[cfe] Don't check override for member signatures.

Closes #40460

Change-Id: If418c0c809ec15febfa63c5363f8353cb16fc9de
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/134521
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

pkg/_fe_analyzer_shared/test/inheritance/data/member_from_opt_in/main.dart

@@ -0,0 +1,24 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=2.6
+
+/*library: nnbd=false*/
+
+import 'opt_in.dart';
+
+/*class: LegacyClass:Class,LegacyClass,Object*/
+class LegacyClass extends Class {
+  /*member: LegacyClass.method:int* Function(int*)**/
+}
+
+/*class: LegacyInterface:Interface,LegacyInterface,Object*/
+abstract class LegacyInterface implements Interface {
+  /*member: LegacyInterface.method:int* Function(int*)**/
+}
+
+/*class: LegacySubClass:Class,Interface,LegacyClass,LegacyInterface,LegacySubClass,Object*/
+class LegacySubClass extends LegacyClass implements LegacyInterface {
+  /*member: LegacySubClass.method:int* Function(int*)**/
+}

pkg/_fe_analyzer_shared/test/inheritance/data/member_from_opt_in/opt_in.dart

@@ -0,0 +1,17 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/*library: nnbd=true*/
+
+/*class: Class:Class,Object*/
+class Class {
+  /*member: Class.method:int! Function(int?)!*/
+  int method(int? i) => i ?? 0;
+}
+
+/*class: Interface:Interface,Object*/
+abstract class Interface {
+  /*member: Interface.method:int? Function(int!)!*/
+  int? method(int i);
+}

pkg/_fe_analyzer_shared/test/inheritance/data/nsm_from_opt_in/main.dart

@@ -0,0 +1,25 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/*library: nnbd=false*/
+
+// @dart=2.6
+
+import 'opt_in.dart';
+
+/*class: B2:A,B2,C2,Object*/
+abstract class B2 extends A implements C2 {
+  /*member: B2.method:int* Function(int*,{dynamic optional})**/
+
+  /*member: B2.noSuchMethod:dynamic Function(Invocation*)**/
+  noSuchMethod(Invocation invocation) {
+    return super.noSuchMethod(invocation);
+  }
+}
+
+/*class: C2:C2,Object*/
+abstract class C2 {
+  /*member: C2.method:int* Function(int*,{dynamic optional})**/
+  int method(int i, {optional});
+}

pkg/_fe_analyzer_shared/test/inheritance/data/nsm_from_opt_in/opt_in.dart

@@ -0,0 +1,27 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/*library: nnbd=true*/
+
+/*class: A:A,Object*/
+class A {
+  /*member: A.method:int! Function(int?)!*/
+  int method(int? i) => i ?? 0;
+}
+
+/*class: B1:A,B1,C1,Object*/
+abstract class B1 extends A implements C1 {
+  /*member: B1.method:int! Function(int?,{dynamic optional})!*/
+
+  /*member: B1.noSuchMethod:dynamic Function(Invocation!)!*/
+  noSuchMethod(Invocation invocation) {
+    return super.noSuchMethod(invocation);
+  }
+}
+
+/*class: C1:C1,Object*/
+abstract class C1 {
+  /*member: C1.method:int! Function(int?,{dynamic optional})!*/
+  int method(int? i, {optional});
+}

pkg/_fe_analyzer_shared/test/inheritance/data/object_equals/core.dart

@@ -14,6 +14,10 @@ class Object {
   const Object();
 
   bool operator ==(Object other) => true;
+
+  noSuchMethod(Invocation invocation) => null;
+
+  String toString() => '';
 }
 
 /*class: Null:Null,Object*/
@@ -61,3 +65,6 @@ class Symbol {}
 
 /*class: Type:Object,Type*/
 class Type {}
+
+/*class: Invocation:Invocation,Object*/
+class Invocation {}

pkg/_fe_analyzer_shared/test/inheritance/data/object_equals/opt_out.dart

@@ -8,38 +8,77 @@
 
 /*class: Class1:Class1,Object*/
 class Class1 {
+  /*member: Class1.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: Class1.toString:String* Function()**/
+
   /*member: Class1.==:bool! Function(dynamic)**/
   operator ==(other) => true;
 }
 
