode. The input always has type
[StreamTransformer], and the is check isn't generic in spec mode, so this will
always return [transformer] unmodified.

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
File lib/src/stream_sink_transformer/typed.dart (right):

https://codereview.chromium.org/1947923003/diff/1/lib/src/stream_sink_transfo...
lib/src/stream_sink_transformer/typed.dart:11: /// transformer.
On 2016/05/09 19:20:12, Lasse Reichstein Nielsen wrote:
> "coerces" isn't specific enough. At least say what it is coerced to.

Done.

https://codereview.chromium.org/1947923003/diff/1/lib/src/typed_stream_transf...
File lib/src/typed_stream_transformer.dart (right):

https://codereview.chromium.org/1947923003/diff/1/lib/src/typed_stream_transf...
lib/src/typed_stream_transformer.dart:14: /// provided. If they're not, the
stream throws a [CastError].
On 2016/05/09 19:20:12, Lasse Reichstein Nielsen wrote:
> Also say that t expects the argument to bind to be a Stream<S> (but it doesn't
> actually check that the events are S instances).

This isn't really an aspect of the behavior of the transformer (at least in
strong mode, which is the only mode in which wrapping can actually happen). The
bind() method is annotated as Stream<S>, but that's already statically required
by the fact that this returns a StreamTransformer<S, T>—there's no way for
bind() to actually receive an argument with any other type.