[analysis_server] Swap from dynamic to Object? in LSP generated code

Change-Id: Ib8ce2c722806b53b727d256c73859becbc1dbd11
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/206120
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/lsp/client_capabilities.dart

@@ -132,8 +132,9 @@ class LspClientCapabilities {
             raw.workspace?.symbol?.symbolKind?.valueSet,
             defaults: defaultSupportedSymbolKinds),
         experimentalSnippetTextEdit =
-            raw.experimental is Map<String, dynamic> &&
-                raw.experimental['snippetTextEdit'] == true;
+            raw.experimental is Map<String, Object?> &&
+                (raw.experimental as Map<String, Object?>)['snippetTextEdit'] ==
+                    true;
 
   static Set<MarkupKind>? _completionDocumentationFormats(
       ClientCapabilities raw) {

pkg/analysis_server/lib/src/lsp/handlers/commands/simple_edit_handler.dart

@@ -78,8 +78,8 @@ abstract class SimpleEditCommandHandler
     // sent - and may have failed to apply - was related to this command
     // execution).
     // We need to fromJson to convert the JSON map to the real types.
-    final editResponseResult =
-        ApplyWorkspaceEditResponse.fromJson(editResponse.result);
+    final editResponseResult = ApplyWorkspaceEditResponse.fromJson(
+        editResponse.result as Map<String, Object?>);
     if (editResponseResult.applied) {
       return success(null);
     } else {

pkg/analysis_server/lib/src/lsp/handlers/handler_execute_command.dart

@@ -51,9 +51,6 @@ class ExecuteCommandHandler
         : server.clientCapabilities?.workDoneProgress ?? false
             ? ProgressReporter.serverCreated(server)
             : ProgressReporter.noop;
-    // TODO(dantup): Remove this cast and update codegen to use `Object?` in
-    //   place of the `dynamics`.
-    return handler.handle(
-        params.arguments?.cast<Object?>(), progress, cancellationToken);
+    return handler.handle(params.arguments, progress, cancellationToken);
   }
 }

pkg/analysis_server/lib/src/lsp/lsp_analysis_server.dart

@@ -614,7 +614,7 @@ class LspAnalysisServer extends AbstractAnalysisServer {
       ShowMessageRequestParams(type: type, message: message, actions: actions),
     );
 
-    return MessageActionItem.fromJson(response.result);
+    return MessageActionItem.fromJson(response.result as Map<String, Object?>);
   }
 
   @override

pkg/analysis_server/test/integration/lsp_server/integration_tests.dart

@@ -38,7 +38,7 @@ abstract class AbstractLspAnalysisServerIntegrationTest
           ? null as T
           : throw 'Expected Null response but got ${resp.result}';
     } else {
-      return fromJson(resp.result);
+      return fromJson(resp.result as R);
     }
   }
 

pkg/analysis_server/test/lsp/code_actions_refactor_test.dart

@@ -37,7 +37,8 @@ class ExtractMethodRefactorCodeActionsTest extends AbstractCodeActionsTest {
     requestsFromServer
         .where((r) => r.method == Method.window_workDoneProgress_create)
         .listen((request) async {
-      final params = WorkDoneProgressCreateParams.fromJson(request.params);
+      final params = WorkDoneProgressCreateParams.fromJson(
+          request.params as Map<String, Object?>);
       if (params.token != analyzingProgressToken) {
         controller.add('CREATE');
       }
@@ -45,7 +46,8 @@ class ExtractMethodRefactorCodeActionsTest extends AbstractCodeActionsTest {
     notificationsFromServer
         .where((n) => n.method == Method.progress)
         .listen((notification) {
-      final params = ProgressParams.fromJson(notification.params);
+      final params =
+          ProgressParams.fromJson(notification.params as Map<String, Object?>);
       if (params.token != analyzingProgressToken) {
         if (WorkDoneProgressBegin.canParse(params.value, nullLspJsonReporter)) {
           controller.add('BEGIN');
@@ -118,7 +120,8 @@ void newMethod() {
     late WorkspaceEdit edit;
     requestsFromServer.listen((request) async {
       if (request.method == Method.workspace_applyEdit) {
-        final params = ApplyWorkspaceEditParams.fromJson(request.params);
+        final params = ApplyWorkspaceEditParams.fromJson(
+            request.params as Map<String, Object?>);
         edit = params.edit;
         respondTo(request, ApplyWorkspaceEditResponse(applied: true));
       }

pkg/analysis_server/test/lsp/completion_dart_test.dart

@@ -154,7 +154,8 @@ void f() {
 
     // By default, there should be no commit characters.
     var reg = registration(Method.textDocument_completion);
-    var options = CompletionRegistrationOptions.fromJson(reg.registerOptions);
+    var options = CompletionRegistrationOptions.fromJson(
+        reg.registerOptions as Map<String, Object?>);
     expect(options.allCommitCharacters, isNull);
 
