Fixed a bug that results in a false negative when a class explicitly inherits from a protocol that defines an instance variable but the child re-declares as a ClassVar without an explicit type. This addresses #7455. (#7463)

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

@@ -6132,9 +6132,11 @@ export class Checker extends ParseTreeWalker {
             }
 
             // If the symbol has no declaration, and the type is inferred,
-            // skip this check.
-            if (!symbol.hasTypedDeclarations() && !this._evaluator.isFinalVariable(symbol)) {
-                return;
+            // skip the type validation but still check for other issues like
+            // Final overrides and class/instance variable mismatches.
+            let validateType = true;
+            if (!symbol.hasTypedDeclarations()) {
+                validateType = false;
             }
 
             // Get the symbol type defined in this class.
@@ -6169,7 +6171,13 @@ export class Checker extends ParseTreeWalker {
 
                 firstOverride = firstOverride ?? baseClassAndSymbol;
 
-                this._validateBaseClassOverride(baseClassAndSymbol, symbol, typeOfSymbol, classType, name);
+                this._validateBaseClassOverride(
+                    baseClassAndSymbol,
+                    symbol,
+                    validateType ? typeOfSymbol : AnyType.create(),
+                    classType,
+                    name
+                );
             }
 
             if (!firstOverride) {

packages/pyright-internal/src/tests/samples/protocol3.py

@@ -110,14 +110,12 @@ _Self = TypeVar("_Self")
 
 class Class5:
     @property
-    def real(self: _Self) -> _Self:
-        ...
+    def real(self: _Self) -> _Self: ...
 
 
 class MockClass5(Protocol[_T_co]):
     @property
-    def real(self) -> _T_co:
-        ...
+    def real(self) -> _T_co: ...
 
 
 foo5 = Class5()
@@ -130,14 +128,12 @@ C6 = TypeVar("C6", bound="Class6")
 
 class MockClass6(Protocol):
     @property
-    def bar(self: P6) -> ContextManager[P6]:
-        ...
+    def bar(self: P6) -> ContextManager[P6]: ...
 
 
 class Class6:
     @property
-    def bar(self: C6) -> ContextManager[C6]:
-        ...
+    def bar(self: C6) -> ContextManager[C6]: ...
 
 
 i: MockClass6 = Class6()
@@ -158,8 +154,7 @@ a: Proto7 = Class7("")
 
 class Proto8(Protocol):
     @property
-    def x(self) -> str:
-        ...
+    def x(self) -> str: ...
 
 
 class Class8(NamedTuple):
@@ -171,12 +166,10 @@ b: Proto8 = Class8("")
 
 class Proto9(Protocol):
     @property
-    def x(self) -> str:
-        ...
+    def x(self) -> str: ...
 
     @x.setter
-    def x(self, n: str) -> None:
-        ...
+    def x(self, n: str) -> None: ...
 
 
 class Proto10(Protocol):
@@ -231,11 +224,11 @@ p11_1: Proto11 = Concrete11()
 
 
 class Proto12(Protocol):
-    val1: Sequence[int]
+    val1: list[int]
 
 
 class Concrete12:
-    val1: ClassVar[Sequence[int]]
+    val1: ClassVar = [1, 2, 3]
 
 
 # This should generate an error because of a ClassVar mismatch.
@@ -255,12 +248,10 @@ T13 = TypeVar("T13", covariant=True)
 
 class Proto13(Protocol[T13]):
     @property
-    def prop1(self) -> T13:
-        ...
+    def prop1(self) -> T13: ...
 
 
-class Proto14(Proto13[T13], Protocol):
-    ...
+class Proto14(Proto13[T13], Protocol): ...
 
 
 class Concrete14(Generic[T13]):
@@ -268,8 +259,7 @@ class Concrete14(Generic[T13]):
         self.prop1 = val
 
 
-def func14(val: Proto14[T13]):
-    ...
+def func14(val: Proto14[T13]): ...
 
 
 func14(Concrete14(1))

packages/pyright-internal/src/tests/samples/protocolExplicit1.py

@@ -26,8 +26,7 @@ class Protocol3(Protocol2, Protocol):
     cm11: int
 
 
-class Concrete1(Protocol1):
-    ...
+class Concrete1(Protocol1): ...
 
 
 # This should generate an error because some attributes are not implemented.
@@ -67,8 +66,7 @@ Concrete4()
 
 
 class Protocol5(Protocol):
-    def method1(self) -> int:
-        ...
+    def method1(self) -> int: ...
 
 
 # This should generate an error because "method1" is
@@ -93,8 +91,7 @@ class Concrete6(Mixin, Protocol6):
 
 class Protocol7(Protocol):
     @abstractmethod
-    def method1(self):
-        ...
+    def method1(self): ...
 
 
 class Mixin7(Protocol7, ABC):
@@ -112,3 +109,12 @@ class Concrete7A(Protocol7):
 @final
 class Concrete7B(Mixin7, Protocol7):
     pass
+
+
+class Protocol8(Protocol):
+    x: int
+
+
+class Concrete8(Protocol8):
+    # This should generate an error because x is a ClassVar.
+    x: ClassVar = 1

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

@@ -1414,7 +1414,7 @@ test('Protocol48', () => {
 test('ProtocolExplicit1', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['protocolExplicit1.py']);
 
-    TestUtils.validateResults(analysisResults, 4);
+    TestUtils.validateResults(analysisResults, 5);
 });
 
 test('ProtocolExplicit3', () => {