diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
index 0755e0d715f..da02e67a268 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@@ -326,12 +326,12 @@ class KernelTarget extends TargetImplementation {
       loader.computeHierarchy();
       loader.performTopLevelInference(myClasses);
       loader.checkSupertypes(myClasses);
-      loader.checkTypes();
       loader.checkOverrides(myClasses);
       loader.checkAbstractMembers(myClasses);
       loader.addNoSuchMethodForwarders(myClasses);
       loader.checkMixins(myClasses);
       loader.buildOutlineExpressions(loader.coreTypes);
+      loader.checkTypes();
       loader.checkRedirectingFactories(myClasses);
       _updateDelayedParameterTypes();
       installAllComponentProblems(loader.allComponentProblems);
diff --git a/pkg/front_end/lib/src/fasta/source/source_class_builder.dart b/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
index dd4152e4dbf..c1cbe7d4a8a 100644
--- a/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_class_builder.dart
@@ -16,6 +16,7 @@ import 'package:kernel/type_environment.dart';
 
 import '../builder/builder.dart';
 import '../builder/class_builder.dart';
+import '../builder/constructor_builder.dart';
 import '../builder/constructor_reference_builder.dart';
 import '../builder/field_builder.dart';
 import '../builder/function_builder.dart';
@@ -582,7 +583,16 @@ class SourceClassBuilder extends ClassBuilderImpl
 
       // Check initializers.
       if (builder is FunctionBuilder &&
-          !builder.isAbstract &&
+          !(builder.isAbstract || builder.isExternal) &&
+          builder.formals != null) {
+        libraryBuilder.checkInitializersInFormals(
+            builder.formals, typeEnvironment);
+      }
+    });
+
+    constructors.local.forEach((String name, MemberBuilder builder) {
+      if (builder is ConstructorBuilder &&
+          !builder.isExternal &&
           builder.formals != null) {
         libraryBuilder.checkInitializersInFormals(
             builder.formals, typeEnvironment);
diff --git a/pkg/front_end/test/patching/data/const_constructors/patch.dart b/pkg/front_end/test/patching/data/const_constructors/patch.dart
index c2396919303..1b92dab46cb 100644
--- a/pkg/front_end/test/patching/data/const_constructors/patch.dart
+++ b/pkg/front_end/test/patching/data/const_constructors/patch.dart
@@ -16,5 +16,5 @@ class PatchedClass {
    patch
   */
   @patch
-  const PatchedClass({int field}) : _field = field;
+  const PatchedClass({int field: 0}) : _field = field;
 }
diff --git a/pkg/front_end/testcases/nnbd/issue42143.dart b/pkg/front_end/testcases/nnbd/issue42143.dart
index a711b13e8cc..03266d7e7e6 100644
--- a/pkg/front_end/testcases/nnbd/issue42143.dart
+++ b/pkg/front_end/testcases/nnbd/issue42143.dart
@@ -1,3 +1,7 @@
+// 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.
+
 import 'dart:async';
 
