From ced5b4e25d32159a7fb609e56831219b472d8f75 Mon Sep 17 00:00:00 2001
From: Johnni Winther <johnniwinther@google.com>
Date: Fri, 17 Nov 2023 14:06:50 +0000
Subject: [PATCH] [cfe] Ensure nullable result type for ??= for effect

Closes #54069

Change-Id: I4caaad1b86f9ef68f1d36d7b2f9afc92364ce83c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/336662
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>
---
 .../type_inference/inference_visitor.dart     |  2 +-
 .../test/spell_checking_list_tests.txt        |  1 +
 .../testcases/dart2wasm/issue54069.dart       | 22 +++++++++++
 .../dart2wasm/issue54069.dart.strong.expect   | 26 +++++++++++++
 .../issue54069.dart.strong.transformed.expect | 37 +++++++++++++++++++
 .../issue54069.dart.textual_outline.expect    |  6 +++
 ...54069.dart.textual_outline_modelled.expect |  6 +++
 .../extensions/null_aware2.dart.strong.expect |  4 +-
 ...null_aware2.dart.strong.transformed.expect |  4 +-
 .../extensions/null_aware2.dart.weak.expect   |  4 +-
 .../null_aware2.dart.weak.modular.expect      |  4 +-
 .../null_aware2.dart.weak.transformed.expect  |  4 +-
 .../testcases/general/if_null_assign.dart     |  8 ++++
 .../general/if_null_assign.dart.strong.expect |  8 ++++
 ...null_assign.dart.strong.transformed.expect |  8 ++++
 ...if_null_assign.dart.textual_outline.expect |  1 +
 ...ssign.dart.textual_outline_modelled.expect |  1 +
 .../general/if_null_assign.dart.weak.expect   |  8 ++++
 .../if_null_assign.dart.weak.modular.expect   |  8 ++++
 .../if_null_assign.dart.weak.outline.expect   |  6 +++
 ...f_null_assign.dart.weak.transformed.expect |  8 ++++
 .../invalid_assignment.dart.strong.expect     |  4 +-
 ..._assignment.dart.strong.transformed.expect |  4 +-
 .../invalid_assignment.dart.weak.expect       |  4 +-
 ...nvalid_assignment.dart.weak.modular.expect |  4 +-
 ...id_assignment.dart.weak.transformed.expect |  4 +-
 .../general/null_aware2.dart.strong.expect    |  4 +-
 ...null_aware2.dart.strong.transformed.expect |  4 +-
 .../general/null_aware2.dart.weak.expect      |  4 +-
 .../null_aware2.dart.weak.modular.expect      |  4 +-
 .../null_aware2.dart.weak.transformed.expect  |  4 +-
 .../no_outline_change_22.yaml.world.1.expect  |  4 +-
 .../no_outline_change_22.yaml.world.2.expect  |  4 +-
 ...ull_aware_static_access.dart.strong.expect |  2 +-
 ...atic_access.dart.strong.transformed.expect |  2 +-
 .../null_aware_static_access.dart.weak.expect |  2 +-
 ...are_static_access.dart.weak.modular.expect |  2 +-
 ...static_access.dart.weak.transformed.expect |  2 +-
 .../null_aware_this_access.dart.strong.expect |  2 +-
 ...this_access.dart.strong.transformed.expect |  2 +-
 .../null_aware_this_access.dart.weak.expect   |  2 +-
 ...aware_this_access.dart.weak.modular.expect |  2 +-
 ...e_this_access.dart.weak.transformed.expect |  2 +-
 ...y_non_nullable_warnings.dart.strong.expect |  2 +-
 ...le_warnings.dart.strong.transformed.expect |  2 +-
 ...tly_non_nullable_warnings.dart.weak.expect |  2 +-
 ...nullable_warnings.dart.weak.modular.expect |  2 +-
 ...able_warnings.dart.weak.transformed.expect |  2 +-
 .../unsound_checks.dart.weak.expect           |  2 +-
 .../unsound_checks.dart.weak.modular.expect   |  2 +-
 ...nsound_checks.dart.weak.transformed.expect |  2 +-
 ...che_lookups.dart.strong.transformed.expect |  4 +-
 ...cache_lookups.dart.weak.transformed.expect |  4 +-
 ...g_constants.dart.strong.transformed.expect |  4 +-
 ...ing_constants.dart.weak.transformed.expect |  4 +-
 ...lement_once.dart.strong.transformed.expect |  4 +-
 ..._element_once.dart.weak.transformed.expect |  4 +-
 ...tive_length.dart.strong.transformed.expect |  4 +-
 ...gative_length.dart.weak.transformed.expect |  4 +-
 .../rasta/issue_000081.dart.strong.expect     |  2 +-
 ...ssue_000081.dart.strong.transformed.expect |  2 +-
 .../rasta/issue_000081.dart.weak.expect       |  2 +-
 .../issue_000081.dart.weak.modular.expect     |  2 +-
 .../issue_000081.dart.weak.transformed.expect |  2 +-
 .../testcases/rasta/static.dart.strong.expect |  2 +-
 .../static.dart.strong.transformed.expect     |  2 +-
 .../testcases/rasta/static.dart.weak.expect   |  2 +-
 .../rasta/static.dart.weak.modular.expect     |  2 +-
 .../rasta/static.dart.weak.transformed.expect |  2 +-
 .../testcases/rasta/super.dart.strong.expect  |  2 +-
 .../super.dart.strong.transformed.expect      |  2 +-
 .../testcases/rasta/super.dart.weak.expect    |  2 +-
 .../rasta/super.dart.weak.modular.expect      |  2 +-
 .../rasta/super.dart.weak.transformed.expect  |  2 +-
 74 files changed, 238 insertions(+), 84 deletions(-)
 create mode 100644 pkg/front_end/testcases/dart2wasm/issue54069.dart
 create mode 100644 pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.expect
 create mode 100644 pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.transformed.expect
 create mode 100644 pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline.expect
 create mode 100644 pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline_modelled.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.strong.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.strong.transformed.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.textual_outline.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.textual_outline_modelled.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.weak.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.weak.modular.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.weak.outline.expect
 create mode 100644 pkg/front_end/testcases/general/if_null_assign.dart.weak.transformed.expect

diff --git a/pkg/front_end/lib/src/fasta/type_inference/inference_visitor.dart b/pkg/front_end/lib/src/fasta/type_inference/inference_visitor.dart
index bc7432df2fb..d21febf63db 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/inference_visitor.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/inference_visitor.dart
@@ -5234,7 +5234,7 @@ class InferenceVisitorImpl extends InferenceVisitorBase
           equalsNull,
           writeResult.expression,
           new NullLiteral()..fileOffset = node.fileOffset,
-          inferredType)
+          computeNullable(inferredType))
         ..fileOffset = node.fileOffset;
     } else {
       // Encode `a ??= b` as:
diff --git a/pkg/front_end/test/spell_checking_list_tests.txt b/pkg/front_end/test/spell_checking_list_tests.txt
index 55d0542bcfc..e4ea2b77980 100644
--- a/pkg/front_end/test/spell_checking_list_tests.txt
+++ b/pkg/front_end/test/spell_checking_list_tests.txt
@@ -553,6 +553,7 @@ party
 pause
 paused
 pays
+pb
 pc
 periodic
 periodically
diff --git a/pkg/front_end/testcases/dart2wasm/issue54069.dart b/pkg/front_end/testcases/dart2wasm/issue54069.dart
new file mode 100644
index 00000000000..a0b03298f4f
--- /dev/null
+++ b/pkg/front_end/testcases/dart2wasm/issue54069.dart
@@ -0,0 +1,22 @@
+// Copyright (c) 2023, 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:typed_data';
+
+Future<Uint8List> getBinaryTestProto() => readFileWeb("test.binary.pb");
+
+Future<Uint8List> readFileWeb(String path) async {
+  throw '';
+}
+
+void runBench([Uint8List? data]) async {
+  data ??= await getBinaryTestProto();
+  print(data);
+}
+
+void main() async {
+  Uint8List data = await getBinaryTestProto();
+  print("File successfully read, contents: $data");
+  runBench(data);
+}
diff --git a/pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.expect b/pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.expect
new file mode 100644
index 00000000000..c940b009a60
--- /dev/null
+++ b/pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.expect
@@ -0,0 +1,26 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:typed_data" as typ;
+import "dart:core" as core;
+
+import "dart:typed_data";
+
+static method getBinaryTestProto() → asy::Future<typ::Uint8List>
+  return self::readFileWeb("test.binary.pb");
+static method readFileWeb(core::String path) → asy::Future<typ::Uint8List> async /* futureValueType= typ::Uint8List */ {
+  throw "";
+}
+static method runBench([typ::Uint8List? data = #C1]) → void async /* futureValueType= void */ {
+  data == null ?{typ::Uint8List?} data = await self::getBinaryTestProto() : null;
+  core::print(data{typ::Uint8List});
+}
+static method main() → void async /* futureValueType= void */ {
+  typ::Uint8List data = await self::getBinaryTestProto();
+  core::print("File successfully read, contents: ${data}");
+  self::runBench(data);
+}
+
+constants  {
+  #C1 = null
+}
diff --git a/pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.transformed.expect b/pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.transformed.expect
new file mode 100644
index 00000000000..4595cee3a5a
--- /dev/null
+++ b/pkg/front_end/testcases/dart2wasm/issue54069.dart.strong.transformed.expect
@@ -0,0 +1,37 @@
+library;
+import self as self;
+import "dart:async" as asy;
+import "dart:typed_data" as typ;
+import "dart:core" as core;
+
+import "dart:typed_data";
+
+static method getBinaryTestProto() → asy::Future<typ::Uint8List>
+  return self::readFileWeb("test.binary.pb");
+static method readFileWeb(core::String path) → asy::Future<typ::Uint8List> async /* futureValueType= typ::Uint8List */ {
+  throw "";
+}
+static method runBench([typ::Uint8List? data = #C1]) → void async /* futureValueType= void */ {
+  typ::Uint8List :async_temporary_0;
+  typ::Uint8List? :async_temporary_1;
+  if(data == null) {
+    :async_temporary_0 = await self::getBinaryTestProto();
+    :async_temporary_1 = data = :async_temporary_0 as{ForLegacy} dynamic;
+  }
+  else {
+    :async_temporary_1 = null;
+  }
+  :async_temporary_1 as{ForLegacy} dynamic;
+  core::print(data{typ::Uint8List});
+}
+static method main() → void async /* futureValueType= void */ {
+  typ::Uint8List :async_temporary_0;
+  :async_temporary_0 = await self::getBinaryTestProto();
+  typ::Uint8List data = :async_temporary_0 as{ForLegacy} dynamic;
+  core::print("File successfully read, contents: ${data}");
+  self::runBench(data);
+}
+
+constants  {
+  #C1 = null
+}
diff --git a/pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline.expect b/pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline.expect
new file mode 100644
index 00000000000..e30902200e3
--- /dev/null
+++ b/pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline.expect
@@ -0,0 +1,6 @@
+import 'dart:typed_data';
+
+Future<Uint8List> getBinaryTestProto() => readFileWeb("test.binary.pb");
+Future<Uint8List> readFileWeb(String path) async {}
+void runBench([Uint8List? data]) async {}
+void main() async {}
diff --git a/pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..f05c5506c65
--- /dev/null
+++ b/pkg/front_end/testcases/dart2wasm/issue54069.dart.textual_outline_modelled.expect
@@ -0,0 +1,6 @@
