[cfe] Handle late lowered fields in addUnpromotablePrivateFieldNames

Closes #52452

Change-Id: I39b3045b5e8b95493ea954ffa678b9caede901c8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/311741
Reviewed-by: Jens Johansen <jensj@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

pkg/front_end/lib/src/fasta/source/source_class_builder.dart

@@ -4,6 +4,7 @@
 
 library fasta.source_class_builder;
 
+import 'package:front_end/src/api_prototype/lowering_predicates.dart';
 import 'package:kernel/ast.dart';
 import 'package:kernel/class_hierarchy.dart'
     show ClassHierarchy, ClassHierarchyBase, ClassHierarchyMembers;
@@ -1256,7 +1257,19 @@ class SourceClassBuilder extends ClassBuilderImpl
       if (field.isInstanceMember &&
           !field.isFinal &&
           _isPrivateNameInThisLibrary(field.name)) {
-        unpromotablePrivateFieldNames.add(field.name.text);
+        if (isLateLoweredField(field)) {
+          // Late lowered fields do not have the finality of the declaration
+          // so we use lookup the corresponding [SourceFieldBuilder].
+          String fieldName = extractFieldNameFromLateLoweredField(field).text;
+          Builder? builder = scope.lookupLocalMember(fieldName, setter: false);
+          assert(builder is SourceFieldBuilder,
+              "Unexpected late-lowered field '$fieldName' in $this: $builder");
+          if (builder is SourceFieldBuilder && !builder.isFinal) {
+            unpromotablePrivateFieldNames.add(fieldName);
+          }
+        } else if (!isLateLoweredIsSetField(field)) {
+          unpromotablePrivateFieldNames.add(field.name.text);
+        }
       }
     }
     for (Procedure procedure in cls.procedures) {
@@ -1265,13 +1278,17 @@ class SourceClassBuilder extends ClassBuilderImpl
       // abstract non-final field makes fields with the same name unpromotable.
       if (procedure.isInstanceMember &&
           _isPrivateNameInThisLibrary(procedure.name)) {
-        if (procedure.isGetter && !procedure.isAbstract) {
+        if (procedure.isGetter &&
+            !procedure.isAbstract &&
+            !isLateLoweredFieldGetter(procedure)) {
           ProcedureStubKind procedureStubKind = procedure.stubKind;
           if (procedureStubKind == ProcedureStubKind.Regular ||
               procedureStubKind == ProcedureStubKind.NoSuchMethodForwarder) {
             unpromotablePrivateFieldNames.add(procedure.name.text);
           }
-        } else if (procedure.isSetter && procedure.isAbstractFieldAccessor) {
+        } else if (procedure.isSetter &&
+            procedure.isAbstractFieldAccessor &&
+            !isLateLoweredFieldSetter(procedure)) {
           unpromotablePrivateFieldNames.add(procedure.name.text);
         }
       }

pkg/front_end/testcases/dart2wasm/inference_update_2/folder.options

@@ -0,0 +1,2 @@
+--target=wasm
+--enable-experiment=inference-update-2

pkg/front_end/testcases/dart2wasm/inference_update_2/issue52452.dart

@@ -0,0 +1,85 @@
+// 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.
+
+// Tests that field promotion is prevented if there is a synthetic instance
+// getter of the same name in the library that's a noSuchMethod forwarder.
+
+// SharedOptions=--enable-experiment=inference-update-2
+
+class C {
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+}
+
+class A {
+  A(int? i);
+}
+
+mixin M3 {}
+
+abstract class D extends A with M3 {
+  final int? _f4;
+
+  D(int? i)
+      : _f4 = i,
+        super(i);
+}
+
+mixin M1 {
+  late int? _f2;
+  late final int? _f3;
+  late final int? _f4 = 0;
+}
+
+class B {
+  B(int? i);
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  // Inherits _f4 from M1, so there is no noSuchMethod forwarder
+
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+void acceptsInt(int x) {}
+
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {
+  if (c._f2 != null) {
+    var x = c._f2;
+    // `x` has type `int?` so this is ok
+    x = null;
+  }
+}
+
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {
+  if (c._f3 != null) {
+    var x = c._f3;
+    // `x` has type `int` so this is ok
+    acceptsInt(x);
+  }
+}
+
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {
+  if (c._f4 != null) {
+    var x = c._f4;
+    // `x` has type `int` so this is ok
+    acceptsInt(x);
+  }
+}
+
+main() {
+  for (var c in [C(null), C(0)]) {
+    testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}

pkg/front_end/testcases/dart2wasm/inference_update_2/issue52452.dart.strong.expect