 void h1<T extends FutureOr<T?>?>(T? t) {}
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart b/pkg/front_end/testcases/nnbd/issue42362.dart
new file mode 100644
index 00000000000..fe7cc97b615
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart
@@ -0,0 +1,109 @@
+// 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.
+
+class A {
+  final int i;
+
+  A.constructor1([this.i]); // error
+
+  A.constructor2({this.i}); // error
+
+  A.constructor3([int i]) // error
+      : this.i = i; // ok
+
+  A.constructor4({int i}) // error
+      : this.i = i; // ok
+
+  A.constructor5([int? i]) // ok
+      : this.i = i; // error
+
+  A.constructor6({int? i}) // ok
+      : this.i = i; // error
+
+  A.constructor7({required int i}) // ok
+      : this.i = i; // ok
+
+  external A.constructor8([int i]); // ok
+
+  external A.constructor9({int i}); // ok
+
+  factory A.factory3([int i]) = A.constructor3; // ok
+
+  factory A.factory4({int i}) = A.constructor4; // ok
+
+  factory A.factory5([int? i]) = A.constructor5; // ok
+
+  factory A.factory6({int? i}) = A.constructor6; // ok
+
+  factory A.factory7({required int i}) = A.constructor7; // ok
+
+  method3([int i]) {} // error
+
+  method4({int i}) {} // error
+
+  method5([int? i]) {} // ok
+
+  method6({int? i}) {} // ok
+
+  method7({required int i}) {} // ok
+
+  external method8([int i]); // ok
+
+  external method9({int i}); // ok
+}
+
+abstract class B {
+  var i = 42;
+
+  method3([int i]); // ok
+
+  method4({int i}); // ok
+
+  method5([int? i]); // ok
+
+  method6({int? i}); // ok
+
+  method7({required int i}); // ok
+}
+
+class C implements B {
+  var i;
+
+  C.constructor1([this.i]); // error
+
+  C.constructor2({this.i}); // error
+
+  C.constructor3([int i]) : this.i = i; // error
+
+  C.constructor4({int i}) : this.i = i; // error
+
+  C.constructor5([int? i]) : this.i = i; // error
+
+  C.constructor6({int? i}) : this.i = i; // error
+
+  C.constructor7({required int i}) // ok
+      : this.i = i; // ok
+
+  factory C.factory3([int i]) = C.constructor3; // ok
+
+  factory C.factory4({int i}) = C.constructor4; // ok
+
+  factory C.factory5([int? i]) = C.constructor5; // ok
+
+  factory C.factory6({int? i}) = C.constructor6; // ok
+
+  factory C.factory7({required int i}) = C.constructor7; // ok
+
+  method3([i]) {} // error
+
+  method4({i}) {} // error
+
+  method5([i]) {} // ok
+
+  method6({i}) {} // ok
+
+  method7({required i}) {} // ok
+}
+
+void main() {}
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue42362.dart.outline.expect
new file mode 100644
index 00000000000..2911d31ea63
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart.outline.expect
@@ -0,0 +1,149 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:41:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([int i]) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:43:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({int i}) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:8:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:10:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:12:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor3([int i]) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:15:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor4({int i}) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:98:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([i]) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:100:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({i}) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:73:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:75:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:77:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor3([int i]) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:79:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor4({int i}) : this.i = i; // error
+//                       ^
+//
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  final field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::A::factory3, self::A::factory4, self::A::factory5, self::A::factory6, self::A::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i]) → self::A
+    ;
+  constructor constructor2({core::int i}) → self::A
+    ;
+  constructor constructor3([core::int i]) → self::A
+    ;
+  constructor constructor4({core::int i}) → self::A
+    ;
+  constructor constructor5([core::int? i]) → self::A
+    ;
+  constructor constructor6({core::int? i}) → self::A
+    ;
+  constructor constructor7({required core::int i}) → self::A
+    ;
+  external constructor constructor8([core::int i]) → self::A
+    ;
+  external constructor constructor9({core::int i}) → self::A
+    ;
+  static factory factory3([core::int i]) → self::A
+    let dynamic #redirecting_factory = self::A::constructor3 in invalid-expression;
+  static factory factory4({core::int i}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor4 in invalid-expression;
+  static factory factory5([core::int? i]) → self::A
+    let dynamic #redirecting_factory = self::A::constructor5 in invalid-expression;
+  static factory factory6({core::int? i}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor6 in invalid-expression;
+  static factory factory7({required core::int i}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor7 in invalid-expression;
+  method method3([core::int i]) → dynamic
+    ;
+  method method4({core::int i}) → dynamic
+    ;
+  method method5([core::int? i]) → dynamic
+    ;
+  method method6({core::int? i}) → dynamic
+    ;
+  method method7({required core::int i}) → dynamic
+    ;
+  external method method8([core::int i]) → dynamic;
+  external method method9({core::int i}) → dynamic;
+}
+abstract class B extends core::Object {
+  field core::int i;
+  synthetic constructor •() → self::B
+    ;
+  abstract method method3([core::int i]) → dynamic;
+  abstract method method4({core::int i}) → dynamic;
+  abstract method method5([core::int? i]) → dynamic;
+  abstract method method6({core::int? i}) → dynamic;
+  abstract method method7({required core::int i}) → dynamic;
+}
+class C extends core::Object implements self::B {
+  field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::C::factory3, self::C::factory4, self::C::factory5, self::C::factory6, self::C::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i]) → self::C
+    ;
+  constructor constructor2({core::int i}) → self::C
+    ;
+  constructor constructor3([core::int i]) → self::C
+    ;
+  constructor constructor4({core::int i}) → self::C
+    ;
+  constructor constructor5([core::int? i]) → self::C
+    ;
+  constructor constructor6({core::int? i}) → self::C
+    ;
+  constructor constructor7({required core::int i}) → self::C
+    ;
+  static factory factory3([core::int i]) → self::C
+    let dynamic #redirecting_factory = self::C::constructor3 in invalid-expression;
