Incorrect handling of template literals + intersections

[jakebailey]

Bug Report

🔎 Search Terms

intersection template literals

🕗 Version & Regression Information

• This changed between versions 5.0 and nightly

⏯ Playground Link

Playground Link

💻 Code

type MaybeCat = `c${string}` & `${string}t`;
type MaybeScats = `s${MaybeCat}s`;

declare var x: MaybeScats;

x = "scats"; // should be OK
x = "scas"; // should error

🙁 Actual behavior

In 5.0, neither error, even though the second one should.

In nightly, after #52836, both error.

🙂 Expected behavior

First one is okay, second is an error.

Noted in: #53406 (review)

Unsure if this is a regression per-se; neither behavior is really right, I just managed to change it and expose what I believe is a new bug to do with how we handle template literals.

[ahejlsberg]

Fixed by #54188.