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tests/cases/compiler/genericRestTypes.ts(21,11): error TS2322: Type '(cb: (x: string, ...rest: T) => void) => void' is not assignable to type '(cb: (...args: never) => void) => void'.
Types of parameters 'cb' and 'cb' are incompatible.
Types of parameters 'args' and 'x' are incompatible.
Type '[x: string, ...rest: T]' is not assignable to type 'never'.
==== tests/cases/compiler/genericRestTypes.ts (1 errors) ====
// Repro from #25793
// Gets the parameters of a function type as a tuple
// Removes the first element from a tuple
type Tail<T extends any[]> = ((...args: T) => any) extends ((head: any, ...tail: infer U) => any) ? U : never;
type MyFunctionType = (foo: number, bar: string) => boolean;
type Explicit = (...args: Tail<Parameters<MyFunctionType>>) => ReturnType<MyFunctionType>; // (bar: string) => boolean
type Bind1<T extends (head: any, ...tail: any[]) => any> = (...args: Tail<Parameters<T>>) => ReturnType<T>;
type Generic = Bind1<MyFunctionType>; // (bar: string) => boolean
function assignmentWithComplexRest<T extends any[]>() {
const fn1: (x: string, ...rest: T) => void = (x, ..._) => x;
const fn2: (...args: never) => void = fn1;
}
function assignmentWithComplexRest2<T extends any[]>() {
const fn1: (cb: (x: string, ...rest: T) => void) => void = (cb) => {};
const fn2: (cb: (...args: never) => void) => void = fn1;
~~~
!!! error TS2322: Type '(cb: (x: string, ...rest: T) => void) => void' is not assignable to type '(cb: (...args: never) => void) => void'.
!!! error TS2322: Types of parameters 'cb' and 'cb' are incompatible.
!!! error TS2322: Types of parameters 'args' and 'x' are incompatible.
!!! error TS2322: Type '[x: string, ...rest: T]' is not assignable to type 'never'.
}
function assignmentWithComplexRest3<T extends any[]>() {
const fn1: (x: string, ...rest: T) => void = (x, ..._) => x;
const fn2: (...args: {x: "a"} & {x: "b"}) => void = fn1;
}
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