function {:existential true} {:inline} b1(x: bool) : bool
{
  false
}
fail1.bpl(16,3): Error BP5001: This assertion might not hold.
Execution trace:
    fail1.bpl(11,3): anon0
    fail1.bpl(12,11): anon4_Then
    fail1.bpl(16,3): anon3

Boogie program verifier finished with 0 verified, 1 error