Implement dynamic function checks.

Implement dynamic function checks.

R=johnniwinther@google.com

Committed: https://code.google.com/p/dart/source/detail?r=30932

[ahe, 2013-10-29 22:42:49]

Needs a lot of cleaning up, but I think I'm pretty much there. Only two tests
are failing, see below. I plan to ask Karl and Johnni for suggestions for how to
implement this last part.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:628:
new jsAst.Throw(js.string('Cannot read type variable ${element}'))];
This is the only thing that causes tests to fail, and the only two remaining
failures are:

language/function_subtype_bound_closure5_test
language/function_subtype_local5_test

[Johnni Winther, 2013-10-30 11:40:23]

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:617:
superclass = superclass.superclass;
The superclass chain is not properly substuted. For the hierarchy

class A<T> {}
class B<S> extends A<S> {}
class C<U> extends B<U> {}

you will visit C<U>, B<U>, A<S> if [cls] is C. Use

GenericType type = cls.thisType.asInstanceOf(superclass);

to obtain the correct superclass.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:628:
new jsAst.Throw(js.string('Cannot read type variable ${element}'))];
On 2013/10/29 22:42:49, ahe wrote:
> This is the only thing that causes tests to fail, and the only two remaining
> failures are:
> 
> language/function_subtype_bound_closure5_test
> language/function_subtype_local5_test

The change above should solve this.

[Johnni Winther, 2013-10-30 12:02:18]

LPTM (Look Promising To Me)!

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:617:
superclass = superclass.superclass;
On 2013/10/30 11:40:23, Johnni Winther wrote:
> The superclass chain is not properly substuted. For the hierarchy
> 
> class A<T> {}
> class B<S> extends A<S> {}
> class C<U> extends B<U> {}
> 
> you will visit C<U>, B<U>, A<S> if [cls] is C. Use
> 
> GenericType type = cls.thisType.asInstanceOf(superclass);
> 
> to obtain the correct superclass.

Actually you will visit C<U>, B<S>, A<T> if [cls] is C. Anyway, the fix is the
same.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File dart/sdk/lib/_internal/compiler/implementation/ssa/builder.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/ssa/builder.dart:2936:
List<HInstruction> typeVariables = <HInstruction>[];
Make [typeVariables] a Map<TypeVariableElement, HInstruction> instead. This way
you can reuse the instructions and handle typedefs.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File dart/sdk/lib/_internal/compiler/implementation/ssa/codegen.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/ssa/codegen.dart:2612: void
visitType(DartType type, A argument) {
'A argument' -> '_'.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/lib/js...
File dart/sdk/lib/_internal/lib/js_helper.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/lib/js...
dart/sdk/lib/_internal/lib/js_helper.dart:2014: bool isTest(expression);
Several subtypes have no implementation for this.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/lib/js...
dart/sdk/lib/_internal/lib/js_helper.dart:2151: }
Named parameters not handled.

[ahe, 2013-10-30 12:04:05]

Thank you, Johnni!

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:617:
superclass = superclass.superclass;
On 2013/10/30 11:40:23, Johnni Winther wrote:
> The superclass chain is not properly substuted. For the hierarchy
> 
> class A<T> {}
> class B<S> extends A<S> {}
> class C<U> extends B<U> {}
> 
> you will visit C<U>, B<U>, A<S> if [cls] is C. Use
> 
> GenericType type = cls.thisType.asInstanceOf(superclass);
> 
> to obtain the correct superclass.

I don't think that is enough.

Consider this situation:

class Foo<T> {
}

class Bar extends Foo<String> {}

What I'm trying to achieve here is to override the method $tv_T in Bar, so that
we get:

Foo.prototype.$tv_T = function() { return /* the value of T */ };

Bar.prototype.$tv_T = function() { return JsString; }

Karl has pointed me to rti.computeSubstitution.

[ngeoffray, 2013-11-01 13:54:02]

DBC

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File dart/sdk/lib/_internal/compiler/implementation/ssa/codegen.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/ssa/codegen.dart:2600: class
TypeBuilder implements DartTypeVisitor<dynamic, SsaCodeGenerator> {
Doing this at codegen time prevents doing all potential optimizations (like
inlining).

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart:2765: class
HFunctionType extends HInstruction {
Could you remind me why can't you just do a new like we do for regular
allocations?

[ahe, 2013-11-04 17:23:45]

Nicolas,

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File dart/sdk/lib/_internal/compiler/implementation/ssa/codegen.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/ssa/codegen.dart:2600: class
TypeBuilder implements DartTypeVisitor<dynamic, SsaCodeGenerator> {
On 2013/11/01 13:54:02, ngeoffray wrote:
> Doing this at codegen time prevents doing all potential optimizations (like
> inlining).

That is a good point. We talked about this earlier today, and I have tried
building up these objects in the builder and my first attempt broke GVN. Perhaps
I'll make another try tomorrow.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart:2765: class
HFunctionType extends HInstruction {
On 2013/11/01 13:54:02, ngeoffray wrote:
> Could you remind me why can't you just do a new like we do for regular
> allocations?

