diff --git a/.dart_tool/package_config.json b/.dart_tool/package_config.json
index d468fbd..d50d6f5 100644
--- a/.dart_tool/package_config.json
+++ b/.dart_tool/package_config.json
@@ -88,7 +88,7 @@
       "name": "analyzer_cli",
       "rootUri": "../pkg/analyzer_cli",
       "packageUri": "lib/",
-      "languageVersion": "2.7"
+      "languageVersion": "2.14"
     },
     {
       "name": "analyzer_plugin",
diff --git a/pkg/analyzer_cli/lib/src/analyzer_impl.dart b/pkg/analyzer_cli/lib/src/analyzer_impl.dart
index c52c6ee..19caf6d 100644
--- a/pkg/analyzer_cli/lib/src/analyzer_impl.dart
+++ b/pkg/analyzer_cli/lib/src/analyzer_impl.dart
@@ -44,25 +44,22 @@
   /// specified on the command line as though it is reached via a "package:"
   /// URI, but avoid suppressing its output in the event that the user has not
   /// specified the "--package-warnings" option.
-  String _selfPackageName;
+  String? _selfPackageName;
 
   AnalyzerImpl(this.analysisOptions, this.analysisDriver, this.libraryFile,
       this.options, this.stats, this.startTime);
 
   void addCompilationUnitSource(
       CompilationUnitElement unit, Set<CompilationUnitElement> units) {
-    if (unit == null || !units.add(unit)) {
+    if (!units.add(unit)) {
       return;
     }
-    var source = unit.source;
-    if (source != null) {
-      files.add(source.fullName);
-    }
+    files.add(unit.source.fullName);
   }
 
   void addLibrarySources(LibraryElement library, Set<LibraryElement> libraries,
       Set<CompilationUnitElement> units) {
-    if (library == null || !libraries.add(library)) {
+    if (!libraries.add(library)) {
       return;
     }
     // Maybe skip library.
@@ -102,7 +99,7 @@
         if (_defaultSeverityProcessor(error) == null) {
           continue;
         }
-        status = status.max(computeSeverity(error, options, analysisOptions));
+        status = status.max(computeSeverity(error, options, analysisOptions)!);
       }
     }
     return status;
@@ -160,7 +157,7 @@
     return computeMaxErrorSeverity();
   }
 
-  ErrorSeverity _defaultSeverityProcessor(AnalysisError error) =>
+  ErrorSeverity? _defaultSeverityProcessor(AnalysisError error) =>
       determineProcessedSeverity(error, options, analysisOptions);
 
   /// Returns true if we want to report diagnostics for this library.
@@ -191,7 +188,7 @@
     } else if (options.showPackageWarningsPrefix == null) {
       return true;
     } else {
-      return packageName.startsWith(options.showPackageWarningsPrefix);
+      return packageName.startsWith(options.showPackageWarningsPrefix!);
     }
   }
 
@@ -235,14 +232,14 @@
 
   @override
   void logException(dynamic exception,
-      [StackTrace stackTrace,
-      List<InstrumentationServiceAttachment> attachments = const []]) {
+      [StackTrace? stackTrace,
+      List<InstrumentationServiceAttachment>? attachments = const []]) {
     errorSink.writeln(exception);
     errorSink.writeln(stackTrace);
   }
 
   @override
-  void logInfo(String message, [Object exception]) {
+  void logInfo(String message, [Object? exception]) {
     outSink.writeln(message);
     if (exception != null) {
       outSink.writeln(exception);
diff --git a/pkg/analyzer_cli/lib/src/driver.dart b/pkg/analyzer_cli/lib/src/driver.dart
index 28e3590..b2dd53f 100644
--- a/pkg/analyzer_cli/lib/src/driver.dart
+++ b/pkg/analyzer_cli/lib/src/driver.dart
@@ -41,10 +41,10 @@
 import 'package:yaml/yaml.dart';
 
 /// Shared IO sink for standard error reporting.
-StringSink errorSink = io.stderr;
+late StringSink errorSink = io.stderr;
 
 /// Shared IO sink for standard out reporting.
-StringSink outSink = io.stdout;
+late StringSink outSink = io.stdout;
 
 /// Test this option map to see if it specifies lint rules.
 bool containsLintRuleEntry(YamlMap options) {
@@ -55,13 +55,14 @@
 class Driver implements CommandLineStarter {
   static final ByteStore analysisDriverMemoryByteStore = MemoryByteStore();
 
-  _AnalysisContextProvider _analysisContextProvider;
-  DriverBasedAnalysisContext analysisContext;
+  bool _isStarted = false;
 
-  /// The driver that was most recently created by a call to [_analyzeAll], or
-  /// `null` if [_analyzeAll] hasn't been called yet.
+  late _AnalysisContextProvider _analysisContextProvider;
+  DriverBasedAnalysisContext? analysisContext;
+
+  /// The driver that was most recently created by a call to [_analyzeAll].
   @visibleForTesting
-  AnalysisDriver analysisDriver;
+  AnalysisDriver? analysisDriver;
 
   /// The total number of source files loaded by an AnalysisContext.
   int _analyzedFileCount = 0;
@@ -73,7 +74,7 @@
   final AnalysisStats stats = AnalysisStats();
 
   /// The [PathFilter] for excluded files with wildcards, etc.
-  PathFilter pathFilter;
+  late PathFilter pathFilter;
 
   /// Create a new Driver instance.
   Driver({@Deprecated('This parameter has no effect') bool isTesting = false});
@@ -88,9 +89,10 @@
 
   @override
   Future<void> start(List<String> arguments) async {
-    if (analysisDriver != null) {
+    if (_isStarted) {
       throw StateError('start() can only be called once');
     }
+    _isStarted = true;
     var startTime = DateTime.now().millisecondsSinceEpoch;
 
     StringUtilities.INTERNER = MappedInterner();
@@ -98,7 +100,7 @@
     linter.registerLintRules();
 
     // Parse commandline options.
-    var options = CommandLineOptions.parse(resourceProvider, arguments);
+    var options = CommandLineOptions.parse(resourceProvider, arguments)!;
 
     _analysisContextProvider = _AnalysisContextProvider(resourceProvider);
 
@@ -106,7 +108,7 @@
     if (options.batchMode) {
       var batchRunner = BatchRunner(outSink, errorSink);
       batchRunner.runAsBatch(arguments, (List<String> args) async {
-        var options = CommandLineOptions.parse(resourceProvider, args);
+        var options = CommandLineOptions.parse(resourceProvider, args)!;
         return await _analyzeAll(options);
       });
     } else {
@@ -129,7 +131,7 @@
       for (var i = 0; i < 3; i++) {
         buildSdkSummary(
           resourceProvider: PhysicalResourceProvider.INSTANCE,
-          sdkPath: options.dartSdkPath,
+          sdkPath: options.dartSdkPath!,
         );
       }
 
@@ -137,13 +139,13 @@
     }
 
     if (analysisDriver != null) {
-      _analyzedFileCount += analysisDriver.knownFiles.length;
+      _analyzedFileCount += analysisDriver!.knownFiles.length;
     }
 
     if (options.perfReport != null) {
       var json = makePerfReport(
           startTime, currentTimeMillis, options, _analyzedFileCount, stats);
-      io.File(options.perfReport).writeAsStringSync(json);
+      io.File(options.perfReport!).writeAsStringSync(json);
     }
   }
 
@@ -175,7 +177,7 @@
     SeverityProcessor defaultSeverityProcessor;
     defaultSeverityProcessor = (AnalysisError error) {
       return determineProcessedSeverity(
-          error, options, analysisDriver.analysisOptions);
+          error, options, analysisDriver!.analysisOptions);
     };
 
     // We currently print out to stderr to ensure that when in batch mode we
@@ -213,7 +215,8 @@
     for (var sourcePath in pathList) {
       _analysisContextProvider.configureForPath(sourcePath);
       analysisContext = _analysisContextProvider.analysisContext;
-      analysisDriver = _analysisContextProvider.analysisDriver;
+      final analysisDriver =
+          this.analysisDriver = _analysisContextProvider.analysisDriver;
       pathFilter = _analysisContextProvider.pathFilter;
 
       // Add all the files to be analyzed en masse to the context. Skip any
@@ -250,8 +253,8 @@
             analysisDriver.currentSession.analysisContext.contextRoot.root.path,
           );
           formatter.formatErrors([
-            ErrorsResultImpl(analysisDriver.currentSession, path, null,
-                lineInfo, false, errors)
+            ErrorsResultImpl(analysisDriver.currentSession, path,
+                pathContext.toUri(path), lineInfo, false, errors)
           ]);
           for (var error in errors) {
             var severity = determineProcessedSeverity(
@@ -272,7 +275,7 @@
               errors.addAll(validator.validate(node.nodes));
             }
 
-            if (analysisDriver != null && analysisDriver.analysisOptions.lint) {
+            if (analysisDriver.analysisOptions.lint) {
               var visitors = <LintRule, PubspecVisitor>{};
               for (var linter in analysisDriver.analysisOptions.lintRules) {
                 if (linter is LintRule) {
@@ -301,13 +304,13 @@
             if (errors.isNotEmpty) {
               for (var error in errors) {
                 var severity = determineProcessedSeverity(
-                    error, options, analysisDriver.analysisOptions);
+                    error, options, analysisDriver.analysisOptions)!;
                 allResult = allResult.max(severity);
               }
               var lineInfo = LineInfo.fromContent(content);
               formatter.formatErrors([
-                ErrorsResultImpl(analysisDriver.currentSession, path, null,
-                    lineInfo, false, errors)
+                ErrorsResultImpl(analysisDriver.currentSession, path,
+                    pathContext.toUri(path), lineInfo, false, errors)
               ]);
             }
           } catch (exception) {
@@ -322,12 +325,12 @@
             var errors = validator.validate(
                 content, analysisDriver.analysisOptions.chromeOsManifestChecks);
             formatter.formatErrors([
-              ErrorsResultImpl(analysisDriver.currentSession, path, null,
-                  lineInfo, false, errors)
+              ErrorsResultImpl(analysisDriver.currentSession, path,
+                  pathContext.toUri(path), lineInfo, false, errors)
             ]);
             for (var error in errors) {
               var severity = determineProcessedSeverity(
-                  error, options, analysisDriver.analysisOptions);
+                  error, options, analysisDriver.analysisOptions)!;
               allResult = allResult.max(severity);
             }
           } catch (exception) {
@@ -360,7 +363,7 @@
     // The next batch should not be affected by a previous batch.
     // E.g. the same parts in both batches, but with different libraries.
     for (var path in dartFiles) {
-      analysisDriver.removeFile(path);
+      analysisDriver!.removeFile(path);
     }
 
     // Any dangling parts still in this list were definitely dangling.
@@ -412,6 +415,7 @@
   Future<ErrorSeverity> _runAnalyzer(
       FileState file, CommandLineOptions options, ErrorFormatter formatter) {
     var startTime = currentTimeMillis;
+    final analysisDriver = this.analysisDriver!;
     var analyzer = AnalyzerImpl(analysisDriver.analysisOptions, analysisDriver,
         file, options, stats, startTime);
     return analyzer.analyze(formatter);
@@ -446,9 +450,8 @@
 
