Vyper: Circumventing `@constant` with multiple return values and tuple assignment

[smarx]

Modifying state is not allowed in @constant functions, but you can bypass the check by using multiple return values:

x: public(uint256)

@private
@constant
def returnTwo() -> (uint256, uint256):
    return 1, 2

@public
@constant
def foo():
    a: uint256 = 0
    a, self.x = self.returnTwo() # BUG

[jacqueswww]

Meeting Notes: fix it.