+import 'dart:typed_data';
+
+Future<Uint8List> getBinaryTestProto() => readFileWeb("test.binary.pb");
+Future<Uint8List> readFileWeb(String path) async {}
+void main() async {}
+void runBench([Uint8List? data]) async {}
diff --git a/pkg/front_end/testcases/extensions/null_aware2.dart.strong.expect b/pkg/front_end/testcases/extensions/null_aware2.dart.strong.expect
index d9098f93601..ac2f7122414 100644
--- a/pkg/front_end/testcases/extensions/null_aware2.dart.strong.expect
+++ b/pkg/front_end/testcases/extensions/null_aware2.dart.strong.expect
@@ -67,9 +67,9 @@ static method test2(self::Class? c) → dynamic {
   self::expect(42, let final self::Class? #t52 = c in #t52 == null ?{core::int?} null : let final core::int? #t53 = self::Extension|get#property(#t52{self::Class}) in #t53 == null ?{core::int} let final core::int #t54 = 87 in let final void #t55 = self::Extension|set#property(#t52{self::Class}, #t54) in #t54 : #t53{core::int});
   let final self::Class? #t56 = c in #t56 == null ?{void} null : self::Extension|set#property(#t56{self::Class}, null);
   self::expect(null, let final self::Class? #t57 = c in #t57 == null ?{core::int?} null : self::Extension|get#property(#t57{self::Class}));
-  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int} self::Extension|set#property(#t58{self::Class}, 42) : null;
+  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int?} self::Extension|set#property(#t58{self::Class}, 42) : null;
   self::expect(42, let final self::Class? #t59 = c in #t59 == null ?{core::int?} null : self::Extension|get#property(#t59{self::Class}));
-  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int} self::Extension|set#property(#t60{self::Class}, 87) : null;
+  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int?} self::Extension|set#property(#t60{self::Class}, 87) : null;
   self::expect(42, let final self::Class? #t61 = c in #t61 == null ?{core::int?} null : self::Extension|get#property(#t61{self::Class}));
   let final self::Class? #t62 = c in #t62 == null ?{void} null : self::Extension|set#property(#t62{self::Class}, null);
   let final self::Class? #t63 = c in #t63 == null ?{dynamic} null : self::Extension|testImplicitThis(#t63{self::Class});
diff --git a/pkg/front_end/testcases/extensions/null_aware2.dart.strong.transformed.expect b/pkg/front_end/testcases/extensions/null_aware2.dart.strong.transformed.expect
index 890da8e4b2c..72a75b66d6f 100644
--- a/pkg/front_end/testcases/extensions/null_aware2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/extensions/null_aware2.dart.strong.transformed.expect
@@ -67,9 +67,9 @@ static method test2(self::Class? c) → dynamic {
   self::expect(42, let final self::Class? #t52 = c in #t52 == null ?{core::int?} null : let final core::int? #t53 = self::Extension|get#property(#t52{self::Class}) in #t53 == null ?{core::int} let final core::int #t54 = 87 in let final void #t55 = self::Extension|set#property(#t52{self::Class}, #t54) in #t54 : #t53{core::int});
   let final self::Class? #t56 = c in #t56 == null ?{void} null : self::Extension|set#property(#t56{self::Class}, null);
   self::expect(null, let final self::Class? #t57 = c in #t57 == null ?{core::int?} null : self::Extension|get#property(#t57{self::Class}));
-  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int} self::Extension|set#property(#t58{self::Class}, 42) : null;
+  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int?} self::Extension|set#property(#t58{self::Class}, 42) : null;
   self::expect(42, let final self::Class? #t59 = c in #t59 == null ?{core::int?} null : self::Extension|get#property(#t59{self::Class}));
-  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int} self::Extension|set#property(#t60{self::Class}, 87) : null;
+  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int?} self::Extension|set#property(#t60{self::Class}, 87) : null;
   self::expect(42, let final self::Class? #t61 = c in #t61 == null ?{core::int?} null : self::Extension|get#property(#t61{self::Class}));
   let final self::Class? #t62 = c in #t62 == null ?{void} null : self::Extension|set#property(#t62{self::Class}, null);
   let final self::Class? #t63 = c in #t63 == null ?{dynamic} null : self::Extension|testImplicitThis(#t63{self::Class});
diff --git a/pkg/front_end/testcases/extensions/null_aware2.dart.weak.expect b/pkg/front_end/testcases/extensions/null_aware2.dart.weak.expect
index d9098f93601..ac2f7122414 100644
--- a/pkg/front_end/testcases/extensions/null_aware2.dart.weak.expect
+++ b/pkg/front_end/testcases/extensions/null_aware2.dart.weak.expect
@@ -67,9 +67,9 @@ static method test2(self::Class? c) → dynamic {
   self::expect(42, let final self::Class? #t52 = c in #t52 == null ?{core::int?} null : let final core::int? #t53 = self::Extension|get#property(#t52{self::Class}) in #t53 == null ?{core::int} let final core::int #t54 = 87 in let final void #t55 = self::Extension|set#property(#t52{self::Class}, #t54) in #t54 : #t53{core::int});
   let final self::Class? #t56 = c in #t56 == null ?{void} null : self::Extension|set#property(#t56{self::Class}, null);
   self::expect(null, let final self::Class? #t57 = c in #t57 == null ?{core::int?} null : self::Extension|get#property(#t57{self::Class}));
-  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int} self::Extension|set#property(#t58{self::Class}, 42) : null;
+  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int?} self::Extension|set#property(#t58{self::Class}, 42) : null;
   self::expect(42, let final self::Class? #t59 = c in #t59 == null ?{core::int?} null : self::Extension|get#property(#t59{self::Class}));
-  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int} self::Extension|set#property(#t60{self::Class}, 87) : null;
+  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int?} self::Extension|set#property(#t60{self::Class}, 87) : null;
   self::expect(42, let final self::Class? #t61 = c in #t61 == null ?{core::int?} null : self::Extension|get#property(#t61{self::Class}));
   let final self::Class? #t62 = c in #t62 == null ?{void} null : self::Extension|set#property(#t62{self::Class}, null);
   let final self::Class? #t63 = c in #t63 == null ?{dynamic} null : self::Extension|testImplicitThis(#t63{self::Class});
diff --git a/pkg/front_end/testcases/extensions/null_aware2.dart.weak.modular.expect b/pkg/front_end/testcases/extensions/null_aware2.dart.weak.modular.expect
index d9098f93601..ac2f7122414 100644
--- a/pkg/front_end/testcases/extensions/null_aware2.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/extensions/null_aware2.dart.weak.modular.expect
@@ -67,9 +67,9 @@ static method test2(self::Class? c) → dynamic {
   self::expect(42, let final self::Class? #t52 = c in #t52 == null ?{core::int?} null : let final core::int? #t53 = self::Extension|get#property(#t52{self::Class}) in #t53 == null ?{core::int} let final core::int #t54 = 87 in let final void #t55 = self::Extension|set#property(#t52{self::Class}, #t54) in #t54 : #t53{core::int});
   let final self::Class? #t56 = c in #t56 == null ?{void} null : self::Extension|set#property(#t56{self::Class}, null);
   self::expect(null, let final self::Class? #t57 = c in #t57 == null ?{core::int?} null : self::Extension|get#property(#t57{self::Class}));
-  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int} self::Extension|set#property(#t58{self::Class}, 42) : null;
+  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int?} self::Extension|set#property(#t58{self::Class}, 42) : null;
   self::expect(42, let final self::Class? #t59 = c in #t59 == null ?{core::int?} null : self::Extension|get#property(#t59{self::Class}));
-  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int} self::Extension|set#property(#t60{self::Class}, 87) : null;
+  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int?} self::Extension|set#property(#t60{self::Class}, 87) : null;
   self::expect(42, let final self::Class? #t61 = c in #t61 == null ?{core::int?} null : self::Extension|get#property(#t61{self::Class}));
   let final self::Class? #t62 = c in #t62 == null ?{void} null : self::Extension|set#property(#t62{self::Class}, null);
   let final self::Class? #t63 = c in #t63 == null ?{dynamic} null : self::Extension|testImplicitThis(#t63{self::Class});
diff --git a/pkg/front_end/testcases/extensions/null_aware2.dart.weak.transformed.expect b/pkg/front_end/testcases/extensions/null_aware2.dart.weak.transformed.expect
index 890da8e4b2c..72a75b66d6f 100644
--- a/pkg/front_end/testcases/extensions/null_aware2.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/extensions/null_aware2.dart.weak.transformed.expect
@@ -67,9 +67,9 @@ static method test2(self::Class? c) → dynamic {
   self::expect(42, let final self::Class? #t52 = c in #t52 == null ?{core::int?} null : let final core::int? #t53 = self::Extension|get#property(#t52{self::Class}) in #t53 == null ?{core::int} let final core::int #t54 = 87 in let final void #t55 = self::Extension|set#property(#t52{self::Class}, #t54) in #t54 : #t53{core::int});
   let final self::Class? #t56 = c in #t56 == null ?{void} null : self::Extension|set#property(#t56{self::Class}, null);
   self::expect(null, let final self::Class? #t57 = c in #t57 == null ?{core::int?} null : self::Extension|get#property(#t57{self::Class}));
-  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int} self::Extension|set#property(#t58{self::Class}, 42) : null;
+  let final self::Class? #t58 = c in #t58 == null ?{core::int?} null : self::Extension|get#property(#t58{self::Class}) == null ?{core::int?} self::Extension|set#property(#t58{self::Class}, 42) : null;
   self::expect(42, let final self::Class? #t59 = c in #t59 == null ?{core::int?} null : self::Extension|get#property(#t59{self::Class}));
-  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int} self::Extension|set#property(#t60{self::Class}, 87) : null;
+  let final self::Class? #t60 = c in #t60 == null ?{core::int?} null : self::Extension|get#property(#t60{self::Class}) == null ?{core::int?} self::Extension|set#property(#t60{self::Class}, 87) : null;
   self::expect(42, let final self::Class? #t61 = c in #t61 == null ?{core::int?} null : self::Extension|get#property(#t61{self::Class}));
   let final self::Class? #t62 = c in #t62 == null ?{void} null : self::Extension|set#property(#t62{self::Class}, null);
   let final self::Class? #t63 = c in #t63 == null ?{dynamic} null : self::Extension|testImplicitThis(#t63{self::Class});
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart b/pkg/front_end/testcases/general/if_null_assign.dart
new file mode 100644
index 00000000000..29f16e7fc98
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart
@@ -0,0 +1,8 @@
+// Copyright (c) 2023, 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.
