Missing implicit move in assignment

[arnetheduck]

Nim Version

2.2.4, both orc and refc

Update: cannot repro with orc, must have been a fluke - only refc broken

Description

type PageRef = ref object
  store: ref seq[byte]

func init*(_: type PageRef, data: sink seq[byte]): PageRef =
  let a = addr data[0]
  let tmp = PageRef(store: new seq[byte])
  tmp.store[] = data

  assert a == addr tmp.store[][0]
  tmp


discard PageRef.init(@[byte 1, 2, 3])

Last use of data is assignment, it should be moved implicitly

Current Output

Expected Output

Known Workarounds

No response

Additional Information

No response

[arnetheduck]

Notably, this works correctly for move-only types as far as I can tell:

type MoveOnly = object
  a: int

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

type PageRef = ref object
  store: ref MoveOnly

func init*(_: type PageRef, data: sink MoveOnly): PageRef =
  let tmp = PageRef(store: new MoveOnly)
  tmp.store[] = data
  tmp


debugEcho PageRef.init(MoveOnly(a: 5))[].store[]

[arnetheduck]

related: #25051

[ringabout]

2.2.4, both orc and refc

Doesn't orc pass tests? It works on macOS and uses =sink internally in orc.

[arnetheduck]

Doesn't orc pass tests? It works on macOS and use =sink internally in orc.

My bad it seems - just reran this test and the code indeed correctly moves with ORC - I must have passed the wrong params when testing. Broken with refc however.

[ringabout]

Does refc seqs support move analysis since it is not destructor-based which uses genericSeqAssign under the hood

[arnetheduck]

support move analysis

there is nothing fundamental about move analysis that depends on destructors - ie the idea with this series of patches is to disentangle the two concepts and ensure the two memory managers work the same way, so that we don't have to special-case downstream libraries for the two allocators to get efficient code. Basically, move analysis is useful independently of destructors and writing good libraries is made a lot easier if the compiler follows this natural division of the features.