     // When we change config, we should get a re-registration (unregister then
@@ -162,7 +163,8 @@ void f() {
     await monitorDynamicReregistration(
         registrations, () => updateConfig({'previewCommitCharacters': true}));
     reg = registration(Method.textDocument_completion);
-    options = CompletionRegistrationOptions.fromJson(reg.registerOptions);
+    options = CompletionRegistrationOptions.fromJson(
+        reg.registerOptions as Map<String, Object?>);
     expect(options.allCommitCharacters, equals(dartCompletionCommitCharacters));
   }
 

pkg/analysis_server/test/lsp/initialization_test.dart

@@ -26,7 +26,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
     Method method,
   ) {
     return TextDocumentRegistrationOptions.fromJson(
-        registrationFor(registrations, method)?.registerOptions);
+        registrationFor(registrations, method)?.registerOptions
+            as Map<String, Object?>);
   }
 
   Future<void> test_bazelWorkspace() async {
@@ -64,14 +65,15 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
       ),
     );
 
-    final initResult = InitializeResult.fromJson(initResponse.result);
+    final initResult =
+        InitializeResult.fromJson(initResponse.result as Map<String, Object?>);
     expect(initResult.capabilities, isNotNull);
 
     // Check Dart-only registration.
     final dartRegistration =
         registrationForDart(registrations, Method.textDocument_completion);
     final dartOptions = CompletionRegistrationOptions.fromJson(
-        dartRegistration.registerOptions);
+        dartRegistration.registerOptions as Map<String, Object?>);
     expect(dartOptions.documentSelector, hasLength(1));
     expect(dartOptions.documentSelector![0].language, dartLanguageId);
     expect(dartOptions.triggerCharacters, isNotEmpty);
@@ -81,7 +83,7 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
         r.method == Method.textDocument_completion.toJson() &&
         r != dartRegistration);
     final nonDartOptions = CompletionRegistrationOptions.fromJson(
-        nonDartRegistration.registerOptions);
+        nonDartRegistration.registerOptions as Map<String, Object?>);
     final otherLanguages = nonDartOptions.documentSelector!
         .map((selector) => selector.language)
         .toList();
@@ -109,7 +111,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
     // Because we support dynamic registration for synchronization, we won't send
     // static registrations for them.
     // https://github.com/dart-lang/sdk/issues/38490
-    final initResult = InitializeResult.fromJson(initResponse.result);
+    final initResult =
+        InitializeResult.fromJson(initResponse.result as Map<String, Object?>);
     expect(initResult.serverInfo!.name, 'Dart SDK LSP Analysis Server');
     expect(initResult.serverInfo!.version, isNotNull);
     expect(initResult.capabilities, isNotNull);
@@ -123,7 +126,7 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
         registrationOptionsFor(registrations, Method.textDocument_didChange);
     final rename = FileOperationRegistrationOptions.fromJson(
         registrationFor(registrations, Method.workspace_willRenameFiles)
-            ?.registerOptions);
+            ?.registerOptions as Map<String, Object?>);
     expect(registrationOptionsFor(registrations, Method.textDocument_didOpen),
         isNotNull);
     expect(registrationOptionsFor(registrations, Method.textDocument_didClose),
@@ -164,7 +167,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
     final initResponse = await initialize();
     await pumpEventQueue();
 
-    final initResult = InitializeResult.fromJson(initResponse.result);
+    final initResult =
+        InitializeResult.fromJson(initResponse.result as Map<String, Object?>);
     expect(initResult.capabilities, isNotNull);
     // When dynamic registration is not supported, we will always statically
     // request text document open/close and incremental updates.
@@ -229,7 +233,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
       ),
     );
 