   /// Return whether the [newOptions] are equal to the [previous].
   static bool _equalCommandLineOptions(
-      CommandLineOptions previous, CommandLineOptions newOptions) {
+      CommandLineOptions? previous, CommandLineOptions newOptions) {
     return previous != null &&
-        newOptions != null &&
         newOptions.defaultPackagesPath == previous.defaultPackagesPath &&
         _equalMaps(newOptions.declaredVariables, previous.declaredVariables) &&
         newOptions.log == previous.log &&
@@ -460,7 +463,8 @@
         newOptions.lints == previous.lints &&
         newOptions.defaultLanguageVersion == previous.defaultLanguageVersion &&
         newOptions.disableCacheFlushing == previous.disableCacheFlushing &&
-        _equalLists(newOptions.enabledExperiments, previous.enabledExperiments);
+        _equalLists(
+            newOptions.enabledExperiments!, previous.enabledExperiments!);
   }
 
   /// Perform a deep comparison of two string lists.
@@ -494,27 +498,27 @@
   final ResourceProvider _resourceProvider;
   final FileContentCache _fileContentCache;
 
-  CommandLineOptions _commandLineOptions;
-  List<String> _pathList;
+  CommandLineOptions? _commandLineOptions;
+  late List<String> _pathList;
 
-  final Map<Folder, DriverBasedAnalysisContext> _folderContexts = {};
-  AnalysisContextCollectionImpl _collection;
-  DriverBasedAnalysisContext _analysisContext;
+  final Map<Folder, DriverBasedAnalysisContext?> _folderContexts = {};
+  AnalysisContextCollectionImpl? _collection;
+  DriverBasedAnalysisContext? _analysisContext;
 
   _AnalysisContextProvider(this._resourceProvider)
       : _fileContentCache = FileContentCache(_resourceProvider);
 
-  DriverBasedAnalysisContext get analysisContext {
+  DriverBasedAnalysisContext? get analysisContext {
     return _analysisContext;
   }
 
   AnalysisDriver get analysisDriver {
-    return _analysisContext.driver;
+    return _analysisContext!.driver;
   }
 
   /// TODO(scheglov) Use analyzedFiles()
   PathFilter get pathFilter {
-    var contextRoot = analysisContext.contextRoot;
+    var contextRoot = analysisContext!.contextRoot;
     var optionsFile = contextRoot.optionsFile;
 
     // If there is no options file, there can be no excludes.
@@ -524,7 +528,7 @@
 
     // Exclude patterns are relative to the directory with the options file.
     return PathFilter(contextRoot.root.path, optionsFile.parent2.path,
-        analysisContext.analysisOptions.excludePatterns);
+        analysisContext!.analysisOptions.excludePatterns);
   }
 
   void configureForPath(String path) {
@@ -554,10 +558,10 @@
     _collection = AnalysisContextCollectionImpl(
       byteStore: Driver.analysisDriverMemoryByteStore,
       includedPaths: _pathList,
-      optionsFile: _commandLineOptions.defaultAnalysisOptionsPath,
-      packagesFile: _commandLineOptions.defaultPackagesPath,
+      optionsFile: _commandLineOptions!.defaultAnalysisOptionsPath,
+      packagesFile: _commandLineOptions!.defaultPackagesPath,
       resourceProvider: _resourceProvider,
-      sdkPath: _commandLineOptions.dartSdkPath,
+      sdkPath: _commandLineOptions!.dartSdkPath,
       updateAnalysisOptions: _updateAnalysisOptions,
       fileContentCache: _fileContentCache,
     );
@@ -580,10 +584,10 @@
   }
 
   void _setContextForPath(String path) {
-    _analysisContext = _collection.contextFor(path);
+    _analysisContext = _collection!.contextFor(path);
   }
 
   void _updateAnalysisOptions(AnalysisOptionsImpl analysisOptions) {
-    _commandLineOptions.updateAnalysisOptions(analysisOptions);
+    _commandLineOptions!.updateAnalysisOptions(analysisOptions);
   }
 }
diff --git a/pkg/analyzer_cli/lib/src/error_formatter.dart b/pkg/analyzer_cli/lib/src/error_formatter.dart
index f43b471..51c7002 100644
--- a/pkg/analyzer_cli/lib/src/error_formatter.dart
+++ b/pkg/analyzer_cli/lib/src/error_formatter.dart
@@ -34,7 +34,7 @@
 
 /// Returns desired severity for the given [error] (or `null` if it's to be
 /// suppressed).
-typedef SeverityProcessor = ErrorSeverity Function(AnalysisError error);
+typedef SeverityProcessor = ErrorSeverity? Function(AnalysisError error);
 
 /// Analysis statistics counter.
 class AnalysisStats {
@@ -113,20 +113,20 @@
   final String message;
   final List<ContextMessage> contextMessages;
   final String errorCode;
-  final String correction;
-  final String url;
+  final String? correction;
+  final String? url;
 
   CLIError({
-    this.severity,
-    this.sourcePath,
-    this.offset,
-    this.line,
-    this.column,
-    this.message,
-    this.contextMessages,
-    this.errorCode,
-    this.correction,
-    this.url,
+    required this.severity,
+    required this.sourcePath,
+    required this.offset,
+    required this.line,
+    required this.column,
+    required this.message,
+    required this.contextMessages,
+    required this.errorCode,
+    required this.correction,
+    required this.url,
   });
 
   @override
@@ -150,7 +150,8 @@
   @override
   int compareTo(CLIError other) {
     // severity
-    var compare = _severityCompare[other.severity] - _severityCompare[severity];
+    var compare =
+        _severityCompare[other.severity]! - _severityCompare[severity]!;
     if (compare != 0) return compare;
 
     // path
@@ -179,12 +180,11 @@
   final StringSink out;
   final CommandLineOptions options;
   final AnalysisStats stats;
-  SeverityProcessor _severityProcessor;
+  final SeverityProcessor _severityProcessor;
 
   ErrorFormatter(this.out, this.options, this.stats,
-      {SeverityProcessor severityProcessor}) {
-    _severityProcessor = severityProcessor ?? _severityIdentity;
-  }
+      {SeverityProcessor? severityProcessor})
+      : _severityProcessor = severityProcessor ?? _severityIdentity;
 
   /// Call to write any batched up errors from [formatErrors].
   void flush();
@@ -213,22 +213,20 @@
 
   /// Compute the severity for this [error] or `null` if this error should be
   /// filtered.
-  ErrorSeverity _computeSeverity(AnalysisError error) =>
+  ErrorSeverity? _computeSeverity(AnalysisError error) =>
       _severityProcessor(error);
 }
 
 class HumanErrorFormatter extends ErrorFormatter {
-  AnsiLogger ansi;
+  late final AnsiLogger ansi = AnsiLogger(options.color);
 
   // This is a Set in order to de-dup CLI errors.
   final Set<CLIError> batchedErrors = {};
 
   HumanErrorFormatter(
       StringSink out, CommandLineOptions options, AnalysisStats stats,
-      {SeverityProcessor severityProcessor})
-      : super(out, options, stats, severityProcessor: severityProcessor) {
-    ansi = AnsiLogger(this.options.color);
-  }
+      {SeverityProcessor? severityProcessor})
+      : super(out, options, stats, severityProcessor: severityProcessor);
 
   @override
   void flush() {
@@ -281,10 +279,10 @@
   void formatError(
       Map<AnalysisError, ErrorsResult> errorToLine, AnalysisError error) {
     var source = error.source;
-    var result = errorToLine[error];
+    var result = errorToLine[error]!;
     var location = result.lineInfo.getLocation(error.offset);
 
-    var severity = _severityProcessor(error);
+    var severity = _severityProcessor(error)!;
 
     // Get display name; translate INFOs into LINTS and HINTS.
     var errorType = severity.displayName;
@@ -314,7 +312,7 @@
       if (session is DriverBasedAnalysisContext) {
         var fileResult = session.driver.getFileSync(message.filePath);
         if (fileResult is FileResult) {
-          var lineInfo = fileResult?.lineInfo;
+          var lineInfo = fileResult.lineInfo;
           var location = lineInfo.getLocation(message.offset);
           contextMessages.add(ContextMessage(
               message.filePath,
@@ -343,7 +341,7 @@
 class JsonErrorFormatter extends ErrorFormatter {
   JsonErrorFormatter(
       StringSink out, CommandLineOptions options, AnalysisStats stats,
-      {SeverityProcessor severityProcessor})
+      {SeverityProcessor? severityProcessor})
       : super(out, options, stats, severityProcessor: severityProcessor);
 
   @override
@@ -430,7 +428,7 @@
 
   MachineErrorFormatter(
       StringSink out, CommandLineOptions options, AnalysisStats stats,
-      {SeverityProcessor severityProcessor})
+      {SeverityProcessor? severityProcessor})
       : super(out, options, stats, severityProcessor: severityProcessor);
 
   @override
@@ -444,7 +442,7 @@
       return;
     }
     var source = error.source;
-    var location = errorToLine[error].lineInfo.getLocation(error.offset);
+    var location = errorToLine[error]!.lineInfo.getLocation(error.offset);
     var length = error.length;
 
     var severity = _severityProcessor(error);
diff --git a/pkg/analyzer_cli/lib/src/error_severity.dart b/pkg/analyzer_cli/lib/src/error_severity.dart
index dc7e4ec..23bfe3e 100644
--- a/pkg/analyzer_cli/lib/src/error_severity.dart
+++ b/pkg/analyzer_cli/lib/src/error_severity.dart
@@ -12,17 +12,15 @@
 /// - if [options.enableTypeChecks] is false, then de-escalate checked-mode
 ///   compile time errors to a severity of [ErrorSeverity.INFO].
 /// - if [options.lintsAreFatal] is true, escalate lints to errors.
-ErrorSeverity computeSeverity(
+ErrorSeverity? computeSeverity(
   AnalysisError error,
   CommandLineOptions commandLineOptions,
   AnalysisOptions analysisOptions,
 ) {
-  if (analysisOptions != null) {
-    var processor = ErrorProcessor.getProcessor(analysisOptions, error);
-    // If there is a processor for this error, defer to it.
-    if (processor != null) {
-      return processor.severity;
-    }
+  var processor = ErrorProcessor.getProcessor(analysisOptions, error);
+  // If there is a processor for this error, defer to it.
+  if (processor != null) {
+    return processor.severity;
   }
 
   if (commandLineOptions.lintsAreFatal && error.errorCode is LintCode) {
@@ -34,7 +32,7 @@
 
