diff --git a/pkg/dartdev/lib/src/commands/fix.dart b/pkg/dartdev/lib/src/commands/fix.dart
index 9f4d350..6cb007f 100644
--- a/pkg/dartdev/lib/src/commands/fix.dart
+++ b/pkg/dartdev/lib/src/commands/fix.dart
@@ -17,7 +17,9 @@
 class FixCommand extends DartdevCommand {
   static const String cmdName = 'fix';
 
-  // This command is hidden as it's currently experimental.
+  static final NumberFormat _numberFormat = NumberFormat.decimalPattern();
+
+  /// This command is hidden as it's currently experimental.
   FixCommand() : super(cmdName, 'Fix Dart source code.', hidden: true) {
     argParser.addFlag('dry-run',
         abbr: 'n',
@@ -74,69 +76,67 @@
     if (edits.isEmpty) {
       log.stdout('Nothing to fix!');
     } else {
-      if (dryRun) {
-        var details = fixes.details;
-        details.sort((f1, f2) => path
-            .relative(f1.path, from: dir.path)
-            .compareTo(path.relative(f2.path, from: dir.path)));
+      var details = fixes.details;
+      details.sort((f1, f2) => path
+          .relative(f1.path, from: dir.path)
+          .compareTo(path.relative(f2.path, from: dir.path)));
 
-        var fileCount = 0;
-        var fixCount = 0;
+      var fileCount = 0;
+      var fixCount = 0;
 
-        details.forEach((d) {
-          ++fileCount;
-          d.fixes.forEach((f) {
-            fixCount += f.occurrences;
-          });
+      details.forEach((d) {
+        ++fileCount;
+        d.fixes.forEach((f) {
+          fixCount += f.occurrences;
         });
+      });
 
+      if (dryRun) {
         log.stdout('');
-
-        final bullet = log.ansi.bullet;
-
-        for (var detail in details) {
-          log.stdout(path.relative(detail.path, from: dir.path));
-          final fixes = detail.fixes.toList();
-          fixes.sort((a, b) => a.code.compareTo(b.code));
-          for (var fix in fixes) {
-            log.stdout('  ${fix.code} $bullet '
-                '${_format(fix.occurrences)} ${_pluralFix(fix.occurrences)}');
-          }
-          log.stdout('');
-        }
-
         log.stdout('${_format(fixCount)} proposed ${_pluralFix(fixCount)} '
             'in ${_format(fileCount)} ${pluralize("file", fileCount)}.');
+        _printDetails(details, dir);
       } else {
         progress = log.progress('Applying fixes');
-        var fileCount = await _applyFixes(edits);
+        _applyFixes(edits);
         progress.finish(showTiming: true);
-        if (fileCount > 0) {
-          log.stdout(
-              'Fixed ${_format(fileCount)} ${pluralize("file", fileCount)}.');
-        }
+        _printDetails(details, dir);
+        log.stdout('${_format(fixCount)} ${_pluralFix(fixCount)} made in '
+            '${_format(fileCount)} ${pluralize("file", fileCount)}.');
       }
     }
 
     return 0;
   }
 
-  Future<int> _applyFixes(List<SourceFileEdit> edits) async {
-    var files = <String>{};
+  void _applyFixes(List<SourceFileEdit> edits) {
     for (var edit in edits) {
       var fileName = edit.file;
-      files.add(fileName);
       var file = io.File(fileName);
-      var code = await file.exists() ? await file.readAsString() : '';
+      var code = file.existsSync() ? file.readAsStringSync() : '';
       code = SourceEdit.applySequence(code, edit.edits);
-      await file.writeAsString(code);
+      file.writeAsStringSync(code);
     }
-    return files.length;
   }
 
   String _pluralFix(int count) => count == 1 ? 'fix' : 'fixes';
 
-  static final NumberFormat _numberFormat = NumberFormat.decimalPattern();
+  void _printDetails(List<BulkFix> details, io.Directory workingDir) {
+    log.stdout('');
+
+    final bullet = log.ansi.bullet;
+
+    for (var detail in details) {
+      log.stdout(path.relative(detail.path, from: workingDir.path));
+      final fixes = detail.fixes.toList();
+      fixes.sort((a, b) => a.code.compareTo(b.code));
+      for (var fix in fixes) {
+        log.stdout('  ${fix.code} $bullet '
+            '${_format(fix.occurrences)} ${_pluralFix(fix.occurrences)}');
+      }
+      log.stdout('');
+    }
+  }
 
   static String _format(int value) => _numberFormat.format(value);
 }
diff --git a/pkg/dartdev/test/commands/fix_test.dart b/pkg/dartdev/test/commands/fix_test.dart
index ff885d6..3303da3 100644
--- a/pkg/dartdev/test/commands/fix_test.dart
+++ b/pkg/dartdev/test/commands/fix_test.dart
@@ -44,7 +44,13 @@
     var result = p.runSync('fix', [], workingDir: p.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
-    expect(result.stdout, contains('Fixed 1 file.'));
+    expect(
+        result.stdout,
+        stringContainsInOrder([
+          'Applying fixes...',
+          'lib${Platform.pathSeparator}main.dart',
+          '  prefer_single_quotes $bullet 1 fix',
+        ]));
   });
 
   test('dry-run', () {
@@ -68,10 +74,14 @@
     var result = p.runSync('fix', ['--dry-run', '.'], workingDir: p.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
-    expect(result.stdout, contains('3 proposed fixes in 1 file.'));
-    expect(result.stdout, contains('lib${Platform.pathSeparator}main.dart'));
-    expect(result.stdout, contains('  annotate_overrides $bullet 1 fix'));
-    expect(result.stdout, contains('  prefer_single_quotes $bullet 2 fixes'));
+    expect(
+        result.stdout,
+        stringContainsInOrder([
+          '3 proposed fixes in 1 file.',
+          'lib${Platform.pathSeparator}main.dart',
+          '  annotate_overrides $bullet 1 fix',
+          '  prefer_single_quotes $bullet 2 fixes',
+        ]));
   });
 
   test('.', () {
@@ -88,7 +98,14 @@
     var result = p.runSync('fix', ['.'], workingDir: p.dirPath);
     expect(result.exitCode, 0);
     expect(result.stderr, isEmpty);
-    expect(result.stdout, contains('Fixed 1 file.'));
+    expect(
+        result.stdout,
+        stringContainsInOrder([
+          'Applying fixes...',
+          'lib${Platform.pathSeparator}main.dart',
+          '  prefer_single_quotes $bullet 1 fix',
+          '1 fix made in 1 file.',
+        ]));
   });
 
   test('excludes', () {
diff --git a/pkg/dev_compiler/test/expression_compiler/expression_compiler_test.dart b/pkg/dev_compiler/test/expression_compiler/expression_compiler_test.dart
index 48eb3ed..0580af9 100644
--- a/pkg/dev_compiler/test/expression_compiler/expression_compiler_test.dart
+++ b/pkg/dev_compiler/test/expression_compiler/expression_compiler_test.dart
@@ -50,27 +50,36 @@
 
 class SetupCompilerOptions {
   static final sdkRoot = computePlatformBinariesLocation();
-  static final sdkSummaryPath = p.join(sdkRoot.path, 'ddc_sdk.dill');
+  static final sdkUnsoundSummaryPath = p.join(sdkRoot.path, 'ddc_sdk.dill');
+  static final sdkSoundSummaryPath =
+      p.join(sdkRoot.path, 'ddc_outline_sound.dill');
   static final librariesSpecificationUri =
       p.join(p.dirname(p.dirname(getSdkPath())), 'libraries.json');
 
-  static CompilerOptions getOptions() {
+  static CompilerOptions getOptions(bool soundNullSafety) {
     var options = CompilerOptions()
       ..verbose = false // set to true for debugging
       ..sdkRoot = sdkRoot
       ..target = DevCompilerTarget(TargetFlags())
       ..librariesSpecificationUri = Uri.base.resolve('sdk/lib/libraries.json')
       ..omitPlatform = true
-      ..sdkSummary = sdkRoot.resolve(sdkSummaryPath)
+      ..sdkSummary = sdkRoot.resolve(
+          soundNullSafety ? sdkSoundSummaryPath : sdkUnsoundSummaryPath)
       ..environmentDefines = const {};
     return options;
   }
 
-  List<String> errors;
-  final CompilerOptions options;
+  static final String dartUnsoundComment = '// @dart = 2.9';
+  static final String dartSoundComment = '//';
 
-  SetupCompilerOptions() : options = getOptions() {
-    errors = <String>[];
+  final List<String> errors = [];
+  final CompilerOptions options;
+  final String dartLangComment;
+
+  SetupCompilerOptions(bool soundNullSafety)
+      : options = getOptions(soundNullSafety),
+        dartLangComment =
+            soundNullSafety ? dartSoundComment : dartUnsoundComment {
     options.onDiagnostic = (DiagnosticMessage m) {
       errors.addAll(m.plainTextFormatted);
     };
@@ -281,1563 +290,1564 @@
 }
 
 void main() {
-  var options = SetupCompilerOptions();
+  group('Unsound null safety', () {
+    var options = SetupCompilerOptions(false);
 
-  group('Expression compiler tests in extension method:', () {
-    const source = '''
-      // @dart = 2.9
-      extension NumberParsing on String {
-        int parseInt() {
-          var ret = int.parse(this);
-          /* evaluation placeholder */
-          return ret;
-        }
-      }
-      main() => 0;
-    ''';
-
-    TestDriver driver;
-
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
-
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'ret': '1234'},
-          expression: 'typo',
-          expectedError: "Error: Getter not found: 'typo'");
-    });
-
-    test('local (trimmed scope)', () async {
-      // Test that current expression evaluation works in extension methods.
-      //
-      // Note: the actual scope is {#this, ret}, but #this is effectively
-      // removed in the expression compilator because it does not exist
-      // in JavaScript code.
-      // See (full scope) tests for what will the evaluation will look like
-      // when the mapping from dart symbols to JavaScipt symbols is added.
-      await driver.check(
-          scope: <String, String>{'ret': '1234'},
-          expression: 'ret',
-          expectedResult: '''
-          (function(ret) {
+    group('Expression compiler tests in extension method:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            var ret = int.parse(this);
+            /* evaluation placeholder */
             return ret;
-          }(
-            1234
-          ))
-          ''');
-    });
-
-    test('local (full scope)', () async {
-      // Test evalution in extension methods in the future when the mapping
-      // from kernel symbols to dartdevc symbols is added.
-      //
-      // Note: this currently fails due to
-      // - incremental compiler not allowing #this as a parameter name
-      await driver.check(
-          scope: <String, String>{'ret': '1234', '#this': 'this'},
-          expression: 'ret',
-          expectedError:
-              "Illegal parameter name '#this' found during expression compilation.");
-    });
-
-    test('this (full scope)', () async {
-      // Test evalution in extension methods in the future when the mapping
-      // from kernel symbols to dartdevc symbols is added.
-      //
-      // Note: this currently fails due to
-      // - incremental compiler not allowing #this as a parameter name
-      // - incremental compiler not mapping 'this' from user input to '#this'
-      await driver.check(
-          scope: <String, String>{'ret': '1234', '#this': 'this'},
-          expression: 'this',
-          expectedError:
-              "Illegal parameter name '#this' found during expression compilation.");
-    });
-  });
-
-  group('Expression compiler tests in static function:', () {
-    const source = '''
-      // @dart = 2.9
-      int foo(int x, {int y}) {
-        int z = 0;
-        /* evaluation placeholder */
-        return x + y + z;
-      }
-
-      main() => 0;
+          }
+        }
+        main() => 0;
       ''';
 