-    final initResult = InitializeResult.fromJson(initResponse.result);
+    final initResult =
+        InitializeResult.fromJson(initResponse.result as Map<String, Object?>);
     expect(initResult.capabilities, isNotNull);
 
     // Ensure no static registrations. This list should include all server equivilents
@@ -289,8 +294,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
         ..interestingFiles = ['*.foo'];
       pluginManager.pluginsChangedController.add(null);
     });
-    final unregistrations =
-        UnregistrationParams.fromJson(unregisterRequest.params)
+    final unregistrations = UnregistrationParams.fromJson(
+            unregisterRequest.params as Map<String, Object?>)
         .unregisterations;
 
     // folding method should have been unregistered as the server now supports
@@ -321,7 +326,9 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
         .firstWhere((r) => r.method == Method.client_unregisterCapability)
         .then((request) {
       respondTo(request, null);
-      return UnregistrationParams.fromJson(request.params).unregisterations;
+      return UnregistrationParams.fromJson(
+              request.params as Map<String, Object?>)
+          .unregisterations;
     });
 
     final request = await expectRequest(Method.client_registerCapability, () {
@@ -332,7 +339,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
     });
 
     final registrations =
-        RegistrationParams.fromJson(request.params).registrations;
+        RegistrationParams.fromJson(request.params as Map<String, Object?>)
+            .registrations;
 
     final documentFilterSql =
         DocumentFilter(scheme: 'file', pattern: '**/*.sql');
@@ -343,7 +351,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
       contains(isA<Registration>()
           .having((r) => r.method, 'method', 'textDocument/foldingRange')
           .having(
-            (r) => TextDocumentRegistrationOptions.fromJson(r.registerOptions)
+            (r) => TextDocumentRegistrationOptions.fromJson(
+                    r.registerOptions as Map<String, Object?>)
                 .documentSelector,
             'registerOptions.documentSelector',
             containsAll([documentFilterSql, documentFilterDart]),
@@ -483,7 +492,8 @@ class InitializationTest extends AbstractLspAnalysisServerTest {
     expect(response.result, isNotNull);
     expect(InitializeResult.canParse(response.result, nullLspJsonReporter),
         isTrue);
-    final result = InitializeResult.fromJson(response.result);
+    final result =
+        InitializeResult.fromJson(response.result as Map<String, Object?>);
     expect(result.capabilities, isNotNull);
     // Check some basic capabilities that are unlikely to change.
     expect(result.capabilities.textDocumentSync, isNotNull);

pkg/analysis_server/test/lsp/rename_test.dart

@@ -176,7 +176,8 @@ class RenameTest extends AbstractLspAnalysisServerTest {
       throw error;
     }
 
-    final result = WorkspaceEdit.fromJson(response.result);
+    final result =
+        WorkspaceEdit.fromJson(response.result as Map<String, Object?>);
 
     // Ensure applying the changes will give us the expected content.
     final contents = {
@@ -205,7 +206,7 @@ class RenameTest extends AbstractLspAnalysisServerTest {
     // Expect a successful empty response if cancelled.
     expect(response.error, isNull);
     expect(
-      WorkspaceEdit.fromJson(response.result),
+      WorkspaceEdit.fromJson(response.result as Map<String, Object?>),
       equals(emptyWorkspaceEdit),
     );
   }

pkg/analysis_server/test/lsp/server_abstract.dart

@@ -102,7 +102,7 @@ abstract class AbstractLspAnalysisServerTest
       throw error;
     } else {
       // resp.result should only be null when error != null if T allows null.
-      return resp.result == null ? null as T : fromJson(resp.result);
+      return resp.result == null ? null as T : fromJson(resp.result as R);
     }
   }
 
@@ -122,7 +122,8 @@ abstract class AbstractLspAnalysisServerTest
   ) {
     return registrations.singleWhere((r) =>
         r.method == method.toJson() &&
-        (TextDocumentRegistrationOptions.fromJson(r.registerOptions)
+        (TextDocumentRegistrationOptions.fromJson(
+                    r.registerOptions as Map<String, Object?>)
                 .documentSelector
                 ?.any((selector) => selector.language == dartLanguageId) ??
             false));
@@ -875,7 +876,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
     final notificationFromServer = await firstError.timeout(timeout);
 
     expect(notificationFromServer, isNotNull);
-    return ShowMessageParams.fromJson(notificationFromServer.params);
+    return ShowMessageParams.fromJson(
+        notificationFromServer.params as Map<String, Object?>);
   }
 
