Straighten up invocation of an Object method on dynamic.

Fixes https://github.com/dart-lang/sdk/issues/39609

Change-Id: I9b98d9bff8d4e9b75ab7625323f62eb6b6701a94
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/164256
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/dart/resolver/invocation_inference_helper.dart

@@ -9,7 +9,6 @@ import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/type_algebra.dart';
-import 'package:analyzer/src/dart/element/type_provider.dart';
 import 'package:analyzer/src/dart/element/type_system.dart';
 import 'package:analyzer/src/dart/resolver/flow_analysis_visitor.dart';
 import 'package:analyzer/src/error/codes.dart';
@@ -22,7 +21,6 @@ class InvocationInferenceHelper {
   final ErrorReporter _errorReporter;
   final FlowAnalysisHelper _flowAnalysis;
   final TypeSystemImpl _typeSystem;
-  final TypeProviderImpl _typeProvider;
   final MigrationResolutionHooks _migrationResolutionHooks;
 
   List<DartType> _typeArgumentTypes;
@@ -37,7 +35,6 @@ class InvocationInferenceHelper {
       : _resolver = resolver,
         _errorReporter = errorReporter,
         _typeSystem = typeSystem,
-        _typeProvider = typeSystem.typeProvider,
         _flowAnalysis = flowAnalysis,
         _migrationResolutionHooks = migrationResolutionHooks;
 
@@ -157,45 +154,6 @@ class InvocationInferenceHelper {
     return null;
   }
 
-  /// Given a method invocation [node], attempt to infer a better
-  /// type for the result if the target is dynamic and the method
-  /// being called is one of the object methods.
-  bool inferMethodInvocationObject(MethodInvocation node) {
-    // If we have a call like `toString()` or `libraryPrefix.toString()`, don't
-    // infer it.
-    Expression target = node.realTarget;
-    if (target == null ||
-        target is SimpleIdentifier && target.staticElement is PrefixElement) {
-      return false;
-    }
-    DartType nodeType = node.staticInvokeType;
-    if (nodeType == null ||
-        !nodeType.isDynamic ||
-        node.argumentList.arguments.isNotEmpty) {
-      return false;
-    }
-    // Object methods called on dynamic targets can have their types improved.
-    String name = node.methodName.name;
-    MethodElement inferredElement =
-        _typeProvider.objectType.element.getMethod(name);
-    if (inferredElement == null || inferredElement.isStatic) {
-      return false;
-    }
-    inferredElement = _resolver.toLegacyElement(inferredElement);
-    DartType inferredType = inferredElement.type;
-    if (inferredType is FunctionType) {
-      DartType returnType = inferredType.returnType;
-      if (inferredType.parameters.isEmpty &&
-          returnType is InterfaceType &&
-          _typeProvider.nonSubtypableClasses.contains(returnType.element)) {
-        node.staticInvokeType = inferredType;
-        recordStaticType(node, inferredType.returnType);
-        return true;
-      }
-    }
-    return false;
-  }
-
   /// Given an uninstantiated generic function type, referenced by the
   /// [identifier] in the tear-off [expression], try to infer the instantiated
   /// generic function type from the surrounding context.

pkg/analyzer/lib/src/dart/resolver/method_invocation_resolver.dart

@@ -150,7 +150,7 @@ class MethodInvocationResolver {
     }
 
     if (receiverType is DynamicTypeImpl) {
-      _resolveReceiverDynamic(node, name);
+      _resolveReceiverDynamic(node);
       return;
     }
 
@@ -291,15 +291,10 @@ class MethodInvocationResolver {
       node.methodName.staticType,
     );
 
-    // TODO(scheglov) Call this only when member lookup failed?
-    var inferred = _inferenceHelper.inferMethodInvocationObject(node);
-
-    if (!inferred) {
-      DartType staticStaticType = _inferenceHelper.computeInvokeReturnType(
-        node.staticInvokeType,
-      );
-      _inferenceHelper.recordStaticType(node, staticStaticType);
-    }
+    DartType staticStaticType = _inferenceHelper.computeInvokeReturnType(
+      node.staticInvokeType,
+    );
+    _inferenceHelper.recordStaticType(node, staticStaticType);
   }
 
   /// Given that we are accessing a property of the given [classElement] with the
@@ -387,8 +382,33 @@ class MethodInvocationResolver {
     _setResolution(node, member.type);
   }
 
