Recover from exension type declarations with no representation field

Change-Id: I2fdd0c281ba8a8458248d00b91a0cb1abfed02da
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/331749
Commit-Queue: Brian Wilkerson <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: bwilkerson

pkg/analysis_server/test/services/completion/dart/location/extension_type_declaration_test.dart

@@ -52,7 +52,6 @@ suggestions
 ''');
   }
 
-  @FailingTest(reason: 'The AstBuilder drops the incomplete extension type')
   Future<void> test_afterType_beforeEof() async {
     await computeSuggestions('''
 extension type ^

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

@@ -1634,23 +1634,38 @@ class AstBuilder extends StackListener {
       Token typeKeyword, Token endToken) {
     final implementsClause =
         pop(NullValues.IdentifierList) as ImplementsClauseImpl?;
-    final representation = pop(const NullValue<RepresentationDeclarationImpl>())
+    var representation = pop(const NullValue<RepresentationDeclarationImpl>())
         as RepresentationDeclarationImpl?;
     final constKeyword = pop() as Token?;
 
     if (enableInlineClass) {
       final builder = _classLikeBuilder as _ExtensionTypeDeclarationBuilder;
-      if (representation != null) {
-        // TODO(scheglov): Handle missing primary constructor.
-        declarations.add(
-          builder.build(
-            typeKeyword: typeKeyword,
-            constKeyword: constKeyword,
-            representation: representation,
-            implementsClause: implementsClause,
-          ),
+      if (representation == null) {
+        var leftParenthesis = parser.rewriter.insertParens(builder.name, true);
+        var typeName = leftParenthesis.next!;
+        var rightParenthesis = leftParenthesis.endGroup!;
+        var fieldName = parser.rewriter.insertSyntheticIdentifier(typeName);
+        representation = RepresentationDeclarationImpl(
+          constructorName: null,
+          leftParenthesis: leftParenthesis,
+          fieldMetadata: [],
+          fieldType: NamedTypeImpl(
+              importPrefix: null,
+              name2: typeName,
+              question: null,
+              typeArguments: null),
+          fieldName: fieldName,
+          rightParenthesis: rightParenthesis,
         );
       }
+      declarations.add(
+        builder.build(
+          typeKeyword: typeKeyword,
+          constKeyword: constKeyword,
+          representation: representation,
+          implementsClause: implementsClause,
+        ),
+      );
     } else {
       _reportFeatureNotEnabled(
         feature: ExperimentalFeatures.inline_class,

pkg/analyzer/lib/src/test_utilities/find_node.dart

@@ -391,6 +391,10 @@ class FindNode {
     return _node(search, (n) => n is ExtensionOverride);
   }
 
+  ExtensionTypeDeclaration extensionTypeDeclaration(String search) {
+    return _node(search, (n) => n is ExtensionTypeDeclaration);
+  }
+
   FieldDeclaration fieldDeclaration(String search) {
     return _node(search, (n) => n is FieldDeclaration);
   }

pkg/analyzer/test/src/dart/parser/extension_type_test.dart

@@ -778,6 +778,33 @@ ExtensionTypeDeclaration
 ''');
   }
 
+  void test_primaryConstructor_missing() {
+    var parseResult = parseStringWithErrors(r'''
+extension type E {}
+''');
+    parseResult.assertErrors(
+        [error(ParserErrorCode.MISSING_PRIMARY_CONSTRUCTOR, 15, 1)]);
+
+    final node = parseResult.findNode.extensionTypeDeclaration('E');
+    assertParsedNodeText(
+        node,
+        r'''
+ExtensionTypeDeclaration
+  extensionKeyword: extension @0
+  typeKeyword: type @10
+  name: E @15
+  representation: RepresentationDeclaration
+    leftParenthesis: ( @17 <synthetic>
+    fieldType: NamedType
+      name: <empty> @17 <synthetic>
+    fieldName: <empty> @17 <synthetic>
+    rightParenthesis: ) @17 <synthetic>
+  leftBracket: { @17
+  rightBracket: } @18
+''',
+        withOffsets: true);
+  }
+
   test_primaryConstructor_named() {
     final parseResult = parseStringWithErrors(r'''
 extension type A.named(int it) {}

pkg/analyzer/test/verify_docs_test.dart

@@ -43,6 +43,15 @@ class SnippetTester {
   SnippetTester._(
       this.provider, this.docFolder, this.snippetDirPath, this.snippetPath);
 
+  /// Return `true` if the given error is a diagnostic produced by a lint that
+  /// is allowed to occur in documentation.
+  bool isAllowedLint(AnalysisError error) {
+    var errorCode = error.errorCode;
+    return errorCode is LintCode &&
+        errorCode.name == 'non_constant_identifier_names' &&
+        error.message.contains("'test_");
+  }
+
   Future<void> verify() async {
     await verifyFolder(docFolder);
   }
@@ -128,8 +137,10 @@ $snippet
       if (results is ErrorsResult) {
         Iterable<AnalysisError> errors = results.errors.where((error) {
           ErrorCode errorCode = error.errorCode;
+          // TODO(brianwilkerson)
           return errorCode != WarningCode.UNUSED_IMPORT &&
-              errorCode != HintCode.UNUSED_LOCAL_VARIABLE;
+              errorCode != HintCode.UNUSED_LOCAL_VARIABLE &&
+              !isAllowedLint(error);
         });
         if (errors.isNotEmpty) {
           String filePath =