swc/crates/swc_ecma_parser/tests/tsc/subtypingWithOptionalProperties.ts

10 lines
302 B
TypeScript

// subtyping is not transitive due to optional properties but the subtyping algorithm assumes it is for the 99% case
// returns { s?: number; }
function f<T>(a: T) {
var b: { s?: number } = a;
return b;
}
var r = f({ s: new Object() }); // ok
r.s && r.s.toFixed(); // would blow up at runtime