I'm not sure how this interacts with GVN. Also, I'd like to turn some of these
into compile-time constants.

[ahe, 2013-11-29 13:10:17]

PTAL

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
File dart/sdk/lib/_internal/compiler/implementation/ssa/builder.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/compil...
dart/sdk/lib/_internal/compiler/implementation/ssa/builder.dart:2936:
List<HInstruction> typeVariables = <HInstruction>[];
On 2013/10/30 12:02:19, Johnni Winther wrote:
> Make [typeVariables] a Map<TypeVariableElement, HInstruction> instead. This
way
> you can reuse the instructions and handle typedefs.

Just tried it, it doesn't work. I don't think you can use an instruction
multiple times (unless you do something special).

I found a different solution: generate type variables as needed. GVN should take
care of the rest.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/lib/js...
File dart/sdk/lib/_internal/lib/js_helper.dart (right):

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/lib/js...
dart/sdk/lib/_internal/lib/js_helper.dart:2014: bool isTest(expression);
On 2013/10/30 12:02:19, Johnni Winther wrote:
> Several subtypes have no implementation for this.

Done.

https://codereview.chromium.org/50313007/diff/1/dart/sdk/lib/_internal/lib/js...
dart/sdk/lib/_internal/lib/js_helper.dart:2151: }
On 2013/10/30 12:02:19, Johnni Winther wrote:
> Named parameters not handled.

Done.

[ahe, 2013-11-29 19:28:53]

+kasperl, this is a prerequisite for CL 27524003.

[Johnni Winther, 2013-12-03 10:33:15]

lgtm

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:574:
for (TypeVariableType parameter in type.typeArguments) {
Replace `type.typeArguments` with `superclass.typeVariables` and delete the
`type` variable.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:596:
substitution.getCode(backend.rti, true)['apply'](
Seems the last argument to getCode should be named. I cannot locally see what
`true` means.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File dart/sdk/lib/_internal/compiler/implementation/js_emitter/js_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/js_emitter.dart:22:
GenericType;
Remove together with previously mentioned `type` variable.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/type_test_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/type_test_emitter.dart:252:
if (!knownSubtype) {
Remove `if (!knownSubtype) {` and the loop below with `if (knownSubtype)`.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart (right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart:2879: HInstruction
typeArguments,
typeArguments -> typeArgument.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
File dart/sdk/lib/_internal/lib/js_helper.dart (right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2065: //
Primitives.printString("<<$pretty is $this (${self}) [$result]>>");
Remove debug code.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2072: // Type inferrer don't think
this is called with dynamic arguments.
don't -> doesn't

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2098: JS('', '#[#]()', interceptor,
JS_SIGNATURE_NAME());
Share code between l.2057-2059 and l.2094-2098 ?

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2247: * A "meta helper" is a helper
function that is never called by simulates how
by -> but

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2285: } else {
How about type variables?

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2328: class
FunctionTypeInfoDecoderRing {
Why FunctionTypeInfoDecoderRing and not just FunctionTypeInfoDecoder ?

[ahe, 2013-12-05 14:24:23]

Thank you, all!

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:574:
for (TypeVariableType parameter in type.typeArguments) {
On 2013/12/03 10:33:16, Johnni Winther wrote:
> Replace `type.typeArguments` with `superclass.typeVariables` and delete the
> `type` variable.

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:596:
substitution.getCode(backend.rti, true)['apply'](
On 2013/12/03 10:33:16, Johnni Winther wrote:
> Seems the last argument to getCode should be named. I cannot locally see what
> `true` means.

I like to avoid adding named arguments as they add extra overhead at runtime,
and because they have a tendency to be followed by more.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File dart/sdk/lib/_internal/compiler/implementation/js_emitter/js_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/js_emitter.dart:22:
GenericType;
On 2013/12/03 10:33:16, Johnni Winther wrote:
> Remove together with previously mentioned `type` variable.

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/type_test_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/type_test_emitter.dart:252:
if (!knownSubtype) {
On 2013/12/03 10:33:16, Johnni Winther wrote:
> Remove `if (!knownSubtype) {` and the loop below with `if (knownSubtype)`.

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
File dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart (right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/ssa/nodes.dart:2879: HInstruction
typeArguments,
On 2013/12/03 10:33:16, Johnni Winther wrote:
> typeArguments -> typeArgument.

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
File dart/sdk/lib/_internal/lib/js_helper.dart (right):

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2065: //
Primitives.printString("<<$pretty is $this (${self}) [$result]>>");
On 2013/12/03 10:33:16, Johnni Winther wrote:
> Remove debug code.

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2072: // Type inferrer don't think
this is called with dynamic arguments.
On 2013/12/03 10:33:16, Johnni Winther wrote:
> don't -> doesn't

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2098: JS('', '#[#]()', interceptor,
JS_SIGNATURE_NAME());
On 2013/12/03 10:33:16, Johnni Winther wrote:
> Share code between l.2057-2059 and l.2094-2098 ?