-    TestDriver driver;
+      TestDriver driver;
 
-    setUp(() {
-      driver = TestDriver(options, source);
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'ret': '1234'},
+            expression: 'typo',
+            expectedError: "Error: Getter not found: 'typo'");
+      });
+
+      test('local (trimmed scope)', () async {
+        // Test that current expression evaluation works in extension methods.
+        //
+        // Note: the actual scope is {#this, ret}, but #this is effectively
+        // removed in the expression compilator because it does not exist
+        // in JavaScript code.
+        // See (full scope) tests for what will the evaluation will look like
+        // when the mapping from dart symbols to JavaScipt symbols is added.
+        await driver.check(
+            scope: <String, String>{'ret': '1234'},
+            expression: 'ret',
+            expectedResult: '''
+            (function(ret) {
+              return ret;
+            }(
+              1234
+            ))
+            ''');
+      });
+
+      test('local (full scope)', () async {
+        // Test evalution in extension methods in the future when the mapping
+        // from kernel symbols to dartdevc symbols is added.
+        //
+        // Note: this currently fails due to
+        // - incremental compiler not allowing #this as a parameter name
+        await driver.check(
+            scope: <String, String>{'ret': '1234', '#this': 'this'},
+            expression: 'ret',
+            expectedError:
+                "Illegal parameter name '#this' found during expression compilation.");
+      });
+
+      test('this (full scope)', () async {
+        // Test evalution in extension methods in the future when the mapping
+        // from kernel symbols to dartdevc symbols is added.
+        //
+        // Note: this currently fails due to
+        // - incremental compiler not allowing #this as a parameter name
+        // - incremental compiler not mapping 'this' from user input to '#this'
+        await driver.check(
+            scope: <String, String>{'ret': '1234', '#this': 'this'},
+            expression: 'this',
+            expectedError:
+                "Illegal parameter name '#this' found during expression compilation.");
+      });
     });
 
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
-          expression: 'typo',
-          expectedError: "Getter not found: \'typo\'");
-    });
-
-    test('local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
-          expression: 'x',
-          expectedResult: '''
-          (function(x, y, z) {
-            return x;
-          }(
-            1,
-            2,
-            3
-          ))
-          ''');
-    });
-
-    test('formal', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
-          expression: 'y',
-          expectedResult: '''
-          (function(x, y, z) {
-            return y;
-          }(
-            1,
-            2,
-            3
-          ))
-          ''');
-    });
-
-    test('named formal', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
-          expression: 'z',
-          expectedResult: '''
-          (function(x, y, z) {
-            return z;
-          }(
-            1,
-            2,
-            3
-          ))
-          ''');
-    });
-
-    test('function', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
-          expression: 'main',
-          expectedResult: '''
-          (function(x, y, z) {
-            var VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.fnType(dart.dynamic, [])))();
-            dart.defineLazy(CT, {
-              get C0() {
-                return C0 = dart.fn(foo.main, VoidTodynamic());
-              }
-            }, false);
-            var C0;
-            return C0 || CT.C0;
-          }(
-            1,
-            2,
-            3
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in method:', () {
-    const source = '''
-      // @dart = 2.9
-      extension NumberParsing on String {
-        int parseInt() {
-          return int.parse(this);
-        }
-      }
-
-      int global = 42;
-
-      class C {
-        C(int this.field, int this._field);
-
-        static int staticField = 0;
-        static int _staticField = 1;
-
-        int _field;
-        int field;
-
-        int methodFieldAccess(int x) {
+    group('Expression compiler tests in static function:', () {
+      var source = '''
+        ${options.dartLangComment}
+        int foo(int x, {int y}) {
+          int z = 0;
           /* evaluation placeholder */
-          return x + _field + _staticField;
+          return x + y + z;
         }
 
-        Future<int> asyncMethod(int x) async {
-          return x;
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'typo',
+            expectedError: "Getter not found: \'typo\'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x, y, z) {
+              return x;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      });
+
+      test('formal', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'y',
+            expectedResult: '''
+            (function(x, y, z) {
+              return y;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      });
+
+      test('named formal', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'z',
+            expectedResult: '''
+            (function(x, y, z) {
+              return z;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      });
+
+      test('function', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'main',
+            expectedResult: '''
+            (function(x, y, z) {
+              var VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.fnType(dart.dynamic, [])))();
+              dart.defineLazy(CT, {
+                get C0() {
+                  return C0 = dart.fn(foo.main, VoidTodynamic());
+                }
+              }, false);
+              var C0;
+              return C0 || CT.C0;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in method:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
         }
-      }
 
-      main() => 0;
-      ''';
+        int global = 42;
 
-    TestDriver driver;
+        class C {
+          C(int this.field, int this._field);
 
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
+          static int staticField = 0;
+          static int _staticField = 1;
 
-    tearDown(() {
-      driver.delete();
-    });
+          int _field;
+          int field;
 
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'typo',
-          expectedError: "The getter 'typo' isn't defined for the class 'C'");
-    });
+          int methodFieldAccess(int x) {
+            /* evaluation placeholder */
+            return x + _field + _staticField;
+          }
 
-    test('local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x',
-          expectedResult: '''
-          (function(x) {
+          Future<int> asyncMethod(int x) async {
             return x;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('this', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'this',
-          expectedResult: '''
-          (function(x) {
-            return this;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using locals', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + 1',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + 1;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using static fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + staticField',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.C.staticField);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using private static fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + _staticField',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.C._staticField);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + field',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(this.field);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using private fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + _field',
-          expectedResult: '''
-          (function(x) {
-            let _field = dart.privateName(foo, "_field");
-            return dart.notNull(x) + dart.notNull(this[_field]);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using globals', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + global',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.global);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'methodFieldAccess(2)',
-          expectedResult: '''
-          (function(x) {
-            return this.methodFieldAccess(2);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('async method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'asyncMethod(2)',
-          expectedResult: '''
-          (function(x) {
-            return this.asyncMethod(2);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('extension method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '"1234".parseInt()',
-          expectedResult: '''
-          (function(x) {
-            return foo['NumberParsing|parseInt']("1234");
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('private field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '_field = 2',
-          expectedResult: '''
-          (function(x) {
-            let _field = dart.privateName(foo, "_field");
-            return this[_field] = 2;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'field = 2',
-          expectedResult: '''
-          (function(x) {
-            return this.field = 2;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('private static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '_staticField = 2',
-          expectedResult: '''
-          (function(x) {
-            return foo.C._staticField = 2;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'staticField = 2',
-          expectedResult: '''
-          (function(x) {
-            return foo.C.staticField = 2;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in method with no field access:', () {
-    const source = '''
-      // @dart = 2.9
-      extension NumberParsing on String {
-        int parseInt() {
-          return int.parse(this);
+          }
         }
-      }
 
-      int global = 42;
+        main() => 0;
+        ''';
 
-      class C {
-        C(int this.field, int this._field);
+      TestDriver driver;
 
-        static int staticField = 0;
-        static int _staticField = 1;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
 
-        int _field;
-        int field;
+      tearDown(() {
+        driver.delete();
+      });
 
-        int methodNoFieldAccess(int x) {
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x) {
+              return x;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('this', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'this',
+            expectedResult: '''
+            (function(x) {
+              return this;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using locals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + 1',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + 1;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C.staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C._staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + field',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(this.field);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using private fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _field',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return dart.notNull(x) + dart.notNull(this[_field]);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using globals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + global',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.global);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'methodFieldAccess(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.methodFieldAccess(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('async method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'asyncMethod(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.asyncMethod(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('extension method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '"1234".parseInt()',
+            expectedResult: '''
+            (function(x) {
+              return foo['NumberParsing|parseInt']("1234");
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_field = 2',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return this[_field] = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'field = 2',
+            expectedResult: '''
+            (function(x) {
+              return this.field = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C._staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C.staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in method with no field access:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
+        }
+
+        int global = 42;
+
+        class C {
+          C(int this.field, int this._field);
+
+          static int staticField = 0;
+          static int _staticField = 1;
+
+          int _field;
+          int field;
+
+          int methodNoFieldAccess(int x) {
+            /* evaluation placeholder */
+            return x;
+          }
+
+          Future<int> asyncMethod(int x) async {
+            return x;
+          }
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('expression using static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C.staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C._staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + field',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(this.field);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using private fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _field',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return dart.notNull(x) + dart.notNull(this[_field]);
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_field = 2',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return this[_field] = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'field = 2',
+            expectedResult: '''
+            (function(x) {
+              return this.field = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C._staticField = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C.staticField = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in async method:', () {
+      var source = '''
+        ${options.dartLangComment}
+        class C {
+          C(int this.field, int this._field);
+
+          int _field;
+          int field;
+
+          Future<int> asyncMethod(int x) async {
+            /* evaluation placeholder */
+            return x;
+          }
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x) {
+              return x;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('this', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'this',
+            expectedResult: '''
+            (function(x) {
+              return this;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in global function:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
+        }
+
+        int global = 42;
+
+        class C {
+          C(int this.field, int this._field);
+
+          static int staticField = 0;
+          static int _staticField = 1;
+
+          int _field;
+          int field;
+
+          int methodFieldAccess(int x) {
+            return (x + _field + _staticField);
+          }
+          int methodFieldAccess(int x) {
+            return (x)
+          }
+
+          Future<int> asyncMethod(int x) async {
+            return x;
+          }
+        }
+
+        int main() {
+          int x = 15;
+          var c = C(1, 2);
           /* evaluation placeholder */
-          return x;
+          return 0;
         }
+        ''';
 
