Collect metaclass members while calculating class member names (PY-21408)

python/src/com/jetbrains/python/psi/types/PyClassTypeImpl.java

@@ -662,6 +662,9 @@ public class PyClassTypeImpl extends UserDataHolderBase implements PyClassType {
   @NotNull
   @Override
   public Set<String> getMemberNames(boolean inherited, @NotNull TypeEvalContext context) {
+    // PyNamedTupleType.getMemberNames provide names that we are not able to visit,
+    // so this method could not be replaced with PyClassLikeType.visitMembers
+
     final Set<String> result = new LinkedHashSet<>();
 
     for (PyFunction function : myClass.getMethods()) {
@@ -692,11 +695,35 @@ public class PyClassTypeImpl extends UserDataHolderBase implements PyClassType {
           result.addAll(ancestorType.getMemberNames(false, context));
         }
       }
+
+      result.addAll(getMetaClassMemberNames(context));
     }
 
     return result;
   }
 
+  @NotNull
+  private Set<String> getMetaClassMemberNames(@NotNull TypeEvalContext context) {
+    if (!myClass.isNewStyleClass(context)) {
+      return Collections.emptySet();
+    }
+
+    final PyClassLikeType typeType = getMetaClassType(context, true);
+    if (typeType == null) {
+      return Collections.emptySet();
+    }
+
+    if (isDefinition()) {
+      return typeType.getMemberNames(true, context);
+    }
+    else if (typeType instanceof PyClassType) {
+      final List<PyTargetExpression> typeInstanceAttributes = ((PyClassType)typeType).getPyClass().getInstanceAttributes();
+      return ContainerUtil.map2SetNotNull(typeInstanceAttributes, PyTargetExpression::getName);
+    }
+
+    return Collections.emptySet();
+  }
+
   private void addOwnClassMembers(PsiElement expressionHook,
                                   Set<String> namesAlready,
                                   boolean suppressParentheses,

python/testData/inspections/PyTypeCheckerInspection/ClassMetaAttrsAgainstStructural.py

@@ -0,0 +1,37 @@
+class B1(type):
+    meta_attr = "meta_attr"
+
+
+class A1(metaclass=B1):
+    pass
+
+
+def print_A1(a):
+    print(a.__name__)
+    print(a.meta_attr)
+
+
+def print_unknown(a):
+    print(a.unknown)
+
+
+print_A1(A1)
+print_unknown(<warning descr="Type 'Type[A1]' doesn't have expected attribute 'unknown'">A1</warning>)
+
+
+class B2(type):
+    def __init__(self, what, bases, dict):
+        self.meta_attr = "meta_attr"
+        super().__init__(what, bases, dict)
+
+
+class A2(metaclass=B2):
+    pass
+
+
+def print_A2(a):
+    print(a.meta_attr)
+
+
+print_A2(A2())
+print_unknown(<warning descr="Type 'A2' doesn't have expected attribute 'unknown'">A2()</warning>)

python/testSrc/com/jetbrains/python/inspections/PyTypeCheckerInspectionTest.java

@@ -446,4 +446,9 @@ public class PyTypeCheckerInspectionTest extends PyInspectionTestCase {
   public void testMatchingOpenFunctionCallTypesPy2() {
     doMultiFileTest();
   }
+
+  // PY-21408
+  public void testClassMetaAttrsAgainstStructural() {
+    runWithLanguageLevel(LanguageLevel.PYTHON30, this::doTest);
+  }
 }