@@ -0,0 +1,154 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t1 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t1;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _#M1#_f2() → core::int?
+    return super.{self::M1::_#M1#_f2};
+  mixin-super-stub set _#M1#_f2(core::int? value) → void
+    return super.{self::M1::_#M1#_f2} = value;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? _f2#param) → void
+    return super.{self::M1::_f2} = _f2#param;
+  mixin-super-stub get _#M1#_f2#isSet() → core::bool
+    return super.{self::M1::_#M1#_f2#isSet};
+  mixin-super-stub set _#M1#_f2#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f2#isSet} = value;
+  mixin-super-stub get _#M1#_f3() → core::int?
+    return super.{self::M1::_#M1#_f3};
+  mixin-super-stub set _#M1#_f3(core::int? value) → void
+    return super.{self::M1::_#M1#_f3} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? _f3#param) → void
+    return super.{self::M1::_f3} = _f3#param;
+  mixin-super-stub get _#M1#_f3#isSet() → core::bool
+    return super.{self::M1::_#M1#_f3#isSet};
+  mixin-super-stub set _#M1#_f3#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f3#isSet} = value;
+  mixin-super-stub get _#M1#_f4() → core::int?
+    return super.{self::M1::_#M1#_f4};
+  mixin-super-stub set _#M1#_f4(core::int? value) → void
+    return super.{self::M1::_#M1#_f4} = value;
+  mixin-super-stub get _#M1#_f4#isSet() → core::bool
+    return super.{self::M1::_#M1#_f4#isSet};
+  mixin-super-stub set _#M1#_f4#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f4#isSet} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/dart2wasm/inference_update_2/issue52452.dart.strong.transformed.expect

@@ -0,0 +1,157 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 extends self::A implements self::M3 /*isAnonymousMixin,isEliminatedMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t1 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t1;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 extends self::B implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t2 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t2;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  {
+    synthesized core::Iterator<self::C> #forIterator = <self::C>[new self::C::•(null), new self::C::•(0)].{core::Iterable::iterator}{core::Iterator<self::C>};
+    for (; #forIterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
+      self::C c = #forIterator.{core::Iterator::current}{self::C};
+      {
+        self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+        self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+        self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/dart2wasm/inference_update_2/issue52452.dart.textual_outline.expect

@@ -0,0 +1,44 @@
+class C {
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+}
+
+class A {
+  A(int? i);
+}
+
+mixin M3 {}
+
+abstract class D extends A with M3 {
+  final int? _f4;
+  D(int? i)
+      : _f4 = i,
+        super(i);
+}
+
+mixin M1 {
+  late int? _f2;
+  late final int? _f3;
+  late final int? _f4 = 0;
+}
+
+class B {
+  B(int? i);
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+void acceptsInt(int x) {}
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {}
+main() {}

pkg/front_end/testcases/dart2wasm/inference_update_2/issue52452.dart.textual_outline_modelled.expect

