Incorrect rewrite for defer

[alaviss]

import cps

type
  InfiniteLoop = CatchableError
  Cont* = ref object of RootObj
    when cpsMutant:
      fn*: proc(c: var Cont) {.nimcall.}
    else:
      fn*: proc(c: Cont): Cont {.nimcall.}

var jumps: int

proc trampoline(c: Cont) =
  jumps = 0
  var c = c
  while c != nil and c.fn != nil:
    c = c.fn(c)
    inc jumps
    if jumps > 1000:
      raise newException(InfiniteLoop, $jumps & " iterations")

proc noop*(c: Cont): Cont {.cpsMagic.} = c

template check(cond: bool, msg: string) =
  if not cond:
    raise newException(Defect, "not " & astToStr(cond) & ": " & msg)

var r = 0

proc foo() {.cps: Cont.} =
  defer:
    check r == 2, "defer run before end of scope"
    inc r

  inc r
  noop()
  inc r

trampoline foo()
check r == 3, "expected 3, got: " & $r

Current output:

Error: unhandled exception: not r == 2: defer run before end of scope [Defect]

[disruptek]

As far as where defer actually ends up, it's a bit of a head-scratcher. The best solution is probably to rewrite it in a very early pass as we do for. Did you happen to try using the same getTransformImpl hack?

[disruptek]

This is stalled pending a compiler bug which @alaviss may decide to link here. 😘

[alaviss]

blocked by nim-lang/Nim#18059