 /// Check various configuration options to get a desired severity for this
 /// [error] (or `null` if it's to be suppressed).
-ErrorSeverity determineProcessedSeverity(AnalysisError error,
+ErrorSeverity? determineProcessedSeverity(AnalysisError error,
     CommandLineOptions commandLineOptions, AnalysisOptions analysisOptions) {
   var severity = computeSeverity(error, commandLineOptions, analysisOptions);
   // Skip TODOs categorically unless escalated to ERROR or HINT (#26215).
diff --git a/pkg/analyzer_cli/lib/src/options.dart b/pkg/analyzer_cli/lib/src/options.dart
index fa01214..4ad9d00 100644
--- a/pkg/analyzer_cli/lib/src/options.dart
+++ b/pkg/analyzer_cli/lib/src/options.dart
@@ -35,6 +35,8 @@
 
 T cast<T>(dynamic value) => value as T;
 
+T? castNullable<T>(dynamic value) => value as T?;
+
 /// Print the given [message] to stderr and exit with the given [exitCode].
 void printAndFail(String message, {int exitCode = 15}) {
   errorSink.writeln(message);
@@ -53,18 +55,18 @@
   /// The file path of the analysis options file that should be used in place of
   /// any file in the root directory or a parent of the root directory,
   /// or `null` if the normal lookup mechanism should be used.
-  String defaultAnalysisOptionsPath;
+  String? defaultAnalysisOptionsPath;
 
   /// The file path of the .packages file that should be used in place of any
   /// file found using the normal (Package Specification DEP) lookup mechanism,
   /// or `null` if the normal lookup mechanism should be used.
-  String defaultPackagesPath;
+  String? defaultPackagesPath;
 
   /// A table mapping variable names to values for the declared variables.
   final Map<String, String> declaredVariables = {};
 
   /// The path to the dart SDK.
-  String dartSdkPath;
+  String? dartSdkPath;
 
   /// Whether to disable cache flushing. This option can improve analysis
   /// speed at the expense of memory usage. It may also be useful for working
@@ -91,7 +93,7 @@
 
   /// The path to a file to write a performance log.
   /// (Or null if not enabled.)
-  final String perfReport;
+  final String? perfReport;
 
   /// Batch mode (for unit testing)
   final bool batchMode;
@@ -100,7 +102,7 @@
   final bool showPackageWarnings;
 
   /// If not null, show package: warnings only for matching packages.
-  final String showPackageWarningsPrefix;
+  final String? showPackageWarningsPrefix;
 
   /// Whether to show SDK warnings
   final bool showSdkWarnings;
@@ -133,7 +135,7 @@
     ResourceProvider resourceProvider,
     ArgResults args,
   )   : _argResults = args,
-        dartSdkPath = cast(args[_sdkPathOption]),
+        dartSdkPath = castNullable(args[_sdkPathOption]),
         disableCacheFlushing = cast(args['disable-cache-flushing']),
         disableHints = cast(args['no-hints']),
         displayVersion = cast(args['version']),
@@ -141,12 +143,13 @@
         log = cast(args['log']),
         jsonFormat = args['format'] == 'json',
         machineFormat = args['format'] == 'machine',
-        perfReport = cast(args['x-perf-report']),
+        perfReport = castNullable(args['x-perf-report']),
         batchMode = cast(args['batch']),
         showPackageWarnings = cast(args['show-package-warnings']) ||
             cast(args['package-warnings']) ||
             args['x-package-warnings-prefix'] != null,
-        showPackageWarningsPrefix = cast(args['x-package-warnings-prefix']),
+        showPackageWarningsPrefix =
+            castNullable(args['x-package-warnings-prefix']),
         showSdkWarnings = cast(args['sdk-warnings']),
         sourceFiles = args.rest,
         infosAreFatal = cast(args['fatal-infos']) || cast(args['fatal-hints']),
@@ -160,11 +163,11 @@
     //
     defaultAnalysisOptionsPath = _absoluteNormalizedPath(
       resourceProvider,
-      cast(args[_analysisOptionsFileOption]),
+      castNullable(args[_analysisOptionsFileOption]),
     );
     defaultPackagesPath = _absoluteNormalizedPath(
       resourceProvider,
-      cast(args[_packagesOption]),
+      castNullable(args[_packagesOption]),
     );
 
     //
@@ -192,20 +195,20 @@
 
   /// The default language version for files that are not in a package.
   /// (Or null if no default language version to force.)
-  String get defaultLanguageVersion {
-    return cast(_argResults[_defaultLanguageVersionOption]);
+  String? get defaultLanguageVersion {
+    return castNullable(_argResults[_defaultLanguageVersionOption]);
   }
 
   /// A list of the names of the experiments that are to be enabled.
-  List<String> get enabledExperiments {
-    return cast(_argResults[_enableExperimentOption]);
+  List<String>? get enabledExperiments {
+    return castNullable(_argResults[_enableExperimentOption]);
   }
 
-  bool get implicitCasts => _argResults[_implicitCastsFlag] as bool;
+  bool? get implicitCasts => _argResults[_implicitCastsFlag] as bool?;
 
-  bool get lints => _argResults[_lintsFlag] as bool;
+  bool? get lints => _argResults[_lintsFlag] as bool?;
 
-  bool get noImplicitDynamic => _argResults[_noImplicitDynamicFlag] as bool;
+  bool? get noImplicitDynamic => _argResults[_noImplicitDynamicFlag] as bool?;
 
   /// Update the [analysisOptions] with flags that the user specified
   /// explicitly. The [analysisOptions] are usually loaded from one of
@@ -222,7 +225,7 @@
           .restrictToVersion(nonPackageLanguageVersion);
     }
 
-    var enabledExperiments = this.enabledExperiments;
+    var enabledExperiments = this.enabledExperiments!;
     if (enabledExperiments.isNotEmpty) {
       analysisOptions.contextFeatures = FeatureSet.fromEnableFlags2(
         sdkLanguageVersion: ExperimentStatus.currentVersion,
@@ -303,7 +306,7 @@
   /// Parse [args] into [CommandLineOptions] describing the specified
   /// analyzer options. In case of a format error, calls [printAndFail], which
   /// by default prints an error message to stderr and exits.
-  static CommandLineOptions parse(
+  static CommandLineOptions? parse(
       ResourceProvider resourceProvider, List<String> args,
       {void Function(String msg) printAndFail = printAndFail}) {
     var options = _parse(resourceProvider, args);
@@ -335,9 +338,9 @@
     return options;
   }
 
-  static String _absoluteNormalizedPath(
+  static String? _absoluteNormalizedPath(
     ResourceProvider resourceProvider,
-    String path,
+    String? path,
   ) {
     if (path == null) {
       return null;
@@ -425,7 +428,7 @@
     }
   }
 
-  static CommandLineOptions _parse(
+  static CommandLineOptions? _parse(
     ResourceProvider resourceProvider,
     List<String> args,
   ) {
diff --git a/pkg/analyzer_cli/pubspec.yaml b/pkg/analyzer_cli/pubspec.yaml
index 5297838..0580b81 100644
--- a/pkg/analyzer_cli/pubspec.yaml
+++ b/pkg/analyzer_cli/pubspec.yaml
@@ -5,7 +5,7 @@
 publish_to: none
 
 environment:
-  sdk: "^2.7.0"
+  sdk: "^2.14.0"
 
 dependencies:
   analyzer: any
diff --git a/pkg/analyzer_cli/test/analysis_options_test.dart b/pkg/analyzer_cli/test/analysis_options_test.dart
index 0c68a22..72e1bb4 100644
--- a/pkg/analyzer_cli/test/analysis_options_test.dart
+++ b/pkg/analyzer_cli/test/analysis_options_test.dart
@@ -18,15 +18,10 @@
 
 @reflectiveTest
 class OptionsTest {
-  _Runner runner;
-
-  void setUp() {
-    runner = _Runner.setUp();
-  }
+  final _Runner runner = _Runner.setUp();
 
   void tearDown() {
     runner.tearDown();
-    runner = null;
   }
 
   Future<void> test_options() async {
diff --git a/pkg/analyzer_cli/test/driver_test.dart b/pkg/analyzer_cli/test/driver_test.dart
index a974629..de57da2 100644
--- a/pkg/analyzer_cli/test/driver_test.dart
+++ b/pkg/analyzer_cli/test/driver_test.dart
@@ -34,16 +34,16 @@
 class BaseTest {
   static const emptyOptionsFile = 'data/empty_options.yaml';
 
-  StringSink _savedOutSink, _savedErrorSink;
-  int _savedExitCode;
-  ExitHandler _savedExitHandler;
+  late StringSink _savedOutSink, _savedErrorSink;
+  late int _savedExitCode;
+  late ExitHandler _savedExitHandler;
 
-  Driver driver;
+  late Driver driver;
 
-  AnalysisOptions get analysisOptions => driver.analysisDriver.analysisOptions;
+  AnalysisOptions get analysisOptions => driver.analysisDriver!.analysisOptions;
 
   /// Normalize text with bullets.
-  String bulletToDash(StringSink item) => '$item'.replaceAll('•', '-');
+  String bulletToDash(StringSink? item) => '$item'.replaceAll('•', '-');
 
   /// Start a driver for the given [source], optionally providing additional
   /// [args] and an [options] file path. The value of [options] defaults to an
@@ -60,7 +60,7 @@
   /// Like [drive], but takes an array of sources.
   Future<void> driveMany(
     List<String> sources, {
-    String options = emptyOptionsFile,
+    String? options = emptyOptionsFile,
     List<String> args = const <String>[],
   }) async {
     options = _posixToPlatformPath(options);
@@ -112,7 +112,7 @@
   ///
   /// This is a utility method for testing; paths passed in to other methods in
   /// this class are never converted automatically.
-  String _posixToPlatformPath(String filePath) {
+  String? _posixToPlatformPath(String? filePath) {
     if (filePath == null) {
       return null;
     }
@@ -464,7 +464,7 @@
     ]);
     expect(processorFor(missing_return).severity, ErrorSeverity.ERROR);
     expect(bulletToDash(outSink),
-        contains("error - This function has a return type of 'int'"));
+        contains("error - The body might complete normally"));
     expect(outSink.toString(), contains('1 error and 1 warning found.'));
   }
 
diff --git a/pkg/analyzer_cli/test/embedder_test.dart b/pkg/analyzer_cli/test/embedder_test.dart
index 3420843..584f477 100644
--- a/pkg/analyzer_cli/test/embedder_test.dart
+++ b/pkg/analyzer_cli/test/embedder_test.dart
@@ -12,8 +12,8 @@
 
 void main() {
   group('_embedder.yaml', () {
-    StringSink savedOutSink, savedErrorSink;
-    int savedExitCode;
+    late StringSink savedOutSink, savedErrorSink;
+    late int savedExitCode;
 
     setUp(() {
       savedOutSink = outSink;
diff --git a/pkg/analyzer_cli/test/errors_reported_once_test.dart b/pkg/analyzer_cli/test/errors_reported_once_test.dart
index d25a78e..9fdabc2 100644
--- a/pkg/analyzer_cli/test/errors_reported_once_test.dart
+++ b/pkg/analyzer_cli/test/errors_reported_once_test.dart
@@ -18,9 +18,9 @@
 
