Add WhereIterable.map

Add WhereIterable.map

This makes some nice code improvements for dart2js. dart2js can't
inline the MappedIterable factory constructor and specialize by
optimization, so specializing by hand removes the test "is
EfficientLength" for code like "x.where(f).map(g)".

R=lrn@google.com

Committed: https://github.com/dart-lang/sdk/commit/127b419fc158446fc5a22eef9a6287b383d42c65

[sra1, 2016-09-20 20:31:55]

sra@google.com changed reviewers:
+ lrn@google.com

[sra1, 2016-09-20 20:31:56]

WDYT?

[Lasse Reichstein Nielsen, 2016-09-21 07:17:13]

https://codereview.chromium.org/2354093002/diff/1/sdk/lib/internal/iterable.dart
File sdk/lib/internal/iterable.dart (right):

https://codereview.chromium.org/2354093002/diff/1/sdk/lib/internal/iterable.d...
sdk/lib/internal/iterable.dart:432: new MappedIterable<E, dynamic/*=T*/>._(this,
f);
I don't see why this makes any difference - the method is completely identical
to the one inherited from Iterable?
There is nothing about EfficientLength in the Iterable version either.

[sra1, 2016-09-21 16:26:22]

https://codereview.chromium.org/2354093002/diff/1/sdk/lib/internal/iterable.dart
File sdk/lib/internal/iterable.dart (right):

https://codereview.chromium.org/2354093002/diff/1/sdk/lib/internal/iterable.d...
sdk/lib/internal/iterable.dart:432: new MappedIterable<E, dynamic/*=T*/>._(this,
f);
On 2016/09/21 07:17:13, Lasse Reichstein Nielsen wrote:
> I don't see why this makes any difference - the method is completely identical
> to the one inherited from Iterable?
> There is nothing about EfficientLength in the Iterable version either.

The difference is
new MappedIterable<E, T>(this, f)
new MappedIterable<E, T>._(this, f)

The former has the expensive type test and two classes in the return type, and
cannot be inlined by dart2js (too big)
The latter has no type test and a single class in the return type which enables
further optimizations and/or inlining

[Lasse Reichstein Nielsen, 2016-09-21 19:42:17]

LGTM!

https://codereview.chromium.org/2354093002/diff/1/sdk/lib/internal/iterable.dart
File sdk/lib/internal/iterable.dart (right):

https://codereview.chromium.org/2354093002/diff/1/sdk/lib/internal/iterable.d...
sdk/lib/internal/iterable.dart:432: new MappedIterable<E, dynamic/*=T*/>._(this,
f);
Ah, I completely missed that difference :)

[sra1, 2016-09-22 17:36:28]

Description was changed from

==========
Add WhereIterable.map

This makes some nice code improvements for dart2js. dart2js can't
inline the MappedIterable factory constructor and specialize by
optimization, so specializing by hand removes the test "is
EfficientLength" for code like "x.where(f).map(g)".
==========

to

==========
Add WhereIterable.map

This makes some nice code improvements for dart2js. dart2js can't
inline the MappedIterable factory constructor and specialize by
optimization, so specializing by hand removes the test "is
EfficientLength" for code like "x.where(f).map(g)".

R=lrn@google.com

Committed:
https://github.com/dart-lang/sdk/commit/127b419fc158446fc5a22eef9a6287b383d42c65
==========

[sra1, 2016-09-22 17:36:29]

Committed patchset #1 (id:1) manually as
127b419fc158446fc5a22eef9a6287b383d42c65 (presubmit successful).