Implement type variable 'more specific than' and 'subtype'.

Implement type variable 'more specific than' and 'subtype'.

R=brianwilkerson@google.com, jwren@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=28457

[Brian Wilkerson, 2013-10-10 13:31:35]

LGTM

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/type/TypeParameterTypeImpl.java
(right):

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/type/TypeParameterTypeImpl.java:105:
if (s == DynamicTypeImpl.getInstance()) {
Can we use .isBottom() and .isDynamic() here instead of identity tests?

[scheglov, 2013-10-10 15:19:36]

Committed patchset #1 manually as r28457 (presubmit successful).

[jwren, 2013-10-10 17:34:57]

A few comments.  Also, we should make sure that any warning generated on
dart2js/sdk aren't false positives.

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/StaticTypeWarningCode.java
(right):

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/StaticTypeWarningCode.java:183:
TYPE_PARAMETER_SUPERTYPE_OF_ITS_BOUND("'%s' cannot be a supertype of its upper
bound"),
This code and part of the spec are already covered by
STWC.TYPE_ARGUMENT_NOT_MATCHING_BOUNDS.  If the goal was to split this case off
of the other code, then the logic which generates it should also be converted to
use the new code. Also, if you do keep this one, do reference the other in the
javadoc to make navigating the error codes easier.

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/type/TypeParameterTypeImpl.java
(right):

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/type/TypeParameterTypeImpl.java:193:
return upperBound.isMoreSpecificThan(s);
Shouldn't it be s.isMoreSpecificThan(upperBound)?

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java
(right):

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java:927:
checkForTypeArgumentNotMatchingBounds(node);
Can this call be unified with the new method
checkForTypeParameterSupertypeOfItsBound() ?

[scheglov, 2013-10-10 22:24:23]

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/StaticTypeWarningCode.java
(right):

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/error/StaticTypeWarningCode.java:183:
TYPE_PARAMETER_SUPERTYPE_OF_ITS_BOUND("'%s' cannot be a supertype of its upper
bound"),
On 2013/10/10 17:34:57, jwren wrote:
> This code and part of the spec are already covered by
> STWC.TYPE_ARGUMENT_NOT_MATCHING_BOUNDS.  If the goal was to split this case
off
> of the other code, then the logic which generates it should also be converted
to
> use the new code. Also, if you do keep this one, do reference the other in the
> javadoc to make navigating the error codes easier.
> 

I've added @see references.
However "is a supertype of its upper bound" never reported before, so I'm not
sure what to convert.

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/type/TypeParameterTypeImpl.java
(right):

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/type/TypeParameterTypeImpl.java:193:
return upperBound.isMoreSpecificThan(s);
On 2013/10/10 17:34:57, jwren wrote:
> Shouldn't it be s.isMoreSpecificThan(upperBound)?

Hm... No.

<T extends B>, so T << B.
So, if B << S then also T << S.

But S << B  =>  T << S does not looks true for me.

For example B = num, T = int, S = double, but int << double is not correct.

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
File
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java
(right):

https://codereview.chromium.org/26745004/diff/1/editor/tools/plugins/com.goog...
editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/verifier/ErrorVerifier.java:927:
checkForTypeArgumentNotMatchingBounds(node);
On 2013/10/10 17:34:57, jwren wrote:
> Can this call be unified with the new method
> checkForTypeParameterSupertypeOfItsBound() ?

Hm...
I remember I've tried to unify it with something, but it did not look good.
I think problem is that here we check usage of generic type, and
checkForTypeParameterSupertypeOfItsBound() checks its declaration.