   Future<T> expectNotification<T>(
@@ -1253,7 +1255,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
     });
 
     // Handle the request from the server and send the response back.
-    final clientsResponse = await handler(fromJson(incomingRequest.params));
+    final clientsResponse =
+        await handler(fromJson(incomingRequest.params as Map<String, Object?>));
     respondTo(incomingRequest, clientsResponse);
 
     // Return a future that completes when the response to the original request
@@ -1649,7 +1652,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
                 'but client supports workDoneProgress');
           }
 
-          final params = AnalyzerStatusParams.fromJson(message.params);
+          final params = AnalyzerStatusParams.fromJson(
+              message.params as Map<String, Object?>);
           return params.isAnalyzing == analyzing;
         } else if (message.method == Method.progress) {
           if (_clientCapabilities!.window?.workDoneProgress != true) {
@@ -1658,7 +1662,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
                 'but client supports workDoneProgress');
           }
 
-          final params = ProgressParams.fromJson(message.params);
+          final params =
+              ProgressParams.fromJson(message.params as Map<String, Object?>);
 
           // Skip unrelated progress notifications.
           if (params.token != analyzingProgressToken) {
@@ -1688,8 +1693,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
     await serverToClient.firstWhere((message) {
       if (message is NotificationMessage &&
           message.method == CustomMethods.publishClosingLabels) {
-        closingLabelsParams =
-            PublishClosingLabelsParams.fromJson(message.params);
+        closingLabelsParams = PublishClosingLabelsParams.fromJson(
+            message.params as Map<String, Object?>);
 
         return closingLabelsParams.uri == uri.toString();
       }
@@ -1704,7 +1709,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
         (message) {
       if (message is NotificationMessage &&
           message.method == Method.textDocument_publishDiagnostics) {
-        diagnosticParams = PublishDiagnosticsParams.fromJson(message.params);
+        diagnosticParams = PublishDiagnosticsParams.fromJson(
+            message.params as Map<String, Object?>);
         return diagnosticParams!.uri == uri.toString();
       }
       return false;
@@ -1717,7 +1723,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
     await serverToClient.firstWhere((message) {
       if (message is NotificationMessage &&
           message.method == CustomMethods.publishFlutterOutline) {
-        outlineParams = PublishFlutterOutlineParams.fromJson(message.params);
+        outlineParams = PublishFlutterOutlineParams.fromJson(
+            message.params as Map<String, Object?>);
 
         return outlineParams.uri == uri.toString();
       }
@@ -1731,7 +1738,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
     await serverToClient.firstWhere((message) {
       if (message is NotificationMessage &&
           message.method == CustomMethods.publishOutline) {
-        outlineParams = PublishOutlineParams.fromJson(message.params);
+        outlineParams = PublishOutlineParams.fromJson(
+            message.params as Map<String, Object?>);
 
         return outlineParams.uri == uri.toString();
       }
@@ -1760,7 +1768,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
       (input) => input.cast<Map<String, dynamic>>().map(fromJson).toList();
 
   Future<void> _handleProgress(NotificationMessage request) async {
-    final params = ProgressParams.fromJson(request.params);
+    final params =
+        ProgressParams.fromJson(request.params as Map<String, Object?>);
     if (params.token != clientProvidedTestWorkDoneToken &&
         !validProgressTokens.contains(params.token)) {
       throw Exception('Server sent a progress notification for a token '
@@ -1777,7 +1786,8 @@ mixin LspAnalysisServerTestMixin implements ClientCapabilitiesHelperMixin {
       throw Exception('Server sent ${Method.window_workDoneProgress_create} '
           'but client capabilities do not allow');
     }
-    final params = WorkDoneProgressCreateParams.fromJson(request.params);
+    final params = WorkDoneProgressCreateParams.fromJson(
+        request.params as Map<String, Object?>);
     if (validProgressTokens.contains(params.token)) {
       throw Exception('Server tried to create already-active progress token');
     }

