`elt` in generator expressions have incorrect type annotations

[zsol]

The fine docs say that elt in the various comprehension nodes are of type BaseAssignTargetExpression. This is a lie. Observe: in the syntactically correct and semantically plausible expression (i ** 2 for i in _), the elt is constructed from i**2 which is a BinaryOperation:

> echo "(i**2 for _ in _)" | python -m libcst.tool print -
Module(
  body=[
    SimpleStatementLine(
      body=[
        Expr(
          value=GeneratorExp(
            elt=BinaryOperation(
              left=Name(
                value='i',
              ),
              operator=Power(),
              right=Integer(
                value='2',
              ),
            ),
            for_in=CompFor(
              target=Name(
                value='i',
              ),
              iter=Name(
                value='_',
              ),
            ),
          ),
        ),
      ],
    ),
  ],
)

But alas, BinaryOperation is not a BaseAssignTargetExpression.

>>> issubclass(cst.BinaryOperation, cst.BaseAssignTargetExpression)
False

What is the correct type for elt here? BaseExpression?

[zsol]

The Python ast docs say it can be any expression.