TypeScript/tests/cases/compiler/compareTypeParameterConstrainedByLiteralToLiteral.ts

// Test for #26758

function foo<T extends "a" | "b">(t: T) {
    t === "a";  // Should be allowed
    t === "x";  // Should be error
}
Remove the rule that replaces a union of literal types with the base type when comparing equality to a type that isn't a union of literal types. (#27588) type when comparing equality to a type that isn't a union of literal types. The rule is redundant because a primitive type is already directed- comparable to a value of that primitive type, and it causes errors to be missed when comparing a type parameter _constrained_ by a union of literal types to another union of literal types. The baseline changes look like improvements to me. Fixes #26758. 2019-04-23 21:59:07 +02:00			`// Test for #26758`

			`function foo<T extends "a" \| "b">(t: T) {`
			`t === "a"; // Should be allowed`
			`t === "x"; // Should be error`
			`}`