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Leading Rest element in tuples are kinda broken !? #61842
Description
🔎 Search Terms
Rest Element
Tuples
Leading Rest Element Tuple
🕗 Version & Regression Information
Nightly
⏯ Playground Link
💻 Code
type T = [...string[], number, boolean, symbol];
type First = T[0];🙁 Actual behavior
type T = [...string[], number, boolean, symbol];
type First = T[0];
// ^? First = string | number | boolean | symbol🙂 Expected behavior
type T = [...string[], number, boolean, symbol];
type First = T[0];
// ^? First = string | numberAdditional information about the issue
Is this a common thing it doesn't make sense, like T[0] can never be boolean or symbol am I missing something.
Although I can be used to create type guard to check for leading rest element in arrays.
type IsLeadingRestElement<T extends UnknownArray> = If<IsAny<T>, false,
number extends T['length']
? T[number] extends T[0]
? true
: false
: false
>;
Activity
MartinJohns commentedon Jun 10, 2025
Duplicate of #56885.
benzaria commentedon Jun 10, 2025
True !