-        Future<int> asyncMethod(int x) async {
-          return x;
-        }
-      }
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
 
-      main() => 0;
-      ''';
+      tearDown(() {
+        driver.delete();
+      });
 
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'typo',
+            expectedError: "Getter not found: 'typo'.");
+      });
 
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'typo',
-          expectedError: "The getter 'typo' isn't defined for the class 'C'");
-    });
-
-    test('expression using static fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + staticField',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.C.staticField);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using private static fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + _staticField',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.C._staticField);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + field',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(this.field);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using private fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + _field',
-          expectedResult: '''
-          (function(x) {
-            let _field = dart.privateName(foo, "_field");
-            return dart.notNull(x) + dart.notNull(this[_field]);
-          }.bind(this)(
-          1
-          ))
-          ''');
-    });
-
-    test('private field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '_field = 2',
-          expectedResult: '''
-          (function(x) {
-            let _field = dart.privateName(foo, "_field");
-            return this[_field] = 2;
-          }.bind(this)(
-          1
-          ))
-          ''');
-    });
-
-    test('field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'field = 2',
-          expectedResult: '''
-          (function(x) {
-            return this.field = 2;
-          }.bind(this)(
-          1
-          ))
-          ''');
-    });
-
-    test('private static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '_staticField = 2',
-          expectedResult: '''
-          (function(x) {
-            return foo.C._staticField = 2;
-          }.bind(this)(
-          1
-          ))
-          ''');
-    });
-
-    test('static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'staticField = 2',
-          expectedResult: '''
-          (function(x) {
-            return foo.C.staticField = 2;
-          }.bind(this)(
-          1
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in async method:', () {
-    const source = '''
-      // @dart = 2.9
-      class C {
-        C(int this.field, int this._field);
-
-        int _field;
-        int field;
-
-        Future<int> asyncMethod(int x) async {
-          /* evaluation placeholder */
-          return x;
-        }
-      }
-
-      main() => 0;
-      ''';
-
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
-
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'typo',
-          expectedError: "The getter 'typo' isn't defined for the class 'C'");
-    });
-
-    test('local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x',
-          expectedResult: '''
-          (function(x) {
-            return x;
-          }.bind(this)(
-          1
-          ))
-          ''');
-    });
-
-    test('this', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'this',
-          expectedResult: '''
-          (function(x) {
-            return this;
-          }.bind(this)(
-          1
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in global function:', () {
-    const source = '''
-      // @dart = 2.9
-      extension NumberParsing on String {
-        int parseInt() {
-          return int.parse(this);
-        }
-      }
-
-      int global = 42;
-
-      class C {
-        C(int this.field, int this._field);
-
-        static int staticField = 0;
-        static int _staticField = 1;
-
-        int _field;
-        int field;
-
-        int methodFieldAccess(int x) {
-          return (x + _field + _staticField);
-        }
-        int methodFieldAccess(int x) {
-          return (x)
-        }
-
-        Future<int> asyncMethod(int x) async {
-          return x;
-        }
-      }
-
-      int main() {
-        int x = 15;
-        var c = C(1, 2);
-        /* evaluation placeholder */
-        return 0;
-      }
-      ''';
-
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
-
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'typo',
-          expectedError: "Getter not found: 'typo'.");
-    });
-
-    test('local with primitive type', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'x',
-          expectedResult: '''
-          (function(x, c) {
-            return x;
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('local object', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'c',
-          expectedResult: '''
-          (function(x, c) {
-            return c;
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('create new object', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'C(1,3)',
-          expectedResult: '''
+      test('local with primitive type', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'x',
+            expectedResult: '''
             (function(x, c) {
-              return new foo.C.new(1, 3);
+              return x;
             }(
               1,
               null
             ))
             ''');
-    });
+      });
 
-    test('access field of new object', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'C(1,3)._field',
-          expectedResult: '''
-          (function(x, c) {
-            let _field = dart.privateName(foo, "_field");
-            return new foo.C.new(1, 3)[_field];
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('access static field', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'C.staticField',
-          expectedResult: '''
-          (function(x, c) {
-            return foo.C.staticField;
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('expression using private static fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'C._staticField',
-          expectedError: "Error: Getter not found: '_staticField'.");
-    });
-
-    test('access field', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'c.field',
-          expectedResult: '''
-          (function(x, c) {
-            return c.field;
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('access private field', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'c._field',
-          expectedResult: '''
-          (function(x, c) {
-            let _field = dart.privateName(foo, "_field");
-            return c[_field];
-          }(
+      test('local object', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c',
+            expectedResult: '''
+            (function(x, c) {
+              return c;
+            }(
               1,
               null
-          ))
-          ''');
+            ))
+            ''');
+      });
+
+      test('create new object', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C(1,3)',
+            expectedResult: '''
+              (function(x, c) {
+                return new foo.C.new(1, 3);
+              }(
+                1,
+                null
+              ))
+              ''');
+      });
+
+      test('access field of new object', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C(1,3)._field',
+            expectedResult: '''
+            (function(x, c) {
+              let _field = dart.privateName(foo, "_field");
+              return new foo.C.new(1, 3)[_field];
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('access static field', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C.staticField',
+            expectedResult: '''
+            (function(x, c) {
+              return foo.C.staticField;
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C._staticField',
+            expectedError: "Error: Getter not found: '_staticField'.");
+      });
+
+      test('access field', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.field',
+            expectedResult: '''
+            (function(x, c) {
+              return c.field;
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('access private field', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c._field',
+            expectedResult: '''
+            (function(x, c) {
+              let _field = dart.privateName(foo, "_field");
+              return c[_field];
+            }(
+                1,
+                null
+            ))
+            ''');
+      });
+
+      test('method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.methodFieldAccess(2)',
+            expectedResult: '''
+            (function(x, c) {
+              return c.methodFieldAccess(2);
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('async method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.asyncMethod(2)',
+            expectedResult: '''
+            (function(x, c) {
+              return c.asyncMethod(2);
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('extension method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: '"1234".parseInt()',
+            expectedResult: '''
+            (function(x, c) {
+              return foo['NumberParsing|parseInt']("1234");
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c._field = 2',
+            expectedResult: '''
+            (function(x, c) {
+              let _field = dart.privateName(foo, "_field");
+              return c[_field] = 2;
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.field = 2',
+            expectedResult: '''
+            (function(x, c) {
+              return c.field = 2;
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C._staticField = 2',
+            expectedError: "Setter not found: '_staticField'.");
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C.staticField = 2',
+            expectedResult: '''
+            (function(x, c) {
+              return foo.C.staticField = 2;
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('call global function from core library', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'print(x)',
+            expectedResult: '''
+            (function(x, c) {
+              return core.print(x);
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
     });
 
