Extracting generator comprehension may produce invalid code

[lieryan]

Describe the bug

Extracting generator comprehension may produce invalid code after extraction.

To Reproduce Steps to reproduce the behavior:

1. Code before refactoring:

foo = sum(x for x in y)

2. Extract x for x in y, without selecting the outer parentheses

3. Expected code after extract variable refactoring:

extracted = (x for x in y)
foo = sum(extracted)

or after extract method refactoring:

foo = sum(extracted())
def extracted():
    return (x for x in y)

4. Instead, we currently produce invalid code when extracting local variable:

extracted = x for x in y
foo = sum(extracted)

5. And "Unhandled exception in Pymode: invalid syntax (, line 2)" when extracting method"

• [ ] fix extract variable
• [ ] fix extract method