Reusing function type with different parameters amount (overloading)

Bug Report

Is there any reason it's not possible to re-use a function type that is overloaded aka has different possible amount of arguments?

In the playground I put some code that shows this issue, but I will put a quick snippet here:

declare function foo(c: {a: number; b: string}): void
declare function foo(a: number, b: string): void


foo({ a: 1, b: "2" })

foo(1, "2")

// This doesn't work but is relatively understandable
const bar1: typeof foo = (a_c, b) => {
    a_c
    b
}

// This should work, why it doesn't?
const bar2: typeof foo = (...args) => {
    args
}

// it works fine, but you can't access the second parameter
const bar3: typeof foo = (a_c) => {  
    a_c
}

// it works fine, but you can't access the parameters
const bar4: typeof foo = () => {
}

bar2 in this example doesn't work, and the error that is given is Type '(args_0: number | { a: number; b: string; }, args_1: unknown) => void' is not assignable to type '{ (c: { a: number; b: string; }): void; (a: number, b: string): void; }'.

🔎 Search Terms

arguments overload parameter function

🕗 Version & Regression Information

In 4.4.0-beta & 4.3.5:

In 4.2.3 and before:

⏯ Playground Link

https://www.typescriptlang.org/play?target=99&jsx=0&ts=4.3.5#code/CYUwxgNghgTiAEAzArgOzAFwJYHtVJxwAowAueAbynNWQFsAjEGAbngfIGcMYtUBzAL4BKcgDccWYAFgAUKEiwEKdNjwFi1eLUbMANOy48+-UfAlS5V2YkJEK8LQEYDHeACIATO-gjrt4hcPb2FrAHow+AAVAAssTnhgHBBOVAByDHgAdxwYAGt2ZEz4+DhobDEQCABPeDRQGG4oVGAoBggQOTA8bnZYJ3IMaoAHEBxEDXgAXngiKAB9MFdhaYA+Sjl4LcdFze2GOUFwyNiSzhicZAhgbNy8gyyY2qxMpJT0jAB+Lp7MhlhPIMRmMJgFprMAHRQ2D8TgrKbrCh7LYwziHY7wF63fIJRB8ECuIrwaqXeBgZoZRxgMApBIYGIITjgPA3YawKB0EAYZg-VC9f4wADMQNG40mMzmi3hiK2yJ2YHRsjkEUxmRyOKQ+MJmRJyDJFMyUGptPg9IQbJgHK5zDRsm6fL+sAALCKQeLZtKNrIjrIgA

🙁 Actual behavior

It just errors out when trying to use "...args" to get all the possible arguments of the function

🙂 Expected behavior

To be able to use "...args" or similar to get the arguments and typescript to not complain just for trying to use it

まず、報告されているバージョン 4.3.5 と 4.4.0-beta を使って、リンク先の TypeScript Playground でオーバーロードの代入動作を再現します。受け入れられる例と拒否される例を比較し、その後、オーバーロードされた関数の rest パラメーター実装に対して意図される動作を判断します。動作と期待される型付けが確立され、適切な compiler test でカバーされれば完了です。