error TS-1: Pre-emit (1) and post-emit (2) diagnostic counts do not match! This can indicate that a semantic _error_ was added by the emit resolver - such an error may not be reflected on the command line or in the editor, but may be captured in a baseline here!
YieldExpression12_es6.ts(3,6): error TS1163: A 'yield' expression is only allowed in a generator body.


!!! error TS-1: Pre-emit (1) and post-emit (2) diagnostic counts do not match! This can indicate that a semantic _error_ was added by the emit resolver - such an error may not be reflected on the command line or in the editor, but may be captured in a baseline here!
!!! related TS-1: The excess diagnostics are:
!!! related TS2304 YieldExpression12_es6.ts:3:12: Cannot find name 'foo'.
==== YieldExpression12_es6.ts (1 errors) ====
    class C {
      constructor() {
         yield foo
         ~~~~~
!!! error TS1163: A 'yield' expression is only allowed in a generator body.
      }
    }