pkg/analysis_server/test/mocks_lsp.dart

@@ -40,12 +40,14 @@ class MockLspServerChannel implements LspServerCommunicationChannel {
     // `window/showMessage`.
     _serverToClient.stream.listen((message) {
       if (message is lsp.NotificationMessage &&
-          message.method == Method.window_showMessage &&
-          message.params is lsp.ShowMessageParams) {
-        if (message.params?.type == MessageType.Error) {
-          shownErrors.add(message.params);
-        } else if (message.params?.type == MessageType.Warning) {
-          shownWarnings.add(message.params);
+          message.method == Method.window_showMessage) {
+        final params = message.params;
+        if (params is lsp.ShowMessageParams) {
+          if (params.type == MessageType.Error) {
+            shownErrors.add(params);
+          } else if (params.type == MessageType.Warning) {
+            shownWarnings.add(params);
+          }
         }
       }
     });
@@ -170,7 +172,9 @@ class MockLspServerChannel implements LspServerCommunicationChannel {
         (throwOnError &&
             message is lsp.NotificationMessage &&
             message.method == Method.window_showMessage &&
-            lsp.ShowMessageParams.fromJson(message.params).type ==
+            lsp.ShowMessageParams.fromJson(
+                        message.params as Map<String, Object?>)
+                    .type ==
                 MessageType.Error));
 
     if (response is lsp.ResponseMessage) {

pkg/analysis_server/test/tool/lsp_spec/dart_test.dart

@@ -11,8 +11,8 @@ void main() {
     test('handles basic types', () {
       expect(_simple('string').dartType, equals('String'));
       expect(_simple('boolean').dartType, equals('bool'));
-      expect(_simple('any').dartType, equals('dynamic'));
-      expect(_simple('object').dartType, equals('dynamic'));
+      expect(_simple('any').dartType, equals('Object?'));
+      expect(_simple('object').dartType, equals('Object?'));
       expect(_simple('int').dartType, equals('int'));
       expect(_simple('num').dartType, equals('num'));
     });

pkg/analysis_server/tool/lsp_spec/codegen_dart.dart

@@ -177,6 +177,20 @@ String _rewriteCommentReference(String comment) {
   });
 }
 
+/// Returns a String representing the underlying Dart type for the provided
+/// spec [type].
+///
+/// This is `Map<String, Object?>` for complex types but can be a simple type
+/// for enums.
+String _specJsonType(TypeBase type) {
+  if (type is Type && _namespaces.containsKey(type.name)) {
+    final valueType = _namespaces[type.name]!.members.cast<Const>().first.type;
+    return resolveTypeAlias(valueType, resolveEnumClasses: true)
+        .dartTypeWithTypeArgs;
+  }
+  return 'Map<String, Object?>';
+}
+
 Iterable<String> _wrapLines(List<String> lines, int maxLength) sync* {
   lines = lines.map((l) => l.trimRight()).toList();
   for (var line in lines) {
@@ -204,7 +218,7 @@ void _writeCanParseMethod(IndentableStringBuffer buffer, Interface interface) {
     ..writeIndentedln(
         'static bool canParse(Object? obj, LspJsonReporter reporter) {')
     ..indent()
-    ..writeIndentedln('if (obj is Map<String, dynamic>) {')
+    ..writeIndentedln('if (obj is Map<String, Object?>) {')
     ..indent();
   // In order to consider this valid for parsing, all fields that must not be
   // undefined must be present and also type check for the correct type.
@@ -227,9 +241,12 @@ void _writeCanParseMethod(IndentableStringBuffer buffer, Interface interface) {
         ..outdent()
         ..writeIndentedln('}');
     }
+    // Add a local variable to allow type promotion (and avoid multiple lookups).
+    final localName = _makeValidIdentifier(field.name);
+    buffer.writeIndentedln("final $localName = obj['${field.name}'];");
     if (!field.allowsNull && !field.allowsUndefined) {
       buffer
-        ..writeIndentedln("if (obj['${field.name}'] == null) {")
+        ..writeIndentedln('if ($localName == null) {')
         ..indent()
         ..writeIndentedln("reporter.reportError('must not be null');")
         ..writeIndentedln('return false;')
@@ -238,11 +255,11 @@ void _writeCanParseMethod(IndentableStringBuffer buffer, Interface interface) {
     }
     buffer.writeIndented('if (');
     if (field.allowsNull || field.allowsUndefined) {
-      buffer.write("obj['${field.name}'] != null && ");
+      buffer.write('$localName != null && ');
     }
     buffer.write('!(');
     _writeTypeCheckCondition(
-        buffer, interface, "obj['${field.name}']", field.type, 'reporter');
+        buffer, interface, localName, field.type, 'reporter');
     buffer
       ..write(')) {')
       ..indent()
@@ -469,47 +486,56 @@ void _writeField(IndentableStringBuffer buffer, Field field) {
 }
 