-  void _resolveReceiverDynamic(MethodInvocation node, String name) {
-    _setDynamicResolution(node);
+  void _resolveReceiverDynamic(MethodInvocationImpl node) {
+    var nameNode = node.methodName;
+
+    var objectElement = _typeSystem.typeProvider.objectElement;
+    var target = objectElement.getMethod(nameNode.name);
+
+    var hasMatchingObjectMethod = false;
+    if (target is MethodElement) {
+      var arguments = node.argumentList.arguments;
+      hasMatchingObjectMethod = arguments.length == target.parameters.length &&
+          !arguments.any((e) => e is NamedExpression);
+      if (hasMatchingObjectMethod) {
+        target = _resolver.toLegacyElement(target);
+        nameNode.staticElement = target;
+        node.staticInvokeType = target.type;
+        node.staticType = target.returnType;
+      }
+    }
+
+    if (!hasMatchingObjectMethod) {
+      nameNode.staticType = DynamicTypeImpl.instance;
+      node.staticInvokeType = DynamicTypeImpl.instance;
+      node.staticType = DynamicTypeImpl.instance;
+    }
+
+    _setExplicitTypeArgumentTypes();
+    node.argumentList.accept(_resolver);
   }
 
   void _resolveReceiverFunctionType(MethodInvocation node, Expression receiver,

pkg/analyzer/test/src/dart/resolution/method_invocation_test.dart

@@ -1165,11 +1165,12 @@ main() {
 ''', [
       error(CompileTimeErrorCode.USE_OF_VOID_RESULT, 23, 3),
     ]);
-    // TODO(scheglov) Resolve fully, or don't resolve at all.
-    assertMethodInvocation(
+    assertMethodInvocation2(
       findNode.methodInvocation('toString()'),
-      null,
-      'String Function()',
+      element: null,
+      typeArgumentTypes: [],
+      invokeType: 'dynamic',
+      type: 'dynamic',
     );
   }
 
@@ -1182,16 +1183,16 @@ main() {
 ''', [
       error(CompileTimeErrorCode.USE_OF_VOID_RESULT, 23, 3),
     ]);
-    // TODO(scheglov) Resolve fully, or don't resolve at all.
-    assertMethodInvocation(
+    assertMethodInvocation2(
       findNode.methodInvocation('toString()'),
-      null,
-      'String Function()',
+      element: null,
+      typeArgumentTypes: [],
+      invokeType: 'dynamic',
+      type: 'dynamic',
     );
   }
 
   test_error_useOfVoidResult_receiver_withNull() async {
-    var question = typeToStringWithNullability ? '?' : '';
     await assertErrorsInCode(r'''
 main() {
   void foo;
@@ -1200,12 +1201,12 @@ main() {
 ''', [
       error(CompileTimeErrorCode.USE_OF_VOID_RESULT, 23, 3),
     ]);
-    // TODO(scheglov) Resolve fully, or don't resolve at all.
-    assertMethodInvocation(
+    assertMethodInvocation2(
       findNode.methodInvocation('toString()'),
-      null,
-      'String Function()',
-      expectedType: 'String$question',
+      element: null,
+      typeArgumentTypes: [],
+      invokeType: 'dynamic',
+      type: 'dynamic',
     );
   }
 
@@ -1944,14 +1945,39 @@ main() {
     assertType(foo, 'void Function(int)');
   }
 
-  test_objectMethodOnDynamic() async {
+  test_objectMethodOnDynamic_argumentsDontMatch() async {
     await assertNoErrorsInCode(r'''
-main() {
-  var v;
-  v.toString(42);
+void f(a, int b) {
+  a.toString(b);
 }
 ''');
-    _assertUnresolvedMethodInvocation('toString(42);');
+    assertMethodInvocation2(
+      findNode.methodInvocation('toString(b)'),
+      element: null,
+      typeArgumentTypes: [],
+      invokeType: 'dynamic',
+      type: 'dynamic',
+    );
+
+    assertType(findNode.simple('b);'), 'int');
+  }
+
+  test_objectMethodOnDynamic_argumentsMatch() async {
+    await assertNoErrorsInCode(r'''
+void f(a) {
+  a.toString();
+}
+''');
+    assertMethodInvocation2(
+      findNode.methodInvocation('toString()'),
+      element: elementMatcher(
+        objectElement.getMethod('toString'),
+        isLegacy: isNullSafetySdkAndLegacyLibrary,
+      ),
+      typeArgumentTypes: [],
+      invokeType: 'String Function()',
+      type: 'String',
+    );
   }
 
   test_objectMethodOnFunction() async {

pkg/nnbd_migration/test/api_test.dart

@@ -1710,7 +1710,6 @@ C<int, num?> f(List<int> a) => a;
     await _checkSingleFileChanges(content, expected);
   }
 
-  @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/39609')
   Future<void> test_dynamic_dispatch_to_object_method() async {
     var content = '''
 String f(dynamic x) => x.toString();
@@ -1787,7 +1786,6 @@ main() {
     await _checkSingleFileChanges(content, expected);
   }
 
-  @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/39609')
   Future<void> test_dynamic_toString() async {
     var content = '''
 String f(dynamic x) => x.toString();