@@ -0,0 +1,42 @@
+abstract class D extends A with M3 {
+  D(int? i)
+      : _f4 = i,
+        super(i);
+  final int? _f4;
+}
+
+class A {
+  A(int? i);
+}
+
+class B {
+  B(int? i);
+}
+
+class C {
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+main() {}
+mixin M1 {
+  late final int? _f3;
+  late final int? _f4 = 0;
+  late int? _f2;
+}
+mixin M3 {}
+void acceptsInt(int x) {}
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {}

pkg/front_end/testcases/dartdevc/inference_update_2/folder.options

@@ -0,0 +1,2 @@
+--target=dartdevc
+--enable-experiment=inference-update-2

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart

@@ -0,0 +1,85 @@
+// 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.
+
+// Tests that field promotion is prevented if there is a synthetic instance
+// getter of the same name in the library that's a noSuchMethod forwarder.
+
+// SharedOptions=--enable-experiment=inference-update-2
+
+class C {
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+}
+
+class A {
+  A(int? i);
+}
+
+mixin M3 {}
+
+abstract class D extends A with M3 {
+  final int? _f4;
+
+  D(int? i)
+      : _f4 = i,
+        super(i);
+}
+
+mixin M1 {
+  late int? _f2;
+  late final int? _f3;
+  late final int? _f4 = 0;
+}
+
+class B {
+  B(int? i);
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  // Inherits _f4 from M1, so there is no noSuchMethod forwarder
+
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+void acceptsInt(int x) {}
+
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {
+  if (c._f2 != null) {
+    var x = c._f2;
+    // `x` has type `int?` so this is ok
+    x = null;
+  }
+}
+
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {
+  if (c._f3 != null) {
+    var x = c._f3;
+    // `x` has type `int` so this is ok
+    acceptsInt(x);
+  }
+}
+
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {
+  if (c._f4 != null) {
+    var x = c._f4;
+    // `x` has type `int` so this is ok
+    acceptsInt(x);
+  }
+}
+
+main() {
+  for (var c in [C(null), C(0)]) {
+    testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.strong.expect

@@ -0,0 +1,154 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t1 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t1;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _#M1#_f2() → core::int?
+    return super.{self::M1::_#M1#_f2};
+  mixin-super-stub set _#M1#_f2(core::int? value) → void
+    return super.{self::M1::_#M1#_f2} = value;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? _f2#param) → void
+    return super.{self::M1::_f2} = _f2#param;
+  mixin-super-stub get _#M1#_f2#isSet() → core::bool
+    return super.{self::M1::_#M1#_f2#isSet};
+  mixin-super-stub set _#M1#_f2#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f2#isSet} = value;
+  mixin-super-stub get _#M1#_f3() → core::int?
+    return super.{self::M1::_#M1#_f3};
+  mixin-super-stub set _#M1#_f3(core::int? value) → void
+    return super.{self::M1::_#M1#_f3} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? _f3#param) → void
+    return super.{self::M1::_f3} = _f3#param;
+  mixin-super-stub get _#M1#_f3#isSet() → core::bool
+    return super.{self::M1::_#M1#_f3#isSet};
+  mixin-super-stub set _#M1#_f3#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f3#isSet} = value;
+  mixin-super-stub get _#M1#_f4() → core::int?
+    return super.{self::M1::_#M1#_f4};
+  mixin-super-stub set _#M1#_f4(core::int? value) → void
+    return super.{self::M1::_#M1#_f4} = value;
+  mixin-super-stub get _#M1#_f4#isSet() → core::bool
+    return super.{self::M1::_#M1#_f4#isSet};
+  mixin-super-stub set _#M1#_f4#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f4#isSet} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.strong.transformed.expect

@@ -0,0 +1,154 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t1 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t1;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _#M1#_f2() → core::int?
+    return super.{self::M1::_#M1#_f2};
+  mixin-super-stub set _#M1#_f2(core::int? value) → void
+    return super.{self::M1::_#M1#_f2} = value;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? _f2#param) → void
+    return super.{self::M1::_f2} = _f2#param;
+  mixin-super-stub get _#M1#_f2#isSet() → core::bool
+    return super.{self::M1::_#M1#_f2#isSet};
+  mixin-super-stub set _#M1#_f2#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f2#isSet} = value;
+  mixin-super-stub get _#M1#_f3() → core::int?
+    return super.{self::M1::_#M1#_f3};
+  mixin-super-stub set _#M1#_f3(core::int? value) → void
+    return super.{self::M1::_#M1#_f3} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? _f3#param) → void
+    return super.{self::M1::_f3} = _f3#param;
+  mixin-super-stub get _#M1#_f3#isSet() → core::bool
+    return super.{self::M1::_#M1#_f3#isSet};
+  mixin-super-stub set _#M1#_f3#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f3#isSet} = value;
+  mixin-super-stub get _#M1#_f4() → core::int?
+    return super.{self::M1::_#M1#_f4};
+  mixin-super-stub set _#M1#_f4(core::int? value) → void
+    return super.{self::M1::_#M1#_f4} = value;
+  mixin-super-stub get _#M1#_f4#isSet() → core::bool
+    return super.{self::M1::_#M1#_f4#isSet};
+  mixin-super-stub set _#M1#_f4#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f4#isSet} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.textual_outline.expect