+
+method(int? a, int? b) {
+  int j = a ??= 0;
+  b ??= 0;
+}
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.strong.expect b/pkg/front_end/testcases/general/if_null_assign.dart.strong.expect
new file mode 100644
index 00000000000..3f6267c10f9
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.strong.expect
@@ -0,0 +1,8 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+static method method(core::int? a, core::int? b) → dynamic {
+  core::int j = let final core::int? #t1 = a in #t1 == null ?{core::int} a = 0 : #t1{core::int};
+  b == null ?{core::int?} b = 0 : null;
+}
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.strong.transformed.expect b/pkg/front_end/testcases/general/if_null_assign.dart.strong.transformed.expect
new file mode 100644
index 00000000000..3f6267c10f9
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.strong.transformed.expect
@@ -0,0 +1,8 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+static method method(core::int? a, core::int? b) → dynamic {
+  core::int j = let final core::int? #t1 = a in #t1 == null ?{core::int} a = 0 : #t1{core::int};
+  b == null ?{core::int?} b = 0 : null;
+}
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.textual_outline.expect b/pkg/front_end/testcases/general/if_null_assign.dart.textual_outline.expect
new file mode 100644
index 00000000000..146656cde69
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.textual_outline.expect
@@ -0,0 +1 @@
+method(int? a, int? b) {}
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/general/if_null_assign.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..146656cde69
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.textual_outline_modelled.expect
@@ -0,0 +1 @@
+method(int? a, int? b) {}
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.weak.expect b/pkg/front_end/testcases/general/if_null_assign.dart.weak.expect
new file mode 100644
index 00000000000..3f6267c10f9
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.weak.expect
@@ -0,0 +1,8 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+static method method(core::int? a, core::int? b) → dynamic {
+  core::int j = let final core::int? #t1 = a in #t1 == null ?{core::int} a = 0 : #t1{core::int};
+  b == null ?{core::int?} b = 0 : null;
+}
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.weak.modular.expect b/pkg/front_end/testcases/general/if_null_assign.dart.weak.modular.expect
new file mode 100644
index 00000000000..3f6267c10f9
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.weak.modular.expect
@@ -0,0 +1,8 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+static method method(core::int? a, core::int? b) → dynamic {
+  core::int j = let final core::int? #t1 = a in #t1 == null ?{core::int} a = 0 : #t1{core::int};
+  b == null ?{core::int?} b = 0 : null;
+}
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.weak.outline.expect b/pkg/front_end/testcases/general/if_null_assign.dart.weak.outline.expect
new file mode 100644
index 00000000000..db8ef269bc4
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.weak.outline.expect
@@ -0,0 +1,6 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+static method method(core::int? a, core::int? b) → dynamic
+  ;
diff --git a/pkg/front_end/testcases/general/if_null_assign.dart.weak.transformed.expect b/pkg/front_end/testcases/general/if_null_assign.dart.weak.transformed.expect
new file mode 100644
index 00000000000..3f6267c10f9
--- /dev/null
+++ b/pkg/front_end/testcases/general/if_null_assign.dart.weak.transformed.expect
@@ -0,0 +1,8 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+static method method(core::int? a, core::int? b) → dynamic {
+  core::int j = let final core::int? #t1 = a in #t1 == null ?{core::int} a = 0 : #t1{core::int};
+  b == null ?{core::int?} b = 0 : null;
+}
diff --git a/pkg/front_end/testcases/general/invalid_assignment.dart.strong.expect b/pkg/front_end/testcases/general/invalid_assignment.dart.strong.expect
index 652272751a0..4de6f866da1 100644
--- a/pkg/front_end/testcases/general/invalid_assignment.dart.strong.expect
+++ b/pkg/front_end/testcases/general/invalid_assignment.dart.strong.expect
@@ -31,9 +31,9 @@ static method test(core::int? i, core::String s, self::A a) → dynamic {
   i = s;
       ^" in s as{TypeError} core::int?;
   i = null;
-  i == null ?{core::int} i = 1 : null;
+  i == null ?{core::int?} i = 1 : null;
   i = null;
-  i == null ?{core::Object} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
+  i == null ?{core::Object?} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
   i ??= s;
         ^" in s as{TypeError} core::int? : null;
   a = new self::A::•();
diff --git a/pkg/front_end/testcases/general/invalid_assignment.dart.strong.transformed.expect b/pkg/front_end/testcases/general/invalid_assignment.dart.strong.transformed.expect
index 652272751a0..4de6f866da1 100644
--- a/pkg/front_end/testcases/general/invalid_assignment.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/invalid_assignment.dart.strong.transformed.expect
@@ -31,9 +31,9 @@ static method test(core::int? i, core::String s, self::A a) → dynamic {
   i = s;
       ^" in s as{TypeError} core::int?;
   i = null;
-  i == null ?{core::int} i = 1 : null;
+  i == null ?{core::int?} i = 1 : null;
   i = null;
-  i == null ?{core::Object} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
+  i == null ?{core::Object?} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
   i ??= s;
         ^" in s as{TypeError} core::int? : null;
   a = new self::A::•();
diff --git a/pkg/front_end/testcases/general/invalid_assignment.dart.weak.expect b/pkg/front_end/testcases/general/invalid_assignment.dart.weak.expect
index 652272751a0..4de6f866da1 100644
--- a/pkg/front_end/testcases/general/invalid_assignment.dart.weak.expect
+++ b/pkg/front_end/testcases/general/invalid_assignment.dart.weak.expect
@@ -31,9 +31,9 @@ static method test(core::int? i, core::String s, self::A a) → dynamic {
   i = s;
       ^" in s as{TypeError} core::int?;
   i = null;
-  i == null ?{core::int} i = 1 : null;
+  i == null ?{core::int?} i = 1 : null;
   i = null;
-  i == null ?{core::Object} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
+  i == null ?{core::Object?} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
   i ??= s;
         ^" in s as{TypeError} core::int? : null;
   a = new self::A::•();
diff --git a/pkg/front_end/testcases/general/invalid_assignment.dart.weak.modular.expect b/pkg/front_end/testcases/general/invalid_assignment.dart.weak.modular.expect
index 652272751a0..4de6f866da1 100644
--- a/pkg/front_end/testcases/general/invalid_assignment.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/general/invalid_assignment.dart.weak.modular.expect
@@ -31,9 +31,9 @@ static method test(core::int? i, core::String s, self::A a) → dynamic {
   i = s;
       ^" in s as{TypeError} core::int?;
   i = null;
-  i == null ?{core::int} i = 1 : null;
+  i == null ?{core::int?} i = 1 : null;
   i = null;
-  i == null ?{core::Object} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
+  i == null ?{core::Object?} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
   i ??= s;
         ^" in s as{TypeError} core::int? : null;
   a = new self::A::•();
diff --git a/pkg/front_end/testcases/general/invalid_assignment.dart.weak.transformed.expect b/pkg/front_end/testcases/general/invalid_assignment.dart.weak.transformed.expect
index 652272751a0..4de6f866da1 100644
--- a/pkg/front_end/testcases/general/invalid_assignment.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general/invalid_assignment.dart.weak.transformed.expect
@@ -31,9 +31,9 @@ static method test(core::int? i, core::String s, self::A a) → dynamic {
   i = s;
       ^" in s as{TypeError} core::int?;
   i = null;
-  i == null ?{core::int} i = 1 : null;
+  i == null ?{core::int?} i = 1 : null;
   i = null;
-  i == null ?{core::Object} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
+  i == null ?{core::Object?} i = invalid-expression "pkg/front_end/testcases/general/invalid_assignment.dart:15:9: Error: A value of type 'String' can't be assigned to a variable of type 'int?'.
