Fix per-iteration bindings in for-loop head#27204
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@weswigham, @sandersn: can you take a look? |
weswigham
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Sep 27, 2018
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| function shouldConvertPartOfIterationStatement(node: Node) { | ||
| return (resolver.getNodeCheckFlags(node) & NodeCheckFlags.ContainsCapturedBlockScopeBinding) !== 0; |
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I dislike a non-TS transform relying on typechecking information to be correct. Especially since this means that in the presence of a before transformer, it's very possible that we'll fail to convert something which needs to be.
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We do this in other places, which is the reason we have original pointers for nodes to begin with.
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Geh, you're right. It's actually only a few transforms that can operate without a typechecker available.
weswigham
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Sep 27, 2018
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The ES2015 (and later) specification indicates that a fresh "per-iteration environment" is created in a
for-loop immediately after the initializer is run, and immediately before the incrementor evaluates. This means that block-scoped variables defined in the initializer of aforloop and captured in the initializer, condition, or incrementor need to have the correct closure environment to align with ES2015 semantics.Fixes #17632