fix extension factory declaration in AST

Constructor declarations within extensions are invalid and the parser
reports an error. This modifies AstBuilder to add the declaration
as a method declaration in order to get navigation, search, etc.

Fix dart-lang/sdk#38202

Change-Id: I6071a8d5a742d6598f18a831688ddc97e411f76f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/116100
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/lib/src/fasta/ast_builder.dart

@@ -910,12 +910,59 @@ class AstBuilder extends StackListener {
   @override
   void endExtensionFactoryMethod(
       Token beginToken, Token factoryKeyword, Token endToken) {
+    assert(optional('factory', factoryKeyword));
+    assert(optional(';', endToken) || optional('}', endToken));
     debugEvent("ExtensionFactoryMethod");
-    // TODO(danrubel) Decide how to handle constructor declarations within
-    // extensions. They are invalid and the parser has already reported an
-    // error at this point, but we include them in order to get navigation,
-    // search, etc.
-    endClassFactoryMethod(beginToken, factoryKeyword, endToken);
+
+    Object bodyObject = pop();
+    FormalParameterList parameters = pop();
+    TypeParameterList typeParameters = pop();
+    Object constructorName = pop();
+    _Modifiers modifiers = pop();
+    List<Annotation> metadata = pop();
+
+    FunctionBody body;
+    if (bodyObject is FunctionBody) {
+      body = bodyObject;
+    } else if (bodyObject is _RedirectingFactoryBody) {
+      body = ast.emptyFunctionBody(endToken);
+    } else {
+      // Unhandled situation which should never happen.
+      // Since this event handler is just a recovery attempt,
+      // don't bother adding this declaration to the AST.
+      return;
+    }
+    Comment comment = _findComment(metadata, beginToken);
+
+    assert(parameters != null);
+
+    // Constructor declarations within extensions are invalid and the parser
+    // has already reported an error at this point, but we include them in as
+    // a method declaration in order to get navigation, search, etc.
+
+    SimpleIdentifier methodName;
+    if (constructorName is SimpleIdentifier) {
+      methodName = constructorName;
+    } else if (constructorName is PrefixedIdentifier) {
+      methodName = constructorName.identifier;
+    } else {
+      // Unsure what the method name should be in this situation.
+      // Since this event handler is just a recovery attempt,
+      // don't bother adding this declaration to the AST.
+      return;
+    }
+    currentDeclarationMembers.add(ast.methodDeclaration(
+        comment,
+        metadata,
+        modifiers?.externalKeyword,
+        modifiers?.abstractKeyword ?? modifiers?.staticKeyword,
+        null, // returnType
+        null, // getOrSet
+        null, // operatorKeyword
+        methodName,
+        typeParameters,
+        parameters,
+        body));
   }
 
   void endFieldInitializer(Token assignment, Token token) {

pkg/analyzer/test/generated/invalid_code_test.dart

@@ -230,7 +230,6 @@ class InvalidCodeWithExtensionMethodsTest extends DriverResolutionTest {
     ..contextFeatures = new FeatureSet.forTesting(
         sdkVersion: '2.3.0', additionalFeatures: [Feature.extension_methods]);
 
-  @failingTest
   test_fuzz_14() async {
     // This crashes because parser produces `ConstructorDeclaration`.
     // So, we try to create `ConstructorElement` for it, and it wants

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

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer/dart/analysis/features.dart';
+import 'package:analyzer/src/dart/error/syntactic_errors.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/test_utilities/mock_sdk.dart';
@@ -48,6 +49,31 @@ extension E on Object {
         ])
       ];
 
+  test_constructor() async {
+    await assertErrorsInCode('''
+extension E {
+  E() {}
+}
+''', [
+      error(ParserErrorCode.EXPECTED_TOKEN, 10, 1),
+      error(ParserErrorCode.EXPECTED_TYPE_NAME, 12, 1),
+      error(ParserErrorCode.EXTENSION_DECLARES_CONSTRUCTOR, 16, 1),
+    ]);
+  }
+
+  test_factory() async {
+    await assertErrorsInCode('''
+extension E {
+  factory S() {}
+}
+''', [
+      error(ParserErrorCode.EXPECTED_TOKEN, 10, 1),
+      error(CompileTimeErrorCode.UNDEFINED_CLASS, 12, 0),
+      error(ParserErrorCode.EXPECTED_TYPE_NAME, 12, 1),
+      error(ParserErrorCode.EXTENSION_DECLARES_CONSTRUCTOR, 16, 7),
+    ]);
+  }
+
   test_fromPlatform() async {
     await assertNoErrorsInCode('''
 import 'dart:test2';