   i ??= s;
         ^" in s as{TypeError} core::int? : null;
   a = new self::A::•();
diff --git a/pkg/front_end/testcases/general/null_aware2.dart.strong.expect b/pkg/front_end/testcases/general/null_aware2.dart.strong.expect
index 6d47503b796..0cc2d3b2c2e 100644
--- a/pkg/front_end/testcases/general/null_aware2.dart.strong.expect
+++ b/pkg/front_end/testcases/general/null_aware2.dart.strong.expect
@@ -65,9 +65,9 @@ static method test() → dynamic {
   let final self::Foo #t1 = foo in #t1 == null ?{core::int?} null : #t1.{self::Foo::field} = 5;
   self::Foo::staticField = 5;
   let final self::Foo #t2 = foo in #t2.{self::Foo::field}{core::int} == null ?{core::int} #t2.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   let final self::Foo #t3 = foo in #t3 == null ?{core::int?} null : #t3.{self::Foo::field}{core::int} == null ?{core::int} #t3.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   core::int intValue = let final core::int #t4 = foo.{self::Foo::field}{core::int} in #t4 == null ?{core::int} 6 : #t4;
   core::num numValue = let final core::int #t5 = foo.{self::Foo::field}{core::int} in #t5 == null ?{core::num} 4.5 : #t5;
 }
diff --git a/pkg/front_end/testcases/general/null_aware2.dart.strong.transformed.expect b/pkg/front_end/testcases/general/null_aware2.dart.strong.transformed.expect
index 6d47503b796..0cc2d3b2c2e 100644
--- a/pkg/front_end/testcases/general/null_aware2.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/null_aware2.dart.strong.transformed.expect
@@ -65,9 +65,9 @@ static method test() → dynamic {
   let final self::Foo #t1 = foo in #t1 == null ?{core::int?} null : #t1.{self::Foo::field} = 5;
   self::Foo::staticField = 5;
   let final self::Foo #t2 = foo in #t2.{self::Foo::field}{core::int} == null ?{core::int} #t2.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   let final self::Foo #t3 = foo in #t3 == null ?{core::int?} null : #t3.{self::Foo::field}{core::int} == null ?{core::int} #t3.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   core::int intValue = let final core::int #t4 = foo.{self::Foo::field}{core::int} in #t4 == null ?{core::int} 6 : #t4;
   core::num numValue = let final core::int #t5 = foo.{self::Foo::field}{core::int} in #t5 == null ?{core::num} 4.5 : #t5;
 }
diff --git a/pkg/front_end/testcases/general/null_aware2.dart.weak.expect b/pkg/front_end/testcases/general/null_aware2.dart.weak.expect
index 6d47503b796..0cc2d3b2c2e 100644
--- a/pkg/front_end/testcases/general/null_aware2.dart.weak.expect
+++ b/pkg/front_end/testcases/general/null_aware2.dart.weak.expect
@@ -65,9 +65,9 @@ static method test() → dynamic {
   let final self::Foo #t1 = foo in #t1 == null ?{core::int?} null : #t1.{self::Foo::field} = 5;
   self::Foo::staticField = 5;
   let final self::Foo #t2 = foo in #t2.{self::Foo::field}{core::int} == null ?{core::int} #t2.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   let final self::Foo #t3 = foo in #t3 == null ?{core::int?} null : #t3.{self::Foo::field}{core::int} == null ?{core::int} #t3.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   core::int intValue = let final core::int #t4 = foo.{self::Foo::field}{core::int} in #t4 == null ?{core::int} 6 : #t4;
   core::num numValue = let final core::int #t5 = foo.{self::Foo::field}{core::int} in #t5 == null ?{core::num} 4.5 : #t5;
 }
diff --git a/pkg/front_end/testcases/general/null_aware2.dart.weak.modular.expect b/pkg/front_end/testcases/general/null_aware2.dart.weak.modular.expect
index 6d47503b796..0cc2d3b2c2e 100644
--- a/pkg/front_end/testcases/general/null_aware2.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/general/null_aware2.dart.weak.modular.expect
@@ -65,9 +65,9 @@ static method test() → dynamic {
   let final self::Foo #t1 = foo in #t1 == null ?{core::int?} null : #t1.{self::Foo::field} = 5;
   self::Foo::staticField = 5;
   let final self::Foo #t2 = foo in #t2.{self::Foo::field}{core::int} == null ?{core::int} #t2.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   let final self::Foo #t3 = foo in #t3 == null ?{core::int?} null : #t3.{self::Foo::field}{core::int} == null ?{core::int} #t3.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   core::int intValue = let final core::int #t4 = foo.{self::Foo::field}{core::int} in #t4 == null ?{core::int} 6 : #t4;
   core::num numValue = let final core::int #t5 = foo.{self::Foo::field}{core::int} in #t5 == null ?{core::num} 4.5 : #t5;
 }
diff --git a/pkg/front_end/testcases/general/null_aware2.dart.weak.transformed.expect b/pkg/front_end/testcases/general/null_aware2.dart.weak.transformed.expect
index 6d47503b796..0cc2d3b2c2e 100644
--- a/pkg/front_end/testcases/general/null_aware2.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general/null_aware2.dart.weak.transformed.expect
@@ -65,9 +65,9 @@ static method test() → dynamic {
   let final self::Foo #t1 = foo in #t1 == null ?{core::int?} null : #t1.{self::Foo::field} = 5;
   self::Foo::staticField = 5;
   let final self::Foo #t2 = foo in #t2.{self::Foo::field}{core::int} == null ?{core::int} #t2.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   let final self::Foo #t3 = foo in #t3 == null ?{core::int?} null : #t3.{self::Foo::field}{core::int} == null ?{core::int} #t3.{self::Foo::field} = 5 : null;
-  self::Foo::staticField == null ?{core::int} self::Foo::staticField = 5 : null;
+  self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 5 : null;
   core::int intValue = let final core::int #t4 = foo.{self::Foo::field}{core::int} in #t4 == null ?{core::int} 6 : #t4;
   core::num numValue = let final core::int #t5 = foo.{self::Foo::field}{core::int} in #t5 == null ?{core::num} 4.5 : #t5;
 }
diff --git a/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.1.expect b/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.1.expect
index 4dc35a3e635..6fe4b64bc11 100644
--- a/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.1.expect
+++ b/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.1.expect
@@ -283,7 +283,7 @@ library from "org-dartlang-test:///main.dart" as main {
       dart._internal::Sort::sort<dart.core::int>(this, let final (dart.core::int, dart.core::int) →? dart.core::int #t4 = compare in #t4 == null ?{(dart.core::int, dart.core::int) → dart.core::int} #C6 : #t4{(dart.core::int, dart.core::int) → dart.core::int});
     }
     method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([dart.math::Random? random = #C2]) → void {
-      random == null ?{dart.math::Random} random = dart.math::Random::•() : null;
+      random == null ?{dart.math::Random?} random = dart.math::Random::•() : null;
       dart.core::int length = this.{dart.core::List::length}{dart.core::int};
       while (length.{dart.core::num::>}(1){(dart.core::num) → dart.core::bool}) {
         dart.core::int pos = random{dart.math::Random}.{dart.math::Random::nextInt}(length){(dart.core::int) → dart.core::int};
@@ -303,7 +303,7 @@ library from "org-dartlang-test:///main.dart" as main {
       } =>#t5;
     method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(dart.core::int start, [dart.core::int? end = #C2]) → dart.core::List<dart.core::int> {
       dart.core::int listLength = this.{dart.core::List::length}{dart.core::int};
-      end == null ?{dart.core::int} end = listLength : null;
+      end == null ?{dart.core::int?} end = listLength : null;
       dart.core::RangeError::checkValidRange(start, end{dart.core::int}, listLength);
       return dart.core::List::from<dart.core::int>(this.{dart.collection::ListBase::getRange}(start, end{dart.core::int}){(dart.core::int, dart.core::int) → dart.core::Iterable<dart.core::int>});
     }
diff --git a/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.2.expect b/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.2.expect
index 4dc35a3e635..6fe4b64bc11 100644
--- a/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.2.expect
+++ b/pkg/front_end/testcases/incremental/no_outline_change_22.yaml.world.2.expect
@@ -283,7 +283,7 @@ library from "org-dartlang-test:///main.dart" as main {
       dart._internal::Sort::sort<dart.core::int>(this, let final (dart.core::int, dart.core::int) →? dart.core::int #t4 = compare in #t4 == null ?{(dart.core::int, dart.core::int) → dart.core::int} #C6 : #t4{(dart.core::int, dart.core::int) → dart.core::int});
     }
     method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([dart.math::Random? random = #C2]) → void {
-      random == null ?{dart.math::Random} random = dart.math::Random::•() : null;
+      random == null ?{dart.math::Random?} random = dart.math::Random::•() : null;
       dart.core::int length = this.{dart.core::List::length}{dart.core::int};
       while (length.{dart.core::num::>}(1){(dart.core::num) → dart.core::bool}) {
         dart.core::int pos = random{dart.math::Random}.{dart.math::Random::nextInt}(length){(dart.core::int) → dart.core::int};
@@ -303,7 +303,7 @@ library from "org-dartlang-test:///main.dart" as main {
       } =>#t5;
     method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(dart.core::int start, [dart.core::int? end = #C2]) → dart.core::List<dart.core::int> {
       dart.core::int listLength = this.{dart.core::List::length}{dart.core::int};
-      end == null ?{dart.core::int} end = listLength : null;
+      end == null ?{dart.core::int?} end = listLength : null;
       dart.core::RangeError::checkValidRange(start, end{dart.core::int}, listLength);
       return dart.core::List::from<dart.core::int>(this.{dart.collection::ListBase::getRange}(start, end{dart.core::int}){(dart.core::int, dart.core::int) → dart.core::Iterable<dart.core::int>});
     }
diff --git a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.expect
index 78331865baf..8dabc51d324 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.expect
@@ -91,7 +91,7 @@ static method main() → void {
   self::C::property.{core::List::[]}(0){(core::int) → core::int};
   self::C::property.{core::List::[]=}(0, 0){(core::int, core::int) → void};
   let final core::Map<core::int, core::int?> #t1 = self::C::property2 in let final core::int #t2 = 0 in #t1.{core::Map::[]}(#t2){(core::Object?) → core::int?} == null ?{core::int} #t1.{core::Map::[]=}(#t2, 0){(core::int, core::int?) → void} : null;
-  self::C::staticMember2 == null ?{core::int} self::C::staticMember2 = 42 : null;
+  self::C::staticMember2 == null ?{core::int?} self::C::staticMember2 = 42 : null;
   self::C::staticMember = self::C::staticMember.{core::num::+}(2){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::+}(1){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.transformed.expect
index 192a07a2530..c3f26ad8135 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.strong.transformed.expect
@@ -91,7 +91,7 @@ static method main() → void {
   self::C::property.{core::List::[]}(0){(core::int) → core::int};
   self::C::property.{core::List::[]=}(0, 0){(core::int, core::int) → void};
   let final core::Map<core::int, core::int?> #t1 = self::C::property2 in let final core::int #t2 = 0 in #t1.{core::Map::[]}(#t2){(core::Object?) → core::int?} == null ?{core::int} #t1.{core::Map::[]=}(#t2, 0){(core::int, core::int?) → void} : null;
