Regression in generator args to `result`

[croyzor]

Seems to be due to this commit.

Minimal example that fails:

from guppylang import guppy
from guppylang.std.builtins import array

@guppy
def main() -> None:
    result("fs", array(i * 0.2 for i in range(1)))

main.compile()

gives

guppylang_internals.error.InternalGuppyError: Invalid iterator assign statement

Interestingly, the result is different if the generator element type is int instead of float