Clang crashes on:

$ cat foo.cpp
enum MyEnum {
  something_valid,
  something_invalid
};

bool recurse() {
  MyEnum K;
  switch (K) {
  case something_valid:
  case what_am_i_thinking:
    int *X = 0;
    if (recurse()) {
    }

    break;
  }
}

$ clang foo.cpp -w
x.cpp:11:8: error: use of undeclared identifier 'what_am_i_thinking'
  case what_am_i_thinking:
       ^
Assertion failed: (LabelAndGotoScopes.count(SC) && "Case not visited?"), function VerifyJumps, file JumpDiagnostics.cpp, line 494.
0  clang             0x0000000101f7b0d5 PrintStackTrace(void*) + 53
1  clang             0x0000000101f7b78b SignalHandler(int) + 379
2  libSystem.B.dylib 0x00007fff86fba1ba _sigtramp + 26
3  libSystem.B.dylib 0x000100010044075c _sigtramp + 2034787772
4  clang             0x0000000101f7b45b raise + 27
5  clang             0x0000000101f7b51a abort + 26
6  clang             0x0000000101f7b4f4 __assert_rtn + 132
7  clang             0x0000000100429b6c (anonymous namespace)::JumpScopeChecker::VerifyJumps() + 492
8  clang             0x00000001004289e7 (anonymous namespace)::JumpScopeChecker::JumpScopeChecker(clang::Stmt*, clang::Sema&) + 263
9  clang             0x0000000100428715 (anonymous namespace)::JumpScopeChecker::JumpScopeChecker(clang::Stmt*, clang::Sema&) + 37
10 clang             0x00000001004286d1 clang::Sema::DiagnoseInvalidJumps(clang::Stmt*) + 49
...