-  self::C::staticMember2 == null ?{core::int} self::C::staticMember2 = 42 : null;
+  self::C::staticMember2 == null ?{core::int?} self::C::staticMember2 = 42 : null;
   self::C::staticMember = self::C::staticMember.{core::num::+}(2){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::+}(1){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.expect
index 78331865baf..8dabc51d324 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.expect
@@ -91,7 +91,7 @@ static method main() → void {
   self::C::property.{core::List::[]}(0){(core::int) → core::int};
   self::C::property.{core::List::[]=}(0, 0){(core::int, core::int) → void};
   let final core::Map<core::int, core::int?> #t1 = self::C::property2 in let final core::int #t2 = 0 in #t1.{core::Map::[]}(#t2){(core::Object?) → core::int?} == null ?{core::int} #t1.{core::Map::[]=}(#t2, 0){(core::int, core::int?) → void} : null;
-  self::C::staticMember2 == null ?{core::int} self::C::staticMember2 = 42 : null;
+  self::C::staticMember2 == null ?{core::int?} self::C::staticMember2 = 42 : null;
   self::C::staticMember = self::C::staticMember.{core::num::+}(2){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::+}(1){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.modular.expect b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.modular.expect
index 78331865baf..8dabc51d324 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.modular.expect
@@ -91,7 +91,7 @@ static method main() → void {
   self::C::property.{core::List::[]}(0){(core::int) → core::int};
   self::C::property.{core::List::[]=}(0, 0){(core::int, core::int) → void};
   let final core::Map<core::int, core::int?> #t1 = self::C::property2 in let final core::int #t2 = 0 in #t1.{core::Map::[]}(#t2){(core::Object?) → core::int?} == null ?{core::int} #t1.{core::Map::[]=}(#t2, 0){(core::int, core::int?) → void} : null;
-  self::C::staticMember2 == null ?{core::int} self::C::staticMember2 = 42 : null;
+  self::C::staticMember2 == null ?{core::int?} self::C::staticMember2 = 42 : null;
   self::C::staticMember = self::C::staticMember.{core::num::+}(2){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::+}(1){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.transformed.expect
index 192a07a2530..c3f26ad8135 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_static_access.dart.weak.transformed.expect
@@ -91,7 +91,7 @@ static method main() → void {
   self::C::property.{core::List::[]}(0){(core::int) → core::int};
   self::C::property.{core::List::[]=}(0, 0){(core::int, core::int) → void};
   let final core::Map<core::int, core::int?> #t1 = self::C::property2 in let final core::int #t2 = 0 in #t1.{core::Map::[]}(#t2){(core::Object?) → core::int?} == null ?{core::int} #t1.{core::Map::[]=}(#t2, 0){(core::int, core::int?) → void} : null;
-  self::C::staticMember2 == null ?{core::int} self::C::staticMember2 = 42 : null;
+  self::C::staticMember2 == null ?{core::int?} self::C::staticMember2 = 42 : null;
   self::C::staticMember = self::C::staticMember.{core::num::+}(2){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::+}(1){(core::num) → core::int};
   self::C::staticMember = self::C::staticMember.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.expect
index c28a40a5743..c68216bc198 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.expect
@@ -135,7 +135,7 @@ class C extends core::Object {
     this.{self::C::property}{self::C}.{self::C::[]}(0){(core::int) → core::int?};
     this.{self::C::property}{self::C}.{self::C::[]=}(0, 0){(core::int, core::int) → void};
     let final self::C #t2 = this.{self::C::property}{self::C} in let final core::int #t3 = 0 in #t2.{self::C::[]}(#t3){(core::int) → core::int?} == null ?{core::int} #t2.{self::C::[]=}(#t3, 0){(core::int, core::int) → void} : null;
-    this.{self::C::m1}{core::int?} == null ?{core::int} this.{self::C::m1} = 42 : null;
+    this.{self::C::m1}{core::int?} == null ?{core::int?} this.{self::C::m1} = 42 : null;
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(2){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(1){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.transformed.expect
index dfe3be0ae9d..06ed08232a5 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.strong.transformed.expect
@@ -135,7 +135,7 @@ class C extends core::Object {
     this.{self::C::property}{self::C}.{self::C::[]}(0){(core::int) → core::int?};
     this.{self::C::property}{self::C}.{self::C::[]=}(0, 0){(core::int, core::int) → void};
     let final self::C #t2 = this.{self::C::property}{self::C} in let final core::int #t3 = 0 in #t2.{self::C::[]}(#t3){(core::int) → core::int?} == null ?{core::int} #t2.{self::C::[]=}(#t3, 0){(core::int, core::int) → void} : null;
-    this.{self::C::m1}{core::int?} == null ?{core::int} this.{self::C::m1} = 42 : null;
+    this.{self::C::m1}{core::int?} == null ?{core::int?} this.{self::C::m1} = 42 : null;
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(2){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(1){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.expect b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.expect
index c28a40a5743..c68216bc198 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.expect
@@ -135,7 +135,7 @@ class C extends core::Object {
     this.{self::C::property}{self::C}.{self::C::[]}(0){(core::int) → core::int?};
     this.{self::C::property}{self::C}.{self::C::[]=}(0, 0){(core::int, core::int) → void};
     let final self::C #t2 = this.{self::C::property}{self::C} in let final core::int #t3 = 0 in #t2.{self::C::[]}(#t3){(core::int) → core::int?} == null ?{core::int} #t2.{self::C::[]=}(#t3, 0){(core::int, core::int) → void} : null;
-    this.{self::C::m1}{core::int?} == null ?{core::int} this.{self::C::m1} = 42 : null;
+    this.{self::C::m1}{core::int?} == null ?{core::int?} this.{self::C::m1} = 42 : null;
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(2){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(1){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.modular.expect b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.modular.expect
index c28a40a5743..c68216bc198 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.modular.expect
@@ -135,7 +135,7 @@ class C extends core::Object {
     this.{self::C::property}{self::C}.{self::C::[]}(0){(core::int) → core::int?};
     this.{self::C::property}{self::C}.{self::C::[]=}(0, 0){(core::int, core::int) → void};
     let final self::C #t2 = this.{self::C::property}{self::C} in let final core::int #t3 = 0 in #t2.{self::C::[]}(#t3){(core::int) → core::int?} == null ?{core::int} #t2.{self::C::[]=}(#t3, 0){(core::int, core::int) → void} : null;
-    this.{self::C::m1}{core::int?} == null ?{core::int} this.{self::C::m1} = 42 : null;
+    this.{self::C::m1}{core::int?} == null ?{core::int?} this.{self::C::m1} = 42 : null;
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(2){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(1){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.transformed.expect
index dfe3be0ae9d..06ed08232a5 100644
--- a/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/null_aware_this_access.dart.weak.transformed.expect
@@ -135,7 +135,7 @@ class C extends core::Object {
     this.{self::C::property}{self::C}.{self::C::[]}(0){(core::int) → core::int?};
     this.{self::C::property}{self::C}.{self::C::[]=}(0, 0){(core::int, core::int) → void};
     let final self::C #t2 = this.{self::C::property}{self::C} in let final core::int #t3 = 0 in #t2.{self::C::[]}(#t3){(core::int) → core::int?} == null ?{core::int} #t2.{self::C::[]=}(#t3, 0){(core::int, core::int) → void} : null;
-    this.{self::C::m1}{core::int?} == null ?{core::int} this.{self::C::m1} = 42 : null;
+    this.{self::C::m1}{core::int?} == null ?{core::int?} this.{self::C::m1} = 42 : null;
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(2){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::+}(1){(core::num) → core::int};
     this.{self::C::m2} = this.{self::C::m2}{core::int}.{core::num::-}(1){(core::num) → core::int};
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect
index c90185409e2..1eae8d381ed 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.expect
@@ -136,7 +136,7 @@ static method warning(core::String s, core::List<core::String> l, core::Map<core
     #t3.{core::String::length}{core::int};
   } =>#t3;
   let final core::String #t4 = s in #t4 == null ?{core::String} "foo" : #t4;
-  s == null ?{core::String} s = "foo" : null;
+  s == null ?{core::String?} s = "foo" : null;
   {
     final core::List<core::String> #t5 = <core::String>[];
     final core::Iterable<core::String>? #t6 = l;
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect
index 2bd174e8650..7c66b7472a6 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.strong.transformed.expect
@@ -136,7 +136,7 @@ static method warning(core::String s, core::List<core::String> l, core::Map<core
     #t3.{core::String::length}{core::int};
   } =>#t3;
   let final core::String #t4 = s in #t4 == null ?{core::String} "foo" : #t4;
-  s == null ?{core::String} s = "foo" : null;
+  s == null ?{core::String?} s = "foo" : null;
   {
     final core::List<core::String> #t5 = core::_GrowableList::•<core::String>(0);
     final core::Iterable<core::String>? #t6 = l;
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect
index c90185409e2..1eae8d381ed 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.expect
@@ -136,7 +136,7 @@ static method warning(core::String s, core::List<core::String> l, core::Map<core
     #t3.{core::String::length}{core::int};
   } =>#t3;
   let final core::String #t4 = s in #t4 == null ?{core::String} "foo" : #t4;
-  s == null ?{core::String} s = "foo" : null;
+  s == null ?{core::String?} s = "foo" : null;
   {
     final core::List<core::String> #t5 = <core::String>[];
     final core::Iterable<core::String>? #t6 = l;
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.modular.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.modular.expect
index c90185409e2..1eae8d381ed 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.modular.expect
@@ -136,7 +136,7 @@ static method warning(core::String s, core::List<core::String> l, core::Map<core
     #t3.{core::String::length}{core::int};
   } =>#t3;
   let final core::String #t4 = s in #t4 == null ?{core::String} "foo" : #t4;
-  s == null ?{core::String} s = "foo" : null;
+  s == null ?{core::String?} s = "foo" : null;
   {
     final core::List<core::String> #t5 = <core::String>[];
     final core::Iterable<core::String>? #t6 = l;
diff --git a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect
index 2bd174e8650..7c66b7472a6 100644
--- a/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd/strictly_non_nullable_warnings.dart.weak.transformed.expect
@@ -136,7 +136,7 @@ static method warning(core::String s, core::List<core::String> l, core::Map<core
     #t3.{core::String::length}{core::int};
   } =>#t3;
   let final core::String #t4 = s in #t4 == null ?{core::String} "foo" : #t4;
-  s == null ?{core::String} s = "foo" : null;
+  s == null ?{core::String?} s = "foo" : null;