 @reflectiveTest
 class ErrorsReportedOnceTest {
-  StringSink savedOutSink, savedErrorSink;
-  int savedExitCode;
-  ExitHandler savedExitHandler;
+  late StringSink savedOutSink, savedErrorSink;
+  late int savedExitCode;
+  late ExitHandler savedExitHandler;
 
   void setUp() {
     savedOutSink = outSink;
diff --git a/pkg/analyzer_cli/test/errors_upgrade_fails_cli_test.dart b/pkg/analyzer_cli/test/errors_upgrade_fails_cli_test.dart
index 16d79dd..510a9ad 100644
--- a/pkg/analyzer_cli/test/errors_upgrade_fails_cli_test.dart
+++ b/pkg/analyzer_cli/test/errors_upgrade_fails_cli_test.dart
@@ -18,9 +18,9 @@
 
 @reflectiveTest
 class ErrorUpgradeFailsCli {
-  StringSink savedOutSink, savedErrorSink;
-  int savedExitCode;
-  ExitHandler savedExitHandler;
+  late StringSink savedOutSink, savedErrorSink;
+  late int savedExitCode;
+  late ExitHandler savedExitHandler;
 
   void setUp() {
     savedOutSink = outSink;
diff --git a/pkg/analyzer_cli/test/mocks.dart b/pkg/analyzer_cli/test/mocks.dart
index 32e69bf..a8b487a 100644
--- a/pkg/analyzer_cli/test/mocks.dart
+++ b/pkg/analyzer_cli/test/mocks.dart
@@ -32,10 +32,10 @@
   List<DiagnosticMessage> get contextMessages => const [];
 
   @override
-  String get correction => null;
+  String? get correction => null;
 
   @override
-  String get correctionMessage => null;
+  String? get correctionMessage => null;
 
   @override
   DiagnosticMessage get problemMessage => DiagnosticMessageImpl(
@@ -46,7 +46,7 @@
       url: null);
 
   @override
-  Severity get severity => null;
+  Severity get severity => Severity.error;
 }
 
 class MockAnalysisErrorInfo implements AnalysisErrorInfo {
@@ -87,7 +87,7 @@
   String name;
 
   @override
-  String url;
+  String? url;
 
   MockErrorCode(this.type, this.errorSeverity, this.name);
 
@@ -120,7 +120,7 @@
 }
 
 class MockLineInfo implements LineInfo {
-  CharacterLocation defaultLocation;
+  CharacterLocation? defaultLocation;
 
   MockLineInfo({this.defaultLocation});
 
@@ -137,7 +137,7 @@
   @override
   CharacterLocation getLocation(int offset) {
     if (defaultLocation != null) {
-      return defaultLocation;
+      return defaultLocation!;
     }
     throw StateError('Unexpected invocation of getLocation');
   }
diff --git a/pkg/analyzer_cli/test/options_test.dart b/pkg/analyzer_cli/test/options_test.dart
index 4b7167b..1c151dd 100644
--- a/pkg/analyzer_cli/test/options_test.dart
+++ b/pkg/analyzer_cli/test/options_test.dart
@@ -24,11 +24,11 @@
       var outStringBuffer = StringBuffer();
       var errorStringBuffer = StringBuffer();
 
-      StringSink savedOutSink, savedErrorSink;
-      int savedExitCode;
-      ExitHandler savedExitHandler;
+      late StringSink savedOutSink, savedErrorSink;
+      late int savedExitCode;
+      late ExitHandler savedExitHandler;
 
-      CommandLineOptions parse(List<String> args,
+      CommandLineOptions? parse(List<String> args,
           {void Function(String msg) printAndFail = printAndFail}) {
         var resourceProvider = PhysicalResourceProvider.INSTANCE;
         return CommandLineOptions.parse(resourceProvider, args,
@@ -53,7 +53,7 @@
       });
 
       test('defaults', () {
-        var options = parse(['--dart-sdk', '.', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', 'foo.dart'])!;
         expect(options, isNotNull);
         expect(options.dartSdkPath, isNotNull);
         expect(options.disableCacheFlushing, isFalse);
@@ -78,19 +78,19 @@
       });
 
       test('batch', () {
-        var options = parse(['--dart-sdk', '.', '--batch']);
+        var options = parse(['--dart-sdk', '.', '--batch'])!;
         expect(options.batchMode, isTrue);
       });
 
       test('defined variables', () {
-        var options = parse(['--dart-sdk', '.', '-Dfoo=bar', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '-Dfoo=bar', 'foo.dart'])!;
         expect(options.declaredVariables['foo'], equals('bar'));
         expect(options.declaredVariables['bar'], isNull);
       });
 
       test('disable cache flushing', () {
         var options =
-            parse(['--dart-sdk', '.', '--disable-cache-flushing', 'foo.dart']);
+            parse(['--dart-sdk', '.', '--disable-cache-flushing', 'foo.dart'])!;
         expect(options.disableCacheFlushing, isTrue);
       });
 
@@ -126,119 +126,126 @@
         };
 
         test('no values', () {
-          var options =
-              overrideKnownFeatures(knownFeatures, () => parse(['foo.dart']));
+          var options = overrideKnownFeatures(
+              knownFeatures, (() => parse(['foo.dart'])!));
           expect(options.enabledExperiments, isEmpty);
         });
 
         test('single value', () {
           var options = overrideKnownFeatures(knownFeatures,
-              () => parse(['--enable-experiment', 'a', 'foo.dart']));
+              (() => parse(['--enable-experiment', 'a', 'foo.dart'])!));
           expect(options.enabledExperiments, ['a']);
         });
 
         group('multiple values', () {
           test('single flag', () {
             var options = overrideKnownFeatures(knownFeatures,
-                () => parse(['--enable-experiment', 'a,b', 'foo.dart']));
+                (() => parse(['--enable-experiment', 'a,b', 'foo.dart'])!));
             expect(options.enabledExperiments, ['a', 'b']);
           });
 
           test('mixed single and multiple flags', () {
             var options = overrideKnownFeatures(
                 knownFeatures,
-                () => parse([
+                (() => parse([
                       '--enable-experiment',
                       'a,b',
                       '--enable-experiment',
                       'c',
                       'foo.dart'
-                    ]));
+                    ])!));
             expect(options.enabledExperiments, ['a', 'b', 'c']);
           });
 
           test('multiple flags', () {
             var options = overrideKnownFeatures(
                 knownFeatures,
-                () => parse([
+                (() => parse([
                       '--enable-experiment',
                       'a',
                       '--enable-experiment',
                       'b',
                       'foo.dart'
-                    ]));
+                    ])!));
             expect(options.enabledExperiments, ['a', 'b']);
           });
         });
       });
 
       test('hintsAreFatal', () {
-        var options = parse(['--dart-sdk', '.', '--fatal-hints', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '--fatal-hints', 'foo.dart'])!;
         expect(options.infosAreFatal, isTrue);
       });
 
       test('infosAreFatal', () {
-        var options = parse(['--dart-sdk', '.', '--fatal-infos', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '--fatal-infos', 'foo.dart'])!;
         expect(options.infosAreFatal, isTrue);
       });
 
       test('log', () {
-        var options = parse(['--dart-sdk', '.', '--log', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '--log', 'foo.dart'])!;
         expect(options.log, isTrue);
       });
 
       group('format', () {
         test('json', () {
-          var options = parse(['--dart-sdk', '.', '--format=json', 'foo.dart']);
+          var options =
+              parse(['--dart-sdk', '.', '--format=json', 'foo.dart'])!;
           expect(options.jsonFormat, isTrue);
           expect(options.machineFormat, isFalse);
         });
 
         test('machine', () {
           var options =
-              parse(['--dart-sdk', '.', '--format=machine', 'foo.dart']);
+              parse(['--dart-sdk', '.', '--format=machine', 'foo.dart'])!;
           expect(options.jsonFormat, isFalse);
           expect(options.machineFormat, isTrue);
         });
       });
 
       test('no-hints', () {
-        var options = parse(['--dart-sdk', '.', '--no-hints', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '--no-hints', 'foo.dart'])!;
         expect(options.disableHints, isTrue);
       });
 
       test('options', () {
-        var options =
-            parse(['--dart-sdk', '.', '--options', 'options.yaml', 'foo.dart']);
+        var options = parse(
+            ['--dart-sdk', '.', '--options', 'options.yaml', 'foo.dart'])!;
         expect(options.defaultAnalysisOptionsPath, endsWith('options.yaml'));
       });
 
       test('lints', () {
-        var options = parse(['--dart-sdk', '.', '--lints', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '--lints', 'foo.dart'])!;
         expect(options.lints, isTrue);
       });
 
       test('package warnings', () {
         var options =
-            parse(['--dart-sdk', '.', '--package-warnings', 'foo.dart']);
+            parse(['--dart-sdk', '.', '--package-warnings', 'foo.dart'])!;
         expect(options.showPackageWarnings, isTrue);
       });
 
       test('sdk warnings', () {
-        var options = parse(['--dart-sdk', '.', '--sdk-warnings', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '--sdk-warnings', 'foo.dart'])!;
         expect(options.showSdkWarnings, isTrue);
       });
 
       test('sourceFiles', () {
-        var options = parse(
-            ['--dart-sdk', '.', '--log', 'foo.dart', 'foo2.dart', 'foo3.dart']);
+        var options = parse([
+          '--dart-sdk',
+          '.',
+          '--log',
+          'foo.dart',
+          'foo2.dart',
+          'foo3.dart'
+        ])!;
         expect(options.sourceFiles,
             equals(['foo.dart', 'foo2.dart', 'foo3.dart']));
       });
 
       test('warningsAreFatal', () {
         var options =
-            parse(['--dart-sdk', '.', '--fatal-warnings', 'foo.dart']);
+            parse(['--dart-sdk', '.', '--fatal-warnings', 'foo.dart'])!;
         expect(options.warningsAreFatal, isTrue);
       });
 
@@ -250,25 +257,25 @@
           '--dart-sdk',
           '.',
           'foo.dart'
-        ]);
+        ])!;
         expect(options, isNotNull);
         expect(options.sourceFiles, equals(['foo.dart']));
       });
 
       test('hintsAreFatal', () {
-        var options = parse(['--dart-sdk', '.', '--fatal-lints', 'foo.dart']);
+        var options = parse(['--dart-sdk', '.', '--fatal-lints', 'foo.dart'])!;
         expect(options.lintsAreFatal, isTrue);
       });
 
       test('bad SDK dir', () {
-        String failureMessage;
+        String? failureMessage;
         parse(['--dart-sdk', '&&&&&', 'foo.dart'],
             printAndFail: (msg) => failureMessage = msg);
         expect(failureMessage, equals('Invalid Dart SDK path: &&&&&'));
       });
 
       test('--train-snapshot', () {
-        var options = parse(['--train-snapshot', 'foo.dart']);
+        var options = parse(['--train-snapshot', 'foo.dart'])!;
         expect(options.trainSnapshot, isTrue);
       });
     });
@@ -278,13 +285,13 @@
 
 @reflectiveTest
 class ArgumentsTest with ResourceProviderMixin {
-  CommandLineOptions commandLineOptions;
-  String failureMessage;
+  CommandLineOptions? commandLineOptions;
+  String? failureMessage;
 
   void test_declaredVariables() {
     _parse(['-Da=0', '-Db=', 'a.dart']);
 
-    var definedVariables = commandLineOptions.declaredVariables;
+    var definedVariables = commandLineOptions!.declaredVariables;
 
     expect(definedVariables['a'], '0');
     expect(definedVariables['b'], '');
@@ -296,7 +303,7 @@
     _parse(['--options=$expected', 'a.dart']);
 
     expect(
-      commandLineOptions.defaultAnalysisOptionsPath,
+      commandLineOptions!.defaultAnalysisOptionsPath,
       endsWith(expected),
     );
   }
@@ -306,16 +313,16 @@
     _parse(['--packages=$expected', 'a.dart']);
 
     expect(
-      commandLineOptions.defaultPackagesPath,
+      commandLineOptions!.defaultPackagesPath,
       endsWith(expected),
     );
   }
 
   void test_defaults() {
     _parse(['a.dart']);
-    expect(commandLineOptions.declaredVariables, isEmpty);
-    expect(commandLineOptions.defaultAnalysisOptionsPath, isNull);
-    expect(commandLineOptions.defaultPackagesPath, isNull);
+    expect(commandLineOptions!.declaredVariables, isEmpty);
+    expect(commandLineOptions!.defaultAnalysisOptionsPath, isNull);
+    expect(commandLineOptions!.defaultPackagesPath, isNull);
   }
 
   void test_filterUnknownArguments() {
@@ -554,7 +561,7 @@
     var analysisOptions = AnalysisOptionsImpl();
     configureInitial(analysisOptions);
 
-    commandLineOptions.updateAnalysisOptions(analysisOptions);
+    commandLineOptions!.updateAnalysisOptions(analysisOptions);
     checkApplied(analysisOptions);
   }
 
diff --git a/pkg/analyzer_cli/test/package_prefix_test.dart b/pkg/analyzer_cli/test/package_prefix_test.dart
index 157ffe9..9aa0d57 100644
--- a/pkg/analyzer_cli/test/package_prefix_test.dart
+++ b/pkg/analyzer_cli/test/package_prefix_test.dart
@@ -13,7 +13,7 @@
 
 void main() {
   group('--x-package-warnings-prefix', () {
-    _Runner runner;
+    late _Runner runner;
 
     setUp(() {
       runner = _Runner.setUp();
@@ -21,7 +21,6 @@
 
     tearDown(() {
       runner.tearDown();
-      runner = null;
     });
 
     test('shows only the hint whose package matches the prefix', () async {
diff --git a/pkg/analyzer_cli/test/perf_report_test.dart b/pkg/analyzer_cli/test/perf_report_test.dart
index 933b455..321bb89 100644
--- a/pkg/analyzer_cli/test/perf_report_test.dart
+++ b/pkg/analyzer_cli/test/perf_report_test.dart
@@ -15,7 +15,7 @@
     var options = CommandLineOptions.parse(
       PhysicalResourceProvider.INSTANCE,
       ['somefile.dart'],
-    );
+    )!;
     var encoded = makePerfReport(1000, 1234, options, 0, AnalysisStats());
 
     var jsonData = json.decode(encoded);
diff --git a/pkg/analyzer_cli/test/reporter_test.dart b/pkg/analyzer_cli/test/reporter_test.dart
index 3088a6c..cffb0ff 100644
--- a/pkg/analyzer_cli/test/reporter_test.dart
+++ b/pkg/analyzer_cli/test/reporter_test.dart
@@ -2,6 +2,7 @@
 // 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/session.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/source/line_info.dart';
 import 'package:analyzer/src/dart/analysis/results.dart';
@@ -14,10 +15,10 @@
 
 void main() {
   group('reporter', () {
-    StringBuffer out;
-    AnalysisStats stats;
-    MockCommandLineOptions options;
-    ErrorFormatter reporter;
+    late StringBuffer out;
+    late AnalysisStats stats;
+    late MockCommandLineOptions options;
+    late ErrorFormatter reporter;
 
     setUp(() {
       ansi.runningTests = true;
@@ -107,6 +108,11 @@
   var source = MockSource(path, package_path.toUri(path));
   var error = MockAnalysisError(source, code, 20, 'MSG');
 
-  return ErrorsResultImpl(
-      null, source.fullName, null, lineInfo, false, [error]);
+  return ErrorsResultImpl(_MockAnslysisSession(), source.fullName,
+      Uri.file('/'), lineInfo, false, [error]);
+}
+
+class _MockAnslysisSession implements AnalysisSession {
+  @override
+  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 }
diff --git a/pkg/analyzer_cli/test/strong_mode_test.dart b/pkg/analyzer_cli/test/strong_mode_test.dart
index 914a3ef..2f9dc3f 100644
--- a/pkg/analyzer_cli/test/strong_mode_test.dart
+++ b/pkg/analyzer_cli/test/strong_mode_test.dart
@@ -29,7 +29,7 @@
     expect(exitCode, 3);
     var stdout = bulletToDash(outSink);
     expect(stdout, contains("isn't a valid override of"));
-    expect(stdout, contains('error - The list literal type'));
+    expect(stdout, contains('error - A value of type'));
     expect(stdout, contains('2 errors found'));
   }
 }
diff --git a/pkg/analyzer_cli/tool/perf.dart b/pkg/analyzer_cli/tool/perf.dart
index a16cb88..2ad2424 100644
--- a/pkg/analyzer_cli/tool/perf.dart
+++ b/pkg/analyzer_cli/tool/perf.dart
@@ -63,12 +63,12 @@
 int scanTotalChars = 0;
 
 /// Factory to load and resolve app, packages, and sdk sources.
-SourceFactory sources;
+late SourceFactory sources;
 
 /// Add to [files] all sources reachable from [start].
-void collectSources(Source start, Set<Source> files) {
+void collectSources(Source? start, Set<Source?> files) {
   if (!files.add(start)) return;
-  var unit = parseDirectives(start);
+  var unit = parseDirectives(start!);
   for (var directive in unit.directives) {
     if (directive is UriBasedDirective) {
       var next = sources.resolveUri(start, directive.uri.stringValue);
@@ -89,7 +89,7 @@
 }
 
 /// Parses every file in [files] and reports the time spent doing so.
-void parseFiles(Set<Source> files) {
+void parseFiles(Set<Source?> files) {
   // The code below will record again how many chars are scanned and how long it
   // takes to scan them, even though we already did so in [scanReachableFiles].
   // Recording and reporting this twice is unnecessary, but we do so for now to
@@ -99,7 +99,7 @@
   scanTotalChars = 0;
   var parseTimer = Stopwatch()..start();
   for (var source in files) {
-    parseFull(source);
+    parseFull(source!);
   }
   parseTimer.stop();
 
@@ -132,7 +132,7 @@
 }
 
 /// Scans every file in [files] and reports the time spent doing so.
-void scanFiles(Set<Source> files) {
+void scanFiles(Set<Source?> files) {
   // The code below will record again how many chars are scanned and how long it
   // takes to scan them, even though we already did so in [scanReachableFiles].
   // Recording and reporting this twice is unnecessary, but we do so for now to
@@ -141,7 +141,7 @@
   var old = scanTotalChars;
   scanTotalChars = 0;
   for (var source in files) {
-    tokenize(source);
+    tokenize(source!);
   }
 
   // Report size and scanning time again. See discussion above.
@@ -151,8 +151,8 @@
 
 /// Load and scans all files we need to process: files reachable from the
 /// entrypoint and all core libraries automatically included by the VM.
-Set<Source> scanReachableFiles(Uri entryUri) {
-  var files = <Source>{};
+Set<Source?> scanReachableFiles(Uri entryUri) {
+  var files = <Source?>{};
   var loadTimer = Stopwatch()..start();
   collectSources(sources.forUri2(entryUri), files);
 
diff --git a/pkg/nnbd_migration/test/already_migrated_code_decorator_test.dart b/pkg/nnbd_migration/test/already_migrated_code_decorator_test.dart
index abc2788..7eeea96 100644
--- a/pkg/nnbd_migration/test/already_migrated_code_decorator_test.dart
+++ b/pkg/nnbd_migration/test/already_migrated_code_decorator_test.dart
@@ -2,6 +2,8 @@
 // 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/analysis_context_collection.dart';
+import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ -9,9 +11,11 @@
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/generated/source.dart';
-import 'package:analyzer/src/generated/testing/element_factory.dart';
-import 'package:analyzer/src/generated/testing/test_type_provider.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
+import 'package:analyzer/src/test_utilities/find_element.dart';
+import 'package:analyzer/src/test_utilities/find_node.dart';
+import 'package:analyzer/src/test_utilities/mock_sdk.dart';
+import 'package:analyzer/src/test_utilities/resource_provider_mixin.dart';
 import 'package:nnbd_migration/instrumentation.dart';
 import 'package:nnbd_migration/src/already_migrated_code_decorator.dart';
 import 'package:nnbd_migration/src/decorated_type.dart';
@@ -29,35 +33,475 @@
   });
 }
 
-class _AlreadyMigratedCodeDecoratorTestBase extends Object with EdgeTester {
-  final TypeProvider typeProvider;
-
-  final AlreadyMigratedCodeDecorator decorator;
-
-  final NullabilityGraphForTesting graph;
-
+class _AlreadyMigratedCodeDecoratorTestBase {
   final NullabilitySuffix suffix;
 
-  Element element = _MockElement();
-
   final decoratedTypeParameterBounds = DecoratedTypeParameterBounds();
 
-  _AlreadyMigratedCodeDecoratorTestBase(NullabilitySuffix nullabilitySuffix)
-      : this._(
-          nullabilitySuffix,
-          NullabilityGraphForTesting(),
-          TestTypeProvider(),
-        );
+  _AlreadyMigratedCodeDecoratorTestBase(this.suffix);
 