-    test('method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'c.methodFieldAccess(2)',
-          expectedResult: '''
-          (function(x, c) {
-            return c.methodFieldAccess(2);
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('async method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'c.asyncMethod(2)',
-          expectedResult: '''
-          (function(x, c) {
-            return c.asyncMethod(2);
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('extension method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: '"1234".parseInt()',
-          expectedResult: '''
-          (function(x, c) {
-            return foo['NumberParsing|parseInt']("1234");
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('private field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'c._field = 2',
-          expectedResult: '''
-          (function(x, c) {
-            let _field = dart.privateName(foo, "_field");
-            return c[_field] = 2;
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'c.field = 2',
-          expectedResult: '''
-          (function(x, c) {
-            return c.field = 2;
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('private static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'C._staticField = 2',
-          expectedError: "Setter not found: '_staticField'.");
-    });
-
-    test('static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'C.staticField = 2',
-          expectedResult: '''
-          (function(x, c) {
-            return foo.C.staticField = 2;
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-
-    test('call global function from core library', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'print(x)',
-          expectedResult: '''
-          (function(x, c) {
-            return core.print(x);
-          }(
-            1,
-            null
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in closures:', () {
-    const source = r'''
-      // @dart = 2.9
-      int globalFunction() {
-      int x = 15;
-      var c = C(1, 2);
-
-      var outerClosure = (int y) {
-        var closureCaptureInner = (int z) {
-          /* evaluation placeholder */
-          print('$y+$z');
-        };
-        closureCaptureInner(0);
-      };
-
-      outerClosure(3);
-      return 0;
-    }
-
-    main() => 0;
-    ''';
-
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
-
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
-          expression: 'typo',
-          expectedError: "Getter not found: 'typo'.");
-    });
-
-    test('expression using uncaptured variables', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
-          expression: r"'$x+$y+$z'",
-          expectedResult: '''
-          (function(x, c, y, z) {
-            return dart.str(x) + "+" + dart.str(y) + "+" + dart.str(z);
-          }(
-            1,
-            null,
-            3,
-            0
-          ))
-          ''');
-    });
-
-    test('expression using captured variables', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
-          expression: r"'$y+$z'",
-          expectedResult: '''
-          (function(x, c, y, z) {
-            return dart.str(y) + "+" + dart.str(z);
-          }(
-            1,
-            null,
-            3,
-            0
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in method with no type use', () {
-    const source = '''
-      // @dart = 2.9
-      abstract class Key {
-        const factory Key(String value) = ValueKey;
-        const Key.empty();
-      }
-
-      abstract class LocalKey extends Key {
-        const LocalKey() : super.empty();
-      }
-
-      class ValueKey implements LocalKey {
-        const ValueKey(this.value);
-        final String value;
-      }
-
-      class MyClass {
-        const MyClass(this._t);
-        final int _t;
-      }
-
-      int bar(int p){
-        return p;
-      }
-      int baz(String t){
-        return t;
-      }
-      void main() {
-        var k = Key('t');
-        MyClass c = MyClass(0);
-        int p = 1;
-        const t = 1;
-
-        /* evaluation placeholder */
-        print('\$c, \$k, \$t');
-      }
-      ''';
-
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
-
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('call function using type', () async {
-      await driver.check(
-          scope: <String, String>{'p': '1'},
-          expression: 'bar(p)',
-          expectedResult: '''
-          (function(p) {
-            return foo.bar(p);
-          }(
-            1
-          ))
-          ''');
-    });
-
-    test('call function using type', () async {
-      await driver.check(
-          scope: <String, String>{'p': '0'},
-          expression: 'baz(p as String)',
-          expectedResult: '''
-          (function(p) {
-            var StringL = () => (StringL = dart.constFn(dart.legacy(core.String)))();
-            return foo.baz(StringL().as(p));
-          }(
-          0
-          ))
-          ''');
-    });
-
-    test('evaluate new const expression', () async {
-      await driver.check(
-          scope: <String, String>{'p': '1'},
-          expression: 'const MyClass(1)',
-          expectedResult: '''
-          (function(p) {
-             dart.defineLazy(CT, {
-               get C0() {
-                 return C0 = dart.const({
-                   __proto__: foo.MyClass.prototype,
-                   [_t]: 1
-                 });
-               }
-             }, false);
-             var C0;
-             return C0 || CT.C0;
-          }(
-            1
-          ))
-          ''');
-    });
-
-    test('evaluate optimized const expression', () async {
-      await driver.check(
-          scope: <String, String>{},
-          expression: 't',
-          expectedResult: '''
-          (function() {
-            return 1;
-          }(
-          ))
-          ''');
-    },
-        skip: 'Cannot compile constants optimized away by the frontend. '
-            'Issue: https://github.com/dart-lang/sdk/issues/41999');
-
-    test('evaluate factory constructor call', () async {
-      await driver.check(
-          scope: <String, String>{'p': '1'},
-          expression: "Key('t')",
-          expectedResult: '''
-          (function(p) {
-            return new foo.ValueKey.new("t");
-          }(
-            1
-          ))
-          ''');
-    });
-
-    test('evaluate const factory constructor call', () async {
-      await driver.check(
-          scope: <String, String>{'p': '1'},
-          expression: "const Key('t')",
-          expectedResult: '''
-          (function(p) {
-            dart.defineLazy(CT, {
-              get C0() {
-                return C0 = dart.const({
-                  __proto__: foo.ValueKey.prototype,
-                  [value]: "t"
-                  });
-                }
-            }, false);
-            var C0;
-            return C0 || CT.C0;
-          }(
-            1
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in constructor:', () {
-    const source = '''
-      // @dart = 2.9
-      extension NumberParsing on String {
-        int parseInt() {
-          return int.parse(this);
-        }
-      }
-
-      int global = 42;
-
-      class C {
-        C(int this.field, int this._field) {
-          int x = 1;
-          /* evaluation placeholder */
-          print(this.field);
-        }
-
-        static int staticField = 0;
-        static int _staticField = 1;
-
-        int _field;
-        int field;
-
-        int methodFieldAccess(int t) {
-          return t + _field + _staticField;
-        }
-
-        Future<int> asyncMethod(int t) async {
-          return t;
-        }
-      }
-
-      main() => 0;
-      ''';
-
-    TestDriver driver;
-
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
-
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('compilation error', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'typo',
-          expectedError: "The getter 'typo' isn't defined for the class 'C'");
-    });
-
-    test('local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x',
-          expectedResult: '''
-          (function(x) {
-            return x;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('this', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'this',
-          expectedResult: '''
-          (function(x) {
-            return this;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using locals', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + 1',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + 1;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using static fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + staticField',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.C.staticField);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using private static fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + _staticField',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.C._staticField);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + field',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(this.field);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('expression using private fields', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + _field',
-          expectedResult: '''
-          (function(x) {
-            let _field = dart.privateName(foo, "_field");
-            return dart.notNull(x) + dart.notNull(this[_field]);
-          }.bind(this)(
-              1
-          ))
-          ''');
-    });
-
-    test('expression using globals', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'x + global',
-          expectedResult: '''
-          (function(x) {
-            return dart.notNull(x) + dart.notNull(foo.global);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'methodFieldAccess(2)',
-          expectedResult: '''
-          (function(x) {
-            return this.methodFieldAccess(2);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('async method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'asyncMethod(2)',
-          expectedResult: '''
-          (function(x) {
-            return this.asyncMethod(2);
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('extension method call', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '"1234".parseInt()',
-          expectedResult: '''
-        (function(x) {
-          return foo['NumberParsing|parseInt']("1234");
-        }.bind(this)(
-          1
-        ))
-        ''');
-    });
-
-    test('private field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '_field = 2',
-          expectedResult: '''
-        (function(x) {
-          let _field = dart.privateName(foo, "_field");
-          return this[_field] = 2;
-        }.bind(this)(
-          1
-        ))
-        ''');
-    });
-
-    test('field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'field = 2',
-          expectedResult: '''
-          (function(x) {
-            return this.field = 2;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('private static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: '_staticField = 2',
-          expectedResult: '''
-          (function(x) {
-            return foo.C._staticField = 2;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-
-    test('static field modification', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1'},
-          expression: 'staticField = 2',
-          expectedResult: '''
-          (function(x) {
-            return foo.C.staticField = 2;
-          }.bind(this)(
-            1
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in loops:', () {
-    const source = r'''
-      // @dart = 2.9
-      int globalFunction() {
+    group('Expression compiler tests in closures:', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
         int x = 15;
         var c = C(1, 2);
 
-        for(int i = 0; i < 10; i++) {
-          /* evaluation placeholder */
-          print('$i+$x');
+        var outerClosure = (int y) {
+          var closureCaptureInner = (int z) {
+            /* evaluation placeholder */
+            print('\$y+\$z');
+          };
+          closureCaptureInner(0);
         };
+
+        outerClosure(3);
         return 0;
       }
 
       main() => 0;
       ''';
 
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
+            expression: 'typo',
+            expectedError: "Getter not found: 'typo'.");
+      });
+
+      test('expression using uncaptured variables', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
+            expression: r"'$x+$y+$z'",
+            expectedResult: '''
+            (function(x, c, y, z) {
+              return dart.str(x) + "+" + dart.str(y) + "+" + dart.str(z);
+            }(
+              1,
+              null,
+              3,
+              0
+            ))
+            ''');
+      });
+
+      test('expression using captured variables', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
+            expression: r"'$y+$z'",
+            expectedResult: '''
+            (function(x, c, y, z) {
+              return dart.str(y) + "+" + dart.str(z);
+            }(
+              1,
+              null,
+              3,
+              0
+            ))
+            ''');
+      });
     });
 
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('expression using local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'i': '0'},
-          expression: 'x',
-          expectedResult: '''
-          (function(x, c, i) {
-            return x;
-          }(
-            1,
-            null,
-            0
-          ))
-          ''');
-    });
-
-    test('expression using loop variable', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'i': '0'},
-          expression: 'i',
-          expectedResult: '''
-          (function(x, c, i) {
-            return i;
-          }(
-            1,
-            null,
-            0
-          ))
-          ''');
-    });
-  });
-
-  group('Expression compiler tests in conditional (then):', () {
-    const source = r'''
-      // @dart = 2.9
-      int globalFunction() {
-        int x = 1;
-        var c = C(1, 2);
-
-        if (x == 14) {
-          int y = 3;
-          /* evaluation placeholder */
-          print('$y+$x');
-        } else {
-          int z = 3;
-          print('$z+$x');
+    group('Expression compiler tests in method with no type use', () {
+      var source = '''
+        ${options.dartLangComment}
+        abstract class Key {
+          const factory Key(String value) = ValueKey;
+          const Key.empty();
         }
-        return 0;
-      }
 
-      main() => 0;
-      ''';
-
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
-
-    tearDown(() {
-      driver.delete();
-    });
-
-    test('expression using local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'y': '3'},
-          expression: 'y',
-          expectedResult: '''
-          (function(x, c, y) {
-            return y;
-          }(
-            1,
-            null,
-            3
-          ))
-          ''');
-    });
-
-    test('expression using local out of scope', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'y': '3'},
-          expression: 'z',
-          expectedError: "Error: Getter not found: 'z'");
-    });
-  });
-
-  group('Expression compiler tests in conditional (else):', () {
-    const source = r'''
-      // @dart = 2.9
-      int globalFunction() {
-        int x = 1;
-        var c = C(1, 2);
-
-        if (x == 14) {
-          int y = 3;
-          print('$y+$x');
-        } else {
-          int z = 3;
-          /* evaluation placeholder */
-          print('$z+$x');
+        abstract class LocalKey extends Key {
+          const LocalKey() : super.empty();
         }
-        return 0;
-      }
 
-      main() => 0;
-      ''';
+        class ValueKey implements LocalKey {
+          const ValueKey(this.value);
+          final String value;
+        }
 
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
+        class MyClass {
+          const MyClass(this._t);
+          final int _t;
+        }
+
+        int bar(int p){
+          return p;
+        }
+        int baz(String t){
+          return t;
+        }
+        void main() {
+          var k = Key('t');
+          MyClass c = MyClass(0);
+          int p = 1;
+          const t = 1;
+
+          /* evaluation placeholder */
+          print('\$c, \$k, \$t');
+        }
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('call function using type', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: 'bar(p)',
+            expectedResult: '''
+            (function(p) {
+              return foo.bar(p);
+            }(
+              1
+            ))
+            ''');
+      });
+
+      test('call function using type', () async {
+        await driver.check(
+            scope: <String, String>{'p': '0'},
+            expression: 'baz(p as String)',
+            expectedResult: '''
+            (function(p) {
+              var StringL = () => (StringL = dart.constFn(dart.legacy(core.String)))();
+              return foo.baz(StringL().as(p));
+            }(
+            0
+            ))
+            ''');
+      });
+
+      test('evaluate new const expression', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: 'const MyClass(1)',
+            expectedResult: '''
+            (function(p) {
+              dart.defineLazy(CT, {
+                get C0() {
+                  return C0 = dart.const({
+                    __proto__: foo.MyClass.prototype,
+                    [_t]: 1
+                  });
+                }
+              }, false);
+              var C0;
+              return C0 || CT.C0;
+            }(
+              1
+            ))
+            ''');
+      });
+
+      test('evaluate optimized const expression', () async {
+        await driver.check(
+            scope: <String, String>{},
+            expression: 't',
+            expectedResult: '''
+            (function() {
+              return 1;
+            }(
+            ))
+            ''');
+      },
+          skip: 'Cannot compile constants optimized away by the frontend. '
+              'Issue: https://github.com/dart-lang/sdk/issues/41999');
+
+      test('evaluate factory constructor call', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: "Key('t')",
+            expectedResult: '''
+            (function(p) {
+              return new foo.ValueKey.new("t");
+            }(
+              1
+            ))
+            ''');
+      });
+
+      test('evaluate const factory constructor call', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: "const Key('t')",
+            expectedResult: '''
+            (function(p) {
+              dart.defineLazy(CT, {
+                get C0() {
+                  return C0 = dart.const({
+                    __proto__: foo.ValueKey.prototype,
+                    [value]: "t"
+                    });
+                  }
+              }, false);
+              var C0;
+              return C0 || CT.C0;
+            }(
+              1
+            ))
+            ''');
+      });
     });
 