   {
     final core::List<core::String> #t5 = core::_GrowableList::•<core::String>(0);
     final core::Iterable<core::String>? #t6 = l;
diff --git a/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.expect b/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.expect
index d6267eb7d5c..25747057bc7 100644
--- a/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.expect
+++ b/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.expect
@@ -478,7 +478,7 @@ static method ifNullPropertySetOptInForEffect(core::int i) → dynamic {
 static method ifNullSetOptIn(core::int i) → dynamic
   return let final core::int #t65 = i in #t65 == null ?{core::int} i = 42 : #t65;
 static method ifNullSetOptInForEffect(core::int i) → dynamic {
-  i == null ?{core::int} i = 42 : null;
+  i == null ?{core::int?} i = 42 : null;
 }
 static method ifNullSuperIndexSetOptIn(core::int i) → dynamic
   return new uns::OptInClass4::•().{uns::OptInClass4::method}(i){(core::int) → dynamic};
diff --git a/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.modular.expect b/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.modular.expect
index d6267eb7d5c..25747057bc7 100644
--- a/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.modular.expect
@@ -478,7 +478,7 @@ static method ifNullPropertySetOptInForEffect(core::int i) → dynamic {
 static method ifNullSetOptIn(core::int i) → dynamic
   return let final core::int #t65 = i in #t65 == null ?{core::int} i = 42 : #t65;
 static method ifNullSetOptInForEffect(core::int i) → dynamic {
-  i == null ?{core::int} i = 42 : null;
+  i == null ?{core::int?} i = 42 : null;
 }
 static method ifNullSuperIndexSetOptIn(core::int i) → dynamic
   return new uns::OptInClass4::•().{uns::OptInClass4::method}(i){(core::int) → dynamic};
diff --git a/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.transformed.expect
index 00d75df28f6..8a70db64e4e 100644
--- a/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/nnbd_mixed/unsound_checks.dart.weak.transformed.expect
@@ -478,7 +478,7 @@ static method ifNullPropertySetOptInForEffect(core::int i) → dynamic {
 static method ifNullSetOptIn(core::int i) → dynamic
   return let final core::int #t65 = i in #t65 == null ?{core::int} i = 42 : #t65;
 static method ifNullSetOptInForEffect(core::int i) → dynamic {
-  i == null ?{core::int} i = 42 : null;
+  i == null ?{core::int?} i = 42 : null;
 }
 static method ifNullSuperIndexSetOptIn(core::int i) → dynamic
   return new uns::OptInClass4::•().{uns::OptInClass4::method}(i){(core::int) → dynamic};
diff --git a/pkg/front_end/testcases/patterns/cache_lookups.dart.strong.transformed.expect b/pkg/front_end/testcases/patterns/cache_lookups.dart.strong.transformed.expect
index fac8007bbee..a79230a7492 100644
--- a/pkg/front_end/testcases/patterns/cache_lookups.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/patterns/cache_lookups.dart.strong.transformed.expect
@@ -358,7 +358,7 @@ abstract class _CustomList&Object&ListMixin<E extends core::Object? = dynamic> e
     _in::Sort::sort<cac::_CustomList&Object&ListMixin::E%>(this, let final (cac::_CustomList&Object&ListMixin::E%, cac::_CustomList&Object&ListMixin::E%) →? core::int #t6 = compare in #t6 == null ?{(cac::_CustomList&Object&ListMixin::E%, cac::_CustomList&Object&ListMixin::E%) → core::int} #C9 : #t6{(cac::_CustomList&Object&ListMixin::E%, cac::_CustomList&Object&ListMixin::E%) → core::int});
   }
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([math::Random? random = #C5]) → void {
-    random == null ?{math::Random} random = math::Random::•() : null;
+    random == null ?{math::Random?} random = math::Random::•() : null;
     core::int length = this.{core::List::length}{core::int};
     while (length.{core::num::>}(1){(core::num) → core::bool}) {
       core::int pos = random{math::Random}.{math::Random::nextInt}(length){(core::int) → core::int};
@@ -378,7 +378,7 @@ abstract class _CustomList&Object&ListMixin<E extends core::Object? = dynamic> e
     } =>#t7;
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(core::int start, [core::int? end = #C5]) → core::List<cac::_CustomList&Object&ListMixin::E%> {
     core::int listLength = this.{core::List::length}{core::int};
-    end == null ?{core::int} end = listLength : null;
+    end == null ?{core::int?} end = listLength : null;
     core::RangeError::checkValidRange(start, end{core::int}, listLength);
     return core::List::from<cac::_CustomList&Object&ListMixin::E%>(this.{col::ListBase::getRange}(start, end{core::int}){(core::int, core::int) → core::Iterable<cac::_CustomList&Object&ListMixin::E%>});
   }
diff --git a/pkg/front_end/testcases/patterns/cache_lookups.dart.weak.transformed.expect b/pkg/front_end/testcases/patterns/cache_lookups.dart.weak.transformed.expect
index 80217666459..22fbb788880 100644
--- a/pkg/front_end/testcases/patterns/cache_lookups.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/patterns/cache_lookups.dart.weak.transformed.expect
@@ -358,7 +358,7 @@ abstract class _CustomList&Object&ListMixin<E extends core::Object? = dynamic> e
     _in::Sort::sort<cac::_CustomList&Object&ListMixin::E%>(this, let final (cac::_CustomList&Object&ListMixin::E%, cac::_CustomList&Object&ListMixin::E%) →? core::int #t6 = compare in #t6 == null ?{(cac::_CustomList&Object&ListMixin::E%, cac::_CustomList&Object&ListMixin::E%) → core::int} #C9 : #t6{(cac::_CustomList&Object&ListMixin::E%, cac::_CustomList&Object&ListMixin::E%) → core::int});
   }
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([math::Random? random = #C5]) → void {
-    random == null ?{math::Random} random = math::Random::•() : null;
+    random == null ?{math::Random?} random = math::Random::•() : null;
     core::int length = this.{core::List::length}{core::int};
     while (length.{core::num::>}(1){(core::num) → core::bool}) {
       core::int pos = random{math::Random}.{math::Random::nextInt}(length){(core::int) → core::int};
@@ -378,7 +378,7 @@ abstract class _CustomList&Object&ListMixin<E extends core::Object? = dynamic> e
     } =>#t7;
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(core::int start, [core::int? end = #C5]) → core::List<cac::_CustomList&Object&ListMixin::E%> {
     core::int listLength = this.{core::List::length}{core::int};
-    end == null ?{core::int} end = listLength : null;
+    end == null ?{core::int?} end = listLength : null;
     core::RangeError::checkValidRange(start, end{core::int}, listLength);
     return core::List::from<cac::_CustomList&Object&ListMixin::E%>(this.{col::ListBase::getRange}(start, end{core::int}){(core::int, core::int) → core::Iterable<cac::_CustomList&Object&ListMixin::E%>});
   }
diff --git a/pkg/front_end/testcases/patterns/caching_constants.dart.strong.transformed.expect b/pkg/front_end/testcases/patterns/caching_constants.dart.strong.transformed.expect
index 9cb0ea1f9bb..d3a68a3c1c2 100644
--- a/pkg/front_end/testcases/patterns/caching_constants.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/patterns/caching_constants.dart.strong.transformed.expect
@@ -161,8 +161,8 @@ abstract class _MyMap&Object&MapMixin<K extends core::Object? = dynamic, V exten
     return result.{core::StringBuffer::toString}(){() → core::String};
   }
   static method /* from org-dartlang-sdk:///sdk/lib/collection/maps.dart */ _fillMapWithMappedIterable(core::Map<core::Object?, core::Object?> map, core::Iterable<core::Object?> iterable, (core::Object?) →? core::Object? key, (core::Object?) →? core::Object? value) → void {
-    key == null ?{(core::Object?) → core::Object?} key = #C2 : null;
-    value == null ?{(core::Object?) → core::Object?} value = #C2 : null;
+    key == null ?{(core::Object?) →? core::Object?} key = #C2 : null;
+    value == null ?{(core::Object?) →? core::Object?} value = #C2 : null;
     {
       synthesized core::Iterator<core::Object?> :sync-for-iterator = iterable.{core::Iterable::iterator}{core::Iterator<core::Object?>};
       for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
diff --git a/pkg/front_end/testcases/patterns/caching_constants.dart.weak.transformed.expect b/pkg/front_end/testcases/patterns/caching_constants.dart.weak.transformed.expect
index 55029a66b1a..7af2669ff11 100644
--- a/pkg/front_end/testcases/patterns/caching_constants.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/patterns/caching_constants.dart.weak.transformed.expect
@@ -161,8 +161,8 @@ abstract class _MyMap&Object&MapMixin<K extends core::Object? = dynamic, V exten
     return result.{core::StringBuffer::toString}(){() → core::String};
   }
   static method /* from org-dartlang-sdk:///sdk/lib/collection/maps.dart */ _fillMapWithMappedIterable(core::Map<core::Object?, core::Object?> map, core::Iterable<core::Object?> iterable, (core::Object?) →? core::Object? key, (core::Object?) →? core::Object? value) → void {
-    key == null ?{(core::Object?) → core::Object?} key = #C2 : null;
-    value == null ?{(core::Object?) → core::Object?} value = #C2 : null;
+    key == null ?{(core::Object?) →? core::Object?} key = #C2 : null;
+    value == null ?{(core::Object?) →? core::Object?} value = #C2 : null;
     {
       synthesized core::Iterator<core::Object?> :sync-for-iterator = iterable.{core::Iterable::iterator}{core::Iterator<core::Object?>};
       for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
diff --git a/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.strong.transformed.expect b/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.strong.transformed.expect
index b5080701d93..22d445f0952 100644
--- a/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.strong.transformed.expect
@@ -287,7 +287,7 @@ abstract class _A&Object&ListMixin extends core::Object implements col::ListBase
     _in::Sort::sort<core::int>(this, let final (core::int, core::int) →? core::int #t4 = compare in #t4 == null ?{(core::int, core::int) → core::int} #C6 : #t4{(core::int, core::int) → core::int});
   }
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([math::Random? random = #C2]) → void {
-    random == null ?{math::Random} random = math::Random::•() : null;
+    random == null ?{math::Random?} random = math::Random::•() : null;
     core::int length = this.{core::List::length}{core::int};
     while (length.{core::num::>}(1){(core::num) → core::bool}) {
       core::int pos = random{math::Random}.{math::Random::nextInt}(length){(core::int) → core::int};
@@ -307,7 +307,7 @@ abstract class _A&Object&ListMixin extends core::Object implements col::ListBase
     } =>#t5;
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(core::int start, [core::int? end = #C2]) → core::List<core::int> {
     core::int listLength = this.{core::List::length}{core::int};
-    end == null ?{core::int} end = listLength : null;
+    end == null ?{core::int?} end = listLength : null;
     core::RangeError::checkValidRange(start, end{core::int}, listLength);
     return core::List::from<core::int>(this.{col::ListBase::getRange}(start, end{core::int}){(core::int, core::int) → core::Iterable<core::int>});
   }
