extends causing string literal can't be used as index #54886
Description
Bug Report
🔎 Search Terms
cannot be used as an index type
🕗 Version & Regression Information
- This changed between versions 4.9.5 and 5.0.4
⏯ Playground Link
Playground link with relevant code
💻 Code
interface Dict {
foo: 1
bar: 1
}
type A = Dict['foo'] // works
type F = 'foo'
type B = Dict[F] // works
type FF = 'foo' extends ('foo' | 'bar') ? 'foo' : never // in theory, FF === F
type C = Dict[FF] // not working, Type '"foo"' cannot be used as an index type.(2538)🙁 Actual behavior
type C throws error
🙂 Expected behavior
no error