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!
YieldExpression2_es6.ts(1,1): 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 YieldExpression2_es6.ts:1:7: Cannot find name 'foo'.
==== YieldExpression2_es6.ts (1 errors) ====
    yield foo;
    ~~~~~
!!! error TS1163: A 'yield' expression is only allowed in a generator body.