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2247: * A "meta helper" is a helper
function that is never called by simulates how
On 2013/12/03 10:33:16, Johnni Winther wrote:
> by -> but

Done.

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2285: } else {
On 2013/12/03 10:33:16, Johnni Winther wrote:
> How about type variables?

They don't show up here (yet).

https://codereview.chromium.org/50313007/diff/240001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2328: class
FunctionTypeInfoDecoderRing {
On 2013/12/03 10:33:16, Johnni Winther wrote:
> Why FunctionTypeInfoDecoderRing and not just FunctionTypeInfoDecoder ?

http://en.wikipedia.org/wiki/Secret_decoder_ring

[ahe, 2013-12-06 06:47:30]

Committed patchset #11 manually as r30932 (presubmit successful).

[ngeoffray, 2013-12-09 09:48:52]

Post-commit comments.

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/c...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:571:
ClassElement superclass = cls;
superclass -> currentClass ? I find it confusing to assign [cls] to the
superclass.

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
File dart/sdk/lib/_internal/lib/js_helper.dart (right):

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2065: // Type inferrer doesn't think
this is called with dynamic arguments.
Maybe add an 'obfuscate' method that will return the JS expression:

obfuscate(obj) => JS('', '#', obj)

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2145: var result =
JS('JSExtendableArray', '[]');
Why the JS here?

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2147: JS('', '#.push(#)', result,
list[i].toRti());
Why the JS here?

https://codereview.chromium.org/50313007/diff/340001/dart/tests/language/lang...
File dart/tests/language/language_dart2js.status (right):

https://codereview.chromium.org/50313007/diff/340001/dart/tests/language/lang...
dart/tests/language/language_dart2js.status:95: function_type_alias9_test/00:
Crash
Bug number?

https://codereview.chromium.org/50313007/diff/340001/dart/tests/language/lang...
dart/tests/language/language_dart2js.status:319:
const_factory_with_body_test/01: Crash
Ditto.

[ahe, 2013-12-09 15:30:06]

Thank you, Nicolas.

Addressing your comments in https://codereview.chromium.org/104723004.

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/c...
File
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart
(right):

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/c...
dart/sdk/lib/_internal/compiler/implementation/js_emitter/class_emitter.dart:571:
ClassElement superclass = cls;
On 2013/12/09 09:48:52, ngeoffray wrote:
> superclass -> currentClass ? I find it confusing to assign [cls] to the
> superclass.

Done.

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
File dart/sdk/lib/_internal/lib/js_helper.dart (right):

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2065: // Type inferrer doesn't think
this is called with dynamic arguments.
On 2013/12/09 09:48:52, ngeoffray wrote:
> Maybe add an 'obfuscate' method that will return the JS expression:
> 
> obfuscate(obj) => JS('', '#', obj)

Done.

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2145: var result =
JS('JSExtendableArray', '[]');
On 2013/12/09 09:48:52, ngeoffray wrote:
> Why the JS here?

Avoids adding type parameters, for one thing. The generated code was better.

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2147: JS('', '#.push(#)', result,
list[i].toRti());
On 2013/12/09 09:48:52, ngeoffray wrote:
> Why the JS here?

The generated code improved.

https://codereview.chromium.org/50313007/diff/340001/dart/tests/language/lang...
File dart/tests/language/language_dart2js.status (right):

https://codereview.chromium.org/50313007/diff/340001/dart/tests/language/lang...
dart/tests/language/language_dart2js.status:95: function_type_alias9_test/00:
Crash
On 2013/12/09 09:48:52, ngeoffray wrote:
> Bug number?

I don't know how this slipped through. Added a bug.

https://codereview.chromium.org/50313007/diff/340001/dart/tests/language/lang...
dart/tests/language/language_dart2js.status:319:
const_factory_with_body_test/01: Crash
On 2013/12/09 09:48:52, ngeoffray wrote:
> Ditto.

Done.

[ngeoffray, 2013-12-09 15:32:49]

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
File dart/sdk/lib/_internal/lib/js_helper.dart (right):

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2145: var result =
JS('JSExtendableArray', '[]');
On 2013/12/09 15:30:06, ahe wrote:
> On 2013/12/09 09:48:52, ngeoffray wrote:
> > Why the JS here?
> 
> Avoids adding type parameters, for one thing. The generated code was better.

This is surprising, we've made sure in the backend this would get optimized. Can
you check again the difference?

https://codereview.chromium.org/50313007/diff/340001/dart/sdk/lib/_internal/l...
dart/sdk/lib/_internal/lib/js_helper.dart:2147: JS('', '#.push(#)', result,
list[i].toRti());
On 2013/12/09 15:30:06, ahe wrote:
> On 2013/12/09 09:48:52, ngeoffray wrote:
> > Why the JS here?
> 
> The generated code improved.

Ditto.