shallowCopy in iterator yielding full copies

[mratsim]

Here is the test case:

iterator foo(s: seq[int]): seq[int] =
  var sha_cp: seq[int]
  shallowCopy(sha_cp, s)

  echo "\nOriginal seq repr\n" & s.repr
  echo "Copy repr inside iter\n" & s.repr

  for _ in s:
    yield sha_cp

let s = @[1, 2, 3, 4, 5]
for sequence in s.foo:
  echo "#### Yielded repr"
  echo sequence.repr

Output

Original seq repr
0x10075f048[1, 2, 3, 4, 5]

Copy repr inside iter
0x10075f048[1, 2, 3, 4, 5]

#### Yielded repr
0x10075f678[1, 2, 3, 4, 5]

#### Yielded repr
0x10075f990[1, 2, 3, 4, 5]

#### Yielded repr
0x10075fca8[1, 2, 3, 4, 5]

#### Yielded repr
0x10075ffc0[1, 2, 3, 4, 5]

#### Yielded repr
0x100769318[1, 2, 3, 4, 5]

[Araq]

The compiler is allowed to do this.

[andreaferretti]

Is it? What is the reason?

[stale]

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