+  static factory factory4({core::int i}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor4 in invalid-expression;
+  static factory factory5([core::int? i]) → self::C
+    let dynamic #redirecting_factory = self::C::constructor5 in invalid-expression;
+  static factory factory6({core::int? i}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor6 in invalid-expression;
+  static factory factory7({required core::int i}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor7 in invalid-expression;
+  method method3([core::int i]) → dynamic
+    ;
+  method method4({core::int i}) → dynamic
+    ;
+  method method5([core::int? i]) → dynamic
+    ;
+  method method6({core::int? i}) → dynamic
+    ;
+  method method7({required core::int i}) → dynamic
+    ;
+}
+static method main() → void
+  ;
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue42362.dart.strong.expect
new file mode 100644
index 00000000000..7579211ef38
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart.strong.expect
@@ -0,0 +1,183 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:41:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([int i]) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:43:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({int i}) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:8:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:10:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:12:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor3([int i]) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:15:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor4({int i}) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:98:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([i]) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:100:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({i}) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:73:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:75:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:77:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor3([int i]) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:79:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor4({int i}) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor5([int? i]) : this.i = i; // error
+//                                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor6({int? i}) : this.i = i; // error
+//                                       ^
+//
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  final field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::A::factory3, self::A::factory4, self::A::factory5, self::A::factory6, self::A::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::A
+    : self::A::i = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::A
+    : self::A::i = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  external constructor constructor8([core::int i = #C1]) → self::A
+    : super core::Object::•()
+    ;
+  external constructor constructor9({core::int i = #C1}) → self::A
+    : super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::A
+    let dynamic #redirecting_factory = self::A::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::A
+    let dynamic #redirecting_factory = self::A::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+  external method method8([core::int i = #C1]) → dynamic;
+  external method method9({core::int i = #C1}) → dynamic;
+}
+abstract class B extends core::Object {
+  field core::int i = 42;
+  synthetic constructor •() → self::B
+    : super core::Object::•()
+    ;
+  abstract method method3([core::int i = #C1]) → dynamic;
+  abstract method method4({core::int i = #C1}) → dynamic;
+  abstract method method5([core::int? i = #C1]) → dynamic;
+  abstract method method6({core::int? i = #C1}) → dynamic;
+  abstract method method7({required core::int i = #C1}) → dynamic;
+}
+class C extends core::Object implements self::B {
+  field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::C::factory3, self::C::factory4, self::C::factory5, self::C::factory6, self::C::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::C
+    : self::C::i = let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor5([int? i]) : this.i = i; // error
+                                      ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::C
+    : self::C::i = let final<BottomType> #t4 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor6({int? i}) : this.i = i; // error
+                                      ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::C
+    let dynamic #redirecting_factory = self::C::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::C
+    let dynamic #redirecting_factory = self::C::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+}
+static method main() → void {}
+
+constants  {
+  #C1 = null
+}
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue42362.dart.strong.transformed.expect
new file mode 100644
index 00000000000..c847fd5935e
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart.strong.transformed.expect
@@ -0,0 +1,183 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:41:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([int i]) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:43:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({int i}) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:8:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:10:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:12:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor3([int i]) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:15:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor4({int i}) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:98:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([i]) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:100:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({i}) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:73:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:75:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:77:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor3([int i]) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:79:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor4({int i}) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor5([int? i]) : this.i = i; // error
+//                                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor6({int? i}) : this.i = i; // error
+//                                       ^
+//
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  final field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::A::factory3, self::A::factory4, self::A::factory5, self::A::factory6, self::A::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::A
