Fix NPE when extension override is invoked without a call method (issue 38505)

Change-Id: Ia2ad1168441cf07e379184ad82f592701f5ef2bc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/118481
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

Author: bwilkerson

pkg/analyzer/lib/error/error.dart

@@ -196,6 +196,7 @@ const List<ErrorCode> errorCodeValues = const [
   CompileTimeErrorCode.INVALID_URI,
   CompileTimeErrorCode.INVALID_USE_OF_COVARIANT,
   CompileTimeErrorCode.INVALID_USE_OF_COVARIANT_IN_EXTENSION,
+  CompileTimeErrorCode.INVOCATION_OF_EXTENSION_WITHOUT_CALL,
   CompileTimeErrorCode.LABEL_IN_OUTER_SCOPE,
   CompileTimeErrorCode.LABEL_UNDEFINED,
   CompileTimeErrorCode.MAP_ENTRY_NOT_IN_MAP,

pkg/analyzer/lib/src/error/codes.dart

@@ -2333,6 +2333,16 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
   static const CompileTimeErrorCode INVALID_URI =
       const CompileTimeErrorCode('INVALID_URI', "Invalid URI syntax: '{0}'.");
 
+  /**
+   * Parameters:
+   * 0: the name of the extension
+   */
+  static const CompileTimeErrorCode INVOCATION_OF_EXTENSION_WITHOUT_CALL =
+      const CompileTimeErrorCode(
+          'INVOCATION_OF_EXTENSION_WITHOUT_CALL',
+          "The extension '{0}' does not define a 'call' method so the override "
+              "can't be used in an invocation.");
+
   /**
    * 13.13 Break: It is a compile-time error if no such statement
    * <i>s<sub>E</sub></i> exists within the innermost function in which

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

@@ -397,13 +397,21 @@ class ElementResolver extends SimpleAstVisitor<void> {
     DartType functionType;
     if (function is ExtensionOverride) {
       var member = _extensionResolver.getOverrideMember(function, 'call');
-      if (member != null && member.isStatic) {
+      if (member == null) {
         _resolver.errorReporter.reportErrorForNode(
-            CompileTimeErrorCode.EXTENSION_OVERRIDE_ACCESS_TO_STATIC_MEMBER,
-            node.argumentList);
+            CompileTimeErrorCode.INVOCATION_OF_EXTENSION_WITHOUT_CALL,
+            function,
+            [function.extensionName.name]);
+        functionType = _resolver.typeProvider.dynamicType;
+      } else {
+        if (member.isStatic) {
+          _resolver.errorReporter.reportErrorForNode(
+              CompileTimeErrorCode.EXTENSION_OVERRIDE_ACCESS_TO_STATIC_MEMBER,
+              node.argumentList);
+        }
+        node.staticElement = member;
+        functionType = member.type;
       }
-      node.staticElement = member;
-      functionType = member.type;
     } else {
       functionType = function.staticType;
     }

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

@@ -0,0 +1,35 @@
+// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/dart/analysis/features.dart';
+import 'package:analyzer/src/error/codes.dart';
+import 'package:analyzer/src/generated/engine.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../dart/resolution/driver_resolution.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(InvocationOfExtensionWithoutCallTest);
+  });
+}
+
+@reflectiveTest
+class InvocationOfExtensionWithoutCallTest extends DriverResolutionTest {
+  @override
+  AnalysisOptionsImpl get analysisOptions => AnalysisOptionsImpl()
+    ..contextFeatures = new FeatureSet.forTesting(
+        sdkVersion: '2.3.0', additionalFeatures: [Feature.extension_methods]);
+
+  test_instance_differentKind() async {
+    await assertErrorsInCode('''
+extension E on Object {}
+f() {
+  E(null)();
+}
+''', [
+      error(CompileTimeErrorCode.INVOCATION_OF_EXTENSION_WITHOUT_CALL, 33, 7),
+    ]);
+  }
+}

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

@@ -149,6 +149,8 @@ import 'invalid_use_of_visible_for_testing_member_test.dart'
     as invalid_use_of_visible_for_testing_member;
 import 'invalid_visibility_annotation_test.dart'
     as invalid_visibility_annotation;
+import 'invocation_of_extension_without_call_test.dart'
+    as invocation_of_extension_without_call;
 import 'is_double_test.dart' as is_double;
 import 'is_int_test.dart' as is_int;
 import 'is_not_double_test.dart' as is_not_double;
@@ -428,6 +430,7 @@ main() {
     invalid_use_of_visible_for_template_member.main();
     invalid_use_of_visible_for_testing_member.main();
     invalid_visibility_annotation.main();
+    invocation_of_extension_without_call.main();
     is_double.main();
     is_int.main();
     is_not_double.main();