B.3.2.1 - Which FunctionDeclaration parse nodes list does it iterate?
#2663
Comments
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I agree that it's odd: the criterion "each FunctionDeclarationthat is directly contained in the StatementList of a Block, CaseClause, or DefaultClause" makes it sound like we need to look at any Block, CaseClause, or DefaultClause, anywhere in the Script. In ES6, that step is:
(emphasis mine), which makes it clear you don't have to go looking everywhere. But the phrase "in varDeclarations" was removed in efbfc88 to resolve https://tc39.es/archives/bugzilla/4427/, which links back to an issue that @bakkot raised in 2015. However, it looks like the change that @allenwb suggested in 4427 wasn't applied correctly: in addition to dropping "in varDeclarations", he also appended "Contained within code" (where code is the FunctionBody of the function that FunctionDeclarationInstantiation is being called on), but that wasn't added. |
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That might still be somewhat problematic because when instantiating function f() {
function g() {
{ function h() {} }
}
}we don't want to look at |
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In the phrase "Contained within code", I suspect the capital 'C' alludes to the 'Contains' SDO, which avoids looking inside nested functionDecls. (To make it a proper invocation of 'Contains', I think it would need to be something like "... any Block, CaseClause, or DefaultClause x such that code Contains x".) |
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I read "directly" as specifying that h (indirectly contained) is not considered. |
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@bathos In my example the function is directly contained in a block. I'll open a PR with "Contains". |
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Ah, got it — “directly contained” only describes the declaration relative to the block, not the block relative to the “root” statement list. |
…tantiation This PR completes a small bugfix from 9 years ago. Fixes tc39#2663. ---- History: 2015-07-17: @bakkot identifies a problem in Annex B's "Changes to FunctionDeclarationInstantiation": https://esdiscuss.org/topic/block-level-function-declarations-web-legacy-compatibility-bug To remedy this, @allenwb submits bug 4427: https://tc39.es/archives/bugzilla/4427/ in which he recommends changing > For each FunctionDeclaration _f_ **in _varDeclarations_** that is directly contained in the |StatementList| of a |Block|, |CaseClause|, or |DefaultClause|, to > For each FunctionDeclaration _f_ that is directly contained in the |StatementList| of a |Block|, |CaseClause|, or |DefaultClause| **Contained within _code_**, (emphasis mine). 2015-10-29: @anba submits PR tc39#141, claiming to fix bug 4427. It deletes "in _varDeclarations_", but doesn't add "Contained within _code_". My guess is, this was just an oversight. 2015-11-02: PR tc39#141 is merged to master as commit efbfc88. 2022-02-13: @nicolo-ribaudo raises issue tc39#2663 about this, and says he'd open a PR to fix it, but I don't think that happened. 2024-06-26: @gibson042 raises the problem again, in a commment on PR tc39#2952: tc39#2952 (comment)
…tantiation This PR completes a small bugfix from 9 years ago. Fixes tc39#2663. ---- History: 2015-07-17: @bakkot identifies a problem in Annex B's "Changes to FunctionDeclarationInstantiation": https://esdiscuss.org/topic/block-level-function-declarations-web-legacy-compatibility-bug To remedy this, @allenwb submits bug 4427: https://tc39.es/archives/bugzilla/4427/ in which he recommends changing > For each FunctionDeclaration _f_ **in _varDeclarations_** that is directly contained in the |StatementList| of a |Block|, |CaseClause|, or |DefaultClause|, to > For each FunctionDeclaration _f_ that is directly contained in the |StatementList| of a |Block|, |CaseClause|, or |DefaultClause| **Contained within _code_**, (emphasis mine). 2015-10-29: @anba submits PR tc39#141, claiming to fix bug 4427. It deletes "in _varDeclarations_", but doesn't add "Contained within _code_". My guess is, this was just an oversight. 2015-11-02: PR tc39#141 is merged to master as commit efbfc88. 2022-02-13: @nicolo-ribaudo raises issue tc39#2663 about this, and says he'd open a PR to fix it, but I don't think that happened. 2024-06-26: @gibson042 raises the problem again, in a commment on PR tc39#2952: tc39#2952 (comment)
Change the 3 occurrences of
a |Block|, |CaseClause|, or |DefaultClause| Contained within _code_
to
any |Block|, |CaseClause|, or |DefaultClause| _x_ such that _code_ Contains _x_ is *true*
(See tc39#2663 (comment))
Change the 3 occurrences of
a |Block|, |CaseClause|, or |DefaultClause| Contained within _code_
to
any |Block|, |CaseClause|, or |DefaultClause| _x_ such that _code_ Contains _x_ is *true*
(See tc39#2663 (comment))
Description:
We are trying to fix the handling of function declarations in blocks in Babel (babel/babel#14203), and I don't understand what the spec does.
At step 29.a of B.3.2.1, it says:
However, usually "For each" iterates the elements of a list. Is it iterating over the functions (deeply) contained within the function that is currently being instantiated? Or is it something like "If the current
FunctionDeclarationInstantiationcall has been caused by evaluating aFunctionDeclarationparse node, letfbe that parse node"?The text was updated successfully, but these errors were encountered: