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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

Contributor guide

Research direction: Investigate the 'Infer from usages' quick fix in the TypeScript compiler, specifically how it handles type assertions and 'satisfies' clauses. Trace the logic that infers types for variables from their usages and ensure literal types are preserved rather than widened.
Tech stack: typescript
Domain: compilers
Issue type: Bug
Difficulty: 3
Estimated time: Half day
Activity status: Active
Clarity: Clear
Prerequisites: TypeScriptType inference
Newbie friendliness: 60