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Restored comments to explain spreading 'arguments' into calls to 'super'.

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This commit is contained in:
Daniel Rosenwasser 2016-08-17 18:10:06 -07:00
parent 01aaff7247
commit 73a857b306
1 changed files with 16 additions and 0 deletions
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16
src/compiler/emitter.ts
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@ -5311,6 +5311,21 @@ const _super = (function (geti, seti) {
emitSignatureParameters(ctor);
}
else {
// The ES2015 spec specifies in 14.5.14. Runtime Semantics: ClassDefinitionEvaluation:
// If constructor is empty, then
// If ClassHeritag_eopt is present and protoParent is not null, then
// Let constructor be the result of parsing the source text
// constructor(...args) { super (...args);}
// using the syntactic grammar with the goal symbol MethodDefinition[~Yield].
// Else,
// Let constructor be the result of parsing the source text
// constructor( ){ }
// using the syntactic grammar with the goal symbol MethodDefinition[~Yield].
//
// While we could emit the '...args' rest parameter, certain later tools in the pipeline might
// downlevel the '...args' portion less efficiently by naively copying the contents of 'arguments' to an array.
// Instead, we'll avoid using a rest parameter and spread into the super call as
// 'super(...arguments)' instead of 'super(...args)', as you can see below.
write("()");
}
}
@ -5349,6 +5364,7 @@ const _super = (function (geti, seti) {
write("_super.apply(this, arguments);");
}
else {
// See comment above on using '...arguments' instead of '...args'.
write("super(...arguments);");
}
emitEnd(baseTypeElement);