enum exhaustiveness checking with --noImplicitReturns doesn't work for nested switches

TypeScript Version: 3.2.0-dev.20180927

Search Terms:

enum nested switch

Code

enum E {
  A = 'A', B = 'B', C = 'C'
};

function one(e: E): number {
  switch (e) {
    case E.A: return 1;
    case E.B: return 2;
    case E.C: return 3;
  }
}

function two(e: E, f: E): number {
  switch (e) {
  case E.A: return 1;
  case E.B: return 2;
  case E.C:
    switch (f!) {
    case E.A: return 31;
    case E.B: return 32;
    case E.C: return 33;
    }
  }
}

Expected behavior:

Successful compilation: if one is OK, then so is two.

Actual behavior:

flutterby:tmp ariels$ tsc --noImplicitReturns x.ts
x.ts:13:27 - error TS7030: Not all code paths return a value.

13 function two(e: E, f: E): number {

Playground Link:
https://www.typescriptlang.org/play/#src=enum%20E%20%7B%0D%0A%20%20A%20%3D%20'A'%2C%20B%20%3D%20'B'%2C%20C%20%3D%20'C'%0D%0A%7D%3B%0D%0A%0D%0Afunction%20one(e%3A%20E)%3A%20number%20%7B%0D%0A%20%20switch%20(e)%20%7B%0D%0A%20%20%20%20case%20E.A%3A%20return%201%3B%0D%0A%20%20%20%20case%20E.B%3A%20return%202%3B%0D%0A%20%20%20%20case%20E.C%3A%20return%203%3B%0D%0A%20%20%7D%0D%0A%7D%0D%0A%0D%0Afunction%20two(e%3A%20E%2C%20f%3A%20E)%3A%20number%20%7B%0D%0A%20%20switch%20(e)%20%7B%0D%0A%20%20%20%20case%20E.A%3A%20return%201%3B%0D%0A%20%20%20%20case%20E.B%3A%20return%202%3B%0D%0A%20%20%20%20case%20E.C%3A%0D%0A%20%20%20%20%20%20switch%20(f!)%20%7B%0D%0A%20%20%20%20%20%20%20%20case%20E.A%3A%20return%2031%3B%0D%0A%20%20%20%20%20%20%20%20case%20E.B%3A%20return%2032%3B%0D%0A%20%20%20%20%20%20%20%20case%20E.C%3A%20return%2033%3B%0D%0A%20%20%20%20%20%20%7D%0D%0A%20%20%20%20%7D%0D%0A%20%20%7D%0D%0A%7D%0D%0A

Related Issues:

Possibly a simpler case of #23572

Possible duplicate of #11572.

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

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enum exhaustiveness checking with --noImplicitReturns doesn't work for nested switches #27388

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enum exhaustiveness checking with --noImplicitReturns doesn't work for nested switches #27388

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mattmccutchen commented on Sep 27, 2018

typescript-bot commented on Dec 14, 2018

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