Missing move for `sink` parameter + closure environment (refc)

[arnetheduck]

Nim Version

2.2.4

Description

proc makeiter(v: sink string): iterator(): string =
  return iterator(): string =
    yield v

var iter = makeiter("test")()
for c in iter:
  echo "works ", c

An environment is created for the v parameter. With orc, v is correctly moved into the closure:

N_LIB_PRIVATE N_NIMCALL(void, _ZN6testit7makeenvE4sinkI6stringE)(
    NimStringV2 v_p0, tyProc__LCMSFwcIs5O0HdDmqpX05g *Result) {
...
    _ZN6system7eqsink_E3varI6stringE6string((&(*colonenv__1).v0), v_p0);
    _ZN6system11eqwasMoved_E3varI6stringE((&v_p0));
...

With refc, the move analysis is missing and a copy is made instead:

N_LIB_PRIVATE N_NIMCALL(void, _ZN6testit8makeiterE4sinkI6stringE)(
    NimStringDesc *v_p0, tyProc__qUd1Y01q9a25ztxBaH1qzRQ *Result) {
...
    (*colonenv__1).v0 = copyStringRC1(v_p0);
...

The same also applies to a proc closure environment!

Current Output

Expected Output

Known Workarounds

No response

Additional Information

No response

[ringabout]

related to #22173

[arnetheduck]

Semantically, it's allowed for move-only types, ie this compiles and works for both refc and orc:

type MoveOnly = object
  a: int

proc `=copy`(a: var MoveOnly, b: MoveOnly) {.error.}

proc makeiter(v: sink MoveOnly): iterator(): lent MoveOnly =
  return iterator(): lent MoveOnly =
    yield v

# works
var iter = makeiter(MoveOnly(a: 5))
for c in iter():
  echo "works ", c