typescript - 推断回调参数的类型

Question

我无法让编译器知道回调参数的类型。

function test3(fn: (foo: string) => any): any;
function test3(fn: (foo: string, payload: number) => any): any;
function test3(fn: (foo: string, payload: number) => any) {

}

test3((foo) => 1); // Ok, typescript knows "foo" is a string
test3((foo, payload) => 1); // KO, typescript does not infer "foo" nor "payload" type

我不明白为什么在第二次调用时，我必须手动编写 foo 的类型，但在第一次调用时却不需要。

推断可以处理这些重载吗？如果是，如何？如果不是，为什么它不起作用？

Answer 1

// change the order for more specific type first
function test3(fn: (foo: string, payload: number) => any): any;
function test3(fn: (foo: string) => any): any;
function test3(fn: (foo: string, payload: number) => any) {

}

test3((foo) => 1);
test3((foo, payload) => 1);

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