@@ -0,0 +1,44 @@
+class C {
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+}
+
+class A {
+  A(int? i);
+}
+
+mixin M3 {}
+
+abstract class D extends A with M3 {
+  final int? _f4;
+  D(int? i)
+      : _f4 = i,
+        super(i);
+}
+
+mixin M1 {
+  late int? _f2;
+  late final int? _f3;
+  late final int? _f4 = 0;
+}
+
+class B {
+  B(int? i);
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+void acceptsInt(int x) {}
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {}
+main() {}

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.textual_outline_modelled.expect

@@ -0,0 +1,42 @@
+abstract class D extends A with M3 {
+  D(int? i)
+      : _f4 = i,
+        super(i);
+  final int? _f4;
+}
+
+class A {
+  A(int? i);
+}
+
+class B {
+  B(int? i);
+}
+
+class C {
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+main() {}
+mixin M1 {
+  late final int? _f3;
+  late final int? _f4 = 0;
+  late int? _f2;
+}
+mixin M3 {}
+void acceptsInt(int x) {}
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {}

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.weak.expect

@@ -0,0 +1,154 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t1 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t1;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _#M1#_f2() → core::int?
+    return super.{self::M1::_#M1#_f2};
+  mixin-super-stub set _#M1#_f2(core::int? value) → void
+    return super.{self::M1::_#M1#_f2} = value;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? _f2#param) → void
+    return super.{self::M1::_f2} = _f2#param;
+  mixin-super-stub get _#M1#_f2#isSet() → core::bool
+    return super.{self::M1::_#M1#_f2#isSet};
+  mixin-super-stub set _#M1#_f2#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f2#isSet} = value;
+  mixin-super-stub get _#M1#_f3() → core::int?
+    return super.{self::M1::_#M1#_f3};
+  mixin-super-stub set _#M1#_f3(core::int? value) → void
+    return super.{self::M1::_#M1#_f3} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? _f3#param) → void
+    return super.{self::M1::_f3} = _f3#param;
+  mixin-super-stub get _#M1#_f3#isSet() → core::bool
+    return super.{self::M1::_#M1#_f3#isSet};
+  mixin-super-stub set _#M1#_f3#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f3#isSet} = value;
+  mixin-super-stub get _#M1#_f4() → core::int?
+    return super.{self::M1::_#M1#_f4};
+  mixin-super-stub set _#M1#_f4(core::int? value) → void
+    return super.{self::M1::_#M1#_f4} = value;
+  mixin-super-stub get _#M1#_f4#isSet() → core::bool
+    return super.{self::M1::_#M1#_f4#isSet};
+  mixin-super-stub set _#M1#_f4#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f4#isSet} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.weak.modular.expect

