`Cannot modify loop variable` issue when trying to append something to an array during a loop.

[rockorama]

Version Information

• vyper Version (output of vyper --version): 0.4.0
• OS: osx
• Python Version (output of python --version): 3.10.0

What's your issue about?

When iterating through an array of addresses, I have to append to another array the ones already processed. When trying to append to that array I get the compilation error Cannot modify loop variable

It works if I don't iterate through the addresses array, but use indices to do so instead.

@external
def foo():
    remainingToRepay: uint256 = 0
    alreadyDone: DynArray[address, 10] = []
    _assets: DynArray[address, 10] = []
    for a: address in _assets:
        if remainingToRepay == 0:
            break
        if not a in alreadyDone:
            continue
        alreadyDone.append(a)

works with:

  for i: uint256 in range(len(_asserts), bound=MAX_ASSETS):
        a: address = _assets[i]
        if remainingToRepay == 0:
            break
        if not a in alreadyDone:
            continue
        alreadyDone.append(a)