diff --git a/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.weak.transformed.expect b/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.weak.transformed.expect
index e9c9d92a64c..d565cad890c 100644
--- a/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/patterns/matching_and_capturing_accesses_list_element_once.dart.weak.transformed.expect
@@ -287,7 +287,7 @@ abstract class _A&Object&ListMixin extends core::Object implements col::ListBase
     _in::Sort::sort<core::int>(this, let final (core::int, core::int) →? core::int #t4 = compare in #t4 == null ?{(core::int, core::int) → core::int} #C6 : #t4{(core::int, core::int) → core::int});
   }
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([math::Random? random = #C2]) → void {
-    random == null ?{math::Random} random = math::Random::•() : null;
+    random == null ?{math::Random?} random = math::Random::•() : null;
     core::int length = this.{core::List::length}{core::int};
     while (length.{core::num::>}(1){(core::num) → core::bool}) {
       core::int pos = random{math::Random}.{math::Random::nextInt}(length){(core::int) → core::int};
@@ -307,7 +307,7 @@ abstract class _A&Object&ListMixin extends core::Object implements col::ListBase
     } =>#t5;
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(core::int start, [core::int? end = #C2]) → core::List<core::int> {
     core::int listLength = this.{core::List::length}{core::int};
-    end == null ?{core::int} end = listLength : null;
+    end == null ?{core::int?} end = listLength : null;
     core::RangeError::checkValidRange(start, end{core::int}, listLength);
     return core::List::from<core::int>(this.{col::ListBase::getRange}(start, end{core::int}){(core::int, core::int) → core::Iterable<core::int>});
   }
diff --git a/pkg/front_end/testcases/patterns/negative_length.dart.strong.transformed.expect b/pkg/front_end/testcases/patterns/negative_length.dart.strong.transformed.expect
index e4fecff5db1..89ce38c52ae 100644
--- a/pkg/front_end/testcases/patterns/negative_length.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/patterns/negative_length.dart.strong.transformed.expect
@@ -287,7 +287,7 @@ abstract class _NegativeLengthList&Object&ListMixin<E extends core::Object? = dy
     _in::Sort::sort<self::_NegativeLengthList&Object&ListMixin::E%>(this, let final (self::_NegativeLengthList&Object&ListMixin::E%, self::_NegativeLengthList&Object&ListMixin::E%) →? core::int #t4 = compare in #t4 == null ?{(self::_NegativeLengthList&Object&ListMixin::E%, self::_NegativeLengthList&Object&ListMixin::E%) → core::int} #C6 : #t4{(self::_NegativeLengthList&Object&ListMixin::E%, self::_NegativeLengthList&Object&ListMixin::E%) → core::int});
   }
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([math::Random? random = #C2]) → void {
-    random == null ?{math::Random} random = math::Random::•() : null;
+    random == null ?{math::Random?} random = math::Random::•() : null;
     core::int length = this.{core::List::length}{core::int};
     while (length.{core::num::>}(1){(core::num) → core::bool}) {
       core::int pos = random{math::Random}.{math::Random::nextInt}(length){(core::int) → core::int};
@@ -307,7 +307,7 @@ abstract class _NegativeLengthList&Object&ListMixin<E extends core::Object? = dy
     } =>#t5;
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(core::int start, [core::int? end = #C2]) → core::List<self::_NegativeLengthList&Object&ListMixin::E%> {
     core::int listLength = this.{core::List::length}{core::int};
-    end == null ?{core::int} end = listLength : null;
+    end == null ?{core::int?} end = listLength : null;
     core::RangeError::checkValidRange(start, end{core::int}, listLength);
     return core::List::from<self::_NegativeLengthList&Object&ListMixin::E%>(this.{col::ListBase::getRange}(start, end{core::int}){(core::int, core::int) → core::Iterable<self::_NegativeLengthList&Object&ListMixin::E%>});
   }
diff --git a/pkg/front_end/testcases/patterns/negative_length.dart.weak.transformed.expect b/pkg/front_end/testcases/patterns/negative_length.dart.weak.transformed.expect
index 15443d83068..118c6c968db 100644
--- a/pkg/front_end/testcases/patterns/negative_length.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/patterns/negative_length.dart.weak.transformed.expect
@@ -287,7 +287,7 @@ abstract class _NegativeLengthList&Object&ListMixin<E extends core::Object? = dy
     _in::Sort::sort<self::_NegativeLengthList&Object&ListMixin::E%>(this, let final (self::_NegativeLengthList&Object&ListMixin::E%, self::_NegativeLengthList&Object&ListMixin::E%) →? core::int #t4 = compare in #t4 == null ?{(self::_NegativeLengthList&Object&ListMixin::E%, self::_NegativeLengthList&Object&ListMixin::E%) → core::int} #C6 : #t4{(self::_NegativeLengthList&Object&ListMixin::E%, self::_NegativeLengthList&Object&ListMixin::E%) → core::int});
   }
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ shuffle([math::Random? random = #C2]) → void {
-    random == null ?{math::Random} random = math::Random::•() : null;
+    random == null ?{math::Random?} random = math::Random::•() : null;
     core::int length = this.{core::List::length}{core::int};
     while (length.{core::num::>}(1){(core::num) → core::bool}) {
       core::int pos = random{math::Random}.{math::Random::nextInt}(length){(core::int) → core::int};
@@ -307,7 +307,7 @@ abstract class _NegativeLengthList&Object&ListMixin<E extends core::Object? = dy
     } =>#t5;
   method /* from org-dartlang-sdk:///sdk/lib/collection/list.dart */ sublist(core::int start, [core::int? end = #C2]) → core::List<self::_NegativeLengthList&Object&ListMixin::E%> {
     core::int listLength = this.{core::List::length}{core::int};
-    end == null ?{core::int} end = listLength : null;
+    end == null ?{core::int?} end = listLength : null;
     core::RangeError::checkValidRange(start, end{core::int}, listLength);
     return core::List::from<self::_NegativeLengthList&Object&ListMixin::E%>(this.{col::ListBase::getRange}(start, end{core::int}){(core::int, core::int) → core::Iterable<self::_NegativeLengthList&Object&ListMixin::E%>});
   }
diff --git a/pkg/front_end/testcases/rasta/issue_000081.dart.strong.expect b/pkg/front_end/testcases/rasta/issue_000081.dart.strong.expect
index e3437dd0d9a..23cfff22715 100644
--- a/pkg/front_end/testcases/rasta/issue_000081.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/issue_000081.dart.strong.expect
@@ -16,7 +16,7 @@ class Sub extends self::Base {
   get hashCode() → core::int
     return let final core::int? #t1 = this.{self::Sub::_hashCode}{core::int?} in #t1 == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : #t1{core::int};
   method foo() → dynamic {
-    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
+    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int?} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
   }
 }
 static method main() → dynamic {
diff --git a/pkg/front_end/testcases/rasta/issue_000081.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/issue_000081.dart.strong.transformed.expect
index e863deae59c..a9787107fef 100644
--- a/pkg/front_end/testcases/rasta/issue_000081.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000081.dart.strong.transformed.expect
@@ -16,7 +16,7 @@ class Sub extends self::Base {
   get hashCode() → core::int
     return let final core::int? #t1 = this.{self::Sub::_hashCode}{core::int?} in #t1 == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : #t1{core::int};
   method foo() → dynamic {
-    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
+    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int?} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
   }
 }
 static method main() → dynamic {
diff --git a/pkg/front_end/testcases/rasta/issue_000081.dart.weak.expect b/pkg/front_end/testcases/rasta/issue_000081.dart.weak.expect
index e3437dd0d9a..23cfff22715 100644
--- a/pkg/front_end/testcases/rasta/issue_000081.dart.weak.expect
+++ b/pkg/front_end/testcases/rasta/issue_000081.dart.weak.expect
@@ -16,7 +16,7 @@ class Sub extends self::Base {
   get hashCode() → core::int
     return let final core::int? #t1 = this.{self::Sub::_hashCode}{core::int?} in #t1 == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : #t1{core::int};
   method foo() → dynamic {
-    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
+    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int?} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
   }
 }
 static method main() → dynamic {
diff --git a/pkg/front_end/testcases/rasta/issue_000081.dart.weak.modular.expect b/pkg/front_end/testcases/rasta/issue_000081.dart.weak.modular.expect
index e3437dd0d9a..23cfff22715 100644
--- a/pkg/front_end/testcases/rasta/issue_000081.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/rasta/issue_000081.dart.weak.modular.expect
@@ -16,7 +16,7 @@ class Sub extends self::Base {
   get hashCode() → core::int
     return let final core::int? #t1 = this.{self::Sub::_hashCode}{core::int?} in #t1 == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : #t1{core::int};
   method foo() → dynamic {
-    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
+    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int?} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
   }
 }
 static method main() → dynamic {
diff --git a/pkg/front_end/testcases/rasta/issue_000081.dart.weak.transformed.expect b/pkg/front_end/testcases/rasta/issue_000081.dart.weak.transformed.expect
index e863deae59c..a9787107fef 100644
--- a/pkg/front_end/testcases/rasta/issue_000081.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/rasta/issue_000081.dart.weak.transformed.expect
@@ -16,7 +16,7 @@ class Sub extends self::Base {
   get hashCode() → core::int
     return let final core::int? #t1 = this.{self::Sub::_hashCode}{core::int?} in #t1 == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : #t1{core::int};
   method foo() → dynamic {
-    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
+    this.{self::Sub::_hashCode}{core::int?} == null ?{core::int?} this.{self::Sub::_hashCode} = super.{self::Base::hashCode} : null;
   }
 }
 static method main() → dynamic {
diff --git a/pkg/front_end/testcases/rasta/static.dart.strong.expect b/pkg/front_end/testcases/rasta/static.dart.strong.expect
index 21d0f31abf8..ef693572b48 100644
--- a/pkg/front_end/testcases/rasta/static.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/static.dart.strong.expect
@@ -322,7 +322,7 @@ Try correcting the name to the name of an existing method, or defining a method
     self::use(let final core::int #t11 = #C1 in #t11 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:76:13: Error: Setter not found: 'staticConstant'.
     use(Foo.staticConstant ??= 87);
             ^^^^^^^^^^^^^^" : #t11);
-    self::Foo::staticField == null ?{core::int} self::Foo::staticField = 87 : null;
+    self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 87 : null;
     self::use(let final core::int #t12 = self::Foo::staticField in #t12 == null ?{core::int} self::Foo::staticField = 87 : #t12);
     #C2 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:79:9: Error: Setter not found: 'staticFunction'.