-    tearDown(() {
-      driver.delete();
-    });
+    group('Expression compiler tests in constructor:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
+        }
 
-    test('expression using local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'z': '3'},
-          expression: 'z',
-          expectedResult: '''
-          (function(x, c, z) {
-            return z;
-          }(
-            1,
-            null,
-            3
+        int global = 42;
+
+        class C {
+          C(int this.field, int this._field) {
+            int x = 1;
+            /* evaluation placeholder */
+            print(this.field);
+          }
+
+          static int staticField = 0;
+          static int _staticField = 1;
+
+          int _field;
+          int field;
+
+          int methodFieldAccess(int t) {
+            return t + _field + _staticField;
+          }
+
+          Future<int> asyncMethod(int t) async {
+            return t;
+          }
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x) {
+              return x;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('this', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'this',
+            expectedResult: '''
+            (function(x) {
+              return this;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using locals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + 1',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + 1;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C.staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C._staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + field',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(this.field);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using private fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _field',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return dart.notNull(x) + dart.notNull(this[_field]);
+            }.bind(this)(
+                1
+            ))
+            ''');
+      });
+
+      test('expression using globals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + global',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.global);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'methodFieldAccess(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.methodFieldAccess(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('async method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'asyncMethod(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.asyncMethod(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('extension method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '"1234".parseInt()',
+            expectedResult: '''
+          (function(x) {
+            return foo['NumberParsing|parseInt']("1234");
+          }.bind(this)(
+            1
           ))
           ''');
+      });
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_field = 2',
+            expectedResult: '''
+          (function(x) {
+            let _field = dart.privateName(foo, "_field");
+            return this[_field] = 2;
+          }.bind(this)(
+            1
+          ))
+          ''');
+      });
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'field = 2',
+            expectedResult: '''
+            (function(x) {
+              return this.field = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C._staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C.staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
     });
 
-    test('expression using local out of scope', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null', 'z': '3'},
-          expression: 'y',
-          expectedError: "Error: Getter not found: 'y'");
-    });
-  });
+    group('Expression compiler tests in loops:', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+          int x = 15;
+          var c = C(1, 2);
 
-  group('Expression compiler tests after conditionals:', () {
-    const source = r'''
-      // @dart = 2.9
+          for(int i = 0; i < 10; i++) {
+            /* evaluation placeholder */
+            print('\$i+\$x');
+          };
+          return 0;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'i': '0'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x, c, i) {
+              return x;
+            }(
+              1,
+              null,
+              0
+            ))
+            ''');
+      });
+
+      test('expression using loop variable', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'i': '0'},
+            expression: 'i',
+            expectedResult: '''
+            (function(x, c, i) {
+              return i;
+            }(
+              1,
+              null,
+              0
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in conditional (then):', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+          int x = 1;
+          var c = C(1, 2);
+
+          if (x == 14) {
+            int y = 3;
+            /* evaluation placeholder */
+            print('\$y+\$x');
+          } else {
+            int z = 3;
+            print('\$z+\$x');
+          }
+          return 0;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3'},
+            expression: 'y',
+            expectedResult: '''
+            (function(x, c, y) {
+              return y;
+            }(
+              1,
+              null,
+              3
+            ))
+            ''');
+      });
+
+      test('expression using local out of scope', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3'},
+            expression: 'z',
+            expectedError: "Error: Getter not found: 'z'");
+      });
+    });
+
+    group('Expression compiler tests in conditional (else):', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+          int x = 1;
+          var c = C(1, 2);
+
+          if (x == 14) {
+            int y = 3;
+            print('\$y+\$x');
+          } else {
+            int z = 3;
+            /* evaluation placeholder */
+            print('\$z+\$x');
+          }
+          return 0;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'z': '3'},
+            expression: 'z',
+            expectedResult: '''
+            (function(x, c, z) {
+              return z;
+            }(
+              1,
+              null,
+              3
+            ))
+            ''');
+      });
+
+      test('expression using local out of scope', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'z': '3'},
+            expression: 'y',
+            expectedError: "Error: Getter not found: 'y'");
+      });
+    });
+
+    group('Expression compiler tests after conditionals:', () {
+      var source = '''
+      ${options.dartLangComment}
       int globalFunction() {
         int x = 1;
         var c = C(1, 2);
 
         if (x == 14) {
           int y = 3;
-          print('$y+$x');
+          print('\$y+\$x');
         } else {
           int z = 3;
-          print('$z+$x');
+          print('\$z+\$x');
         }
         /* evaluation placeholder */
         return 0;
@@ -1846,20 +1856,20 @@
       main() => 0;
       ''';
 
-    TestDriver driver;
-    setUp(() {
-      driver = TestDriver(options, source);
-    });
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
 
-    tearDown(() {
-      driver.delete();
-    });
+      tearDown(() {
+        driver.delete();
+      });
 
-    test('expression using local', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'x',
-          expectedResult: '''
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'x',
+            expectedResult: '''
           (function(x, c) {
             return x;
           }(
@@ -1867,13 +1877,1612 @@
             null
           ))
           ''');
+      });
+
+      test('expression using local out of scope', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'z',
+            expectedError: "Error: Getter not found: 'z'");
+      });
+    });
+  });
+
+  group('Sound null safety', () {
+    var options = SetupCompilerOptions(true);
+
+    group('Expression compiler tests in extension method:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            var ret = int.parse(this);
+            /* evaluation placeholder */
+            return ret;
+          }
+        }
+        main() => 0;
+      ''';
+
+      TestDriver driver;
+
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'ret': '1234'},
+            expression: 'typo',
+            expectedError: "Error: Getter not found: 'typo'");
+      });
+
+      test('local (trimmed scope)', () async {
+        // Test that current expression evaluation works in extension methods.
+        //
+        // Note: the actual scope is {#this, ret}, but #this is effectively
+        // removed in the expression compilator because it does not exist
+        // in JavaScript code.
+        // See (full scope) tests for what will the evaluation will look like
+        // when the mapping from dart symbols to JavaScipt symbols is added.
+        await driver.check(
+            scope: <String, String>{'ret': '1234'},
+            expression: 'ret',
+            expectedResult: '''
+            (function(ret) {
+              return ret;
+            }(
+              1234
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('local (full scope)', () async {
+        // Test evalution in extension methods in the future when the mapping
+        // from kernel symbols to dartdevc symbols is added.
+        //
+        // Note: this currently fails due to
+        // - incremental compiler not allowing #this as a parameter name
+        await driver.check(
+            scope: <String, String>{'ret': '1234', '#this': 'this'},
+            expression: 'ret',
+            expectedError:
+                "Illegal parameter name '#this' found during expression compilation.");
+      });
+
+      test('this (full scope)', () async {
+        // Test evalution in extension methods in the future when the mapping
+        // from kernel symbols to dartdevc symbols is added.
+        //
+        // Note: this currently fails due to
+        // - incremental compiler not allowing #this as a parameter name
+        // - incremental compiler not mapping 'this' from user input to '#this'
+        await driver.check(
+            scope: <String, String>{'ret': '1234', '#this': 'this'},
+            expression: 'this',
+            expectedError:
+                "Illegal parameter name '#this' found during expression compilation.");
+      });
     });
 
