Microsoft/TypeScript

Infer from usages should not widen literal types

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#52 991 ouverte le 27 févr. 2023

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Description

Bug Report

🔎 Search Terms

string literal to string, infer type from usages, code fix, quickfix

⏯ Playground Link

Playground link with relevant code

💻 Code

let a

a = "foo" as "foo" | "bar"

let b

b = getB()

checkB(b)

function checkB(toCheck: "foo" | "bar") {
}

function getB(): "foo" | "bar" {
    return "foo"
}

🙁 Actual behavior

After running infer from usages quickfix, you get string type in a and b positions

🙂 Expected behavior

Should get inffered type "foo"

I think in case of as and satisfies clauses the type should be just copied literally?

As you can see from example this is common case for string enums, like when some function expects some string enum instead of just string, but this information gets lost

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