Rev31 (January 15, 2015) of the ECMAScript 2015 Language Specification is ready
for review at
http://wiki.ecmascript.org/doku.php?id=harmony:specification_drafts#january_15_2015_draft_rev_31
Changes include: Updated specification to use and support the new built-in
subclassing scheme described at:
https://github.com/tc39/ecma262/blob/master/workingdocs/ES6-super-construct%3Dproposal.md
• Added newTarget parameter to [[Construct]], Reflect.construct, and
proxy ‘construct’ trap.
• Added NewTarget binding to Function Environment Records and abstract
operations/methods of setting and accessing that binding
• Redefined [[Construct]] for ordinary ECMAScript functions so
“derived” constructors don’t preallocate the new object and bind this.
• Changed [[Construct]] for ordinary ECMAScript functions so “derived”
constructors will throw if they try to explicitly return a non-object.
• Within constructors this binding has TDZ access semantics.
• super(...) syntactic form now illegal in
Function/GeneratorDeclaration/Expression
• super(...) and new super(...) propagates current NewTarget to
[[Construct]] call
• super(...) binds this value upon return from [[Construct]] call,
throw if new already bound
• Refactored [[Call]] and [[Construct]] for ordinary ECMAScript
functions so they can continue to shared common spec steps.
• Updated Generator object instantiation to work with new [[Construct]]
design
• Refactored Function constructor and GeneratorFunction to share a
common abstract operation based definition
• Every built-in constructor changed to merge object allocation and
initialization code. In some cases (eg, TypedArray and Promise) significant
refactoring of allocation and initialization logic.
• Updated [[Construct]] of Bound functions to handle newTarget
parameter.
• Several of the above items are tentative because they still lack full
TC39 discussion and review. The following are particularly tentative:
• restrictions on where super(...) is allowed may change
• new supper(...) might go away or change
• Support for the new.target access syntax (yellow highlight in
spec text) is speculative and may move to ES7 and/or change
Other changes
• Merged AllocArrayBuffer and SetArrayBufferData into single abstract
operation
• %TypedArray%.of now requires that its this value is a valid Typed
Array constructor
• Replaced “moduleId” with “sourceCodeId” and eliminated most usage of
such ids in module related abstract operations
• Some tweaking of Language Overview in 4.2
• A new document title
• Resolved bugs: 3543-3527, 3524-3523, 3520, 3517-3516, 3514-3511,
3501-3496, 3494-3479, 3310, 3229, 3136, 2865, 2536, 2495, 2179_______________________________________________
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