Prohibit let in lexical bindings

Prohibit let in lexical bindings

This patch prohibits lexical bindings from being called 'let', even in
sloppy mode, following the ES2015 specification. The change affects
multiple cases of lexical bindings, including simple let/const declarations
and both kinds of for loops. var and legacy const bindings still permit
the name to be let, including in destructuring cases. Tests are added to
verify, though some cases are commented out since they led to (pre-existing)
crashes.

BUG=v8:4403
R=adamk
LOG=Y

Committed: https://crrev.com/7e113c47b7da741761a5e813017f9a738769b41c
Cr-Commit-Position: refs/heads/master@{#31115}

[Dan Ehrenberg, 2015-10-03 01:49:35]

littledan@chromium.org changed reviewers:
+ adamk@chromium.org

[Dan Ehrenberg, 2015-10-03 01:50:00]

The CQ bit was checked by littledan@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-03 01:50:13]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1371263003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1371263003/20001

[commit-bot: I haz the power, 2015-10-03 02:01:21]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-03 02:01:22]

Dry run: Try jobs failed on following builders:
  v8_mac_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_mac_rel/builds/10347)

[Dan Ehrenberg, 2015-10-03 02:14:31]

The CQ bit was checked by littledan@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-03 02:14:40]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1371263003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1371263003/40001

[commit-bot: I haz the power, 2015-10-03 02:23:35]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-03 02:23:35]

Dry run: Try jobs failed on following builders:
  v8_linux_arm64_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_arm64_rel/builds/1...)

[Dan Ehrenberg, 2015-10-05 15:59:27]

The CQ bit was checked by littledan@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-05 15:59:40]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1371263003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1371263003/60001

[adamk, 2015-10-05 16:04:10]

lgtm modulo tests.

Can you also add a test in test/message/ before landing?

https://codereview.chromium.org/1371263003/diff/40001/test/mjsunit/harmony/bl...
File test/mjsunit/harmony/block-let-contextual-sloppy.js (right):

https://codereview.chromium.org/1371263003/diff/40001/test/mjsunit/harmony/bl...
test/mjsunit/harmony/block-let-contextual-sloppy.js:38: (function() { for (let
let = 8; let < 9; let++) sum += let; })();
Looks like you missed a 'var' here?

[Dan Ehrenberg, 2015-10-05 16:24:30]

The CQ bit was checked by littledan@chromium.org

[Dan Ehrenberg, 2015-10-05 16:24:30]

The patchset sent to the CQ was uploaded after l-g-t-m from adamk@chromium.org
Link to the patchset: https://codereview.chromium.org/1371263003/#ps80001
(title: "messages test")

[commit-bot: I haz the power, 2015-10-05 16:24:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1371263003/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1371263003/80001

[adamk, 2015-10-05 16:29:43]

The CQ bit was unchecked by adamk@chromium.org

[adamk, 2015-10-05 16:30:48]

https://codereview.chromium.org/1371263003/diff/80001/test/mjsunit/messages.js
File test/mjsunit/messages.js (right):

https://codereview.chromium.org/1371263003/diff/80001/test/mjsunit/messages.j...
test/mjsunit/messages.js:474: // kLetInLexicalBinding
Sorry, this isn't quite what I meant. You should add a new test file under

test/message/let-in-lexical-binding.js

and an expectation  in

test/message/let-in-lexical-binding.out

That's how we've been doing early error testing.

[Dan Ehrenberg, 2015-10-05 18:21:01]

On 2015/10/05 at 16:30:48, adamk wrote:
> https://codereview.chromium.org/1371263003/diff/80001/test/mjsunit/messages.js
> File test/mjsunit/messages.js (right):
> 
>
https://codereview.chromium.org/1371263003/diff/80001/test/mjsunit/messages.j...
> test/mjsunit/messages.js:474: // kLetInLexicalBinding
> Sorry, this isn't quite what I meant. You should add a new test file under
> 
> test/message/let-in-lexical-binding.js
> 
> and an expectation  in
> 
> test/message/let-in-lexical-binding.out
> 
> That's how we've been doing early error testing.

OK, what do you think of the tests now?

[adamk, 2015-10-05 18:29:26]

lgtm, but please remove the test you added in messages.js (I don't see any other
early errors in there...)

https://codereview.chromium.org/1371263003/diff/100001/test/mjsunit/messages.js
File test/mjsunit/messages.js (right):

https://codereview.chromium.org/1371263003/diff/100001/test/mjsunit/messages....
test/mjsunit/messages.js:474: // kLetInLexicalBinding
You don't need this anymore.

[Dan Ehrenberg, 2015-10-05 20:03:45]

The CQ bit was checked by littledan@chromium.org

[Dan Ehrenberg, 2015-10-05 20:03:45]

The patchset sent to the CQ was uploaded after l-g-t-m from adamk@chromium.org
Link to the patchset: https://codereview.chromium.org/1371263003/#ps120001
(title: "remove messages.js test")

[commit-bot: I haz the power, 2015-10-05 20:04:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1371263003/120001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1371263003/120001

[commit-bot: I haz the power, 2015-10-05 20:29:21]

Committed patchset #7 (id:120001)

[commit-bot: I haz the power, 2015-10-05 20:29:34]

Patchset 7 (id:??) landed as
https://crrev.com/7e113c47b7da741761a5e813017f9a738769b41c
Cr-Commit-Position: refs/heads/master@{#31115}