 void _writeFromJsonCode(
-    IndentableStringBuffer buffer, TypeBase type, String valueCode,
-    {required bool allowsNull, bool requiresBracesInInterpolation = false}) {
+  IndentableStringBuffer buffer,
+  TypeBase type,
+  String valueCode, {
+  required bool allowsNull,
+  bool requiresCast = true,
+}) {
   type = resolveTypeAlias(type);
+  final nullOperator = allowsNull ? '?' : '';
+  final cast = requiresCast && type.dartTypeWithTypeArgs != 'Object?'
+      ? ' as ${type.dartTypeWithTypeArgs}$nullOperator'
+      : '';
 
   if (_isSimpleType(type)) {
-    buffer.write('$valueCode');
+    buffer.write('$valueCode$cast');
   } else if (_isSpecType(type)) {
     // Our own types have fromJson() constructors we can call.
     if (allowsNull) {
       buffer.write('$valueCode != null ? ');
     }
-    buffer.write('${type.dartType}.fromJson${type.typeArgsString}($valueCode)');
+    buffer
+      ..write('${type.dartType}.fromJson${type.typeArgsString}')
+      ..write('($valueCode as ${_specJsonType(type)})');
     if (allowsNull) {
       buffer.write(': null');
     }
   } else if (type is ArrayType) {
     // Lists need to be map()'d so we can recursively call writeFromJsonCode
     // as they may need fromJson on each element.
-    buffer.write('$valueCode?.map((item) => ');
-    _writeFromJsonCode(buffer, type.elementType, 'item',
-        allowsNull: allowsNull);
-    buffer
-        .write(')?.cast<${type.elementType.dartTypeWithTypeArgs}>()?.toList()');
+    final listCast = requiresCast ? ' as List<Object?>$nullOperator' : '';
+    buffer.write('($valueCode$listCast)$nullOperator.map((item) => ');
+    _writeFromJsonCode(buffer, type.elementType, 'item', allowsNull: false);
+    buffer.write(').toList()');
   } else if (type is MapType) {
     // Maps need to be map()'d so we can recursively call writeFromJsonCode as
     // they may need fromJson on each key or value.
-    buffer.write('$valueCode?.map((key, value) => MapEntry(');
-    _writeFromJsonCode(buffer, type.indexType, 'key', allowsNull: allowsNull);
+    final mapCast = requiresCast ? ' as Map<Object, Object?>$nullOperator' : '';
+    buffer
+      ..write('($valueCode$mapCast)$nullOperator.map(')
+      ..write('(key, value) => MapEntry(');
+    _writeFromJsonCode(buffer, type.indexType, 'key', allowsNull: false);
     buffer.write(', ');
-    _writeFromJsonCode(buffer, type.valueType, 'value', allowsNull: allowsNull);
-    buffer.write(
-        '))?.cast<${type.indexType.dartTypeWithTypeArgs}, ${type.valueType.dartTypeWithTypeArgs}>()');
+    _writeFromJsonCode(buffer, type.valueType, 'value', allowsNull: false);
+    buffer.write('))');
   } else if (type is LiteralUnionType) {
     _writeFromJsonCodeForLiteralUnion(buffer, type, valueCode,
         allowsNull: allowsNull);
   } else if (type is UnionType) {
-    _writeFromJsonCodeForUnion(buffer, type, valueCode,
-        allowsNull: allowsNull,
-        requiresBracesInInterpolation: requiresBracesInInterpolation);
+    _writeFromJsonCodeForUnion(buffer, type, valueCode, allowsNull: allowsNull);
   } else {
-    buffer.write('$valueCode');
+    buffer.write('$valueCode$cast');
   }
 }
 
