Preserve constness of generics with tuple types

[jfet97]

Bug Report

🔎 Search Terms

const modifier, generics, tuple types

🕗 Version & Regression Information

It shows up just in the nightly version because const modifiers for generics will be available from TS 5.0

⏯ Playground Link

Playground link with relevant code

💻 Code

declare function inners<const T extends readonly any[]>(...args: readonly [unknown, ...T, unknown]): T;

const test = inners(1,2,3,4,5);

🙁 Actual behavior

T is inferred as [number, number, number] instead of readonly [2,3,4]. There are other ways to write this function by avoiding tuple types at all, but it is a nice example to show that that the constness introduced by the const modifier seems to be lost when tuple types come into play, even with the readonly modifier.

🙂 Expected behavior

T inferred as readonly [2,3,4]