+    : self::A::i = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in let core::int? #t2 = i in #t2.==(null) ?{core::int} #t2 as{TypeError,ForNonNullableByDefault} core::int : #t2{core::int}, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::A
+    : self::A::i = let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in let core::int? #t4 = i in #t4.==(null) ?{core::int} #t4 as{TypeError,ForNonNullableByDefault} core::int : #t4{core::int}, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  external constructor constructor8([core::int i = #C1]) → self::A
+    : super core::Object::•()
+    ;
+  external constructor constructor9({core::int i = #C1}) → self::A
+    : super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+  external method method8([core::int i = #C1]) → dynamic;
+  external method method9({core::int i = #C1}) → dynamic;
+}
+abstract class B extends core::Object {
+  field core::int i = 42;
+  synthetic constructor •() → self::B
+    : super core::Object::•()
+    ;
+  abstract method method3([core::int i = #C1]) → dynamic;
+  abstract method method4({core::int i = #C1}) → dynamic;
+  abstract method method5([core::int? i = #C1]) → dynamic;
+  abstract method method6({core::int? i = #C1}) → dynamic;
+  abstract method method7({required core::int i = #C1}) → dynamic;
+}
+class C extends core::Object implements self::B {
+  field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::C::factory3, self::C::factory4, self::C::factory5, self::C::factory6, self::C::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::C
+    : self::C::i = let final<BottomType> #t5 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor5([int? i]) : this.i = i; // error
+                                      ^" in let core::int? #t6 = i in #t6.==(null) ?{core::int} #t6 as{TypeError,ForNonNullableByDefault} core::int : #t6{core::int}, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::C
+    : self::C::i = let final<BottomType> #t7 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor6({int? i}) : this.i = i; // error
+                                      ^" in let core::int? #t8 = i in #t8.==(null) ?{core::int} #t8 as{TypeError,ForNonNullableByDefault} core::int : #t8{core::int}, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+}
+static method main() → void {}
+
+constants  {
+  #C1 = null
+}
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart.textual_outline.expect b/pkg/front_end/testcases/nnbd/issue42362.dart.textual_outline.expect
new file mode 100644
index 00000000000..7110b99e6af
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart.textual_outline.expect
@@ -0,0 +1,56 @@
+class A {
+  final int i;
+  A.constructor1([this.i]);
+  A.constructor2({this.i});
+  A.constructor3([int i]) : this.i = i;
+  A.constructor4({int i}) : this.i = i;
+  A.constructor5([int? i]) : this.i = i;
+  A.constructor6({int? i}) : this.i = i;
+  A.constructor7({required int i}) : this.i = i;
+  external A.constructor8([int i]);
+  external A.constructor9({int i});
+  factory A.factory3([int i]) = A.constructor3;
+  factory A.factory4({int i}) = A.constructor4;
+  factory A.factory5([int? i]) = A.constructor5;
+  factory A.factory6({int? i}) = A.constructor6;
+  factory A.factory7({required int i}) = A.constructor7;
+  method3([int i]) {}
+  method4({int i}) {}
+  method5([int? i]) {}
+  method6({int? i}) {}
+  method7({required int i}) {}
+  external method8([int i]);
+  external method9({int i});
+}
+
+abstract class B {
+  var i = 42;
+  method3([int i]);
+  method4({int i});
+  method5([int? i]);
+  method6({int? i});
+  method7({required int i});
+}
+
+class C implements B {
+  var i;
+  C.constructor1([this.i]);
+  C.constructor2({this.i});
+  C.constructor3([int i]) : this.i = i;
+  C.constructor4({int i}) : this.i = i;
+  C.constructor5([int? i]) : this.i = i;
+  C.constructor6({int? i}) : this.i = i;
+  C.constructor7({required int i}) : this.i = i;
+  factory C.factory3([int i]) = C.constructor3;
+  factory C.factory4({int i}) = C.constructor4;
+  factory C.factory5([int? i]) = C.constructor5;
+  factory C.factory6({int? i}) = C.constructor6;
+  factory C.factory7({required int i}) = C.constructor7;
+  method3([i]) {}
+  method4({i}) {}
+  method5([i]) {}
+  method6({i}) {}
+  method7({required i}) {}
+}
+
+void main() {}
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/nnbd/issue42362.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..294d4f9ac6a
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart.textual_outline_modelled.expect
@@ -0,0 +1,56 @@
+abstract class B {
+  method3([int i]);
+  method4({int i});
+  method5([int? i]);
+  method6({int? i});
+  method7({required int i});
+  var i = 42;
+}
+
+class A {
+  A.constructor1([this.i]);
+  A.constructor2({this.i});
+  A.constructor3([int i]) : this.i = i;
+  A.constructor4({int i}) : this.i = i;
+  A.constructor5([int? i]) : this.i = i;
+  A.constructor6({int? i}) : this.i = i;
+  A.constructor7({required int i}) : this.i = i;
+  external A.constructor8([int i]);
+  external A.constructor9({int i});
+  external method8([int i]);
+  external method9({int i});
+  factory A.factory3([int i]) = A.constructor3;
+  factory A.factory4({int i}) = A.constructor4;
+  factory A.factory5([int? i]) = A.constructor5;
+  factory A.factory6({int? i}) = A.constructor6;
+  factory A.factory7({required int i}) = A.constructor7;
+  final int i;
+  method3([int i]) {}
+  method4({int i}) {}
+  method5([int? i]) {}
+  method6({int? i}) {}
+  method7({required int i}) {}
+}
+
+class C implements B {
+  C.constructor1([this.i]);
+  C.constructor2({this.i});
+  C.constructor3([int i]) : this.i = i;
+  C.constructor4({int i}) : this.i = i;
+  C.constructor5([int? i]) : this.i = i;
+  C.constructor6({int? i}) : this.i = i;
+  C.constructor7({required int i}) : this.i = i;
+  factory C.factory3([int i]) = C.constructor3;
+  factory C.factory4({int i}) = C.constructor4;
+  factory C.factory5([int? i]) = C.constructor5;
+  factory C.factory6({int? i}) = C.constructor6;
+  factory C.factory7({required int i}) = C.constructor7;
+  method3([i]) {}
+  method4({i}) {}
+  method5([i]) {}
+  method6({i}) {}
+  method7({required i}) {}
+  var i;
+}
+
+void main() {}
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue42362.dart.weak.expect
new file mode 100644
index 00000000000..7579211ef38
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart.weak.expect