@@ -520,14 +546,16 @@ void _writeFromJsonCodeForLiteralUnion(
     if (allowsNull) null,
     ...union.literalTypes.map((t) => t.literal)
   ];
+  final valueType = union.literalTypes.first.dartTypeWithTypeArgs;
+  final cast = ' as $valueType${allowsNull ? '?' : ''}';
   buffer.write(
-      "const {${allowedValues.join(', ')}}.contains($valueCode) ? $valueCode : "
-      "throw '''\${$valueCode} was not one of (${allowedValues.join(', ')})'''");
+      "const {${allowedValues.join(', ')}}.contains($valueCode) ? $valueCode$cast : "
+      "throw '''\$$valueCode was not one of (${allowedValues.join(', ')})'''");
 }
 
 void _writeFromJsonCodeForUnion(
     IndentableStringBuffer buffer, UnionType union, String valueCode,
-    {required bool allowsNull, required bool requiresBracesInInterpolation}) {
+    {required bool allowsNull}) {
   // Write a check against each type, eg.:
   // x is y ? new Either.tx(x) : (...)
   var hasIncompleteCondition = false;
@@ -543,7 +571,7 @@ void _writeFromJsonCodeForUnion(
     final type = union.types[i];
     final isAny = isAnyType(type);
 
-    // Dynamic matches all type checks, so only emit it if required.
+    // "any" matches all type checks, so only emit it if required.
     if (!isAny) {
       _writeTypeCheckCondition(
           buffer, null, valueCode, type, 'nullLspJsonReporter');
@@ -552,10 +580,13 @@ void _writeFromJsonCodeForUnion(
 
     // The code to construct a value with this "side" of the union.
     buffer.write('${union.dartTypeWithTypeArgs}.t${i + 1}(');
-    _writeFromJsonCode(buffer, type, valueCode,
-        allowsNull: false, // null is already handled above this loop
-        requiresBracesInInterpolation:
-            requiresBracesInInterpolation); // Call recursively!
+    // Call recursively as unions may be nested.
+    _writeFromJsonCode(
+      buffer, type, valueCode,
+      // null + type checks are already handled above this loop
+      allowsNull: false,
+      requiresCast: false,
+    );
     buffer.write(')');
 
     // If we output the type condition at the top, prepare for the next condition.
@@ -570,8 +601,7 @@ void _writeFromJsonCodeForUnion(
   // Fill the final parens with a throw because if we fell through all of the
   // cases then the value we had didn't match any of the types in the union.
   if (hasIncompleteCondition) {
-    var interpolation =
-        requiresBracesInInterpolation ? '\${$valueCode}' : '\$$valueCode';
+    var interpolation = '\$$valueCode';
     buffer.write(
         "throw '''$interpolation was not one of (${union.types.map((t) => t.dartTypeWithTypeArgs).join(', ')})'''");
   }
@@ -583,7 +613,7 @@ void _writeFromJsonConstructor(
   final allFields = _getAllFields(interface);
   buffer
     ..writeIndentedln('static ${interface.nameWithTypeArgs} '
-        'fromJson${interface.typeArgsString}(Map<String, dynamic> json) {')
+        'fromJson${interface.typeArgsString}(Map<String, Object?> json) {')
     ..indent();
   // First check whether any of our subclasses can deserialise this.
   for (final subclassName in _subtypes[interface.name] ?? const <String>[]) {
@@ -597,10 +627,13 @@ void _writeFromJsonConstructor(
       ..writeIndentedln('}');
   }
   for (final field in allFields) {
-    buffer.writeIndented('final ${field.name} = ');
-    _writeFromJsonCode(buffer, field.type, "json['${field.name}']",
-        allowsNull: field.allowsNull || field.allowsUndefined,
-        requiresBracesInInterpolation: true);
+    // Add a local variable to allow type promotion (and avoid multiple lookups).
+    final localName = _makeValidIdentifier(field.name);
+    final localNameJson = '${localName}Json';
+    buffer.writeIndented("final $localNameJson = json['${field.name}'];");
+    buffer.writeIndented('final $localName = ');
+    _writeFromJsonCode(buffer, field.type, localNameJson,
+        allowsNull: field.allowsNull || field.allowsUndefined);
     buffer.writeln(';');
   }
   buffer
@@ -760,9 +793,9 @@ void _writeToJsonMethod(IndentableStringBuffer buffer, Interface interface) {
   // It's important the name we use for the map here isn't in use in the object
   // already. 'result' was, so we prefix it with some underscores.
   buffer
-    ..writeIndentedln('Map<String, dynamic> toJson() {')
+    ..writeIndentedln('Map<String, Object?> toJson() {')
     ..indent()
-    ..writeIndentedln('var __result = <String, dynamic>{};');
+    ..writeIndentedln('var __result = <String, Object?>{};');
   // ResponseMessage must confirm to JSON-RPC which says only one of
   // result/error can be included. Since this isn't encoded in the types we
   // need to special-case it's toJson generation.
@@ -806,7 +839,7 @@ void _writeTypeCheckCondition(IndentableStringBuffer buffer,
 