-    test('expression using local out of scope', () async {
-      await driver.check(
-          scope: <String, String>{'x': '1', 'c': 'null'},
-          expression: 'z',
-          expectedError: "Error: Getter not found: 'z'");
+    group('Expression compiler tests in static function:', () {
+      var source = '''
+        ${options.dartLangComment}
+        int foo(int x, {int y}) {
+          int z = 0;
+          /* evaluation placeholder */
+          return x + y + z;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'typo',
+            expectedError: "Getter not found: \'typo\'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x, y, z) {
+              return x;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('formal', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'y',
+            expectedResult: '''
+            (function(x, y, z) {
+              return y;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('named formal', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'z',
+            expectedResult: '''
+            (function(x, y, z) {
+              return z;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('function', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'y': '2', 'z': '3'},
+            expression: 'main',
+            expectedResult: '''
+            (function(x, y, z) {
+              var VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.fnType(dart.dynamic, [])))();
+              dart.defineLazy(CT, {
+                get C0() {
+                  return C0 = dart.fn(foo.main, VoidTodynamic());
+                }
+              }, false);
+              var C0;
+              return C0 || CT.C0;
+            }(
+              1,
+              2,
+              3
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in method:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
+        }
+
+        int global = 42;
+
+        class C {
+          C(int this.field, int this._field);
+
+          static int staticField = 0;
+          static int _staticField = 1;
+
+          int _field;
+          int field;
+
+          int methodFieldAccess(int x) {
+            /* evaluation placeholder */
+            return x + _field + _staticField;
+          }
+
+          Future<int> asyncMethod(int x) async {
+            return x;
+          }
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x) {
+              return x;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('this', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'this',
+            expectedResult: '''
+            (function(x) {
+              return this;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using locals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + 1',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + 1;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C.staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C._staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + field',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(this.field);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using private fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _field',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return dart.notNull(x) + dart.notNull(this[_field]);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using globals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + global',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.global);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'methodFieldAccess(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.methodFieldAccess(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('async method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'asyncMethod(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.asyncMethod(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('extension method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '"1234".parseInt()',
+            expectedResult: '''
+            (function(x) {
+              return foo['NumberParsing|parseInt']("1234");
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_field = 2',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return this[_field] = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'field = 2',
+            expectedResult: '''
+            (function(x) {
+              return this.field = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C._staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C.staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in method with no field access:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
+        }
+
+        int global = 42;
+
+        class C {
+          C(int this.field, int this._field);
+
+          static int staticField = 0;
+          static int _staticField = 1;
+
+          int _field;
+          int field;
+
+          int methodNoFieldAccess(int x) {
+            /* evaluation placeholder */
+            return x;
+          }
+
+          Future<int> asyncMethod(int x) async {
+            return x;
+          }
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('expression using static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C.staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C._staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + field',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(this.field);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using private fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _field',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return dart.notNull(x) + dart.notNull(this[_field]);
+            }.bind(this)(
+            1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_field = 2',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return this[_field] = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'field = 2',
+            expectedResult: '''
+            (function(x) {
+              return this.field = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C._staticField = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C.staticField = 2;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in async method:', () {
+      var source = '''
+        ${options.dartLangComment}
+        class C {
+          C(int this.field, int this._field);
+
+          int _field;
+          int field;
+
+          Future<int> asyncMethod(int x) async {
+            /* evaluation placeholder */
+            return x;
+          }
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x) {
+              return x;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('this', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'this',
+            expectedResult: '''
+            (function(x) {
+              return this;
+            }.bind(this)(
+            1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in global function:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
+        }
+
+        int global = 42;
+
+        class C {
+          C(int this.field, int this._field);
+
+          static int staticField = 0;
+          static int _staticField = 1;
+
+          int _field;
+          int field;
+
+          int methodFieldAccess(int x) {
+            return (x + _field + _staticField);
+          }
+          int methodFieldAccess(int x) {
+            return (x)
+          }
+
+          Future<int> asyncMethod(int x) async {
+            return x;
+          }
+        }
+
+        int main() {
+          int x = 15;
+          var c = C(1, 2);
+          /* evaluation placeholder */
+          return 0;
+        }
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'typo',
+            expectedError: "Getter not found: 'typo'.");
+      });
+
+      test('local with primitive type', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x, c) {
+              return x;
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('local object', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c',
+            expectedResult: '''
+            (function(x, c) {
+              return c;
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('create new object', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C(1,3)',
+            expectedResult: '''
+              (function(x, c) {
+                return new foo.C.new(1, 3);
+              }(
+                1,
+                null
+              ))
+              ''');
+      });
+
+      test('access field of new object', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C(1,3)._field',
+            expectedResult: '''
+            (function(x, c) {
+              let _field = dart.privateName(foo, "_field");
+              return new foo.C.new(1, 3)[_field];
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('access static field', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C.staticField',
+            expectedResult: '''
+            (function(x, c) {
+              return foo.C.staticField;
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C._staticField',
+            expectedError: "Error: Getter not found: '_staticField'.");
+      });
+
+      test('access field', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.field',
+            expectedResult: '''
+            (function(x, c) {
+              return c.field;
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('access private field', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c._field',
+            expectedResult: '''
+            (function(x, c) {
+              let _field = dart.privateName(foo, "_field");
+              return c[_field];
+            }(
+                1,
+                null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.methodFieldAccess(2)',
+            expectedResult: '''
+            (function(x, c) {
+              return c.methodFieldAccess(2);
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('async method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.asyncMethod(2)',
+            expectedResult: '''
+            (function(x, c) {
+              return c.asyncMethod(2);
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('extension method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: '"1234".parseInt()',
+            expectedResult: '''
+            (function(x, c) {
+              return foo['NumberParsing|parseInt']("1234");
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c._field = 2',
+            expectedResult: '''
+            (function(x, c) {
+              let _field = dart.privateName(foo, "_field");
+              return c[_field] = 2;
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'c.field = 2',
+            expectedResult: '''
+            (function(x, c) {
+              return c.field = 2;
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C._staticField = 2',
+            expectedError: "Setter not found: '_staticField'.");
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'C.staticField = 2',
+            expectedResult: '''
+            (function(x, c) {
+              return foo.C.staticField = 2;
+            }(
+              1,
+              null
+            ))
+            ''');
+      });
+
+      test('call global function from core library', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'print(x)',
+            expectedResult: '''
+            (function(x, c) {
+              return core.print(x);
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+    });
+
+    group('Expression compiler tests in closures:', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+        int x = 15;
+        var c = C(1, 2);
+
+        var outerClosure = (int y) {
+          var closureCaptureInner = (int z) {
+            /* evaluation placeholder */
+            print('\$y+\$z');
+          };
+          closureCaptureInner(0);
+        };
+
+        outerClosure(3);
+        return 0;
+      }
+
+      main() => 0;
+      ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
+            expression: 'typo',
+            expectedError: "Getter not found: 'typo'.");
+      });
+
+      test('expression using uncaptured variables', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
+            expression: r"'$x+$y+$z'",
+            expectedResult: '''
+            (function(x, c, y, z) {
+              return dart.str(x) + "+" + dart.str(y) + "+" + dart.str(z);
+            }(
+              1,
+              null,
+              3,
+              0
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using captured variables', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3', 'z': '0'},
+            expression: r"'$y+$z'",
+            expectedResult: '''
+            (function(x, c, y, z) {
+              return dart.str(y) + "+" + dart.str(z);
+            }(
+              1,
+              null,
+              3,
+              0
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+    });
+
+    group('Expression compiler tests in method with no type use', () {
+      var source = '''
+        ${options.dartLangComment}
+        abstract class Key {
+          const factory Key(String value) = ValueKey;
+          const Key.empty();
+        }
+
+        abstract class LocalKey extends Key {
+          const LocalKey() : super.empty();
+        }
+
+        class ValueKey implements LocalKey {
+          const ValueKey(this.value);
+          final String value;
+        }
+
+        class MyClass {
+          const MyClass(this._t);
+          final int _t;
+        }
+
+        int bar(int p){
+          return p;
+        }
+        int baz(String t){
+          return t;
+        }
+        void main() {
+          var k = Key('t');
+          MyClass c = MyClass(0);
+          int p = 1;
+          const t = 1;
+
+          /* evaluation placeholder */
+          print('\$c, \$k, \$t');
+        }
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('call function not using type', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: 'bar(p)',
+            expectedResult: '''
+            (function(p) {
+              return foo.bar(p);
+            }(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('call function using type', () async {
+        await driver.check(
+            scope: <String, String>{'p': '0'},
+            expression: 'baz(p as String)',
+            expectedResult: '''
+            (function(p) {
+              var StringL = () => (StringL = dart.constFn(dart.legacy(core.String)))();
+              return foo.baz(StringL().as(p));
+            }(
+            0
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('evaluate new const expression', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: 'const MyClass(1)',
+            expectedResult: '''
+            (function(p) {
+              dart.defineLazy(CT, {
+                get C0() {
+                  return C0 = dart.const({
+                    __proto__: foo.MyClass.prototype,
+                    [_t]: 1
+                  });
+                }
+              }, false);
+              var C0;
+              return C0 || CT.C0;
+            }(
+              1
+            ))
+            ''');
+      });
+
+      test('evaluate optimized const expression', () async {
+        await driver.check(
+            scope: <String, String>{},
+            expression: 't',
+            expectedResult: '''
+            (function() {
+              return 1;
+            }(
+            ))
+            ''');
+      },
+          skip: 'Cannot compile constants optimized away by the frontend. '
+              'Issue: https://github.com/dart-lang/sdk/issues/41999');
+
+      test('evaluate factory constructor call', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: "Key('t')",
+            expectedResult: '''
+            (function(p) {
+              return new foo.ValueKey.new("t");
+            }(
+              1
+            ))
+            ''');
+      });
+
+      test('evaluate const factory constructor call', () async {
+        await driver.check(
+            scope: <String, String>{'p': '1'},
+            expression: "const Key('t')",
+            expectedResult: '''
+            (function(p) {
+              dart.defineLazy(CT, {
+                get C0() {
+                  return C0 = dart.const({
+                    __proto__: foo.ValueKey.prototype,
+                    [value]: "t"
+                    });
+                  }
+              }, false);
+              var C0;
+              return C0 || CT.C0;
+            }(
+              1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in constructor:', () {
+      var source = '''
+        ${options.dartLangComment}
+        extension NumberParsing on String {
+          int parseInt() {
+            return int.parse(this);
+          }
+        }
+
+        int global = 42;
+
+        class C {
+          C(int this.field, int this._field) {
+            int x = 1;
+            /* evaluation placeholder */
+            print(this.field);
+          }
+
+          static int staticField = 0;
+          static int _staticField = 1;
+
+          int _field;
+          int field;
+
+          int methodFieldAccess(int t) {
+            return t + _field + _staticField;
+          }
+
+          Future<int> asyncMethod(int t) async {
+            return t;
+          }
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('compilation error', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'typo',
+            expectedError: "The getter 'typo' isn't defined for the class 'C'");
+      });
+
+      test('local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x) {
+              return x;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('this', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'this',
+            expectedResult: '''
+            (function(x) {
+              return this;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('expression using locals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + 1',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + 1;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C.staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using private static fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _staticField',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.C._staticField);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + field',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(this.field);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using private fields', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + _field',
+            expectedResult: '''
+            (function(x) {
+              let _field = dart.privateName(foo, "_field");
+              return dart.notNull(x) + dart.notNull(this[_field]);
+            }.bind(this)(
+                1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using globals', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'x + global',
+            expectedResult: '''
+            (function(x) {
+              return dart.notNull(x) + dart.notNull(foo.global);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'methodFieldAccess(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.methodFieldAccess(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('async method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'asyncMethod(2)',
+            expectedResult: '''
+            (function(x) {
+              return this.asyncMethod(2);
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('extension method call', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '"1234".parseInt()',
+            expectedResult: '''
+          (function(x) {
+            return foo['NumberParsing|parseInt']("1234");
+          }.bind(this)(
+            1
+          ))
+          ''');
+      });
+
+      test('private field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_field = 2',
+            expectedResult: '''
+          (function(x) {
+            let _field = dart.privateName(foo, "_field");
+            return this[_field] = 2;
+          }.bind(this)(
+            1
+          ))
+          ''');
+      });
+
+      test('field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'field = 2',
+            expectedResult: '''
+            (function(x) {
+              return this.field = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('private static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: '_staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C._staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+
+      test('static field modification', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1'},
+            expression: 'staticField = 2',
+            expectedResult: '''
+            (function(x) {
+              return foo.C.staticField = 2;
+            }.bind(this)(
+              1
+            ))
+            ''');
+      });
+    });
+
+    group('Expression compiler tests in loops:', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+          int x = 15;
+          var c = C(1, 2);
+
+          for(int i = 0; i < 10; i++) {
+            /* evaluation placeholder */
+            print('\$i+\$x');
+          };
+          return 0;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'i': '0'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x, c, i) {
+              return x;
+            }(
+              1,
+              null,
+              0
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using loop variable', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'i': '0'},
+            expression: 'i',
+            expectedResult: '''
+            (function(x, c, i) {
+              return i;
+            }(
+              1,
+              null,
+              0
+            ))
+            ''');
+      });
+    }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+    group('Expression compiler tests in conditional (then):', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+          int x = 1;
+          var c = C(1, 2);
+
+          if (x == 14) {
+            int y = 3;
+            /* evaluation placeholder */
+            print('\$y+\$x');
+          } else {
+            int z = 3;
+            print('\$z+\$x');
+          }
+          return 0;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3'},
+            expression: 'y',
+            expectedResult: '''
+            (function(x, c, y) {
+              return y;
+            }(
+              1,
+              null,
+              3
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using local out of scope', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'y': '3'},
+            expression: 'z',
+            expectedError: "Error: Getter not found: 'z'");
+      });
+    });
+
+    group('Expression compiler tests in conditional (else):', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+          int x = 1;
+          var c = C(1, 2);
+
+          if (x == 14) {
+            int y = 3;
+            print('\$y+\$x');
+          } else {
+            int z = 3;
+            /* evaluation placeholder */
+            print('\$z+\$x');
+          }
+          return 0;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'z': '3'},
+            expression: 'z',
+            expectedResult: '''
+            (function(x, c, z) {
+              return z;
+            }(
+              1,
+              null,
+              3
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using local out of scope', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null', 'z': '3'},
+            expression: 'y',
+            expectedError: "Error: Getter not found: 'y'");
+      });
+    });
+
+    group('Expression compiler tests after conditionals:', () {
+      var source = '''
+        ${options.dartLangComment}
+        int globalFunction() {
+          int x = 1;
+          var c = C(1, 2);
+
+          if (x == 14) {
+            int y = 3;
+            print('\$y+\$x');
+          } else {
+            int z = 3;
+            print('\$z+\$x');
+          }
+          /* evaluation placeholder */
+          return 0;
+        }
+
+        main() => 0;
+        ''';
+
+      TestDriver driver;
+      setUp(() {
+        driver = TestDriver(options, source);
+      });
+
+      tearDown(() {
+        driver.delete();
+      });
+
+      test('expression using local', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'x',
+            expectedResult: '''
+            (function(x, c) {
+              return x;
+            }(
+              1,
+              null
+            ))
+            ''');
+      }, skip: 'https://github.com/dart-lang/sdk/issues/44235');
+
+      test('expression using local out of scope', () async {
+        await driver.check(
+            scope: <String, String>{'x': '1', 'c': 'null'},
+            expression: 'z',
+            expectedError: "Error: Getter not found: 'z'");
+      });
     });
   });
 }
diff --git a/runtime/tests/vm/dart/strict_null_safety_checks_in_weak_mode_test.dart b/runtime/tests/vm/dart/strict_null_safety_checks_in_weak_mode_test.dart
new file mode 100644
index 0000000..b70a3d4
--- /dev/null
+++ b/runtime/tests/vm/dart/strict_null_safety_checks_in_weak_mode_test.dart
@@ -0,0 +1,152 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// This test verifies that with --strict_null_safety_checks runtime casts and
+// required parameters have strong mode semantics in weak mode.
+// Derived from tests/language/nnbd/subtyping/type_casts_strong_test.dart
+// and tests/language/nnbd/required_named_parameters/required_named_args_strong_test.dart.
+
+// VMOptions=--strict_null_safety_checks --optimization_counter_threshold=10 --deterministic
+// Requirements=nnbd-weak
+
+import 'package:expect/expect.dart';
+
+class C {}
+
+class W<T> {
+  @pragma('vm:never-inline')
+  asT(arg) => arg as T;
+
+  @pragma('vm:never-inline')
+  asNullableT(arg) => arg as T?;
+
+  @pragma('vm:never-inline')
+  asXT(arg) => arg as X<T>;
+
+  @pragma('vm:never-inline')
+  asNullableXT(arg) => arg as X<T>?;
+
+  @pragma('vm:never-inline')
+  asXNullableT(arg) => arg as X<T?>;
+}
+
+class X<T> {}
+
+class Y {}
+
+class Z extends Y {}
+
+testCasts() {
+  // Testing 'arg as T', T = Y
+  final wy = new W<Y>();
+  wy.asT(new Y());
+  wy.asT(new Z());
+  Expect.throwsTypeError(() {
+    wy.asT(null);
+  });
+  Expect.throwsTypeError(() {
+    wy.asT(new C());
+  });
+
+  // Testing 'arg as T?', T = Y
+  wy.asNullableT(new Y());
+  wy.asNullableT(new Z());
+  wy.asNullableT(null);
+  Expect.throwsTypeError(() {
+    wy.asNullableT(new C());
+  });
+
+  // Testing 'arg as X<T>', T = Y
+  wy.asXT(new X<Y>());
+  wy.asXT(new X<Z>());
+  Expect.throwsTypeError(() {
+    wy.asXT(null);
+  });
+  Expect.throwsTypeError(() {
+    wy.asXT(new X<dynamic>());
+  });
+  Expect.throwsTypeError(() {
+    wy.asXT(new X<Y?>());
+  });
+
+  // Testing 'arg as X<T>?', T = Y
+  wy.asNullableXT(new X<Y>());
+  wy.asNullableXT(new X<Z>());
+  wy.asNullableXT(null);
+  Expect.throwsTypeError(() {
+    wy.asNullableXT(new X<dynamic>());
+  });
+  Expect.throwsTypeError(() {
+    wy.asNullableXT(new X<Y?>());
+  });
+
+  // Testing 'arg as X<T?>', T = Y
+  wy.asXNullableT(new X<Y>());
+  wy.asXNullableT(new X<Z>());
+  wy.asXNullableT(new X<Y?>());
+  Expect.throwsTypeError(() {
+    wy.asXNullableT(null);
+  });
+  Expect.throwsTypeError(() {
+    wy.asXNullableT(new X<dynamic>());
+  });
+
+  // Testing 'arg as X<T>', T = Y?
+  final wny = new W<Y?>();
+  wny.asXT(new X<Y>());
+  wny.asXT(new X<Z>());
+  wny.asXT(new X<Y?>());
+  Expect.throwsTypeError(() {
+    wny.asXT(null);
+  });
+  Expect.throwsTypeError(() {
+    wny.asXT(new X<dynamic>());
+  });
+}
+
+func(String q0, {bool p3 = false, required int p1, required String p2}) => "";
+
+testRequiredParameters() {
+  dynamic f = func;
+
+  // Invalid: Subtype may not redeclare optional parameters as required.
+  Expect.throwsTypeError(() {
+    Function(
+      String p0, {
+      required int p1,
+      String p2,
+    }) t2 = f;
+  });
+
+  // Invalid: Subtype may not declare new required named parameters.
+  Expect.throwsTypeError(() {
+    Function(
+      String p0, {
+      required int p1,
+    }) t3 = f;
+  });
+
+  // Invalid: Invocation with explicit null required named argument.
+  Expect.throwsTypeError(() {
+    f("", p1: null, p2: null);
+  });
+  Expect.throwsTypeError(() {
+    Function.apply(f, [""], {#p1: null, #p2: null});
+  });
+
+  // Invalid: Invocation that omits a required named argument.
+  Expect.throwsNoSuchMethodError(() {
+    f("", p1: 100);
+  });
+  Expect.throwsNoSuchMethodError(() {
+    Function.apply(f, [""], {#p1: 100});
+  });
+}
+
+main() {
+  for (int i = 0; i < 20; ++i) {
+    testCasts();
+    testRequiredParameters();
+  }
+}
diff --git a/runtime/vm/compiler/backend/flow_graph_compiler.cc b/runtime/vm/compiler/backend/flow_graph_compiler.cc
index cf20201..546e56c 100644
--- a/runtime/vm/compiler/backend/flow_graph_compiler.cc
+++ b/runtime/vm/compiler/backend/flow_graph_compiler.cc
@@ -2414,7 +2414,8 @@
   // Check immediate superclass equality. If type_class is Object, then testing
   // supertype may yield a wrong result for Null in NNBD strong mode (because
   // Null also extends Object).
-  if (!type_class.IsObjectClass() || !Isolate::Current()->null_safety()) {
+  if (!type_class.IsObjectClass() ||
+      !Isolate::Current()->use_strict_null_safety_checks()) {
     // We don't use TypeTestABI::kScratchReg for the first scratch register as
     // it is not defined on IA32. Instead, we use the subtype test cache
     // register, as it is clobbered by the subtype test cache stub call anyway.
@@ -2785,7 +2786,7 @@
   if (dst_type.IsNull()) {
     __ Comment("AssertAssignable for runtime type");
     // kDstTypeReg should already contain the destination type.
-    const bool null_safety = isolate()->null_safety();
+    const bool null_safety = isolate()->use_strict_null_safety_checks();
     GenerateStubCall(token_pos,
                      StubCode::GetTypeIsTopTypeForSubtyping(null_safety),
                      PcDescriptorsLayout::kOther, locs, deopt_id);
@@ -2906,7 +2907,8 @@
 