-  _AlreadyMigratedCodeDecoratorTestBase._(
-      this.suffix, this.graph, this.typeProvider)
-      : decorator =
-            AlreadyMigratedCodeDecorator(graph, typeProvider, _getLineInfo);
+  DecoratedType? getDecoratedBound(TypeParameterElement element) =>
+      decoratedTypeParameterBounds.get(element);
+
+  void setUp() {
+    DecoratedTypeParameterBounds.current = decoratedTypeParameterBounds;
+  }
+
+  void tearDown() {
+    DecoratedTypeParameterBounds.current = null;
+  }
+
+  Future<void> test_decorate_dynamic() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+    withElement.checkDynamic(
+        withElement.decorate(withElement.typeProvider.dynamicType),
+        'test type');
+  }
+
+  Future<void> test_decorate_functionType_generic_bounded() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class A<T extends num> {}',
+    );
+    var typeFormal = withUnit.findElement.typeParameter('T');
+    var withElement = withUnit.withElement(typeFormal);
+
+    var decoratedType = withElement.decorate(
+      FunctionTypeImpl(
+        typeFormals: [typeFormal],
+        parameters: const [],
+        returnType: TypeParameterTypeImpl(
+          element: typeFormal,
+          nullabilitySuffix: NullabilitySuffix.star,
+        ),
+        nullabilitySuffix: suffix,
+      ),
+    );
+    withElement.checkNum(
+        getDecoratedBound(typeFormal)!,
+        withElement.checkExplicitlyNonNullable,
+        'bound of type formal T of test type');
+    withElement.checkTypeParameter(
+        decoratedType.returnType!,
+        withElement.checkExplicitlyNonNullable,
+        typeFormal,
+        'return type of test type');
+  }
+
+  Future<void> test_decorate_functionType_generic_no_explicit_bound() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class A<T> {}',
+    );
+    var typeFormal = withUnit.findElement.typeParameter('T');
+    var withElement = withUnit.withElement(typeFormal);
+
+    var decoratedType = withElement.decorate(
+      FunctionTypeImpl(
+        typeFormals: [typeFormal],
+        parameters: const [],
+        returnType: TypeParameterTypeImpl(
+          element: typeFormal,
+          nullabilitySuffix: NullabilitySuffix.star,
+        ),
+        nullabilitySuffix: suffix,
+      ),
+    );
+    withElement.checkObject(
+        getDecoratedBound(typeFormal)!,
+        withElement.checkExplicitlyNullable,
+        'bound of type formal T of test type');
+    withElement.checkTypeParameter(
+        decoratedType.returnType!,
+        withElement.checkExplicitlyNonNullable,
+        typeFormal,
+        'return type of test type');
+  }
+
+  Future<void> test_decorate_functionType_named_parameter() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkDynamic(
+        withElement
+            .decorate(
+              FunctionTypeImpl(
+                typeFormals: const [],
+                parameters: [
+                  ParameterElementImpl.synthetic(
+                    'x',
+                    withElement.typeProvider.dynamicType,
+                    ParameterKind.NAMED,
+                  )
+                ],
+                returnType: withElement.typeProvider.voidType,
+                nullabilitySuffix: suffix,
+              ),
+            )
+            .namedParameters!['x'],
+        'parameter x of test type');
+  }
+
+  Future<void> test_decorate_functionType_ordinary_parameters() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    var decoratedType = withElement.decorate(
+      FunctionTypeImpl(
+        typeFormals: const [],
+        parameters: [
+          ParameterElementImpl.synthetic(
+            'x',
+            withElement.typeProvider.dynamicType,
+            ParameterKind.REQUIRED,
+          ),
+          ParameterElementImpl.synthetic(
+            'y',
+            withElement.typeProvider.dynamicType,
+            ParameterKind.REQUIRED,
+          )
+        ],
+        returnType: withElement.typeProvider.voidType,
+        nullabilitySuffix: suffix,
+      ),
+    );
+    withElement.checkDynamic(
+        decoratedType.positionalParameters![0], 'parameter 0 of test type');
+    withElement.checkDynamic(
+        decoratedType.positionalParameters![1], 'parameter 1 of test type');
+  }
+
+  Future<void> test_decorate_functionType_positional_parameter() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkDynamic(
+        withElement
+            .decorate(
+              FunctionTypeImpl(
+                typeFormals: const [],
+                parameters: [
+                  ParameterElementImpl.synthetic(
+                    'x',
+                    withElement.typeProvider.dynamicType,
+                    ParameterKind.POSITIONAL,
+                  )
+                ],
+                returnType: withElement.typeProvider.voidType,
+                nullabilitySuffix: suffix,
+              ),
+            )
+            .positionalParameters![0],
+        'parameter 0 of test type');
+  }
+
+  Future<void> test_decorate_functionType_question() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkExplicitlyNullable(
+        withElement
+            .decorate(
+              FunctionTypeImpl(
+                typeFormals: const [],
+                parameters: const [],
+                returnType: withElement.typeProvider.voidType,
+                nullabilitySuffix: NullabilitySuffix.question,
+              ),
+            )
+            .node,
+        'test type');
+  }
+
+  Future<void> test_decorate_functionType_returnType() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkDynamic(
+        withElement
+            .decorate(
+              FunctionTypeImpl(
+                typeFormals: const [],
+                parameters: const [],
+                returnType: withElement.typeProvider.dynamicType,
+                nullabilitySuffix: suffix,
+              ),
+            )
+            .returnType,
+        'return type of test type');
+  }
+
+  Future<void> test_decorate_functionType_star() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkExplicitlyNonNullable(
+        withElement
+            .decorate(
+              FunctionTypeImpl(
+                typeFormals: const [],
+                parameters: const [],
+                returnType: withElement.typeProvider.voidType,
+                nullabilitySuffix: suffix,
+              ),
+            )
+            .node,
+        'test type');
+  }
+
+  Future<void> test_decorate_interfaceType_parameters() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    var decoratedType = withElement.decorate(InterfaceTypeImpl(
+        element: withElement.typeProvider.mapElement,
+        typeArguments: [
+          withElement.typeProvider.intType,
+          withElement.typeProvider.numType
+        ],
+        nullabilitySuffix: suffix));
+    withElement.checkInt(decoratedType.typeArguments[0]!,
+        withElement.checkExplicitlyNonNullable, 'type argument 0 of test type');
+    withElement.checkNum(decoratedType.typeArguments[1]!,
+        withElement.checkExplicitlyNonNullable, 'type argument 1 of test type');
+  }
+
+  Future<void> test_decorate_interfaceType_simple_question() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkInt(
+        withElement.decorate(
+          InterfaceTypeImpl(
+            element: withElement.typeProvider.intElement,
+            typeArguments: const [],
+            nullabilitySuffix: NullabilitySuffix.question,
+          ),
+        ),
+        withElement.checkExplicitlyNullable,
+        'test type');
+  }
+
+  Future<void> test_decorate_interfaceType_simple_star() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkInt(
+        withElement.decorate(
+          InterfaceTypeImpl(
+            element: withElement.typeProvider.intElement,
+            typeArguments: const [],
+            nullabilitySuffix: suffix,
+          ),
+        ),
+        withElement.checkExplicitlyNonNullable,
+        'test type');
+  }
+
+  Future<void> test_decorate_iterable_dynamic() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    var decorated =
+        withElement.decorate(withElement.typeProvider.iterableDynamicType);
+    withElement.checkIterable(decorated, withElement.checkExplicitlyNonNullable,
+        withElement.checkDynamic, 'test type');
+  }
+
+  Future<void> test_decorate_never() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkNever(
+        withElement.decorate(withElement.typeProvider.neverType), 'test type');
+  }
+
+  Future<void> test_decorate_typeParameterType_question() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class A<T> {}',
+    );
+    var element = withUnit.findElement.typeParameter('T');
+    var withElement = withUnit.withElement(element);
+
+    withElement.checkTypeParameter(
+        withElement.decorate(TypeParameterTypeImpl(
+            element: element, nullabilitySuffix: NullabilitySuffix.question)),
+        withElement.checkExplicitlyNullable,
+        element,
+        'test type');
+  }
+
+  Future<void> test_decorate_typeParameterType_star() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class A<T> {}',
+    );
+    var element = withUnit.findElement.typeParameter('T');
+    var withElement = withUnit.withElement(element);
+
+    withElement.checkTypeParameter(
+        withElement.decorate(
+            TypeParameterTypeImpl(element: element, nullabilitySuffix: suffix)),
+        withElement.checkExplicitlyNonNullable,
+        element,
+        'test type');
+  }
+
+  Future<void> test_decorate_void() async {
+    var withElement = await _ContextWithFiles().withEmptyUnit();
+
+    withElement.checkVoid(
+        withElement.decorate(withElement.typeProvider.voidType), 'test type');
+  }
+
+  Future<void> test_getImmediateSupertypes_future() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement('');
+    var element = withUnit.typeProvider.futureElement;
+    var withElement = withUnit.withElement(element);
+
+    // var class_ = element = typeProvider.futureElement;
+    var class_ = withElement.typeProvider.futureElement;
+    var decoratedSupertypes =
+        withElement.decorator.getImmediateSupertypes(class_).toList();
+    var typeParam = class_.typeParameters[0];
+    expect(decoratedSupertypes, hasLength(2));
+    // TODO(scheglov) Use location matcher.
+    withElement.checkObject(decoratedSupertypes[0],
+        withElement.checkExplicitlyNonNullable, 'Future (async.dart:1:79)');
+    // Since Future<T> is a subtype of FutureOr<T>, we consider FutureOr<T> to
+    // be an immediate supertype, even though the class declaration for Future
+    // doesn't mention FutureOr.
+    // TODO(scheglov) Use location matcher.
+    withElement.checkFutureOr(
+        decoratedSupertypes[1],
+        withElement.checkExplicitlyNonNullable,
+        (t, displayName) => withElement.checkTypeParameter(
+            t!, withElement.checkExplicitlyNonNullable, typeParam, displayName),
+        'Future (async.dart:1:79)');
+  }
+
+  Future<void> test_getImmediateSupertypes_generic() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class C<T> extends Iterable<T> {}',
+    );
+    var unitElement = withUnit.unitElement;
+    var class_ = unitElement.classes.single;
+    var t = class_.typeParameters.single;
+
+    var withElement = withUnit.withElement(class_);
+
+    var decoratedSupertypes =
+        withElement.decorator.getImmediateSupertypes(class_).toList();
+    expect(decoratedSupertypes, hasLength(1));
+    withElement.checkIterable(
+        decoratedSupertypes[0],
+        withElement.checkExplicitlyNonNullable,
+        (type, displayName) => withElement.checkTypeParameter(
+            type!, withElement.checkExplicitlyNonNullable, t, displayName),
+        'C (test.dart:1:7)');
+  }
+
+  Future<void> test_getImmediateSupertypes_interface() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class C implements num {}',
+    );
+    var unitElement = withUnit.unitElement;
+    var class_ = unitElement.classes.single;
+
+    var withElement = withUnit.withElement(class_);
+
+    var decoratedSupertypes =
+        withElement.decorator.getImmediateSupertypes(class_).toList();
+    expect(decoratedSupertypes, hasLength(2));
+    withElement.checkObject(decoratedSupertypes[0],
+        withElement.checkExplicitlyNonNullable, 'C (test.dart:1:7)');
+    withElement.checkNum(decoratedSupertypes[1],
+        withElement.checkExplicitlyNonNullable, 'C (test.dart:1:7)');
+  }
+
+  Future<void> test_getImmediateSupertypes_mixin() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class C with num {}',
+    );
+    var unitElement = withUnit.unitElement;
+    var class_ = unitElement.classes.single;
+
+    var withElement = withUnit.withElement(class_);
+
+    var decoratedSupertypes =
+        withElement.decorator.getImmediateSupertypes(class_).toList();
+    expect(decoratedSupertypes, hasLength(2));
+    withElement.checkObject(decoratedSupertypes[0],
+        withElement.checkExplicitlyNonNullable, 'C (test.dart:1:7)');
+    withElement.checkNum(decoratedSupertypes[1],
+        withElement.checkExplicitlyNonNullable, 'C (test.dart:1:7)');
+  }
+
+  Future<void> test_getImmediateSupertypes_superclassConstraint() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'mixin C on num {}',
+    );
+    var unitElement = withUnit.unitElement;
+    var mixin_ = unitElement.mixins.single;
+
+    var withElement = withUnit.withElement(mixin_);
+
+    var decoratedSupertypes =
+        withElement.decorator.getImmediateSupertypes(mixin_).toList();
+    expect(decoratedSupertypes, hasLength(1));
+    withElement.checkNum(decoratedSupertypes[0],
+        withElement.checkExplicitlyNonNullable, 'C (test.dart:1:7)');
+  }
+
+  Future<void> test_getImmediateSupertypes_supertype() async {
+    var withUnit = await _ContextWithFiles().buildUnitElement(
+      'class C {}',
+    );
+    var unitElement = withUnit.unitElement;
+    var class_ = unitElement.classes.single;
+
+    var withElement = withUnit.withElement(class_);
+
+    var decoratedSupertypes =
+        withElement.decorator.getImmediateSupertypes(class_).toList();
+    expect(decoratedSupertypes, hasLength(1));
+    // TODO(paulberry): displayName should be 'Object supertype of C'
+    withElement.checkObject(decoratedSupertypes[0],
+        withElement.checkExplicitlyNonNullable, 'C (test.dart:1:7)');
+  }
+}
+
+/// Specialization of [_AlreadyMigratedCodeDecoratorTestBase] for testing the
+/// situation where the already migrated code does not contain star types.  In
+/// the final product, by definition all already-migrated code will be free of
+/// star types.  However, since we do not yet migrate using a fully NNBD-aware
+/// SDK, we need to handle both star and non-star variants on a short term
+/// basis.
+@reflectiveTest
+class _AlreadyMigratedCodeDecoratorTestNormal
+    extends _AlreadyMigratedCodeDecoratorTestBase {
+  _AlreadyMigratedCodeDecoratorTestNormal() : super(NullabilitySuffix.none);
+}
+
+/// Specialization of [_AlreadyMigratedCodeDecoratorTestBase] for testing the
+/// situation where the already migrated code contains star types.  In the final
+/// product, this will never happen.  However, since we do not yet migrate using
+/// a fully NNBD-aware SDK, we need to handle both star and non-star variants on
+/// a short term basis.
+@reflectiveTest
+class _AlreadyMigratedCodeDecoratorTestProvisional
+    extends _AlreadyMigratedCodeDecoratorTestBase {
+  _AlreadyMigratedCodeDecoratorTestProvisional()
+      : super(NullabilitySuffix.star);
+}
+
+class _ContextWithElement with EdgeTester {
+  final _ContextWithUnitElement _withUnit;
+  final Element element;
+
+  final NullabilityGraphForTesting graph = NullabilityGraphForTesting();
+
+  _ContextWithElement(this._withUnit, this.element);
 
