Add failing type narrowing test cases

Author: George-Ogden

test-data/unit/check-isinstance.test

@@ -2716,23 +2716,81 @@ if type(x) == type(y) == int:
     reveal_type(y) # N: Revealed type is "builtins.int"
     reveal_type(x) # N: Revealed type is "builtins.int"
 
+z: Any
+if int == type(z) == int:
+    reveal_type(z) # N: Revealed type is "builtins.int"
+
 [case testTypeEqualsCheckUsingIs]
 from typing import Any
 
 y: Any
 if type(y) is int:
     reveal_type(y) # N: Revealed type is "builtins.int"
 
+[case testTypeEqualsCheckUsingImplicitTypes]
+from typing import Any
+
+x: str
+y: Any
+z: object
+if type(y) is type(x):
+    reveal_type(x) # N: Revealed type is "builtins.str"
+    reveal_type(y) # N: Revealed type is "builtins.str"
+
+if type(x) is type(z):
+    reveal_type(x) # N: Revealed type is "builtins.str"
+    reveal_type(z) # N: Revealed type is "builtins.str"
+
+[case testTypeEqualsCheckUsingDifferentSpecializedTypes]
+from collections import defaultdict
+
+x: defaultdict
+y: dict
+z: object
+if type(x) is type(y) is type(z):
+    reveal_type(x) # N: Revealed type is "collections.defaultdict[Any, Any]"
+    reveal_type(y) # N: Revealed type is "collections.defaultdict[Any, Any]"
+    reveal_type(z) # N: Revealed type is "collections.defaultdict[Any, Any]"
+
+[case testUnionTypeEquality]
+from typing import Any, reveal_type
+# flags: --warn-unreachable
+
+x: Any = ()
+if type(x) == (int, str):
+    reveal_type(x) # E: Statement is unreachable
+
+[builtins fixtures/tuple.pyi]
+
+[case testTypeIntersectionWithConcreteTypes]
+class X: x = 1
+class Y: y = 1
+class Z(X, Y): ...
+
+z = Z()
+x: X = z
+y: Y = z
+if type(x) is type(y):
+    reveal_type(x)  # N: Revealed type is "__main__.<subclass of "__main__.X" and "__main__.Y">"
+    reveal_type(y)  # N: Revealed type is "__main__.<subclass of "__main__.Y" and "__main__.X">"
+    x.y + y.x
+
+if isinstance(x, type(y)) and isinstance(y, type(x)):
+    reveal_type(x)  # N: Revealed type is "__main__.<subclass of "__main__.X" and "__main__.Y">"
+    reveal_type(y)  # N: Revealed type is "__main__.<subclass of "__main__.X" and "__main__.Y">"
+    x.y + y.x
+
+[builtins fixtures/isinstance.pyi]
+
 [case testTypeEqualsCheckUsingIsNonOverlapping]
 # flags: --warn-unreachable
 from typing import Union
 
 y: str
-if type(y) is int:  # E: Subclass of "str" and "int" cannot exist: would have incompatible method signatures
-    y  # E: Statement is unreachable
+if type(y) is int:
+    y
 else:
     reveal_type(y) # N: Revealed type is "builtins.str"
-[builtins fixtures/isinstance.pyi]
 
 [case testTypeEqualsCheckUsingIsNonOverlappingChild-xfail]
 # flags: --warn-unreachable
@@ -2762,12 +2820,13 @@ else:
 [case testTypeEqualsMultipleTypesShouldntNarrow]
 # flags: --warn-unreachable
 # make sure we don't do any narrowing if there are multiple types being compared
+# flags: --warn-unreachable
 
 from typing import Union
 
 x: Union[int, str]
 if type(x) == int == str:
-    reveal_type(x)  # N: Revealed type is "builtins.int | builtins.str"
+    reveal_type(x)  # E: Statement is unreachable
 else:
     reveal_type(x)  # N: Revealed type is "builtins.int | builtins.str"
 

test-data/unit/check-narrowing.test

@@ -1262,7 +1262,7 @@ def f(t: Type[C]) -> None:
     if type(t) is M:
         reveal_type(t)  # N: Revealed type is "type[__main__.C]"
     else:
-        reveal_type(t)  # N: Revealed type is "type[__main__.C]"
+       reveal_type(t)  # N: Revealed type is "type[__main__.C]"
     if type(t) is not M:
         reveal_type(t)  # N: Revealed type is "type[__main__.C]"
     else: