🔎 Search Terms

boolean literal type true false assign expression

🕗 Version & Regression Information

• This changed between versions 4.1.5 and 4.2.3
• Not sure but feat(40197): No "did you mean to call" error when invocation is part of a logical expression #40260 could be the reason

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/CYUwxgNghgTiAEEQBd4GcD2BbEAhDGEAXPAEYFJQB2A3AFB1KogAeUWADkgIzwC88ZDACuIek3it2XEACZ+6bHgrwAPqsEixQA

💻 Code

declare let someBool: boolean;

let okay = true;
let weird = someBool || true;

🙁 Actual behavior

weird is assigned the type true, whereas okay is of type boolean.

🙂 Expected behavior

Both variables have the type boolean.

Additional information about the issue

Stumbled upon this while writing react/react#33399.

Very unexpected and confusing behavior, I highly doubt it is intended. Couldn't find anything explaining the change in the release notes for TypeScript 4.2, so pretty sure it's an unwanted regression. Please correct me if I'm wrong.