   if (dst_type.IsObjectType()) {
     // Special case: non-nullable Object.
-    ASSERT(dst_type.IsNonNullable() && isolate()->null_safety());
+    ASSERT(dst_type.IsNonNullable() &&
+           isolate()->use_strict_null_safety_checks());
     __ CompareObject(TypeTestABI::kInstanceReg, Object::null_object());
     __ BranchIf(NOT_EQUAL, done);
     // Fall back to type testing stub in caller to throw the exception.
@@ -2928,7 +2930,8 @@
     // Special case: Instantiate the type parameter on the caller side, invoking
     // the TTS of the corresponding type parameter in the caller.
     const TypeParameter& type_param = TypeParameter::Cast(dst_type);
-    if (isolate()->null_safety() && !type_param.IsNonNullable()) {
+    if (isolate()->use_strict_null_safety_checks() &&
+        !type_param.IsNonNullable()) {
       // If the type parameter is nullable when running in strong mode, we need
       // to handle null before calling the TTS because the type parameter may be
       // instantiated with a non-nullable type, where the TTS rejects null.
diff --git a/runtime/vm/compiler/backend/flow_graph_compiler_ia32.cc b/runtime/vm/compiler/backend/flow_graph_compiler_ia32.cc
index 6b69099..2c29653 100644
--- a/runtime/vm/compiler/backend/flow_graph_compiler_ia32.cc
+++ b/runtime/vm/compiler/backend/flow_graph_compiler_ia32.cc
@@ -358,7 +358,8 @@
   if (dst_type.IsNull()) {
     __ Comment("AssertAssignable for runtime type");
     // kDstTypeReg should already contain the destination type.
-    const bool null_safety = Isolate::Current()->null_safety();
+    const bool null_safety =
+        Isolate::Current()->use_strict_null_safety_checks();
     GenerateStubCall(token_pos,
                      StubCode::GetTypeIsTopTypeForSubtyping(null_safety),
                      PcDescriptorsLayout::kOther, locs, deopt_id);
diff --git a/runtime/vm/compiler/frontend/kernel_to_il.cc b/runtime/vm/compiler/frontend/kernel_to_il.cc
index a8bde81..f7327ba 100644
--- a/runtime/vm/compiler/frontend/kernel_to_il.cc
+++ b/runtime/vm/compiler/frontend/kernel_to_il.cc
@@ -2102,7 +2102,7 @@
     Fragment set,
     Fragment not_set) {
   // Required named arguments only exist if null_safety is enabled.
-  if (!I->null_safety()) return not_set;
+  if (!I->use_strict_null_safety_checks()) return not_set;
 
