Microsoft/TypeScript
Auf GitHub ansehenGeneric constraint is not validated in a recursive type
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#53.895 geöffnet am 18. Apr. 2023
BugDomain: Conditional TypesHelp Wanted
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Beschreibung
Bug Report
🕗 Version & Regression Information
- This is the behavior in every version I tried, starting from 4.1 where recursive conditional types were added
⏯ Playground Link
Playground link with relevant code
💻 Code
export type ComputeRangeLoose<
N extends number,
Result extends Array<number> = [],
> = Result['length'] extends N ? Result : ComputeRangeLoose<N, [...Result, Result['length']]>
type A = ComputeRangeLoose<{ foo: true }>
export type ComputeRangeStrict<
N extends number,
Result extends Array<number> = [],
> = N extends number
? Result['length'] extends N ? Result : ComputeRangeStrict<N, [...Result, Result['length']]>
: never
type B = ComputeRangeStrict<{ foo: true }>
🙁 Actual behavior
ComputeRangeLoose<{ foo: true }> allows to pass a type that is not related to number, throwing Type instantiation is excessively deep and possibly infinite.
ComputeRangeStrict<{ foo: true }> throws an expected Type '{ foo: true; }' does not satisfy the constraint 'number'
🙂 Expected behavior
Both ComputeRangeLoose and ComputeRangeStrict throw Type '{ foo: true; }' does not satisfy the constraint 'number'
As the issue is reproducible since 4.1, I'm pretty sure it was already mentioned somewhere however I failed to find a suitable issue