   final dartType = type.dartType;
   final fullDartType = type.dartTypeWithTypeArgs;
-  if (fullDartType == 'dynamic') {
+  if (fullDartType == 'Object?') {
     buffer.write('true');
   } else if (_isSimpleType(type)) {
     buffer.write('$valueCode is $fullDartType');
@@ -816,7 +849,7 @@ void _writeTypeCheckCondition(IndentableStringBuffer buffer,
     buffer.write('$dartType.canParse($valueCode, $reporter)');
   } else if (type is ArrayType) {
     buffer.write('($valueCode is List');
-    if (fullDartType != 'dynamic') {
+    if (fullDartType != 'Object?') {
       // TODO(dantup): If we're happy to assume we never have two lists in a union
       // we could skip this bit.
       buffer.write(' && ($valueCode.every((item) => ');
@@ -827,7 +860,7 @@ void _writeTypeCheckCondition(IndentableStringBuffer buffer,
     buffer.write(')');
   } else if (type is MapType) {
     buffer.write('($valueCode is Map');
-    if (fullDartType != 'dynamic') {
+    if (fullDartType != 'Object?') {
       buffer..write(' && (')..write('$valueCode.keys.every((item) => ');
       _writeTypeCheckCondition(
           buffer, interface, 'item', type.indexType, reporter);

pkg/analysis_server/tool/lsp_spec/typescript.dart

@@ -98,7 +98,7 @@ String? getImprovedType(String interfaceName, String? fieldName) {
     },
     'ResponseError': {
       'code': 'ErrorCodes',
-      // This is dynamic normally, but since this class can be serialised
+      // This is Object? normally, but since this class can be serialised
       // we will crash if it data is set to something that can't be converted to
       // JSON (for ex. Uri) so this forces anyone setting this to convert to a
       // String.

pkg/analysis_server/tool/lsp_spec/typescript_parser.dart

@@ -507,17 +507,17 @@ class Parser {
   /// Returns the next token without advancing.
   Token _peek() => _tokenAt(_current);
 
-  /// Remove any duplicate types (for ex. if we map multiple types into dynamic)
-  /// we don't want to end up with `dynamic | dynamic`. Key on dartType to
+  /// Remove any duplicate types (for ex. if we map multiple types into Object?)
+  /// we don't want to end up with `Object? | Object?`. Key on dartType to
   /// ensure we different types that will map down to the same type.
   TypeBase _simplifyUnionTypes(List<TypeBase> types) {
     final uniqueTypes = Map.fromEntries(
       types.map((t) => MapEntry(t.uniqueTypeIdentifier, t)),
     ).values.toList();
 
-    // If our list includes something that maps to dynamic as well as other
-    // types, we should just treat the whole thing as dynamic as we get no value
-    // typing Either4<bool, String, num, dynamic> but it becomes much more
+    // If our list includes something that maps to Object? as well as other
+    // types, we should just treat the whole thing as Object? as we get no value
+    // typing Either4<bool, String, num, Object?> but it becomes much more
     // difficult to use.
     if (uniqueTypes.any(isAnyType)) {
       return uniqueTypes.firstWhere(isAnyType);
@@ -954,8 +954,8 @@ class Type extends TypeBase {
       'number': 'num',
       'integer': 'int',
       'uinteger': 'int',
-      'any': 'dynamic',
-      'object': 'dynamic',
+      'any': 'Object?',
+      'object': 'Object?',
       // Simplify MarkedString from
       //     string | { language: string; value: string }
       // to just String
@@ -1001,7 +1001,7 @@ abstract class TypeBase {
   String get typeArgsString;
 
   /// A unique identifier for this type. Used for folding types together
-  /// (for example two types that resolve to "dynamic" in Dart).
+  /// (for example two types that resolve to "Object?" in Dart).
   String get uniqueTypeIdentifier => dartTypeWithTypeArgs;
 }