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Parsing error for for (await using of of of) {}Β #55555
Description
π Search Terms
"using of"
π Version & Regression Information
- This changed between versions 5.1 and 5.2_
β― Playground Link
π» Code
{
for (await using of of of);
}π Actual behavior
Parsing error The left-hand side of a 'for...of' statement must be a variable or a property access.
π Expected behavior
Parse successful.
Additional information about the issue
Context: https://github.com/prettier/prettier/pull/15321/files#r1308180336
Spec: https://tc39.es/proposal-explicit-resource-management/#sec-for-in-and-for-of-statements
Babel can parse for (await using of of of) {}. ref: https://github.com/babel/babel/blob/b804bb08912d262133213dcd7f40d81645f97489/packages/babel-parser/test/fixtures/experimental/async-explicit-resource-management/valid-for-using-binding-of-of/input.js
Activity
fisker commentedon Aug 29, 2023
sosukesuzuki commentedon Aug 29, 2023
MartinJohns commentedon Aug 29, 2023
Does this ever happen with real code, or is it just an attempt to intentionally break the parser?
sosukesuzuki commentedon Aug 29, 2023
I didn't see this with real code but I didn't intentionally break the parser, I just noticed it while developing the code formatter.
DanielRosenwasser commentedon Aug 29, 2023
(congrats on issue #55555!)
rbuckton commentedon Oct 30, 2023
It's a spec conformance issue. The spec specifically forbids
for (using of ofsince that can be ambiguous (usingcould be an identifier likexinfor (x of of, orofcould be either an identifier or a keyword), whilefor (await using of ofis unambiguous (await usingcan only imply the declaration, thusawait using ofmust declare an identifier).