   NullabilityNode get always => graph.always;
 
+  AlreadyMigratedCodeDecorator get decorator {
+    return AlreadyMigratedCodeDecorator(
+        graph, typeProvider, (_) => LineInfo([0]));
+  }
+
   NullabilityNode get never => graph.never;
 
+  TypeProvider get typeProvider {
+    return _withUnit.typeProvider;
+  }
+
   void checkAlwaysNullable(NullabilityNode node, String displayName) {
     var edge = assertEdge(always, node, hard: true, checkable: false);
     var origin = graph.getEdgeOrigin(edge)!;
@@ -88,10 +532,11 @@
   }
 
   void checkFutureOr(
-      DecoratedType decoratedType,
-      void Function(NullabilityNode?, String) checkNullability,
-      void Function(DecoratedType?, String) checkArgument,
-      String displayName) {
+    DecoratedType decoratedType,
+    void Function(NullabilityNode?, String) checkNullability,
+    void Function(DecoratedType?, String) checkArgument,
+    String displayName,
+  ) {
     expect(decoratedType.type!.element, typeProvider.futureOrElement);
     checkNullability(decoratedType.node, displayName);
     checkArgument(
@@ -99,18 +544,20 @@
   }
 
   void checkInt(
-      DecoratedType decoratedType,
-      void Function(NullabilityNode?, String) checkNullability,
-      String displayName) {
+    DecoratedType decoratedType,
+    void Function(NullabilityNode?, String) checkNullability,
+    String displayName,
+  ) {
     expect(decoratedType.type!.element, typeProvider.intType.element);
     checkNullability(decoratedType.node, displayName);
   }
 
   void checkIterable(
-      DecoratedType decoratedType,
-      void Function(NullabilityNode?, String) checkNullability,
-      void Function(DecoratedType?, String) checkArgument,
-      String displayName) {
+    DecoratedType decoratedType,
+    void Function(NullabilityNode?, String) checkNullability,
+    void Function(DecoratedType?, String) checkArgument,
+    String displayName,
+  ) {
     expect(
         decoratedType.type!.element, typeProvider.iterableDynamicType.element);
     checkNullability(decoratedType.node, displayName);
@@ -124,26 +571,29 @@
   }
 
   void checkNum(
-      DecoratedType decoratedType,
-      void Function(NullabilityNode?, String) checkNullability,
-      String displayName) {
+    DecoratedType decoratedType,
+    void Function(NullabilityNode?, String) checkNullability,
+    String displayName,
+  ) {
     expect(decoratedType.type!.element, typeProvider.numType.element);
     checkNullability(decoratedType.node, displayName);
   }
 
   void checkObject(
-      DecoratedType decoratedType,
-      void Function(NullabilityNode?, String) checkNullability,
-      String displayName) {
+    DecoratedType decoratedType,
+    void Function(NullabilityNode?, String) checkNullability,
+    String displayName,
+  ) {
     expect(decoratedType.type!.element, typeProvider.objectType.element);
     checkNullability(decoratedType.node, displayName);
   }
 
   void checkTypeParameter(
-      DecoratedType decoratedType,
-      void Function(NullabilityNode?, String) checkNullability,
-      TypeParameterElement expectedElement,
-      String displayName) {
+    DecoratedType decoratedType,
+    void Function(NullabilityNode?, String) checkNullability,
+    TypeParameterElement expectedElement,
+    String displayName,
+  ) {
     var type = decoratedType.type as TypeParameterTypeImpl;
     expect(type.element, same(expectedElement));
     checkNullability(decoratedType.node, displayName);
@@ -160,397 +610,57 @@
     expect(decoratedType.type, same(type));
     return decoratedType;
   }
+}
 
-  DecoratedType? getDecoratedBound(TypeParameterElement element) =>
-      decoratedTypeParameterBounds.get(element);
+class _ContextWithFiles with ResourceProviderMixin {
+  Future<_ContextWithUnitElement> buildUnitElement(String content) async {
+    var file = newFile('/home/test/lib/test.dart', content: content);
 
-  void setUp() {
-    DecoratedTypeParameterBounds.current = decoratedTypeParameterBounds;
-  }
-
-  void tearDown() {
-    DecoratedTypeParameterBounds.current = null;
-  }
-
-  void test_decorate_dynamic() {
-    checkDynamic(decorate(typeProvider.dynamicType), 'test type');
-  }
-
-  void test_decorate_functionType_generic_bounded() {
-    var typeFormal = element = TypeParameterElementImpl.synthetic('T')
-      ..bound = typeProvider.numType;
-    var decoratedType = decorate(
-      FunctionTypeImpl(
-        typeFormals: [typeFormal],
-        parameters: const [],
-        returnType: TypeParameterTypeImpl(
-          element: typeFormal,
-          nullabilitySuffix: NullabilitySuffix.star,
-        ),
-        nullabilitySuffix: suffix,
-      ),
+    var sdkRoot = newFolder('/sdk');
+    createMockSdk(
+      resourceProvider: resourceProvider,
+      root: sdkRoot,
     );
-    checkNum(getDecoratedBound(typeFormal)!, checkExplicitlyNonNullable,
-        'bound of type formal T of test type');
-    checkTypeParameter(decoratedType.returnType!, checkExplicitlyNonNullable,
-        typeFormal, 'return type of test type');
-  }
 
-  void test_decorate_functionType_generic_no_explicit_bound() {
-    var typeFormal = element = TypeParameterElementImpl.synthetic('T');
-    var decoratedType = decorate(
-      FunctionTypeImpl(
-        typeFormals: [typeFormal],
-        parameters: const [],
-        returnType: TypeParameterTypeImpl(
-          element: typeFormal,
-          nullabilitySuffix: NullabilitySuffix.star,
-        ),
-        nullabilitySuffix: suffix,
-      ),
+    var contextCollection = AnalysisContextCollection(
+      resourceProvider: resourceProvider,
+      includedPaths: [file.path],
+      sdkPath: sdkRoot.path,
     );
-    checkObject(getDecoratedBound(typeFormal)!, checkExplicitlyNullable,
-        'bound of type formal T of test type');
-    checkTypeParameter(decoratedType.returnType!, checkExplicitlyNonNullable,
-        typeFormal, 'return type of test type');
+    var analysisContext = contextCollection.contextFor(file.path);
+    var analysisSession = analysisContext.currentSession;
+    var result = await analysisSession.getResolvedUnit(file.path);
+    return _ContextWithUnitElement(result as ResolvedUnitResult);
   }
 
