PY-24930 Fixed: False negative: no parameter info when implicitly calling __call__

Update PyCallExpressionHelper to support a case when callee resolves to call expression and this call expression returns class with `__call__`.

python/src/com/jetbrains/python/psi/impl/PyCallExpressionHelper.java

@@ -196,7 +196,9 @@ public class PyCallExpressionHelper {
                                function -> new ClarifiedResolveResult(resolveResult, function, null, true));
     }
     else if (resolved instanceof PyCallExpression) { // foo = classmethod(foo)
-      final Pair<String, PyFunction> wrapperInfo = interpretAsModifierWrappingCall((PyCallExpression)resolved);
+      final PyCallExpression resolvedCall = (PyCallExpression)resolved;
+
+      final Pair<String, PyFunction> wrapperInfo = interpretAsModifierWrappingCall(resolvedCall);
       if (wrapperInfo != null) {
         final String wrapperName = wrapperInfo.getFirst();
         final PyFunction.Modifier wrappedModifier = PyNames.CLASSMETHOD.equals(wrapperName)
@@ -208,6 +210,22 @@ public class PyCallExpressionHelper {
         final ClarifiedResolveResult result = new ClarifiedResolveResult(resolveResult, wrapperInfo.getSecond(), wrappedModifier, false);
         return Collections.singletonList(result);
       }
+      else {
+        final PyType resolvedCallType = resolveContext.getTypeEvalContext().getType(resolvedCall);
+        if (resolvedCallType instanceof PyClassLikeType) {
+          final List<? extends RatedResolveResult> dunderCall =
+            ((PyClassLikeType)resolvedCallType).resolveMember(PyNames.CALL, resolvedCall, AccessDirection.READ, resolveContext, true);
+
+          if (!ContainerUtil.isEmpty(dunderCall)) {
+            return StreamEx
+              .of(dunderCall)
+              .map(RatedResolveResult::getElement)
+              .nonNull()
+              .map(element -> new ClarifiedResolveResult(resolveResult, element, null, false))
+              .toList();
+          }
+        }
+      }
     }
     else if (resolved instanceof PyFunction) {
       final PyFunction function = (PyFunction)resolved;

python/testData/inspections/PyArgumentListInspection/callOperator.py

@@ -0,0 +1,7 @@
+class Foo:
+    def __call__(self, arg: int):
+        return arg
+
+bar = Foo()
+bar.__call__(<warning descr="Parameter 'arg' unfilled">)</warning>
+bar(<warning descr="Parameter 'arg' unfilled">)</warning>

python/testData/inspections/PyTypeCheckerInspection/CallOperator.py

@@ -0,0 +1,7 @@
+class Foo:
+    def __call__(self, arg: int):
+        return arg
+
+bar = Foo()
+bar.__call__(<warning descr="Expected type 'int', got 'str' instead">"s"</warning>)
+bar(<warning descr="Expected type 'int', got 'str' instead">"s"</warning>)

python/testData/paramInfo/CallOperator.py

@@ -0,0 +1,7 @@
+class Foo:
+    def __call__(self, arg: int):
+        return arg
+
+bar = Foo()
+bar.__call__(<arg1>)
+bar(<arg2>)

python/testSrc/com/jetbrains/python/PyParameterInfoTest.java

@@ -696,6 +696,18 @@ public class PyParameterInfoTest extends LightMarkedTestCase {
     );
   }
 
+  // PY-24930
+  public void testCallOperator() {
+    runWithLanguageLevel(
+      LanguageLevel.PYTHON35,
+      () -> {
+        for (int offset : StreamEx.of(loadTest(2).values()).map(PsiElement::getTextOffset)) {
+          feignCtrlP(offset).check("self: Foo, arg: int", new String[]{"arg: int"}, new String[]{"self: Foo, "});
+        }
+      }
+    );
+  }
+
   /**
    * Imitates pressing of Ctrl+P; fails if results are not as expected.
    * @param offset offset of 'cursor' where Ctrl+P is pressed.

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

@@ -317,6 +317,11 @@ public class PyArgumentListInspectionTest extends PyTestCase {
     doTest();
   }
 
+  // PY-24930
+  public void testCallOperator() {
+    runWithLanguageLevel(LanguageLevel.PYTHON35, this::doTest);
+  }
+
   private void doMultiFileTest() {
     final String folderPath = "inspections/PyArgumentListInspection/" + getTestName(false) + "/";
 

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

@@ -417,4 +417,9 @@ public class PyTypeCheckerInspectionTest extends PyTestCase {
   public void testPromotingBytearrayToStrAndUnicode() {
     doTest();
   }
+
+  // PY-24930
+  public void testCallOperator() {
+    runWithLanguageLevel(LanguageLevel.PYTHON35, this::doTest);
+  }
 }