Improved type narrowing for issubclass in the negative ("else") cas…

…e when the subject type is `type` or `Any`. This addresses #9656. (#9704)
microsoft · Jan 14, 2025 · 575c639 · 575c639
1 parent 1593a7c
commit 575c639
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Showing 2 changed files with 30 additions and 10 deletions.
diff --git a/packages/pyright-internal/src/analyzer/typeGuards.ts b/packages/pyright-internal/src/analyzer/typeGuards.ts
@@ -1249,20 +1249,15 @@ function narrowTypeForInstanceOrSubclassInternal(
         if (!isInstanceCheck) {
             const isTypeInstance = isClassInstance(subtype) && ClassType.isBuiltIn(subtype, 'type');
 
+            // Handle metaclass instances specially.
             if (isMetaclassInstance(subtype) && !isTypeInstance) {
-                // Handle metaclass instances specially.
                 adjFilterTypes = filterTypes.map((filterType) => convertToInstantiable(filterType));
             } else {
-                const convSubtype = convertToInstance(subtype);
+                adjSubtype = convertToInstance(subtype);
 
-                // Handle type[Any] specially for this case.
-                if (isClassInstance(subtype) && ClassType.isBuiltIn(subtype, 'type') && isAnyOrUnknown(convSubtype)) {
-                    adjSubtype = convertToInstance(evaluator.getObjectType());
-                } else {
-                    adjSubtype = convSubtype;
+                if (!isAnyOrUnknown(subtype) || isPositiveTest) {
+                    resultRequiresAdj = true;
                 }
-
-                resultRequiresAdj = true;
             }
         }
 
@@ -1276,7 +1271,18 @@ function narrowTypeForInstanceOrSubclassInternal(
             errorNode
         );
 
-        return resultRequiresAdj ? convertToInstantiable(narrowedResult) : narrowedResult;
+        if (!resultRequiresAdj) {
+            return narrowedResult;
+        }
+
+        if (isAnyOrUnknown(narrowedResult)) {
+            const typeClass = evaluator.getTypeClassType();
+            if (typeClass) {
+                return ClassType.specialize(ClassType.cloneAsInstance(typeClass), [narrowedResult]);
+            }
+        }
+
+        return convertToInstantiable(narrowedResult);
     });
 
     return result;

diff --git a/packages/pyright-internal/src/tests/samples/typeNarrowingIsinstance1.py b/packages/pyright-internal/src/tests/samples/typeNarrowingIsinstance1.py
@@ -135,6 +135,20 @@ def func6_2(ty: type[int] | int):
         reveal_type(ty, expected_text="int")
 
 
+def func6_3(ty: type):
+    if issubclass(ty, str):
+        reveal_type(ty, expected_text="type[str]")
+    else:
+        reveal_type(ty, expected_text="type[Unknown]")
+
+
+def func6_4(ty: Any):
+    if issubclass(ty, str):
+        reveal_type(ty, expected_text="type[str]")
+    else:
+        reveal_type(ty, expected_text="Any")
+
+
 # Test the handling of protocol classes that support runtime checking.
 def func7(a: Union[list[int], int]):
     if isinstance(a, Sized):