LambdaOldExpressions.bpl(29,1): Error BP5003: A postcondition might not hold on this return path.
LambdaOldExpressions.bpl(23,3): Related location: This is the postcondition that might not hold.
Execution trace:
    LambdaOldExpressions.bpl(27,7): anon0

Boogie program verifier finished with 4 verified, 1 error