Empty rest parameter type inferred from candidate function with no rest parameters when "best match" contains a contextually typed argument

Bug Report

🔎 Search Terms

Rest parameter inference contextual

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about type inference

⏯ Playground Link

Playground link with relevant code

💻 Code

const doSomething = <Args extends unknown[]>(
    fn1: (aNumber: number, ...rest: Args) => void,
    fn2: (aNumber: number, ...rest: Args) => void,
) => {}

// OK, no contextual types
doSomething(
    (explicit: number, rest: string) => {}, // Args = [string]
    () => {},
)

// OK (both contain contextually typed arg)
doSomething(
    (contextual, rest: string) => {}, // Args = [string]
    (contextual) => {},
)

// Contextually type only fn1 - Not ok
doSomething(
    (contextual, rest: string) => {}, // ERROR
    () => {}, // Args = []
)
doSomething(
    (contextual, rest: string) => {}, // ERROR
    (explicit: number) => {}, // Args = []
)

🙁 Actual behavior

When fn1 (and only fn1) contains a contextually typed argument, it is ignored in favour of fn2

🙂 Expected behavior

In all of the examples, fn2 specifies no rest parameters at all.

I would expect functions that do not specify any rest parameters to always be the least preferable candidate (lowest weight?) for rest parameter inference, since "no rest parameters" can always be assigned to any rest parameter type.

リンクされた TypeScript Playground の再現例から始め、3 つの doSomething 呼び出しを減らして、コンテキスト型付けが rest パラメーターの推論にどのような影響を与えるかを切り分けます。推論候補を選択する型チェックの経路を追跡し、続いて示されたケースの回帰テストを追加します。fn1 の [string] rest 型が fn2 の [] に置き換えられなければ完了です。