Recursion in the VM under orc/arc mutates contents of a seq to their default values

[deech]

Recursion mutates the contents of an immutable seq argument to their default values.

Example

proc recurse(strings:seq[string],recursionsLeft:int) =
  if recursionsLeft != 0:
    echo "Before call: " & $strings
    recurse(strings & @["another string"],recursionsLeft-1)
    echo "After call: " & $strings
  else:
    discard

static:
  recurse(@["string"],1)

Current Output

Before call: @["string"]
After call: @[""]

Expected Output

Before call: @["string"]
After call: @["string"]

Compile Command

nim cpp --forceBuild:on --gc:orc -r --verbosity\:0 --hint\[Processing\]\:off --excessiveStackTrace\:on /home/deech/NimScratch/recbug.nim

$ nim -v
Nim Compiler Version 1.5.1 [Linux: amd64]
Compiled at 2021-03-07
Copyright (c) 2006-2021 by Andreas Rumpf

git hash: d1e093207acdd10ad375705bd1732fc6f0db9f55
active boot switches: -d:release

[ghost]

Duplicate of #17199