using transform throws when a for body binding shadows the for head binding
#61714
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This seems like a bizarre thing to write; we might just choose to error instead. |
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This example is also valid JS and TS so far has no complaints: class Foo {}
for (const foo of []) {
const foo = new Foo();
}If TS decides to error instead, this will introduce inconsistency between |
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It seems like a likely code error to do that, though. You could have written instead |
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Yes, you are right. They are just valid pedantic examples. So I am calling for consistency. If TS thinks for (using foo of []) {
const foo = new Foo();
}is bad and should throw an error (though currently the error is unintentional because of the transform result). Then the same error should be applied to for (const foo of []) {
const foo = new Foo();
}as well. The fact that the former is throwing while the latter is okay seems inconsistent. |
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🔎 Search Terms
explicit resource management, using, await using, loop initializer, Symbol.dispose, Symbol.asyncDispose, iteration, shadows
🕗 Version & Regression Information
⏯ Playground Link
https://www.typescriptlang.org/play/?ts=5.9.0-dev.20250516#code/MYGwhgzhAEBiD29oG8C+BYAUAM3gJ2gAoBXCASwDsBzaXJebaAbQF0BKFLaaYeCiAC61E0ALzQKAUwDucRITYBuLKiA
💻 Code
🙁 Actual behavior
The transformed output throws "redeclaration of const foo "
🙂 Expected behavior
The transformed output should not throw.
Additional information about the issue
Babel is also affected by this issue: babel/babel#17318. We plan to wrap the for body within a new block when it contains shadowed binding.
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