Improve satisfies semantics: return never when target type is never

[Vinayak Mohakud (Vynxvoid)]

PR: Make satisfies Narrow to never When Target Type Is never

Issue---> #62807 — "Switch doesn't narrow type when type isn't a discriminated union"

This PR updates the TypeScript compiler so that a satisfies expression produces the type never when its target type is exactly the intrinsic never type. This allows patterns like:
assertNever(foo satisfies never);

[TypeScript Bot (typescript-bot)]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[Martin Johns (MartinJohns)]

Won't this change allow foo satisfies never when foo does not satisfy never?

[Ryan Cavanaugh (RyanCavanaugh)]

I don't understand the goal here and this isn't an approved change. In foo satisfies never, if foo isn't never, the program already has an error, so this doesn't change whether or not the line assertNever(foo satisfies never) has an error, and it's not clear why you'd write assertNever(foo satisfies never) in the first place -- assertNever(foo) is equivalent.