Removed Type-Defect label.
Added Type-Enhancement, Area-UnitTest, Triaged labels.

Removed Area-UnitTest label.
Added Area-Pkg, Pkg-Unittest labels.

Removed Pkg-Unittest label.
Added Pkg-matcher label.

This comment was originally written by @vicb

This is something I have implemented in Guinness as:

    bool matches(obj, Map matchState) =>
        mirrors.reflect(obj).type.isSubtypeOf(mirrors.reflectClass(_type));

see https://github.com/vsavkin/guinness/blob/5f9e291f9c0937a19ab278b0afe7c377bfae25fe/lib/src/common/unittest_backend.dart#L191 for the full Matcher

We have started to discuss this with Kevin: https://plus.google.com/u/0/+VictorBerchet/posts/bdDgAfUB9bW?cfem=1

I'm not clear on how this would affect the generated code size:

• we don't need more info as what the current impl (isInstanceOf<T>(T t)) uses, would there be a way to prevent the JS size to sky rocket ?
• even if there is no way to limit the JS size, would that be a pb - considering we are running tests ?

(I've not really considered JS & its code size for my use case. The reasoning being that if the tests pass with Dart, they should pass after dart2js, if not then this is a dart2js and not your own code issue. The tests are supposed to test your own code, not dart2js - still I'm all for testing with dart2js to help stabilize the tools as long as there is no constraint on my development flow).

This comment was originally written by greg...@gmail.com

I was under the impression that this was already possible:

  bool isInstance(obj, Type type) => obj is type;
  
But it looks like this is possible - yet?

"malformed type: line 5 pos 18: using 't' in this context is invalid"

I wonder if there is a bug for implementing this - or if it is not possible. In the VM it must just be an int check. Not sure about dart2js.

This comment was originally written by greg.lo...@gmail.com

Erm - "But it looks like this is NOT possible - yet?"

This comment was originally written by @seaneagan

In issue #10406 gbracha indicates that this will only be possible via mirrors. Matchers that use mirrors are currently put here:

http://www.dartdocs.org/documentation/matcher/0.11.1/index.html#matcher/matcher-mirror_matchers

Also this issue is a duplicate of issue #10407 which was wrongly merged with issue #8138.

This comment was originally written by @seaneagan

Once this is fixed, all the custom throwsArgumentError etc. matchers could easily be removed / cleaned up, since you could just do throwsA(ArgumentError).

This issue has been moved to dart-lang/matcher#17.