@@ -0,0 +1,183 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:41:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([int i]) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:43:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({int i}) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:8:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:10:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:12:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor3([int i]) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:15:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor4({int i}) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:98:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([i]) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:100:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({i}) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:73:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:75:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:77:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor3([int i]) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:79:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor4({int i}) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor5([int? i]) : this.i = i; // error
+//                                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor6({int? i}) : this.i = i; // error
+//                                       ^
+//
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  final field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::A::factory3, self::A::factory4, self::A::factory5, self::A::factory6, self::A::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::A
+    : self::A::i = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::A
+    : self::A::i = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  external constructor constructor8([core::int i = #C1]) → self::A
+    : super core::Object::•()
+    ;
+  external constructor constructor9({core::int i = #C1}) → self::A
+    : super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::A
+    let dynamic #redirecting_factory = self::A::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::A
+    let dynamic #redirecting_factory = self::A::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::A
+    let dynamic #redirecting_factory = self::A::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+  external method method8([core::int i = #C1]) → dynamic;
+  external method method9({core::int i = #C1}) → dynamic;
+}
+abstract class B extends core::Object {
+  field core::int i = 42;
+  synthetic constructor •() → self::B
+    : super core::Object::•()
+    ;
+  abstract method method3([core::int i = #C1]) → dynamic;
+  abstract method method4({core::int i = #C1}) → dynamic;
+  abstract method method5([core::int? i = #C1]) → dynamic;
+  abstract method method6({core::int? i = #C1}) → dynamic;
+  abstract method method7({required core::int i = #C1}) → dynamic;
+}
+class C extends core::Object implements self::B {
+  field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::C::factory3, self::C::factory4, self::C::factory5, self::C::factory6, self::C::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::C
+    : self::C::i = let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor5([int? i]) : this.i = i; // error
+                                      ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::C
+    : self::C::i = let final<BottomType> #t4 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor6({int? i}) : this.i = i; // error
+                                      ^" in i as{TypeError,ForNonNullableByDefault} core::int, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::C
+    let dynamic #redirecting_factory = self::C::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::C
+    let dynamic #redirecting_factory = self::C::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::C
+    let dynamic #redirecting_factory = self::C::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+}
+static method main() → void {}
+
+constants  {
+  #C1 = null
+}
diff --git a/pkg/front_end/testcases/nnbd/issue42362.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue42362.dart.weak.transformed.expect
new file mode 100644
index 00000000000..d5a08918c7d
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue42362.dart.weak.transformed.expect
@@ -0,0 +1,183 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:41:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([int i]) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:43:16: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({int i}) {} // error
+//                ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:8:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:10:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:12:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor3([int i]) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:15:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   A.constructor4({int i}) // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:98:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method3([i]) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:100:12: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   method4({i}) {} // error
+//            ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:73:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor1([this.i]); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:75:24: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor2({this.i}); // error
+//                        ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:77:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor3([int i]) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:79:23: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
+//   C.constructor4({int i}) : this.i = i; // error
+//                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//       : this.i = i; // error
+//                  ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor5([int? i]) : this.i = i; // error
+//                                       ^
+//
+// pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+//   C.constructor6({int? i}) : this.i = i; // error
+//                                       ^
+//
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  final field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::A::factory3, self::A::factory4, self::A::factory5, self::A::factory6, self::A::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::A
+    : self::A::i = let final<BottomType> #t1 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:19:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in i, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::A
+    : self::A::i = let final<BottomType> #t2 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:22:18: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+      : this.i = i; // error
+                 ^" in i, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::A
+    : self::A::i = i, super core::Object::•()
+    ;
+  external constructor constructor8([core::int i = #C1]) → self::A
+    : super core::Object::•()
+    ;
+  external constructor constructor9({core::int i = #C1}) → self::A
