/
covariantCallbacks.ts
72 lines (55 loc) · 1.2 KB
/
covariantCallbacks.ts
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// @target: es2015
// Test that callback parameters are related covariantly
interface P<T> {
then(cb: (value: T) => void): void;
};
interface A { a: string }
interface B extends A { b: string }
function f1(a: P<A>, b: P<B>) {
a = b;
b = a; // Error
}
function f2(a: Promise<A>, b: Promise<B>) {
a = b;
b = a; // Error
}
interface AList1 {
forEach(cb: (item: A) => void): void;
}
interface BList1 {
forEach(cb: (item: B) => void): void;
}
function f11(a: AList1, b: BList1) {
a = b;
b = a; // Error
}
interface AList2 {
forEach(cb: (item: A) => boolean): void;
}
interface BList2 {
forEach(cb: (item: A) => void): void;
}
function f12(a: AList2, b: BList2) {
a = b;
b = a; // Error
}
interface AList3 {
forEach(cb: (item: A) => void): void;
}
interface BList3 {
forEach(cb: (item: A, context: any) => void): void;
}
function f13(a: AList3, b: BList3) {
a = b;
b = a; // Error
}
interface AList4 {
forEach(cb: (item: A) => A): void;
}
interface BList4 {
forEach(cb: (item: B) => B): void;
}
function f14(a: AList4, b: BList4) {
a = b;
b = a; // Error
}