Exhausting enum values in switch statements without default case.

[tinganho]

For expressivity I don't always include a default case in my switch statements. But I know that variable abc below cannot be any value other than a, b and c. Thus, I think the below code should not error, because I return the correct type for all branches it can take.

let abc: 'a' | 'b' | 'c';
function test(): string {// function lacks ending return statement and return type does not include 'undefined'.
    switch(abc) {
        case 'a':
            return '';
        case 'b':
            return '';
        case 'c':
            return '';
    }
}

And for enums:

enum ABC {
  a,
  b,
  c,
}
let abc: ABC
function test(): string {// function lacks ending return statement and return type does not include 'undefined'.
    switch(abc) {
        case ABC.a:
            return '';
        case ABC.b:
            return '';
        case ABC.c:
            return '';
    }
}

[kitsonk]

Dupe of #2214? Currently planned for TS 2.1...

[tinganho]

@kitsonk IMO little bit different. That one is about types. My OP is about exhausting enum values. But anyway changed title and the content of my OP to reflect my intent.

[DanielRosenwasser]

Hm, looks closer to #8602 actually.

[zpdDG4gta8XKpMCd]

might be related #6155

[tinganho]

Yes, dupe of #6155.