@@ -0,0 +1,154 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t1 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t1;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _#M1#_f2() → core::int?
+    return super.{self::M1::_#M1#_f2};
+  mixin-super-stub set _#M1#_f2(core::int? value) → void
+    return super.{self::M1::_#M1#_f2} = value;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? _f2#param) → void
+    return super.{self::M1::_f2} = _f2#param;
+  mixin-super-stub get _#M1#_f2#isSet() → core::bool
+    return super.{self::M1::_#M1#_f2#isSet};
+  mixin-super-stub set _#M1#_f2#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f2#isSet} = value;
+  mixin-super-stub get _#M1#_f3() → core::int?
+    return super.{self::M1::_#M1#_f3};
+  mixin-super-stub set _#M1#_f3(core::int? value) → void
+    return super.{self::M1::_#M1#_f3} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? _f3#param) → void
+    return super.{self::M1::_f3} = _f3#param;
+  mixin-super-stub get _#M1#_f3#isSet() → core::bool
+    return super.{self::M1::_#M1#_f3#isSet};
+  mixin-super-stub set _#M1#_f3#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f3#isSet} = value;
+  mixin-super-stub get _#M1#_f4() → core::int?
+    return super.{self::M1::_#M1#_f4};
+  mixin-super-stub set _#M1#_f4(core::int? value) → void
+    return super.{self::M1::_#M1#_f4} = value;
+  mixin-super-stub get _#M1#_f4#isSet() → core::bool
+    return super.{self::M1::_#M1#_f4#isSet};
+  mixin-super-stub set _#M1#_f4#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f4#isSet} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.weak.outline.expect

@@ -0,0 +1,113 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2;
+  field core::bool _#M1#_f2#isSet;
+  field core::int? _#M1#_f3;
+  field core::bool _#M1#_f3#isSet;
+  field core::int? _#M1#_f4;
+  field core::bool _#M1#_f4#isSet;
+  get _f2() → core::int?;
+  set _f2(core::int? _f2#param) → void;
+  get _f3() → core::int?;
+  set _f3(core::int? _f3#param) → void;
+  get _f4() → core::int?;
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _#M1#_f2() → core::int?
+    return super.{self::M1::_#M1#_f2};
+  mixin-super-stub set _#M1#_f2(core::int? value) → void
+    return super.{self::M1::_#M1#_f2} = value;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? _f2#param) → void
+    return super.{self::M1::_f2} = _f2#param;
+  mixin-super-stub get _#M1#_f2#isSet() → core::bool
+    return super.{self::M1::_#M1#_f2#isSet};
+  mixin-super-stub set _#M1#_f2#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f2#isSet} = value;
+  mixin-super-stub get _#M1#_f3() → core::int?
+    return super.{self::M1::_#M1#_f3};
+  mixin-super-stub set _#M1#_f3(core::int? value) → void
+    return super.{self::M1::_#M1#_f3} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? _f3#param) → void
+    return super.{self::M1::_f3} = _f3#param;
+  mixin-super-stub get _#M1#_f3#isSet() → core::bool
+    return super.{self::M1::_#M1#_f3#isSet};
+  mixin-super-stub set _#M1#_f3#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f3#isSet} = value;
+  mixin-super-stub get _#M1#_f4() → core::int?
+    return super.{self::M1::_#M1#_f4};
+  mixin-super-stub set _#M1#_f4(core::int? value) → void
+    return super.{self::M1::_#M1#_f4} = value;
+  mixin-super-stub get _#M1#_f4#isSet() → core::bool
+    return super.{self::M1::_#M1#_f4#isSet};
+  mixin-super-stub set _#M1#_f4#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f4#isSet} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @core::override
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    ;
+}
+static method acceptsInt(core::int x) → void
+  ;
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void
+  ;
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void
+  ;
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void
+  ;
+static method main() → dynamic
+  ;
+
+
+Extra constant evaluation status:
+Evaluated: StaticGet @ org-dartlang-testcase:///issue52452.dart:49:4 -> InstanceConstant(const _Override{})
+Extra constant evaluation: evaluated: 36, effectively constant: 1

pkg/front_end/testcases/dartdevc/inference_update_2/issue52452.dart.weak.transformed.expect

