Fixed regression that caused false positive error when protocol match involved a property that returned a type that was generic.

packages/pyright-internal/src/analyzer/properties.ts

@@ -32,7 +32,13 @@ import {
     Type,
     UnknownType,
 } from './types';
-import { CanAssignFlags, computeMroLinearization, getTypeVarScopeId, isProperty } from './typeUtils';
+import {
+    CanAssignFlags,
+    computeMroLinearization,
+    getTypeVarScopeId,
+    isProperty,
+    partiallySpecializeType,
+} from './typeUtils';
 import { TypeVarMap } from './typeVarMap';
 
 export function validatePropertyMethod(evaluator: TypeEvaluator, method: FunctionType, errorNode: ParseNode) {
@@ -89,6 +95,9 @@ export function createProperty(
     const propertyObject = ClassType.cloneAsInstance(propertyClass);
     propertyClass.isAsymmetricDescriptor = false;
 
+    // Update the __set__ and __delete__ methods if present.
+    updateGetSetDelMethodForClonedProperty(propertyObject, evaluator);
+
     // Fill in the fget method.
     const fgetSymbol = Symbol.createWithType(
         SymbolFlags.ClassMember,
@@ -100,9 +109,6 @@ export function createProperty(
         propertyClass.details.flags |= ClassTypeFlags.ClassProperty;
     }
 
-    // Update the __set__ and __set__ methods if present.
-    updateGetSetDelMethodForClonedProperty(propertyObject, evaluator);
-
     // Fill in the __get__ method with an overload.
     addGetMethodToPropertySymbolTable(propertyObject, fget);
 
@@ -187,6 +193,9 @@ export function clonePropertyWithSetter(
         }
     });
 
+    // Update the __get__ and __delete__ methods if present.
+    updateGetSetDelMethodForClonedProperty(propertyObject, evaluator);
+
     // Fill in the fset method.
     const fsetSymbol = Symbol.createWithType(
         SymbolFlags.ClassMember,
@@ -194,9 +203,6 @@ export function clonePropertyWithSetter(
     );
     fields.set('fset', fsetSymbol);
 
-    // Update the __get__ and __delete__ methods if present.
-    updateGetSetDelMethodForClonedProperty(propertyObject, evaluator);
-
     // Fill in the __set__ method.
     addSetMethodToPropertySymbolTable(propertyObject, fset, evaluator);
 
@@ -243,6 +249,9 @@ export function clonePropertyWithDeleter(
         }
     });
 
+    // Update the __get__ and __set__ methods if present.
+    updateGetSetDelMethodForClonedProperty(propertyObject, evaluator);
+
     // Fill in the fdel method.
     const fdelSymbol = Symbol.createWithType(
         SymbolFlags.ClassMember,
@@ -250,9 +259,6 @@ export function clonePropertyWithDeleter(
     );
     fields.set('fdel', fdelSymbol);
 
-    // Update the __get__ and __set__ methods if present.
-    updateGetSetDelMethodForClonedProperty(propertyObject, evaluator);
-
     // Fill in the __delete__ method.
     addDelMethodToPropertySymbolTable(propertyObject, fdel, evaluator);
 
@@ -481,7 +487,7 @@ export function canAssignProperty(
 
         if (destAccessType && isFunction(destAccessType)) {
             const srcAccessSymbol = srcPropertyType.details.fields.get(accessorInfo.name);
-            const srcAccessType = srcAccessSymbol ? evaluator.getDeclaredTypeOfSymbol(srcAccessSymbol) : undefined;
+            let srcAccessType = srcAccessSymbol ? evaluator.getDeclaredTypeOfSymbol(srcAccessSymbol) : undefined;
 
             if (!srcAccessType || !isFunction(srcAccessType)) {
                 if (diag) {
@@ -491,6 +497,8 @@ export function canAssignProperty(
                 return;
             }
 
+            srcAccessType = partiallySpecializeType(srcAccessType, srcClass) as FunctionType;
+
             const boundDestAccessType = evaluator.bindFunctionToClassOrObject(
                 objectToBind,
                 destAccessType,

packages/pyright-internal/src/tests/samples/protocol29.py

@@ -0,0 +1,26 @@
+# This sample tests the special-case handling of properties that return
+# generics within a protocol.
+
+from functools import partial
+from typing_extensions import Protocol, Self
+from typing import Any, Callable, Type, TypeVar
+
+_T = TypeVar("_T")
+
+
+class Partial(Protocol[_T]):
+    @property
+    def func(self) -> Callable[..., _T]:
+        ...
+
+    def __new__(
+        cls: Type[Self], __func: Callable[..., _T], *args: Any, **kwargs: Any
+    ) -> Self:
+        ...
+
+
+def f(x: Partial[int]):
+    ...
+
+
+f(partial(int))

packages/pyright-internal/src/tests/typeEvaluator2.test.ts

@@ -1054,6 +1054,12 @@ test('Protocol28', () => {
     TestUtils.validateResults(analysisResults, 0);
 });
 
+test('Protocol29', () => {
+    const analysisResults = TestUtils.typeAnalyzeSampleFiles(['protocol29.py']);
+
+    TestUtils.validateResults(analysisResults, 0);
+});
+
 test('TypedDict1', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typedDict1.py']);