   Fragment check_required;
   // First, we convert the index to be in terms of the number of optional
@@ -2277,7 +2277,7 @@
   // required named arguments.
   if (info.descriptor.NamedCount() == 0) {
     // No work to do if there are no possible required named parameters.
-    if (!I->null_safety()) {
+    if (!I->use_strict_null_safety_checks()) {
       return Fragment();
     }
     // If the below changes, we can no longer assume that flag slots existing
diff --git a/runtime/vm/compiler/frontend/prologue_builder.cc b/runtime/vm/compiler/frontend/prologue_builder.cc
index 7fd8c35..bc1808e 100644
--- a/runtime/vm/compiler/frontend/prologue_builder.cc
+++ b/runtime/vm/compiler/frontend/prologue_builder.cc
@@ -306,7 +306,8 @@
   } else {
     ASSERT(num_opt_named_params > 0);
 
-    bool null_safety = Isolate::Current()->null_safety();
+    bool check_required_params =
+        Isolate::Current()->use_strict_null_safety_checks();
     const intptr_t first_name_offset =
         compiler::target::ArgumentsDescriptor::first_named_entry_offset() -
         compiler::target::Array::data_offset();
@@ -371,8 +372,8 @@
         good += Drop();
       }
 
-      const bool required =
-          null_safety && function_.IsRequiredAt(opt_param_position[i]);
+      const bool required = check_required_params &&
+                            function_.IsRequiredAt(opt_param_position[i]);
 
       // If this function cannot be invoked dynamically and this is a required
       // named argument, then we can just add this fragment directly without
diff --git a/runtime/vm/flag_list.h b/runtime/vm/flag_list.h
index 341b4fc..022032b 100644
--- a/runtime/vm/flag_list.h
+++ b/runtime/vm/flag_list.h
@@ -109,6 +109,9 @@
   R(enable_asserts, false, bool, false, "Enable assert statements.")           \
   R(null_assertions, false, bool, false,                                       \
     "Enable null assertions for parameters.")                                  \
+  R(strict_null_safety_checks, false, bool, false,                             \
+    "Enable strict type checks for non-nullable types and required "           \
+    "parameters.")                                                             \
   P(enable_kernel_expression_compilation, bool, true,                          \
     "Compile expressions with the Kernel front-end.")                          \
   P(enable_mirrors, bool, true,                                                \
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 0034b81..9bfb94c 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -1337,6 +1337,10 @@
     isolate_flags_ = NullSafetyBit::update(null_safety, isolate_flags_);
   }
 
+  bool use_strict_null_safety_checks() const {
+    return null_safety() || FLAG_strict_null_safety_checks;
+  }
+
   bool has_attempted_stepping() const {
     return HasAttemptedSteppingBit::decode(isolate_flags_);
   }
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index c1a8c93..83e255f 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -5083,7 +5083,7 @@
   Zone* zone = thread->zone();
   Isolate* isolate = thread->isolate();
   // Nullability of left and right hand sides is verified in strong mode only.
-  const bool verified_nullability = !isolate->null_safety() ||
+  const bool verified_nullability = !isolate->use_strict_null_safety_checks() ||
                                     nullability != Nullability::kNullable ||
                                     !other.IsNonNullable();
 
@@ -7854,7 +7854,7 @@
       return false;
     }
   }
-  if (isolate->null_safety()) {
+  if (isolate->use_strict_null_safety_checks()) {
     // Verify that all required named parameters are filled.
     for (intptr_t j = num_parameters - NumOptionalNamedParameters();
          j < num_parameters; j++) {
@@ -8503,7 +8503,7 @@
       return false;
     }
   }
-  if (isolate->null_safety()) {
+  if (isolate->use_strict_null_safety_checks()) {
     // Check that for each required named parameter in this function, there's a
     // corresponding required named parameter in the other function.
     String& param_name = other_param_name;
@@ -18266,7 +18266,7 @@
   // In weak mode type casts, whether in legacy or opted-in libraries, the null
   // instance is detected and handled in inlined code and therefore cannot be
   // encountered here as a Dart null receiver.
-  ASSERT(Isolate::Current()->null_safety() || !IsNull());
+  ASSERT(Isolate::Current()->use_strict_null_safety_checks() || !IsNull());
   // In strong mode, compute NNBD_SUBTYPE(runtimeType, other).
   // In weak mode, compute LEGACY_SUBTYPE(runtimeType, other).
   return RuntimeTypeIsSubtypeOf(other, other_instantiator_type_arguments,
@@ -18317,7 +18317,7 @@
   Zone* zone = thread->zone();
 
   // In weak mode, Null is a bottom type (according to LEGACY_SUBTYPE).
-  if (!isolate->null_safety()) {
+  if (!isolate->use_strict_null_safety_checks()) {
     return true;
   }
   // "Left Null" rule: null is assignable when destination type is either
@@ -18348,7 +18348,7 @@
   Isolate* isolate = thread->isolate();
   Zone* zone = thread->zone();
   // In weak testing mode, Null type is a subtype of any type.
-  if (IsNull() && !isolate->null_safety()) {
+  if (IsNull() && !isolate->use_strict_null_safety_checks()) {
     return true;
   }
   const Class& cls = Class::Handle(zone, clazz());
@@ -18413,7 +18413,7 @@
     return false;
   }
   if (IsNull()) {
-    ASSERT(isolate->null_safety());
+    ASSERT(isolate->use_strict_null_safety_checks());
     if (instantiated_other.IsNullType()) {
       return true;
     }
@@ -19139,7 +19139,8 @@
   if (cid == kInstanceCid) {  // Object type.
     // NNBD weak mode uses LEGACY_SUBTYPE for assignability / 'as' tests,
     // and non-nullable Object is a top type according to LEGACY_SUBTYPE.
-    return !IsNonNullable() || !Isolate::Current()->null_safety();
+    return !IsNonNullable() ||
+           !Isolate::Current()->use_strict_null_safety_checks();
   }
   if (cid == kFutureOrCid) {
     // FutureOr<T> where T is a top type behaves as a top type.
@@ -19298,7 +19299,8 @@
   const bool other_is_dart_function_type = other.IsDartFunctionType();
   if (other_is_dart_function_type || other.IsFunctionType()) {
     if (IsFunctionType()) {
-      if (isolate->null_safety() && IsNullable() && other.IsNonNullable()) {
+      if (isolate->use_strict_null_safety_checks() && IsNullable() &&
+          other.IsNonNullable()) {
         return false;
       }
       if (other_is_dart_function_type) {
@@ -19707,7 +19709,7 @@
   Isolate* isolate = thread->isolate();
   Zone* zone = thread->zone();
   if (kind == TypeEquality::kInSubtypeTest) {
-    if (isolate->null_safety() &&
+    if (isolate->use_strict_null_safety_checks() &&
         this_type_nullability == Nullability::kNullable &&
         other_type_nullability == Nullability::kNonNullable) {
       return false;
@@ -20475,7 +20477,7 @@
   Nullability this_type_param_nullability = nullability();
   Nullability other_type_param_nullability = other_type_param.nullability();
   if (kind == TypeEquality::kInSubtypeTest) {
-    if (Isolate::Current()->null_safety() &&
+    if (Isolate::Current()->use_strict_null_safety_checks() &&
         (this_type_param_nullability == Nullability::kNullable) &&
         (other_type_param_nullability == Nullability::kNonNullable)) {
       return false;
diff --git a/runtime/vm/runtime_entry.cc b/runtime/vm/runtime_entry.cc
index db0d99f..e5065d0 100644
--- a/runtime/vm/runtime_entry.cc
+++ b/runtime/vm/runtime_entry.cc
@@ -808,7 +808,7 @@
 
   // These are guaranteed on the calling side.
   ASSERT(!dst_type.IsDynamicType());
-  ASSERT(!src_instance.IsNull() || isolate->null_safety());
+  ASSERT(!src_instance.IsNull() || isolate->use_strict_null_safety_checks());
 
   const bool is_instance_of = src_instance.IsAssignableTo(
       dst_type, instantiator_type_arguments, function_type_arguments);
diff --git a/runtime/vm/type_testing_stubs.cc b/runtime/vm/type_testing_stubs.cc
index f86d082..5f3d862 100644
--- a/runtime/vm/type_testing_stubs.cc
+++ b/runtime/vm/type_testing_stubs.cc
@@ -95,8 +95,9 @@
   auto isolate = Isolate::Current();
 
   if (type.IsTypeRef()) {
-    return isolate->null_safety() ? StubCode::DefaultTypeTest().raw()
-                                  : StubCode::DefaultNullableTypeTest().raw();
+    return isolate->use_strict_null_safety_checks()
+               ? StubCode::DefaultTypeTest().raw()
+               : StubCode::DefaultNullableTypeTest().raw();
   }
 
   // During bootstrapping we have no access to stubs yet, so we'll just return
@@ -281,7 +282,8 @@
     __ Bind(&continue_checking);
 
   } else if (type.IsObjectType()) {
-    ASSERT(type.IsNonNullable() && Isolate::Current()->null_safety());
+    ASSERT(type.IsNonNullable() &&
+           Isolate::Current()->use_strict_null_safety_checks());
     compiler::Label continue_checking;
     __ CompareObject(TypeTestABI::kInstanceReg, Object::null_object());
     __ BranchIf(EQUAL, &continue_checking);
@@ -493,8 +495,8 @@
     // Weak NNBD mode uses LEGACY_SUBTYPE which ignores nullability.
     // We don't need to check nullability of LHS for nullable and legacy RHS
     // ("Right Legacy", "Right Nullable" rules).
-    if (Isolate::Current()->null_safety() && !type_arg.IsNullable() &&
-        !type_arg.IsLegacy()) {
+    if (Isolate::Current()->use_strict_null_safety_checks() &&
+        !type_arg.IsNullable() && !type_arg.IsLegacy()) {
       // Nullable type is not a subtype of non-nullable type.
       // TODO(dartbug.com/40736): Allocate a register for instance type argument
       // and avoid reloading it.
diff --git a/tools/VERSION b/tools/VERSION
index 3da93db..534b836 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 12
 PATCH 0
-PRERELEASE 58
+PRERELEASE 59
 PRERELEASE_PATCH 0
\ No newline at end of file