Intent to ship: lexical declarations in strict mode

[Dmitry Lomov]

[blink-dev: FYI]

Lexical declarations ('let' and 'const') are part of ES6. The spec for them in Editor's draft is stable. 

The are available in IE11 [1]. Firefox plans to ship them in 35 (Jan 2015) [2].

Lexical declarations has been available in V8 under --harmony-scoping flag for quite some time. 

Our current implementation is up-to-date with the latest ES6 spec.

To mitigate possible web-incompatibility, in particular conflicts with legacy  'const' declarations, we are limiting support for lexical declarations to strict mode code for now. (Sloppy mode support for lexical declarations will be done as a distinct language feature process-wise).

Owners: dsl...@chromium.org, ross...@chromium.org

[1] https://status.modern.ie/blockbindingsletconstfunction

[2] https://developer.mozilla.org/en-US/Firefox/Releases/35

[Darin Fisher]

LGTM

Nice idea limiting this to strict mode for now.

-Darin

[Darin Fisher]

(whoops, ignore the "LGTM" part!)