@@ -0,0 +1,154 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::C
+    return new self::C::•(i);
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::A
+    return new self::A::•(i);
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  field core::int? _#M1#_f2 = null;
+  field core::bool _#M1#_f2#isSet = false;
+  field core::int? _#M1#_f3 = null;
+  field core::bool _#M1#_f3#isSet = false;
+  field core::int? _#M1#_f4 = null;
+  field core::bool _#M1#_f4#isSet = false;
+  get _f2() → core::int?
+    return this.{self::M1::_#M1#_f2#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f2}{core::int?} : throw new _in::LateError::fieldNI("_f2");
+  set _f2(core::int? _f2#param) → void {
+    this.{self::M1::_#M1#_f2#isSet} = true;
+    this.{self::M1::_#M1#_f2} = _f2#param;
+  }
+  get _f3() → core::int?
+    return this.{self::M1::_#M1#_f3#isSet}{core::bool} ?{core::int?} this.{self::M1::_#M1#_f3}{core::int?} : throw new _in::LateError::fieldNI("_f3");
+  set _f3(core::int? _f3#param) → void
+    if(this.{self::M1::_#M1#_f3#isSet}{core::bool})
+      throw new _in::LateError::fieldAI("_f3");
+    else {
+      this.{self::M1::_#M1#_f3#isSet} = true;
+      this.{self::M1::_#M1#_f3} = _f3#param;
+    }
+  get _f4() → core::int? {
+    if(!this.{self::M1::_#M1#_f4#isSet}{core::bool}) {
+      final core::int? #t1 = 0;
+      if(this.{self::M1::_#M1#_f4#isSet}{core::bool})
+        throw new _in::LateError::fieldADI("_f4");
+      this.{self::M1::_#M1#_f4} = #t1;
+      this.{self::M1::_#M1#_f4#isSet} = true;
+    }
+    return this.{self::M1::_#M1#_f4}{core::int?};
+  }
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+  static method _#new#tearOff(core::int? i) → self::B
+    return new self::B::•(i);
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _#M1#_f2() → core::int?
+    return super.{self::M1::_#M1#_f2};
+  mixin-super-stub set _#M1#_f2(core::int? value) → void
+    return super.{self::M1::_#M1#_f2} = value;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? _f2#param) → void
+    return super.{self::M1::_f2} = _f2#param;
+  mixin-super-stub get _#M1#_f2#isSet() → core::bool
+    return super.{self::M1::_#M1#_f2#isSet};
+  mixin-super-stub set _#M1#_f2#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f2#isSet} = value;
+  mixin-super-stub get _#M1#_f3() → core::int?
+    return super.{self::M1::_#M1#_f3};
+  mixin-super-stub set _#M1#_f3(core::int? value) → void
+    return super.{self::M1::_#M1#_f3} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? _f3#param) → void
+    return super.{self::M1::_f3} = _f3#param;
+  mixin-super-stub get _#M1#_f3#isSet() → core::bool
+    return super.{self::M1::_#M1#_f3#isSet};
+  mixin-super-stub set _#M1#_f3#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f3#isSet} = value;
+  mixin-super-stub get _#M1#_f4() → core::int?
+    return super.{self::M1::_#M1#_f4};
+  mixin-super-stub set _#M1#_f4(core::int? value) → void
+    return super.{self::M1::_#M1#_f4} = value;
+  mixin-super-stub get _#M1#_f4#isSet() → core::bool
+    return super.{self::M1::_#M1#_f4#isSet};
+  mixin-super-stub set _#M1#_f4#isSet(core::bool value) → void
+    return super.{self::M1::_#M1#_f4#isSet} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  static method _#new#tearOff(core::int? i) → self::E
+    return new self::E::•(i);
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/inference_update_2/issue52452.dart

@@ -0,0 +1,85 @@
+// 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.
+
+// Tests that field promotion is prevented if there is a synthetic instance
+// getter of the same name in the library that's a noSuchMethod forwarder.
+
+// SharedOptions=--enable-experiment=inference-update-2
+
+class C {
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+}
+
+class A {
+  A(int? i);
+}
+
+mixin M3 {}
+
+abstract class D extends A with M3 {
+  final int? _f4;
+
+  D(int? i)
+      : _f4 = i,
+        super(i);
+}
+
+mixin M1 {
+  late int? _f2;
+  late final int? _f3;
+  late final int? _f4 = 0;
+}
+
+class B {
+  B(int? i);
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  // Inherits _f4 from M1, so there is no noSuchMethod forwarder
+
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+void acceptsInt(int x) {}
+
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {
+  if (c._f2 != null) {
+    var x = c._f2;
+    // `x` has type `int?` so this is ok
+    x = null;
+  }
+}
+
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {
+  if (c._f3 != null) {
+    var x = c._f3;
+    // `x` has type `int` so this is ok
+    acceptsInt(x);
+  }
+}
+
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {
+  if (c._f4 != null) {
+    var x = c._f4;
+    // `x` has type `int` so this is ok
+    acceptsInt(x);
+  }
+}
+
+main() {
+  for (var c in [C(null), C(0)]) {
+    testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}

