Move ExtensionOverride errors into resolveOverride().

R=brianwilkerson@google.com, pquitslund@google.com

Change-Id: Ia9dae5b461210c6fae40e9cf2d5282aa4fea3b3b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112262
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Author: scheglov

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

@@ -5,6 +5,7 @@
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/element/member.dart';
 import 'package:analyzer/src/dart/element/type_algebra.dart';
@@ -15,10 +16,13 @@ import 'package:analyzer/src/generated/type_system.dart';
 
 class ExtensionMemberResolver {
   final ResolverVisitor _resolver;
+
   ExtensionMemberResolver(this._resolver);
 
   DartType get _dynamicType => _typeProvider.dynamicType;
 
+  ErrorReporter get _errorReporter => _resolver.errorReporter;
+
   Scope get _nameScope => _resolver.nameScope;
 
   TypeProvider get _typeProvider => _resolver.typeProvider;
@@ -48,7 +52,7 @@ class ExtensionMemberResolver {
       return extension;
     }
 
-    _resolver.errorReporter.reportErrorForNode(
+    _errorReporter.reportErrorForNode(
       CompileTimeErrorCode.AMBIGUOUS_EXTENSION_METHOD_ACCESS,
       target,
       [
@@ -61,24 +65,51 @@ class ExtensionMemberResolver {
   }
 
   void resolveOverride(ExtensionOverride node) {
+    var nodeImpl = node as ExtensionOverrideImpl;
     var element = node.staticElement;
     var typeParameters = element.typeParameters;
 
-    DartType receiverType;
+    if (!_isValidContext(node)) {
+      _errorReporter.reportErrorForNode(
+        CompileTimeErrorCode.EXTENSION_OVERRIDE_WITHOUT_ACCESS,
+        node,
+      );
+      nodeImpl.staticType = _dynamicType;
+    }
+
     var arguments = node.argumentList.arguments;
-    if (arguments.length == 1) {
-      receiverType = arguments[0].staticType;
+    if (arguments.length != 1) {
+      _errorReporter.reportErrorForNode(
+        CompileTimeErrorCode.INVALID_EXTENSION_ARGUMENT_COUNT,
+        node.argumentList,
+      );
+      nodeImpl.typeArgumentTypes = _listOfDynamic(typeParameters);
+      nodeImpl.extendedType = _dynamicType;
+      return;
     }
-    // TODO(scheglov) Test when not exactly 1 argument.
 
-    var typeArgumentTypes =
-        _inferTypeArguments(element, receiverType, node.typeArguments);
+    var receiverExpression = arguments[0];
+    var receiverType = receiverExpression.staticType;
+
+    var typeArgumentTypes = _inferTypeArguments(
+      element,
+      receiverType,
+      node.typeArguments,
+    );
 
-    var nodeImpl = node as ExtensionOverrideImpl;
     nodeImpl.typeArgumentTypes = typeArgumentTypes;
-    nodeImpl.extendedType =
-        Substitution.fromPairs(typeParameters, typeArgumentTypes)
-            .substituteType(element.extendedType);
+    nodeImpl.extendedType = Substitution.fromPairs(
+      typeParameters,
+      typeArgumentTypes,
+    ).substituteType(element.extendedType);
+
+    if (!_typeSystem.isAssignableTo(receiverType, node.extendedType)) {
+      _errorReporter.reportErrorForNode(
+        CompileTimeErrorCode.EXTENSION_OVERRIDE_ARGUMENT_NOT_ASSIGNABLE,
+        receiverExpression,
+        [receiverType, node.extendedType],
+      );
+    }
   }
 
   /// Return the most specific extension or `null` if no single one can be
@@ -259,7 +290,7 @@ class ExtensionMemberResolver {
         return arguments.map((a) => a.type).toList();
       } else {
         // TODO(scheglov) Report an error.
-        return List.filled(typeParameters.length, _dynamicType);
+        return _listOfDynamic(typeParameters);
       }
     } else {
       if (receiverType != null) {
@@ -275,7 +306,7 @@ class ExtensionMemberResolver {
         );
         return inferrer.infer(typeParameters);
       } else {
-        return List.filled(typeParameters.length, _dynamicType);
+        return _listOfDynamic(typeParameters);
       }
     }
   }
@@ -341,6 +372,22 @@ class ExtensionMemberResolver {
   /// Ask the type system for a subtype check.
   bool _isSubtypeOf(DartType type1, DartType type2) =>
       _typeSystem.isSubtypeOf(type1, type2);
+
+  List<DartType> _listOfDynamic(List<TypeParameterElement> parameters) {
+    return List<DartType>.filled(parameters.length, _dynamicType);
+  }
+
+  /// Return `true` if the extension override [node] is being used as a target
+  /// of an operation that might be accessing an instance member.
+  static bool _isValidContext(ExtensionOverride node) {
+    AstNode parent = node.parent;
+    return parent is BinaryExpression && parent.leftOperand == node ||
+        parent is FunctionExpressionInvocation && parent.function == node ||
+        parent is IndexExpression && parent.target == node ||
+        parent is MethodInvocation && parent.target == node ||
+        parent is PrefixExpression ||
+        parent is PropertyAccess && parent.target == node;
+  }
 }
 
 class InstantiatedExtension {

pkg/analyzer/lib/src/generated/error_verifier.dart

@@ -730,28 +730,6 @@ class ErrorVerifier extends RecursiveAstVisitor<void> {
     _enclosingExtension = null;
   }
 