+    : super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::A
+    let<BottomType> #redirecting_factory = self::A::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+  external method method8([core::int i = #C1]) → dynamic;
+  external method method9({core::int i = #C1}) → dynamic;
+}
+abstract class B extends core::Object {
+  field core::int i = 42;
+  synthetic constructor •() → self::B
+    : super core::Object::•()
+    ;
+  abstract method method3([core::int i = #C1]) → dynamic;
+  abstract method method4({core::int i = #C1}) → dynamic;
+  abstract method method5([core::int? i = #C1]) → dynamic;
+  abstract method method6({core::int? i = #C1}) → dynamic;
+  abstract method method7({required core::int i = #C1}) → dynamic;
+}
+class C extends core::Object implements self::B {
+  field core::int i;
+  static field dynamic _redirecting# = <dynamic>[self::C::factory3, self::C::factory4, self::C::factory5, self::C::factory6, self::C::factory7]/*isNullableByDefault*/;
+  constructor constructor1([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor2({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor3([core::int i = #C1]) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor4({core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  constructor constructor5([core::int? i = #C1]) → self::C
+    : self::C::i = let final<BottomType> #t3 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:81:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor5([int? i]) : this.i = i; // error
+                                      ^" in i, super core::Object::•()
+    ;
+  constructor constructor6({core::int? i = #C1}) → self::C
+    : self::C::i = let final<BottomType> #t4 = invalid-expression "pkg/front_end/testcases/nnbd/issue42362.dart:83:39: Error: A value of type 'int?' can't be assigned to a variable of type 'int'.
+  C.constructor6({int? i}) : this.i = i; // error
+                                      ^" in i, super core::Object::•()
+    ;
+  constructor constructor7({required core::int i = #C1}) → self::C
+    : self::C::i = i, super core::Object::•()
+    ;
+  static factory factory3([core::int i = #C1]) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor3 in invalid-expression;
+  static factory factory4({core::int i = #C1}) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor4 in invalid-expression;
+  static factory factory5([core::int? i = #C1]) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor5 in invalid-expression;
+  static factory factory6({core::int? i = #C1}) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor6 in invalid-expression;
+  static factory factory7({required core::int i = #C1}) → self::C
+    let<BottomType> #redirecting_factory = self::C::constructor7 in invalid-expression;
+  method method3([core::int i = #C1]) → dynamic {}
+  method method4({core::int i = #C1}) → dynamic {}
+  method method5([core::int? i = #C1]) → dynamic {}
+  method method6({core::int? i = #C1}) → dynamic {}
+  method method7({required core::int i = #C1}) → dynamic {}
+}
+static method main() → void {}
+
+constants  {
+  #C1 = null
+}
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect
index cae508d4fa3..25d8360107c 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.outline.expect
@@ -30,10 +30,6 @@ library /*isNonNullableByDefault*/;
 //   void method([int i]) {}
 //                    ^
 //
-// pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:8:36: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
-//   external void patchedMethod([int i]);
-//                                    ^
-//
 // pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:11:18: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
 // void method([int i]) {}
 //                  ^
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect
index 9a4131e7558..0c2e5964617 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.expect
@@ -32,10 +32,6 @@ library /*isNonNullableByDefault*/;
 //   void method([int i]) {}
 //                    ^
 //
-// pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:8:36: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
-//   external void patchedMethod([int i]);
-//                                    ^
-//
 // pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:11:18: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
 // void method([int i]) {}
 //                  ^
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect
index 9a4131e7558..0c2e5964617 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.strong.transformed.expect
@@ -32,10 +32,6 @@ library /*isNonNullableByDefault*/;
 //   void method([int i]) {}
 //                    ^
 //
-// pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:8:36: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
-//   external void patchedMethod([int i]);
-//                                    ^
-//
 // pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:11:18: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
 // void method([int i]) {}
 //                  ^
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect
index 9a4131e7558..0c2e5964617 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.expect
@@ -32,10 +32,6 @@ library /*isNonNullableByDefault*/;
 //   void method([int i]) {}
 //                    ^
 //
-// pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:8:36: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
-//   external void patchedMethod([int i]);
-//                                    ^
-//
 // pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:11:18: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
 // void method([int i]) {}
 //                  ^
diff --git a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect
index 9a4131e7558..0c2e5964617 100644
--- a/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/platform_optional_parameters/main.dart.weak.transformed.expect
@@ -32,10 +32,6 @@ library /*isNonNullableByDefault*/;
 //   void method([int i]) {}
 //                    ^
 //
-// pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:8:36: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
-//   external void patchedMethod([int i]);
-//                                    ^
-//
 // pkg/front_end/testcases/nnbd/platform_optional_parameters/origin_lib.dart:11:18: Error: Optional parameter 'i' should have a default value because its type 'int' doesn't allow null.
 // void method([int i]) {}
 //                  ^
diff --git a/runtime/tests/vm/dart/regress_flutter_57398_test.dart b/runtime/tests/vm/dart/regress_flutter_57398_test.dart
index a2a93abb78d..c98d96c900b 100644
--- a/runtime/tests/vm/dart/regress_flutter_57398_test.dart
+++ b/runtime/tests/vm/dart/regress_flutter_57398_test.dart
@@ -9,7 +9,7 @@ import 'dart:async';
 import 'package:expect/expect.dart';
 