     Foo.staticFunction ??= 87;
diff --git a/pkg/front_end/testcases/rasta/static.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/static.dart.strong.transformed.expect
index 243566f89a5..e2cc4a7196e 100644
--- a/pkg/front_end/testcases/rasta/static.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/static.dart.strong.transformed.expect
@@ -322,7 +322,7 @@ Try correcting the name to the name of an existing method, or defining a method
     self::use(let final core::int #t11 = #C1 in #t11 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:76:13: Error: Setter not found: 'staticConstant'.
     use(Foo.staticConstant ??= 87);
             ^^^^^^^^^^^^^^" : #t11);
-    self::Foo::staticField == null ?{core::int} self::Foo::staticField = 87 : null;
+    self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 87 : null;
     self::use(let final core::int #t12 = self::Foo::staticField in #t12 == null ?{core::int} self::Foo::staticField = 87 : #t12);
     #C2 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:79:9: Error: Setter not found: 'staticFunction'.
     Foo.staticFunction ??= 87;
diff --git a/pkg/front_end/testcases/rasta/static.dart.weak.expect b/pkg/front_end/testcases/rasta/static.dart.weak.expect
index 21d0f31abf8..ef693572b48 100644
--- a/pkg/front_end/testcases/rasta/static.dart.weak.expect
+++ b/pkg/front_end/testcases/rasta/static.dart.weak.expect
@@ -322,7 +322,7 @@ Try correcting the name to the name of an existing method, or defining a method
     self::use(let final core::int #t11 = #C1 in #t11 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:76:13: Error: Setter not found: 'staticConstant'.
     use(Foo.staticConstant ??= 87);
             ^^^^^^^^^^^^^^" : #t11);
-    self::Foo::staticField == null ?{core::int} self::Foo::staticField = 87 : null;
+    self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 87 : null;
     self::use(let final core::int #t12 = self::Foo::staticField in #t12 == null ?{core::int} self::Foo::staticField = 87 : #t12);
     #C2 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:79:9: Error: Setter not found: 'staticFunction'.
     Foo.staticFunction ??= 87;
diff --git a/pkg/front_end/testcases/rasta/static.dart.weak.modular.expect b/pkg/front_end/testcases/rasta/static.dart.weak.modular.expect
index 21d0f31abf8..ef693572b48 100644
--- a/pkg/front_end/testcases/rasta/static.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/rasta/static.dart.weak.modular.expect
@@ -322,7 +322,7 @@ Try correcting the name to the name of an existing method, or defining a method
     self::use(let final core::int #t11 = #C1 in #t11 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:76:13: Error: Setter not found: 'staticConstant'.
     use(Foo.staticConstant ??= 87);
             ^^^^^^^^^^^^^^" : #t11);
-    self::Foo::staticField == null ?{core::int} self::Foo::staticField = 87 : null;
+    self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 87 : null;
     self::use(let final core::int #t12 = self::Foo::staticField in #t12 == null ?{core::int} self::Foo::staticField = 87 : #t12);
     #C2 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:79:9: Error: Setter not found: 'staticFunction'.
     Foo.staticFunction ??= 87;
diff --git a/pkg/front_end/testcases/rasta/static.dart.weak.transformed.expect b/pkg/front_end/testcases/rasta/static.dart.weak.transformed.expect
index 243566f89a5..e2cc4a7196e 100644
--- a/pkg/front_end/testcases/rasta/static.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/rasta/static.dart.weak.transformed.expect
@@ -322,7 +322,7 @@ Try correcting the name to the name of an existing method, or defining a method
     self::use(let final core::int #t11 = #C1 in #t11 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:76:13: Error: Setter not found: 'staticConstant'.
     use(Foo.staticConstant ??= 87);
             ^^^^^^^^^^^^^^" : #t11);
-    self::Foo::staticField == null ?{core::int} self::Foo::staticField = 87 : null;
+    self::Foo::staticField == null ?{core::int?} self::Foo::staticField = 87 : null;
     self::use(let final core::int #t12 = self::Foo::staticField in #t12 == null ?{core::int} self::Foo::staticField = 87 : #t12);
     #C2 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/static.dart:79:9: Error: Setter not found: 'staticFunction'.
     Foo.staticFunction ??= 87;
diff --git a/pkg/front_end/testcases/rasta/super.dart.strong.expect b/pkg/front_end/testcases/rasta/super.dart.strong.expect
index 6be1815dcb9..80776bbd795 100644
--- a/pkg/front_end/testcases/rasta/super.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/super.dart.strong.expect
@@ -625,7 +625,7 @@ Try removing the extra positional arguments.
     self::use(let final () → void #t50 = super.{self::A::m} in #t50 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/super.dart:198:15: Error: Superclass has no setter named 'm'.
     use(super.m ??= 42);
               ^" : #t50);
-    super.{self::A::n} == null ?{core::Object} super.{self::A::n} = 42 : null;
+    super.{self::A::n} == null ?{core::Object?} super.{self::A::n} = 42 : null;
     self::use(let final () → void #t51 = super.{self::A::n} in #t51 == null ?{core::Object} super.{self::A::n} = 42 : #t51);
     super.{self::A::a} = super.{self::A::a}{dynamic}.+(42);
     self::use(super.{self::A::a} = super.{self::A::a}{dynamic}.+(42));
diff --git a/pkg/front_end/testcases/rasta/super.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/super.dart.strong.transformed.expect
index 1726fca752e..70bd54ef714 100644
--- a/pkg/front_end/testcases/rasta/super.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/super.dart.strong.transformed.expect
@@ -625,7 +625,7 @@ Try removing the extra positional arguments.
     self::use(let final () → void #t50 = super.{self::A::m} in #t50 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/super.dart:198:15: Error: Superclass has no setter named 'm'.
     use(super.m ??= 42);
               ^" : #t50);
-    super.{self::A::n} == null ?{core::Object} super.{self::A::n} = 42 : null;
+    super.{self::A::n} == null ?{core::Object?} super.{self::A::n} = 42 : null;
     self::use(let final () → void #t51 = super.{self::A::n} in #t51 == null ?{core::Object} super.{self::A::n} = 42 : #t51);
     super.{self::A::a} = super.{self::A::a}{dynamic}.+(42);
     self::use(super.{self::A::a} = super.{self::A::a}{dynamic}.+(42));
diff --git a/pkg/front_end/testcases/rasta/super.dart.weak.expect b/pkg/front_end/testcases/rasta/super.dart.weak.expect
index 6be1815dcb9..80776bbd795 100644
--- a/pkg/front_end/testcases/rasta/super.dart.weak.expect
+++ b/pkg/front_end/testcases/rasta/super.dart.weak.expect
@@ -625,7 +625,7 @@ Try removing the extra positional arguments.
     self::use(let final () → void #t50 = super.{self::A::m} in #t50 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/super.dart:198:15: Error: Superclass has no setter named 'm'.
     use(super.m ??= 42);
               ^" : #t50);
-    super.{self::A::n} == null ?{core::Object} super.{self::A::n} = 42 : null;
+    super.{self::A::n} == null ?{core::Object?} super.{self::A::n} = 42 : null;
     self::use(let final () → void #t51 = super.{self::A::n} in #t51 == null ?{core::Object} super.{self::A::n} = 42 : #t51);
     super.{self::A::a} = super.{self::A::a}{dynamic}.+(42);
     self::use(super.{self::A::a} = super.{self::A::a}{dynamic}.+(42));
diff --git a/pkg/front_end/testcases/rasta/super.dart.weak.modular.expect b/pkg/front_end/testcases/rasta/super.dart.weak.modular.expect
index 6be1815dcb9..80776bbd795 100644
--- a/pkg/front_end/testcases/rasta/super.dart.weak.modular.expect
+++ b/pkg/front_end/testcases/rasta/super.dart.weak.modular.expect
@@ -625,7 +625,7 @@ Try removing the extra positional arguments.
     self::use(let final () → void #t50 = super.{self::A::m} in #t50 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/super.dart:198:15: Error: Superclass has no setter named 'm'.
     use(super.m ??= 42);
               ^" : #t50);
-    super.{self::A::n} == null ?{core::Object} super.{self::A::n} = 42 : null;
+    super.{self::A::n} == null ?{core::Object?} super.{self::A::n} = 42 : null;
     self::use(let final () → void #t51 = super.{self::A::n} in #t51 == null ?{core::Object} super.{self::A::n} = 42 : #t51);
     super.{self::A::a} = super.{self::A::a}{dynamic}.+(42);
     self::use(super.{self::A::a} = super.{self::A::a}{dynamic}.+(42));
diff --git a/pkg/front_end/testcases/rasta/super.dart.weak.transformed.expect b/pkg/front_end/testcases/rasta/super.dart.weak.transformed.expect
index 1726fca752e..70bd54ef714 100644
--- a/pkg/front_end/testcases/rasta/super.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/rasta/super.dart.weak.transformed.expect
@@ -625,7 +625,7 @@ Try removing the extra positional arguments.
     self::use(let final () → void #t50 = super.{self::A::m} in #t50 == null ?{invalid-type} invalid-expression "pkg/front_end/testcases/rasta/super.dart:198:15: Error: Superclass has no setter named 'm'.
     use(super.m ??= 42);
               ^" : #t50);
-    super.{self::A::n} == null ?{core::Object} super.{self::A::n} = 42 : null;
+    super.{self::A::n} == null ?{core::Object?} super.{self::A::n} = 42 : null;
     self::use(let final () → void #t51 = super.{self::A::n} in #t51 == null ?{core::Object} super.{self::A::n} = 42 : #t51);
     super.{self::A::a} = super.{self::A::a}{dynamic}.+(42);
     self::use(super.{self::A::a} = super.{self::A::a}{dynamic}.+(42));