-  @override
-  void visitExtensionOverride(ExtensionOverride node) {
-    NodeList<Expression> arguments = node.argumentList.arguments;
-    int argCount = arguments.length;
-    if (argCount == 1) {
-      _checkForAssignableExpression(
-        arguments[0],
-        node.extendedType,
-        CompileTimeErrorCode.EXTENSION_OVERRIDE_ARGUMENT_NOT_ASSIGNABLE,
-      );
-    } else {
-      _errorReporter.reportErrorForNode(
-          CompileTimeErrorCode.INVALID_EXTENSION_ARGUMENT_COUNT,
-          node.argumentList);
-    }
-    if (!_isExtensionOverrideInValidContext(node)) {
-      _errorReporter.reportErrorForNode(
-          CompileTimeErrorCode.EXTENSION_OVERRIDE_WITHOUT_ACCESS, node);
-    }
-    super.visitExtensionOverride(node);
-  }
-
   @override
   void visitFieldDeclaration(FieldDeclaration node) {
     _isInStaticVariableDeclaration = node.isStatic;
@@ -6466,21 +6444,6 @@ class ErrorVerifier extends RecursiveAstVisitor<void> {
     return element.name == "List" && element.library.isDartCore;
   }
 
-  /// Return `true` if the extension override [node] is being used as a target
-  /// of an operation that might be accessing an instance member.
-  bool _isExtensionOverrideInValidContext(ExtensionOverride node) {
-    AstNode parent = node.parent;
-    if ((parent is PropertyAccess && parent.target == node) ||
-        (parent is MethodInvocation && parent.target == node) ||
-        (parent is FunctionExpressionInvocation && parent.function == node) ||
-        (parent is BinaryExpression && parent.leftOperand == node) ||
-        (parent is IndexExpression && parent.target == node) ||
-        parent is PrefixExpression) {
-      return true;
-    }
-    return false;
-  }
-
   bool _isFunctionType(DartType type) {
     if (type.isDynamic || type.isDartCoreNull) {
       return true;

pkg/analyzer/test/src/diagnostics/extension_override_without_access_test.dart

@@ -23,7 +23,7 @@ class ExtensionOverrideWithoutAccessTest extends DriverResolutionTest {
         sdkVersion: '2.3.0', additionalFeatures: [Feature.extension_methods]);
 
   test_binaryExpression() async {
-    assertNoErrorsInCode('''
+    await assertNoErrorsInCode('''
 class C {}
 extension E on C {
   int operator +(int x) => x;
@@ -49,7 +49,7 @@ f(C c) {
   }
 
   test_expressionStatement() async {
-    assertErrorsInCode('''
+    await assertErrorsInCode('''
 class C {}
 extension E on C {
   void m() {}
@@ -58,10 +58,11 @@ f(C c) {
   E(c);
 }
 ''', [error(CompileTimeErrorCode.EXTENSION_OVERRIDE_WITHOUT_ACCESS, 57, 4)]);
+    assertTypeDynamic(findNode.extensionOverride('E(c)'));
   }
 
   test_getter() async {
-    assertNoErrorsInCode('''
+    await assertNoErrorsInCode('''
 class C {}
 extension E on C {
   int get g => 0;
@@ -73,7 +74,7 @@ f(C c) {
   }
 
   test_indexExpression_get() async {
-    assertNoErrorsInCode('''
+    await assertNoErrorsInCode('''
 class C {}
 extension E on C {
   int operator [](int i) => 4;
@@ -85,7 +86,7 @@ f(C c) {
   }
 
   test_indexExpression_set() async {
-    assertNoErrorsInCode('''
+    await assertNoErrorsInCode('''
 class C {}
 extension E on C {
   void operator []=(int i, int v) {}
@@ -97,7 +98,7 @@ f(C c) {
   }
 
   test_methodInvocation() async {
-    assertNoErrorsInCode('''
+    await assertNoErrorsInCode('''
 class C {}
 extension E on C {
   void m() {}
@@ -109,7 +110,7 @@ f(C c) {
   }
 
   test_prefixExpression() async {
-    assertNoErrorsInCode('''
+    await assertNoErrorsInCode('''
 class C {}
 extension E on C {
   int operator -() => 7;
@@ -121,7 +122,7 @@ f(C c) {
   }
 
   test_setter() async {
-    assertNoErrorsInCode('''
+    await assertNoErrorsInCode('''
 class C {}
 extension E on C {
   set s(int x) {}

pkg/analyzer/test/src/diagnostics/invalid_extension_argument_count_test.dart

@@ -33,6 +33,7 @@ f() {
 ''', [
       error(CompileTimeErrorCode.INVALID_EXTENSION_ARGUMENT_COUNT, 49, 15),
     ]);
+    assertElementTypeDynamic(findNode.extensionOverride('E(').extendedType);
   }
 
   test_one() async {
@@ -57,5 +58,6 @@ f() {
 ''', [
       error(CompileTimeErrorCode.INVALID_EXTENSION_ARGUMENT_COUNT, 49, 2),
     ]);
+    assertElementTypeDynamic(findNode.extensionOverride('E(').extendedType);
   }
 }