Function overloading of generic functions allows for invalid code about typescript HOT 3 CLOSED

Overloads are checked more loosely than they "should" be, see #13235 among others. You'll probably always be able to find some inconsistency in exactly what is allowed versus rejected.

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Joe and Andrew, I agree that it's virtually impossible for TS to cover all use cases. However, as TS already detects the error in the case below (Playground):

/* overload #1 */ function f0(fn: () => void): (() => void);
/* overload #2 */ function f0(fn: (p1: string) => void): ((p1: string) => void);
/* overload #3 */ function f0(fn: (p1: string, p2: boolean) => void): ((p1: string, p2: boolean) => void);

function f0(fn: (...args: unknown[]) => void): (...args: unknown[]) => void {
  // ...
}

I don't see why it fails to detect the same situation when generic types are present, like the similar code below, considering that string is (sort of) a "subset" (i.e. contained in) of the generic type P1 and boolean is a "subset" of P2 (Playground):

/* overload #1 */ function f0(fn: () => void): (() => void);
/* overload #2 */ function f0<P1>(fn: (p1: P1) => void): ((p1: P1) => void);
/* overload #3 */ function f0<P1, P2>(fn: (p1: P1, p2: P2) => void): ((p1: P1, p2: P2) => void);

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This issue has been marked as "Not a Defect" and has seen no recent activity. It has been automatically closed for house-keeping purposes.

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