regression(0.20.0 => devel): `move` gives wrong results with var params in VM

[timotheecour]

move gives wrong results with var params in VM

Example

when true:
  type Foo = object
    f0: int
  proc fn(a: var Foo) =
    var s: Foo
    s = move(a)
    echo s
    echo a
    a = Foo(f0: 2)
    echo s
  proc main()=
    echo "---"
    var a = Foo(f0: 1)
    fn(a)

  static: main()
  main()

Current Output

---
(f0: 0)
(f0: 0)
(f0: 2)
---
(f0: 1)
(f0: 0)
(f0: 1)

Expected Output

---
(f0: 1)
(f0: 0)
(f0: 1)
---
(f0: 1)
(f0: 0)
(f0: 1)

Additional Information

regression:

• fails with: devel 1.5.1 c39fa0d
• works with: nim 0.20.0
• likewise in other cases where you'd have a copy, eg: var s: seq[Foo] and s.add a
• 2nd root cause for RT vs CT flyx/NimYAML#91 (nimyaml gives wrong results at CT)

note

it's possible that the root cause is the same as #15974, but not obvious to me why it would

[ringabout]

Since #17348 is merged, the content of move is not cleared.

---
(f0: 1)
(f0: 1)
(f0: 1)
---
(f0: 1)
(f0: 0)
(f0: 1)