 /*class: Class2a:Class2a,Object*/
 abstract class Class2a {
+  /*member: Class2a.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: Class2a.toString:String* Function()**/
+
   /*member: Class2a.==:bool* Function(Object*)**/
   bool operator ==(Object other);
 }
 
 /*class: Class2b:Class2a,Class2b,Object*/
 class Class2b extends Class2a {
+  /*member: Class2b.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: Class2b.toString:String* Function()**/
   /*member: Class2b.==:bool* Function(Object*)**/
 }
 
 /*class: Class3a:Class3a,Object*/
 class Class3a {
+  /*member: Class3a.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: Class3a.toString:String* Function()**/
   /*member: Class3a.==:bool* Function(Object*)**/
 }
 
 /*class: Class3b:Class3a,Class3b,Object*/
 abstract class Class3b extends Class3a {
+  /*member: Class3b.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: Class3b.toString:String* Function()**/
+
   /*member: Class3b.==:bool* Function(Object*)**/
   bool operator ==(Object other);
 }
 
 /*class: Class3c:Class3a,Class3b,Class3c,Object*/
 class Class3c extends Class3b {
+  /*member: Class3c.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: Class3c.toString:String* Function()**/
   /*member: Class3c.==:bool* Function(Object*)**/
 }
 
 /*class: Foo:Foo,Object*/
 class Foo extends /*error: TypeNotFound*/ Unresolved {
+  /*member: Foo.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: Foo.toString:String* Function()**/
   /*member: Foo.==:bool* Function(Object*)**/
 }
+
+/*class: A:A,Object*/
+abstract class A {
+  /*member: A.noSuchMethod:dynamic Function(Invocation*)**/
+  /*member: A.==:bool* Function(Object*)**/
+
+  /*member: A.toString:String* Function({bool* withNullability})**/
+  String toString({bool withNullability = false}) {
+    return '';
+  }
+}
+
+/*class: B:A,B,Object*/
+abstract class B implements A {
+  /*member: B.toString:String* Function({bool* withNullability})**/
+  /*member: B.==:bool* Function(Object*)**/
+
+  /*member: B.noSuchMethod:dynamic Function(Invocation*)**/
+  noSuchMethod(Invocation invocation) {
+    return super.noSuchMethod(invocation);
+  }
+}

pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart

@@ -551,8 +551,10 @@ class ClassHierarchyNodeBuilder {
           debug?.log("supertypes: checkValidOverride("
               "${classBuilder.fullNameForErrors}, "
               "${fullName(a)}, ${fullName(b)})");
-          checkValidOverride(a, b);
-          if (a is DelayedMember && !a.isInheritableConflict) {
+          if (a is! DelayedMember) {
+            checkValidOverride(a, b);
+          }
+          if (a is DelayedMember) {
             if (b is DelayedMember) {
               b.addAllDeclarationsTo(a.declarations);
             } else {
@@ -2432,7 +2434,7 @@ class InheritedImplementationInterfaceConflict extends DelayedMember {
     return parent == this.classBuilder
         ? this
         : new InheritedImplementationInterfaceConflict(
-            parent, declarations, isSetter, modifyKernel);
+            parent, declarations.toList(), isSetter, modifyKernel);
   }
 
   static ClassMember combined(
@@ -2497,9 +2499,13 @@ class InterfaceConflict extends DelayedMember {
       unhandled("${member.runtimeType}", "$member", classBuilder.charOffset,
           classBuilder.fileUri);
     }
-    return Substitution.fromInterfaceType(hierarchy.getKernelTypeAsInstanceOf(
-            thisType, member.enclosingClass, classBuilder.library.library))
-        .substituteType(type);
+    InterfaceType instance = hierarchy.getKernelTypeAsInstanceOf(
+        thisType, member.enclosingClass, classBuilder.library.library);
+    assert(
+        instance != null,
+        "No instance of $thisType as ${member.enclosingClass} found for "
+        "$member.");
+    return Substitution.fromInterfaceType(instance).substituteType(type);
   }
 
