[elazarg]

Remember the bound type of the self argument, allowing more consistent error messages.
For example, currently left and right operands are displayed differntly:

$ cat tmp.py
class A:
    def __add__(self, other: A): return self
a = A()
(a, a) + a
a + (a, a)
$ mypy tmp.py
tmp.py:3: error: Unsupported operand types for + ("tuple" and "A")
tmp.py:5: error: Unsupported operand types for + ("A" and "Tuple[A, A]")

Left and right operands are not treated the same way.

[gvanrossum]

The new errors look like this:

__tmp__.py:4: error: Unsupported operand types for + ("Tuple[A, A]" and "A")
__tmp__.py:5: error: Unsupported operand types for + ("A" and "Tuple[A, A]")

Thanks! Reviewing now.

[gvanrossum]

Whoops, does the new attribute need to be serialized?

[elazarg]

I guess it does

[elazarg]

Why not?

[gvanrossum]

Sorry, never mind.