 class W<T> {
-  final FutureOr<T> v;
+  final FutureOr<T>? v;
   W({this.v});
 
   @pragma('vm:never-inline')
diff --git a/sdk/lib/js/_js_annotations.dart b/sdk/lib/js/_js_annotations.dart
index 8c8148d01c6..b28e7b75929 100644
--- a/sdk/lib/js/_js_annotations.dart
+++ b/sdk/lib/js/_js_annotations.dart
@@ -8,7 +8,7 @@
 library _js_annotations;
 
 class JS {
-  final String name;
+  final String? name;
   const JS([this.name]);
 }
 
diff --git a/tests/dart2js/async_stacktrace_test.dart b/tests/dart2js/async_stacktrace_test.dart
index 708706b96ed..fffb9466d1d 100644
--- a/tests/dart2js/async_stacktrace_test.dart
+++ b/tests/dart2js/async_stacktrace_test.dart
@@ -9,7 +9,7 @@ import "package:async_helper/async_helper.dart";
 
 class Tracer {
   final String expected;
-  final String name;
+  final String? name;
   String _trace = "";
 
   Tracer(this.expected, [this.name]);
diff --git a/tests/dart2js/recursive_metadata_test.dart b/tests/dart2js/recursive_metadata_test.dart
index 1c46209626d..c857bc358a2 100644
--- a/tests/dart2js/recursive_metadata_test.dart
+++ b/tests/dart2js/recursive_metadata_test.dart
@@ -8,7 +8,7 @@ import 'package:expect/expect.dart';
 // to other annotated types.
 
 class Annotation {
-  final String value;
+  final String? value;
   const Annotation({this.value});
 }
 
@@ -18,9 +18,9 @@ enum Enum {
 }
 
 class SubAnno extends Annotation {
-  final Enum e;
-  final Type type;
-  const SubAnno({String value, this.e, this.type}) : super(value: value);
+  final Enum? e;
+  final Type? type;
+  const SubAnno({String? value, this.e, this.type}) : super(value: value);
 }
 
 @SubAnno(value: 'super')