   bool isMoreSpecific(ClassHierarchyBuilder hierarchy, DartType a, DartType b) {
@@ -2628,7 +2634,8 @@ class InterfaceConflict extends DelayedMember {
   DelayedMember withParent(ClassBuilder parent) {
     return parent == this.classBuilder
         ? this
-        : new InterfaceConflict(parent, declarations, isSetter, modifyKernel);
+        : new InterfaceConflict(
+            parent, declarations.toList(), isSetter, modifyKernel);
   }
 
   static ClassMember combined(ClassBuilder parent, ClassMember a, ClassMember b,

pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart

@@ -0,0 +1,20 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=2.6
+
+import 'nsm_from_opt_in_lib.dart';
+
+abstract class B2 extends A implements C2 {
+  @override
+  noSuchMethod(Invocation invocation) {
+    return super.noSuchMethod(invocation);
+  }
+}
+
+abstract class C2 {
+  int method(int i, {optional});
+}
+
+main() {}

pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.outline.expect

@@ -0,0 +1,46 @@
+library;
+import self as self;
+import "nsm_from_opt_in_lib.dart" as nsm;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///nsm_from_opt_in_lib.dart";
+
+abstract class B2 extends nsm::A implements self::C2 {
+  synthetic constructor •() → self::B2*
+    ;
+  @core::override
+  method noSuchMethod(core::Invocation* invocation) → dynamic
+    ;
+  abstract forwarding-stub method method(core::int* i, {dynamic optional}) → core::int*;
+}
+abstract class C2 extends core::Object {
+  synthetic constructor •() → self::C2*
+    ;
+  abstract method method(core::int* i, {dynamic optional}) → core::int*;
+}
+static method main() → dynamic
+  ;
+
+library;
+import self as nsm;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → nsm::A
+    ;
+  method method(core::int? i) → core::int
+    ;
+}
+abstract class B1 extends nsm::A implements nsm::C1 {
+  synthetic constructor •() → nsm::B1
+    ;
+  @core::override
+  method noSuchMethod(core::Invocation invocation) → dynamic
+    ;
+  abstract forwarding-stub method method(core::int? i, {dynamic optional}) → core::int;
+}
+abstract class C1 extends core::Object {
+  synthetic constructor •() → nsm::C1
+    ;
+  abstract method method(core::int? i, {dynamic optional}) → core::int;
+}

pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.expect

@@ -0,0 +1,57 @@
+library;
+import self as self;
+import "nsm_from_opt_in_lib.dart" as nsm;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///nsm_from_opt_in_lib.dart";
+
+abstract class B2 extends nsm::A implements self::C2 {
+  synthetic constructor •() → self::B2*
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation* invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+abstract class C2 extends core::Object {
+  synthetic constructor •() → self::C2*
+    : super core::Object::•()
+    ;
+  abstract method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+static method main() → dynamic {}
+
+library;
+import self as nsm;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → nsm::A
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
+abstract class B1 extends nsm::A implements nsm::C1 {
+  synthetic constructor •() → nsm::B1
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+abstract class C1 extends core::Object {
+  synthetic constructor •() → nsm::C1
+    : super core::Object::•()
+    ;
+  abstract method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+
+constants  {
+  #C1 = core::_Override {}
+  #C2 = null
+}

pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.strong.transformed.expect

@@ -0,0 +1,57 @@
+library;
+import self as self;
+import "nsm_from_opt_in_lib.dart" as nsm;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///nsm_from_opt_in_lib.dart";
+
+abstract class B2 extends nsm::A implements self::C2 {
+  synthetic constructor •() → self::B2*
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation* invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+abstract class C2 extends core::Object {
+  synthetic constructor •() → self::C2*
+    : super core::Object::•()
+    ;
+  abstract method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+static method main() → dynamic {}
+
+library;
+import self as nsm;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → nsm::A
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
+abstract class B1 extends nsm::A implements nsm::C1 {
+  synthetic constructor •() → nsm::B1
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+abstract class C1 extends core::Object {
+  synthetic constructor •() → nsm::C1
+    : super core::Object::•()
+    ;
+  abstract method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+
+constants  {
+  #C1 = core::_Override {}
+  #C2 = null
+}

pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.expect

@@ -0,0 +1,57 @@
+library;
+import self as self;
+import "nsm_from_opt_in_lib.dart" as nsm;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///nsm_from_opt_in_lib.dart";
+
+abstract class B2 extends nsm::A implements self::C2 {
+  synthetic constructor •() → self::B2*
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation* invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+abstract class C2 extends core::Object {
+  synthetic constructor •() → self::C2*
+    : super core::Object::•()
+    ;
+  abstract method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+static method main() → dynamic {}
+
+library;
+import self as nsm;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → nsm::A
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
+abstract class B1 extends nsm::A implements nsm::C1 {
+  synthetic constructor •() → nsm::B1
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+abstract class C1 extends core::Object {
+  synthetic constructor •() → nsm::C1
+    : super core::Object::•()
+    ;
+  abstract method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+
+constants  {
+  #C1 = core::_Override {}
+  #C2 = null
+}

pkg/front_end/testcases/nnbd/nsm_from_opt_in.dart.weak.transformed.expect

@@ -0,0 +1,57 @@
+library;
+import self as self;
+import "nsm_from_opt_in_lib.dart" as nsm;
+import "dart:core" as core;
+
+import "org-dartlang-testcase:///nsm_from_opt_in_lib.dart";
+
+abstract class B2 extends nsm::A implements self::C2 {
+  synthetic constructor •() → self::B2*
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation* invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+abstract class C2 extends core::Object {
+  synthetic constructor •() → self::C2*
+    : super core::Object::•()
+    ;
+  abstract method method(core::int* i, {dynamic optional = #C2}) → core::int*;
+}
+static method main() → dynamic {}
+
+library;
+import self as nsm;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → nsm::A
+    : super core::Object::•()
+    ;
+  method method(core::int? i) → core::int
+    return let final core::int? #t1 = i in #t1.{core::num::==}(null) ?{core::int} 0 : #t1{core::int};
+}
+abstract class B1 extends nsm::A implements nsm::C1 {
+  synthetic constructor •() → nsm::B1
+    : super nsm::A::•()
+    ;
+  @#C1
+  method noSuchMethod(core::Invocation invocation) → dynamic {
+    return super.{core::Object::noSuchMethod}(invocation);
+  }
+  abstract forwarding-stub method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+abstract class C1 extends core::Object {
+  synthetic constructor •() → nsm::C1
+    : super core::Object::•()
+    ;
+  abstract method method(core::int? i, {dynamic optional = #C2}) → core::int;
+}
+
+constants  {
+  #C1 = core::_Override {}
+  #C2 = null
+}

pkg/front_end/testcases/nnbd/nsm_from_opt_in_lib.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class A {
+  int method(int? i) => i ?? 0;
+}
+
+abstract class B1 extends A implements C1 {
+  @override
+  noSuchMethod(Invocation invocation) {
+    return super.noSuchMethod(invocation);
+  }
+}
+
+abstract class C1 {
+  int method(int? i, {optional});
+}

pkg/front_end/testcases/text_serialization.status

@@ -1248,6 +1248,7 @@ nnbd/no_null_shorting: TextSerializationFailure
 nnbd/no_null_shorting_explicit_extension: TextSerializationFailure
 nnbd/no_null_shorting_extension: TextSerializationFailure
 nnbd/non_nullable_field_initialization: TextSerializationFailure
+nnbd/nsm_from_opt_in: TextSerializationFailure
 nnbd/null_access: TextSerializationFailure
 nnbd/null_aware_chain: TextSerializationFailure
 nnbd/null_check: TextSerializationFailure