TypeScript 4.2.* can't type check utils/internal/compose.d.ts PickLastInTuple<T>

[rabelloo]

Describe the bug

After updating from TypeScript 4.1.5 to 4.2.2 msw can no longer be type-checked with tsc --noEmit.

node_modules/msw/lib/types/utils/internal/compose.d.ts(6,65):
  error TS2344: Type 'PickLastInTuple<T>' does not satisfy the constraint '(...args: any) => any'.
    Type 'unknown' is not assignable to type '(...args: any) => any'.

I don't think I even use that type, but because it is included in msw/index.d.ts TypeScript wants it to pass :/

Environment

• msw: 0.26.2
• nodejs: 14.13.0
• npm: 7.5.4
• typescript: 4.2.2

To Reproduce

Steps to reproduce the behavior:

1. Install msw@0.26.2 and typescript@4.2.2
2. Create a file that imports anything from msw
3. Try to type-check said file with tsc --noEmit

Expected behavior

TypeScript can type-check msw, in specific PickLastInTuple<T>

[kettanaito]

@rabelloo, thank you for reporting this! The issue is fixed and will be released in the next patch version.

[ngame2011]

A temporary solution that worked for me:

type ParametersOrNot<T> = T extends (...args: any[]) => any ? Parameters<T> : never;

declare type FirstFnParameterType<T extends any[]> = ParametersOrNot<PickLastInTuple<T>>[any];