Poor behavior on missing override for Macaw S-expression programs

[langston-barrett]

(declare @extern () Unit)

(defun @test ((regs X86Regs)) X86Regs
  (start start:
    (funcall @extern)
    (return regs)))

Finished analyzing 'test'. Likely bug: unavoidable error (safety condition is unsatisfiable) at :1:0
:1:0: error: in _start
Global symbol not allocated
Details:
  Global symbol "extern" has no associated allocation

c.f. the following LLVM S-expression program:

(declare @extern () Unit)

(defun @test () Unit
  (start start:
    (funcall @extern)
    (return ())))

All goals passed!
Finished analyzing 'test'.