Closed
Description
TypeScript Version: 2.8.1 & 2.9.0-dev.20180409
Search Terms: noImplicitReturns throw type guard
Code
interface A { type: 'A' }
interface B { type: 'B' }
function isA(val: any): val is A { return val && val.type === 'A'}
function isB(val: any): val is B { return val && val.type === 'B'}
function getAOrThrow(val: A | B): A {
if (isA(val)) {
return val; // val inferred to A
} else if (isB(val)){ // val inferred to B
throw new Error();
}
val // type inferred to never
}Expected behavior:
Type check should pass without error.
Actual behavior:
Happens only with noImplicitReturns turned on.
getAOrThrow errors on its return value with Function lacks ending return statement and return type does not include 'undefined'..
If I remove the second type guard call (isB) and just leave it as a catch-all else, there is no error.
Playground Link:
Cannot reproduce in playground due to noImplicitReturns being turned off.
Related Issues:
Couldn't find any.