fix #470, string interpolation now respects Dart toString

fix #470, string interpolation now respects Dart toString

R=sra@google.com

Committed: https://github.com/dart-lang/dev_compiler/commit/ac3a9d073c3da99093ba040e0d60791b9f91acec

[Jennifer Messerly, 2016-05-17 23:29:13]

jmesserly@google.com changed reviewers:
+ vsm@google.com

[Jennifer Messerly, 2016-05-17 23:29:23]

Description was changed from

==========
fix #470 string interpolation now respects Dart toString
==========

to

==========
fix #470, string interpolation now respects Dart toString
==========

[sra1, 2016-05-17 23:47:57]

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

[sra1, 2016-05-17 23:47:58]

https://codereview.chromium.org/1989663002/diff/1/lib/src/compiler/code_gener...
File lib/src/compiler/code_generator.dart (right):

https://codereview.chromium.org/1989663002/diff/1/lib/src/compiler/code_gener...
lib/src/compiler/code_generator.dart:4215: // Optimization: '$thing' is a common
way to call toString.
It is not a synonym.

'$thing' will throw if toString() returns null.

dart2js has a helper for this case (called "S") that special-cases String and a
few other cases (e.g. number, but not zero which could be "0" or "-0.0") with JS
code.

https://codereview.chromium.org/1989663002/diff/1/tool/input_sdk/private/ddc_...
File tool/input_sdk/private/ddc_runtime/operations.dart (right):

https://codereview.chromium.org/1989663002/diff/1/tool/input_sdk/private/ddc_...
tool/input_sdk/private/ddc_runtime/operations.dart:469: return JS('',
'#.toString()', obj);
It is faster to do:

JS('', '"" + #', obj);

JS engines optimize + expressions with strings.

[sra1, 2016-05-18 00:01:34]

LGTM with a TODO.

[Jennifer Messerly, 2016-05-18 00:23:43]

Thanks! Addressed those

https://codereview.chromium.org/1989663002/diff/1/lib/src/compiler/code_gener...
File lib/src/compiler/code_generator.dart (right):

https://codereview.chromium.org/1989663002/diff/1/lib/src/compiler/code_gener...
lib/src/compiler/code_generator.dart:4215: // Optimization: '$thing' is a common
way to call toString.
On 2016/05/17 23:47:58, sra1 wrote:
> It is not a synonym.
> 
> '$thing' will throw if toString() returns null.
> 
> dart2js has a helper for this case (called "S") that special-cases String and
a
> few other cases (e.g. number, but not zero which could be "0" or "-0.0") with
JS
> code.

Doh. If we want to support that then all readability improvements need to be
removed, since nothing can guarantee toString won't return null =(. A shame
because that has probably never happened in reality. Oh well, maybe we'll get
non-null-by-default types which will fix this at some point. =) For now I just
ripped out all of it.

https://codereview.chromium.org/1989663002/diff/1/tool/input_sdk/private/ddc_...
File tool/input_sdk/private/ddc_runtime/operations.dart (right):

https://codereview.chromium.org/1989663002/diff/1/tool/input_sdk/private/ddc_...
tool/input_sdk/private/ddc_runtime/operations.dart:469: return JS('',
'#.toString()', obj);
On 2016/05/17 23:47:58, sra1 wrote:
> It is faster to do:
> 
> JS('', '"" + #', obj);
> 
> JS engines optimize + expressions with strings.

Done.

[Jennifer Messerly, 2016-05-18 00:24:00]

Description was changed from

==========
fix #470, string interpolation now respects Dart toString
==========

to

==========
fix #470, string interpolation now respects Dart toString

R=sra@google.com

Committed:
https://github.com/dart-lang/dev_compiler/commit/ac3a9d073c3da99093ba040e0d60...
==========

[Jennifer Messerly, 2016-05-18 00:24:03]

Committed patchset #2 (id:20001) manually as
ac3a9d073c3da99093ba040e0d60791b9f91acec (presubmit successful).