Fix mypy_mypyc crash caused by "complex" interaction (#6169)

The type of Num.n is `complex`, though it can in practice also be an
`int` or a `float`, and we case on the actual type to determine which
sort of mypy ast node to use.

In #6114, promotions were disabled in `isinstance` checks, which
caused mypy to decide that the `isinstance` checks for int and float
won't match. Fix this by giving the value the type object instead of
complex.

Typeshed *does* actually annotate `n` as `Union[float, int, complex]`,
but mypy simplifies that into `complex`. (It does *not* do this
simplification for local variables with such an annotation; see
issue #6168.)

Author: msullivan

mypy/fastparse.py

@@ -928,7 +928,11 @@ def visit_Call(self, n: Call) -> CallExpr:
 
     # Num(object n) -- a number as a PyObject.
     def visit_Num(self, n: ast3.Num) -> Union[IntExpr, FloatExpr, ComplexExpr]:
-        val = n.n
+        # The n field has the type complex, but complex isn't *really*
+        # a parent of int and float, and this causes isinstance below
+        # to think that the complex branch is always picked. Avoid
+        # this by throwing away the type.
+        val = n.n  # type: object
         if isinstance(val, int):
             e = IntExpr(val)  # type: Union[IntExpr, FloatExpr, ComplexExpr]
         elif isinstance(val, float):

mypy/fastparse2.py

@@ -902,7 +902,11 @@ def visit_Call(self, n: Call) -> CallExpr:
 
     # Num(object n) -- a number as a PyObject.
     def visit_Num(self, n: ast27.Num) -> Expression:
-        value = n.n
+        # The n field has the type complex, but complex isn't *really*
+        # a parent of int and float, and this causes isinstance below
+        # to think that the complex branch is always picked. Avoid
+        # this by throwing away the type.
+        value = n.n  # type: object
         is_inverse = False
         if str(n.n).startswith('-'):  # Hackish because of complex.
             value = -n.n