Add one more type-checking pass (python#18717)

This helps in rare cases, see discussion in
python#18674

Author: ilevkivskyi

mypy/checker.py

@@ -216,7 +216,7 @@
 
 T = TypeVar("T")
 
-DEFAULT_LAST_PASS: Final = 1  # Pass numbers start at 0
+DEFAULT_LAST_PASS: Final = 2  # Pass numbers start at 0
 
 # Maximum length of fixed tuple types inferred when narrowing from variadic tuples.
 MAX_PRECISE_TUPLE_SIZE: Final = 8

test-data/unit/check-modules.test

@@ -1388,14 +1388,14 @@ import b
 import b
 class C:
     def f1(self) -> None:
-        self.x2
+        reveal_type(self.x2)
     def f2(self) -> None:
         self.x2 = b.b
 [file b.py]
 import a
 b = 1 + int()
 [out]
-tmp/a.py:4: error: Cannot determine type of "x2"
+tmp/a.py:4: note: Revealed type is "builtins.int"
 
 [case testErrorInPassTwo1]
 import b