Generics; ReturnType<Foo> != ReturnType<typeof foo>

TypeScript Version: Version 2.9.0-dev.20180516

Search Terms: generic function returntype

I couldn't think of a good title for this,

Code

type Delegate<T> = () => T;

function executeGeneric<
    X,
    DelegateT extends Delegate<X> 
>(delegate: DelegateT): ReturnType<DelegateT> {
    //Type 'X' is not assignable to type 'ReturnType<DelegateT>'.
    const x: ReturnType<typeof delegate> = delegate();
    //Type 'X' is not assignable to type 'ReturnType<DelegateT>'.
    const y: ReturnType<DelegateT> = delegate();
    //Type 'X' is not assignable to type 'ReturnType<DelegateT>'.
    return delegate();
}

Expected behavior:

Return successfully.

Intuitively, to me,

1. delegate is of typeDelegateT.
2. ReturnType<DelegateT> and ReturnType<typeof delegate> should be the same

However,

Actual behavior:

Type 'X' is not assignable to type 'ReturnType<DelegateT>'.

Playground Link: Here

Related Issues:

Inizia dalla riproduzione collegata di TypeScript Playground e confronta i tipi di ReturnType e ReturnType nella funzione generica. Determina se gli errori di assegnazione segnalati debbano essere eliminati mantenendo la relazione generica indicata, quindi verifica che la riproduzione non segnali più tali errori.