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tests/cases/compiler/extractInferenceImprovement.ts(26,26): error TS2345: Argument of type 'typeof s' is not assignable to parameter of type 'never'.
tests/cases/compiler/extractInferenceImprovement.ts(28,1): error TS2322: Type 'string | number' is not assignable to type 'string'.
Type 'number' is not assignable to type 'string'.
tests/cases/compiler/extractInferenceImprovement.ts(28,26): error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type '"first" | "second"'.
==== tests/cases/compiler/extractInferenceImprovement.ts (3 errors) ====
// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
function getProperty2<T, K extends keyof T>(obj: T, key: Extract<K, string>): T[K] {
return obj[key];
}
function getProperty3<T, K extends Extract<keyof T, string>>(obj: T, key: K): T[K] {
return obj[key];
}
const s = Symbol();
interface StrNum {
first: string;
second: number;
[s]: string;
}
const obj: StrNum = {} as any;
let prop: string;
// should work
prop = getProperty2(obj, 'first');
prop = getProperty3(obj, 'first');
// Should fail
prop = getProperty2(obj, s);
~
!!! error TS2345: Argument of type 'typeof s' is not assignable to parameter of type 'never'.
prop = getProperty3(obj, s);
~~~~
!!! error TS2322: Type 'string | number' is not assignable to type 'string'.
!!! error TS2322: Type 'number' is not assignable to type 'string'.
~
!!! error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type '"first" | "second"'.
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