pkg/front_end/testcases/inference_update_2/issue52452.dart.strong.expect

@@ -0,0 +1,93 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4 = 0;
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? value) → void
+    return super.{self::M1::_f2} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? value) → void
+    return super.{self::M1::_f3} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/inference_update_2/issue52452.dart.strong.transformed.expect

@@ -0,0 +1,92 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 extends self::A implements self::M3 /*isAnonymousMixin,isEliminatedMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4 = 0;
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+}
+abstract class _E&B&M1 extends self::B implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4 = 0;
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  {
+    synthesized core::Iterator<self::C> :sync-for-iterator = core::_GrowableList::_literal2<self::C>(new self::C::•(null), new self::C::•(0)).{core::Iterable::iterator}{core::Iterator<self::C>};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
+      self::C c = :sync-for-iterator.{core::Iterator::current}{self::C};
+      {
+        self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+        self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+        self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/inference_update_2/issue52452.dart.textual_outline.expect

@@ -0,0 +1,44 @@
+class C {
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+}
+
+class A {
+  A(int? i);
+}
+
+mixin M3 {}
+
+abstract class D extends A with M3 {
+  final int? _f4;
+  D(int? i)
+      : _f4 = i,
+        super(i);
+}
+
+mixin M1 {
+  late int? _f2;
+  late final int? _f3;
+  late final int? _f4 = 0;
+}
+
+class B {
+  B(int? i);
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+void acceptsInt(int x) {}
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {}
+main() {}

pkg/front_end/testcases/inference_update_2/issue52452.dart.textual_outline_modelled.expect

@@ -0,0 +1,42 @@
+abstract class D extends A with M3 {
+  D(int? i)
+      : _f4 = i,
+        super(i);
+  final int? _f4;
+}
+
+class A {
+  A(int? i);
+}
+
+class B {
+  B(int? i);
+}
+
+class C {
+  C(int? i)
+      : _f2 = i,
+        _f3 = i,
+        _f4 = i;
+  final int? _f2;
+  final int? _f3;
+  final int? _f4;
+}
+
+class E extends B with M1 implements D {
+  E(super.i);
+  @override
+  dynamic noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
+}
+
+main() {}
+mixin M1 {
+  late final int? _f3;
+  late final int? _f4 = 0;
+  late int? _f2;
+}
+mixin M3 {}
+void acceptsInt(int x) {}
+void testConflictWithNoSuchMethodForwarderIfImplementedInMixin(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(C c) {}
+void testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(C c) {}

pkg/front_end/testcases/inference_update_2/issue52452.dart.weak.expect

@@ -0,0 +1,93 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4 = 0;
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? value) → void
+    return super.{self::M1::_f2} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? value) → void
+    return super.{self::M1::_f3} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/inference_update_2/issue52452.dart.weak.modular.expect

@@ -0,0 +1,93 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4 = 0;
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? value) → void
+    return super.{self::M1::_f2} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? value) → void
+    return super.{self::M1::_f3} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  for (self::C c in <self::C>[new self::C::•(null), new self::C::•(0)]) {
+    self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+    self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}