-  void test_decorate_functionType_named_parameter() {
-    checkDynamic(
-        decorate(
-          FunctionTypeImpl(
-            typeFormals: const [],
-            parameters: [
-              ParameterElementImpl.synthetic(
-                'x',
-                typeProvider.dynamicType,
-                ParameterKind.NAMED,
-              )
-            ],
-            returnType: typeProvider.voidType,
-            nullabilitySuffix: suffix,
-          ),
-        ).namedParameters!['x'],
-        'parameter x of test type');
+  Future<_ContextWithElement> withEmptyUnit() async {
+    var withUnit = await buildUnitElement('');
+    return withUnit.withElement(withUnit.unitElement);
   }
-
-  void test_decorate_functionType_ordinary_parameters() {
-    var decoratedType = decorate(
-      FunctionTypeImpl(
-        typeFormals: const [],
-        parameters: [
-          ParameterElementImpl.synthetic(
-            'x',
-            typeProvider.dynamicType,
-            ParameterKind.REQUIRED,
-          ),
-          ParameterElementImpl.synthetic(
-            'y',
-            typeProvider.dynamicType,
-            ParameterKind.REQUIRED,
-          )
-        ],
-        returnType: typeProvider.voidType,
-        nullabilitySuffix: suffix,
-      ),
-    );
-    checkDynamic(
-        decoratedType.positionalParameters![0], 'parameter 0 of test type');
-    checkDynamic(
-        decoratedType.positionalParameters![1], 'parameter 1 of test type');
-  }
-
-  void test_decorate_functionType_positional_parameter() {
-    checkDynamic(
-        decorate(
-          FunctionTypeImpl(
-            typeFormals: const [],
-            parameters: [
-              ParameterElementImpl.synthetic(
-                'x',
-                typeProvider.dynamicType,
-                ParameterKind.POSITIONAL,
-              )
-            ],
-            returnType: typeProvider.voidType,
-            nullabilitySuffix: suffix,
-          ),
-        ).positionalParameters![0],
-        'parameter 0 of test type');
-  }
-
-  void test_decorate_functionType_question() {
-    checkExplicitlyNullable(
-        decorate(
-          FunctionTypeImpl(
-            typeFormals: const [],
-            parameters: const [],
-            returnType: typeProvider.voidType,
-            nullabilitySuffix: NullabilitySuffix.question,
-          ),
-        ).node,
-        'test type');
-  }
-
-  void test_decorate_functionType_returnType() {
-    checkDynamic(
-        decorate(
-          FunctionTypeImpl(
-            typeFormals: const [],
-            parameters: const [],
-            returnType: typeProvider.dynamicType,
-            nullabilitySuffix: suffix,
-          ),
-        ).returnType,
-        'return type of test type');
-  }
-
-  void test_decorate_functionType_star() {
-    checkExplicitlyNonNullable(
-        decorate(
-          FunctionTypeImpl(
-            typeFormals: const [],
-            parameters: const [],
-            returnType: typeProvider.voidType,
-            nullabilitySuffix: suffix,
-          ),
-        ).node,
-        'test type');
-  }
-
-  void test_decorate_interfaceType_parameters() {
-    var decoratedType = decorate(InterfaceTypeImpl(
-        element: typeProvider.mapElement,
-        typeArguments: [typeProvider.intType, typeProvider.numType],
-        nullabilitySuffix: suffix));
-    checkInt(decoratedType.typeArguments[0]!, checkExplicitlyNonNullable,
-        'type argument 0 of test type');
-    checkNum(decoratedType.typeArguments[1]!, checkExplicitlyNonNullable,
-        'type argument 1 of test type');
-  }
-
-  void test_decorate_interfaceType_simple_question() {
-    checkInt(
-        decorate(
-          InterfaceTypeImpl(
-            element: typeProvider.intElement,
-            typeArguments: const [],
-            nullabilitySuffix: NullabilitySuffix.question,
-          ),
-        ),
-        checkExplicitlyNullable,
-        'test type');
-  }
-
-  void test_decorate_interfaceType_simple_star() {
-    checkInt(
-        decorate(
-          InterfaceTypeImpl(
-            element: typeProvider.intElement,
-            typeArguments: const [],
-            nullabilitySuffix: suffix,
-          ),
-        ),
-        checkExplicitlyNonNullable,
-        'test type');
-  }
-
-  void test_decorate_iterable_dynamic() {
-    var decorated = decorate(typeProvider.iterableDynamicType);
-    checkIterable(
-        decorated, checkExplicitlyNonNullable, checkDynamic, 'test type');
-  }
-
-  void test_decorate_never() {
-    checkNever(decorate(typeProvider.neverType), 'test type');
-  }
-
-  void test_decorate_typeParameterType_question() {
-    var element = TypeParameterElementImpl.synthetic('T');
-    checkTypeParameter(
-        decorate(TypeParameterTypeImpl(
-            element: element, nullabilitySuffix: NullabilitySuffix.question)),
-        checkExplicitlyNullable,
-        element,
-        'test type');
-  }
-
-  void test_decorate_typeParameterType_star() {
-    var element = TypeParameterElementImpl.synthetic('T');
-    checkTypeParameter(
-        decorate(
-            TypeParameterTypeImpl(element: element, nullabilitySuffix: suffix)),
-        checkExplicitlyNonNullable,
-        element,
-        'test type');
-  }
-
-  void test_decorate_void() {
-    checkVoid(decorate(typeProvider.voidType), 'test type');
-  }
-
-  void test_getImmediateSupertypes_future() {
-    var class_ = element = typeProvider.futureElement;
-    var decoratedSupertypes = decorator.getImmediateSupertypes(class_).toList();
-    var typeParam = class_.typeParameters[0];
-    expect(decoratedSupertypes, hasLength(2));
-    // Note: the bogus location `async:1:1` is because we're using a
-    // TestTypeProvider.
-    checkObject(decoratedSupertypes[0], checkExplicitlyNonNullable,
-        'Future (async:1:1)');
-    // Since Future<T> is a subtype of FutureOr<T>, we consider FutureOr<T> to
-    // be an immediate supertype, even though the class declaration for Future
-    // doesn't mention FutureOr.
-    // Note: the bogus location `async:1:1` is because we're using a
-    // TestTypeProvider.
-    checkFutureOr(
-        decoratedSupertypes[1],
-        checkExplicitlyNonNullable,
-        (t, displayName) => checkTypeParameter(
-            t!, checkExplicitlyNonNullable, typeParam, displayName),
-        'Future (async:1:1)');
-  }
-
-  void test_getImmediateSupertypes_generic() {
-    var library = _LibraryElementMock();
-    var t = ElementFactory.typeParameterElement('T');
-    var class_ = element = ElementFactory.classElement3(
-      name: 'C',
-      typeParameters: [t],
-      supertype: typeProvider.iterableType(
-        t.instantiate(nullabilitySuffix: suffix),
-      ),
-    );
-    class_.enclosingElement = library.definingCompilationUnit;
-    var decoratedSupertypes = decorator.getImmediateSupertypes(class_).toList();
-    expect(decoratedSupertypes, hasLength(1));
-    checkIterable(
-        decoratedSupertypes[0],
-        checkExplicitlyNonNullable,
-        (type, displayName) => checkTypeParameter(
-            type!, checkExplicitlyNonNullable, t, displayName),
-        'C (test.dart:1:1)');
-  }
-
-  void test_getImmediateSupertypes_interface() {
-    var library = _LibraryElementMock();
-    var class_ =
-        element = ElementFactory.classElement('C', typeProvider.objectType);
-    class_.interfaces = [typeProvider.numType];
-    class_.enclosingElement = library.definingCompilationUnit;
-    var decoratedSupertypes = decorator.getImmediateSupertypes(class_).toList();
-    expect(decoratedSupertypes, hasLength(2));
-    checkObject(decoratedSupertypes[0], checkExplicitlyNonNullable,
-        'C (test.dart:1:1)');
-    checkNum(decoratedSupertypes[1], checkExplicitlyNonNullable,
-        'C (test.dart:1:1)');
-  }
-
-  void test_getImmediateSupertypes_mixin() {
-    var library = _LibraryElementMock();
-    var class_ =
-        element = ElementFactory.classElement('C', typeProvider.objectType);
-    class_.mixins = [typeProvider.numType];
-    class_.enclosingElement = library.definingCompilationUnit;
-    var decoratedSupertypes = decorator.getImmediateSupertypes(class_).toList();
-    expect(decoratedSupertypes, hasLength(2));
-    checkObject(decoratedSupertypes[0], checkExplicitlyNonNullable,
-        'C (test.dart:1:1)');
-    checkNum(decoratedSupertypes[1], checkExplicitlyNonNullable,
-        'C (test.dart:1:1)');
-  }
-
-  void test_getImmediateSupertypes_superclassConstraint() {
-    var library = _LibraryElementMock();
-    var class_ = element = ElementFactory.mixinElement(
-        name: 'C', constraints: [typeProvider.numType]);
-    class_.enclosingElement = library.definingCompilationUnit;
-    var decoratedSupertypes = decorator.getImmediateSupertypes(class_).toList();
-    expect(decoratedSupertypes, hasLength(1));
-    checkNum(decoratedSupertypes[0], checkExplicitlyNonNullable,
-        'C (test.dart:1:1)');
-  }
-
-  void test_getImmediateSupertypes_supertype() {
-    var library = _LibraryElementMock();
-    var class_ =
-        element = ElementFactory.classElement('C', typeProvider.objectType);
-    class_.enclosingElement = library.definingCompilationUnit;
-    var decoratedSupertypes = decorator.getImmediateSupertypes(class_).toList();
-    expect(decoratedSupertypes, hasLength(1));
-    // TODO(paulberry): displayName should be 'Object supertype of C'
-    checkObject(decoratedSupertypes[0], checkExplicitlyNonNullable,
-        'C (test.dart:1:1)');
-  }
-
-  static LineInfo _getLineInfo(String path) => LineInfo([0]);
 }
 
-/// Specialization of [_AlreadyMigratedCodeDecoratorTestBase] for testing the
-/// situation where the already migrated code does not contain star types.  In
-/// the final product, by definition all already-migrated code will be free of
-/// star types.  However, since we do not yet migrate using a fully NNBD-aware
-/// SDK, we need to handle both star and non-star variants on a short term
-/// basis.
-@reflectiveTest
-class _AlreadyMigratedCodeDecoratorTestNormal
-    extends _AlreadyMigratedCodeDecoratorTestBase {
-  _AlreadyMigratedCodeDecoratorTestNormal() : super(NullabilitySuffix.none);
-}
+class _ContextWithUnitElement {
+  final ResolvedUnitResult _unitResult;
 
-/// Specialization of [_AlreadyMigratedCodeDecoratorTestBase] for testing the
-/// situation where the already migrated code contains star types.  In the final
-/// product, this will never happen.  However, since we do not yet migrate using
-/// a fully NNBD-aware SDK, we need to handle both star and non-star variants on
-/// a short term basis.
-@reflectiveTest
-class _AlreadyMigratedCodeDecoratorTestProvisional
-    extends _AlreadyMigratedCodeDecoratorTestBase {
-  _AlreadyMigratedCodeDecoratorTestProvisional()
-      : super(NullabilitySuffix.star);
-}
+  _ContextWithUnitElement(this._unitResult);
 
-class _CompilationUnitElementMock implements CompilationUnitElementImpl {
-  @override
-  final LibraryElement enclosingElement;
-
-  @override
-  final Source source;
-
-  _CompilationUnitElementMock(this.enclosingElement, this.source);
-
-  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
-}
-
-class _LibraryElementMock implements LibraryElementImpl {
-  @override
-  late CompilationUnitElement definingCompilationUnit;
-
-  @override
-  late Source source;
-
-  _LibraryElementMock() {
-    source = _SourceMock();
-    definingCompilationUnit = _CompilationUnitElementMock(this, source);
+  FindElement get findElement {
+    return FindElement(_unitResult.unit);
   }
 
-  @override
-  Element? get enclosingElement => null;
+  FindNode get findNode {
+    return FindNode(_unitResult.content, _unitResult.unit);
+  }
 
-  @override
-  bool get isNonNullableByDefault => false;
+  TypeProvider get typeProvider {
+    return unitElement.library.typeProvider;
+  }
 
-  @override
-  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
-}
+  CompilationUnitElement get unitElement {
+    return _unitResult.unit.declaredElement!;
+  }
 
-class _MockElement implements Element {
-  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
-}
-
-class _SourceMock implements Source {
-  String get fullName => '/test.dart';
-
-  @override
-  noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+  _ContextWithElement withElement(Element element) {
+    return _ContextWithElement(this, element);
+  }
 }
diff --git a/tools/VERSION b/tools/VERSION
index 3250b93..8e9f552 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 16
 PATCH 0
-PRERELEASE 33
+PRERELEASE 34
 PRERELEASE_PATCH 0
\ No newline at end of file