tmp

Author: hauntsaninja

mypy/checker.py

@@ -8625,15 +8625,16 @@ def and_conditional_maps(m1: TypeMap, m2: TypeMap, *, use_meet: bool = False) ->
     the truth of e2.
     """
     # Both conditions can be true; combine the information. Anything
-    # we learn from either conditions' truth is valid. If the same
-    # expression's type is refined by both conditions, we somewhat
-    # arbitrarily give precedence to m2 unless m1 value is Any.
-    # In the future, we could use an intersection type or meet_types().
+    # we learn from either conditions' truth is valid.
+    # If the same expression's type is refined by both conditions and use_meet=False, we somewhat
+    # arbitrarily give precedence to m2 unless m2's value is Any or Never.
     result = m2.copy()
-    m2_keys = {literal_hash(n2) for n2 in m2}
+    m2_exprs = {literal_hash(n2): n2 for n2 in m2}
     for n1 in m1:
-        if literal_hash(n1) not in m2_keys or isinstance(
-            get_proper_type(m1[n1]), (AnyType, UninhabitedType)
+        n1_hash = literal_hash(n1)
+        if n1_hash not in m2_exprs or (
+            not use_meet
+            and isinstance(get_proper_type(m2[m2_exprs[n1_hash]]), (AnyType, UninhabitedType))
         ):
             result[n1] = m1[n1]
     if use_meet:

test-data/unit/check-isinstance.test

@@ -127,6 +127,26 @@ if int():
     reveal_type(x)  # N: Revealed type is "Any"
 reveal_type(x)  # N: Revealed type is "__main__.A"
 
+[case testIsinstanceNarrowingAfterAnyCondition]
+from typing import Any
+
+class A: pass
+class B(A): pass
+class Foo: pass
+
+value: Any
+if isinstance(value, A) and not isinstance(value, B):
+    reveal_type(value)  # N: Revealed type is "__main__.A"
+if not isinstance(value, B) and isinstance(value, A):
+    reveal_type(value)  # N: Revealed type is "__main__.A"
+
+x: Any
+if x and isinstance(x, Foo):
+    reveal_type(x)  # N: Revealed type is "__main__.Foo"
+if isinstance(x, Foo) and x:
+    reveal_type(x)  # N: Revealed type is "__main__.Foo"
+[builtins fixtures/isinstance.pyi]
+
 [case testSingleMultiAssignment]
 # flags: --warn-unreachable
 x = 'a'

test-data/unit/check-narrowing.test

@@ -1727,7 +1727,7 @@ reveal_type(c)  # N: Revealed type is "__main__.C"
 
 c1: C
 if isinstance(c1, tp) and isinstance(c1, D):
-    reveal_type(c1)  # N: Revealed type is "Any"
+    reveal_type(c1)  # N: Revealed type is "__main__.D"
 else:
     reveal_type(c1)  # N: Revealed type is "__main__.C"
 reveal_type(c1)  # N: Revealed type is "__main__.C"
@@ -1741,7 +1741,7 @@ reveal_type(c2)  # N: Revealed type is "__main__.C"
 
 c3: C
 if isinstance(c3, D) and isinstance(c3, tp):
-    reveal_type(c3)  # N: Revealed type is "Any"
+    reveal_type(c3)  # N: Revealed type is "__main__.D"
 else:
     reveal_type(c3)  # N: Revealed type is "__main__.C"
 reveal_type(c3)  # N: Revealed type is "__main__.C"