Mapped tupples with generic constraints

[npenin]

Bug Report

🔎 Search Terms

mapped tupples generic constraints

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries

⏯ Playground Link

Playground link with relevant code

💻 Code

export interface wasmtype<T extends wasmtypeInstance<T>>
{
    new(initialOp: (number | bigint)[]): T;
    type: number;
}

export interface wasmtypeInstance<T extends wasmtypeInstance<T>>
{
    toOpCodes(): (number | bigint)[];
    type: wasmtype<T>
}

export type parameters<T extends wasmtypeInstance<any>[]> = T extends never[] ? never[] :
    T extends [infer T1] ? [T1['type']] :
    T extends [infer T1, infer T2] ? [T1, T2] :
    T extends [infer T1, infer T2, infer T3] ? [T1, T2, T3] :
    T extends [infer T1, infer T2, infer T3, infer T4] ? [T1, T2, T3, T4] :
    T extends [infer T1, infer T2, infer T3, infer T4, infer T5] ? [T1, T2, T3, T4, T5] :
    T extends [infer T1, infer T2, infer T3, infer T4, infer T5, infer T6] ? [T1, T2, T3, T4, T5, T6] :
    T extends [infer T1, infer T2, infer T3, infer T4, infer T5, infer T6, infer T7] ? [T1, T2, T3, T4, T5, T6, T7] :
    T
    ;

🙁 Actual behavior

The compiler complains that T1 is not a wasmtypeInstance.

🙂 Expected behavior

Since T1 extends wasmtypeInstance (based on the generic constraint), T1['type'] should be an allowed structure as well. Ideally, it would return wasmtype because of the inference, but at least a wasmtype as specified in the constraint is a must.

[npenin]

a somehow connected usecase would be if your replace parameters with the following definition:

export type parameters<T extends wasmtypeInstance<any>[]> = T extends never[] ? never[] :
    T extends [infer T1] ? T1 extends wasmtypeInstance<T1> ? [T1['type']] : never :
    T extends [infer T1, infer T2] ? [T1, T2] :
    T extends [infer T1, infer T2, infer T3] ? [T1, T2, T3] :
    T extends [infer T1, infer T2, infer T3, infer T4] ? [T1, T2, T3, T4] :
    T extends [infer T1, infer T2, infer T3, infer T4, infer T5] ? [T1, T2, T3, T4, T5] :
    T extends [infer T1, infer T2, infer T3, infer T4, infer T5, infer T6] ? [T1, T2, T3, T4, T5, T6] :
    T extends [infer T1, infer T2, infer T3, infer T4, infer T5, infer T6, infer T7] ? [T1, T2, T3, T4, T5, T6, T7] :
    T
    ;

in the condition on T1 , the compiler is complaining about T1 not being a wasmtypeInstance, while it is part of the condition I am trying to validate.

[MartinJohns]

Duplicate of #51108. Used search terms: infer constraint conditional type

As a workaround you can do this: T extends [infer T1 extends wasmtypeInstance<any>]