pkg/front_end/testcases/inference_update_2/issue52452.dart.weak.outline.expect

@@ -0,0 +1,73 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    ;
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    ;
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 = self::A with self::M3 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4;
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    ;
+}
+abstract class _E&B&M1 = self::B with self::M1 /*isAnonymousMixin*/  {
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+  mixin-super-stub get _f2() → core::int?
+    return super.{self::M1::_f2};
+  mixin-super-stub set _f2(core::int? value) → void
+    return super.{self::M1::_f2} = value;
+  mixin-super-stub get _f3() → core::int?
+    return super.{self::M1::_f3};
+  mixin-super-stub set _f3(core::int? value) → void
+    return super.{self::M1::_f3} = value;
+  mixin-super-stub get _f4() → core::int?
+    return super.{self::M1::_f4};
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    ;
+  @core::override
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    ;
+}
+static method acceptsInt(core::int x) → void
+  ;
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void
+  ;
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void
+  ;
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void
+  ;
+static method main() → dynamic
+  ;
+
+
+Extra constant evaluation status:
+Evaluated: StaticGet @ org-dartlang-testcase:///issue52452.dart:49:4 -> InstanceConstant(const _Override{})
+Extra constant evaluation: evaluated: 10, effectively constant: 1

pkg/front_end/testcases/inference_update_2/issue52452.dart.weak.transformed.expect

@@ -0,0 +1,92 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  final field core::int? _f2;
+  final field core::int? _f3;
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::C
+    : self::C::_f2 = i, self::C::_f3 = i, self::C::_f4 = i, super core::Object::•()
+    ;
+}
+class A extends core::Object {
+  constructor •(core::int? i) → self::A
+    : super core::Object::•()
+    ;
+}
+abstract class M3 extends core::Object /*isMixinDeclaration*/  {
+}
+abstract class _D&A&M3 extends self::A implements self::M3 /*isAnonymousMixin,isEliminatedMixin*/  {
+  synthetic constructor •(core::int? i) → self::_D&A&M3
+    : super self::A::•(i)
+    ;
+}
+abstract class D extends self::_D&A&M3 {
+  final field core::int? _f4;
+  constructor •(core::int? i) → self::D
+    : self::D::_f4 = i, super self::_D&A&M3::•(i)
+    ;
+}
+abstract class M1 extends core::Object /*isMixinDeclaration*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4 = 0;
+}
+class B extends core::Object {
+  constructor •(core::int? i) → self::B
+    : super core::Object::•()
+    ;
+}
+abstract class _E&B&M1 extends self::B implements self::M1 /*isAnonymousMixin,isEliminatedMixin*/  {
+  late field core::int? _f2;
+  late final [setter] field core::int? _f3;
+  late final field core::int? _f4 = 0;
+  synthetic constructor •(core::int? i) → self::_E&B&M1
+    : super self::B::•(i)
+    ;
+}
+class E extends self::_E&B&M1 implements self::D {
+  constructor •(core::int? i) → self::E
+    : super self::_E&B&M1::•(i)
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    return super.{core::Object::noSuchMethod}(invocation);
+}
+static method acceptsInt(core::int x) → void {}
+static method testConflictWithNoSuchMethodForwarderIfImplementedInMixin(self::C c) → void {
+  if(!(c.{self::C::_f2}{core::int?} == null)) {
+    core::int? x = c.{self::C::_f2}{core::int?};
+    x = null;
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(self::C c) → void {
+  if(!(c.{self::C::_f3}{core::int?} == null)) {
+    core::int x = c.{self::C::_f3}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(self::C c) → void {
+  if(!(c.{self::C::_f4}{core::int?} == null)) {
+    core::int x = c.{self::C::_f4}{core::int};
+    self::acceptsInt(x);
+  }
+}
+static method main() → dynamic {
+  {
+    synthesized core::Iterator<self::C> :sync-for-iterator = core::_GrowableList::_literal2<self::C>(new self::C::•(null), new self::C::•(0)).{core::Iterable::iterator}{core::Iterator<self::C>};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
+      self::C c = :sync-for-iterator.{core::Iterator::current}{self::C};
+      {
+        self::testConflictWithNoSuchMethodForwarderIfImplementedInMixin(c);
+        self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin1(c);
+        self::testNoConflictWithNoSuchMethodForwarderIfImplementedInMixin2(c);
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = core::_Override {}
+}