[cfe] Handle static type of access on Never

Closes #41273

Change-Id: Ia236481ab47033198d7952086cdf5c9c8f5a34b7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/142366
Commit-Queue: Johnni Winther <[email protected]>
Reviewed-by: Dmitry Stefantsov <[email protected]>

Author: johnniwinther

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

@@ -1036,23 +1036,10 @@ class TypeInferrerImpl implements TypeInferrer {
 
     if (receiverType is FunctionType && name == callName) {
       return const ObjectAccessTarget.callFunction();
-    }
-
-    Class classNode = receiverType is InterfaceType
-        ? receiverType.classNode
-        : coreTypes.objectClass;
-    Member interfaceMember =
-        _getInterfaceMember(classNode, name, setter, fileOffset);
-    ObjectAccessTarget target;
-    if (interfaceMember != null) {
-      target = new ObjectAccessTarget.interfaceMember(interfaceMember);
-    } else if (receiverType is DynamicType) {
-      target = const ObjectAccessTarget.dynamic();
     } else if (receiverType is NeverType) {
       switch (receiverType.nullability) {
         case Nullability.nonNullable:
-          target = const ObjectAccessTarget.never();
-          break;
+          return const ObjectAccessTarget.never();
         case Nullability.nullable:
         case Nullability.legacy:
           // Never? and Never* are equivalent to Null.
@@ -1066,6 +1053,17 @@ class TypeInferrerImpl implements TypeInferrer {
               fileOffset,
               library.fileUri);
       }
+    }
+    Class classNode = receiverType is InterfaceType
+        ? receiverType.classNode
+        : coreTypes.objectClass;
+    Member interfaceMember =
+        _getInterfaceMember(classNode, name, setter, fileOffset);
+    ObjectAccessTarget target;
+    if (interfaceMember != null) {
+      target = new ObjectAccessTarget.interfaceMember(interfaceMember);
+    } else if (receiverType is DynamicType) {
+      target = const ObjectAccessTarget.dynamic();
     } else if (receiverType is InvalidType) {
       target = const ObjectAccessTarget.invalid();
     } else if (receiverType is InterfaceType &&
@@ -1940,6 +1938,10 @@ class TypeInferrerImpl implements TypeInferrer {
     Member equalsMember =
         findInterfaceMember(variable.type, equalsName, variable.fileOffset)
             .member;
+    // Ensure operator == member even for `Never`.
+    equalsMember ??= findInterfaceMember(const DynamicType(), equalsName, -1,
+            instrumented: false)
+        .member;
     return new NullAwareGuard(
         variable, variable.fileOffset, equalsMember, this);
   }
@@ -2736,7 +2738,7 @@ class TypeInferrerImpl implements TypeInferrer {
         isImplicitCall: isImplicitCall);
     assert(name != equalsName);
     return createNullAwareExpressionInferenceResult(
-        result.inferredType,
+        const NeverType(Nullability.nonNullable),
         result.applyResult(new MethodInvocation(receiver, name, arguments)
           ..fileOffset = fileOffset),
         nullAwareGuards);

pkg/front_end/test/spell_checking_list_code.txt

@@ -689,6 +689,7 @@ nulls
 o
 oauth
 obj
+obligated
 observatory
 observe
 obstruct

pkg/front_end/testcases/nnbd/issue41210a/issue41210_lib1.dart.strong.transformed.expect

@@ -0,0 +1,63 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{self::C::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41210a/issue41210_lib1.dart.weak.transformed.expect

@@ -0,0 +1,63 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+  abstract forwarding-stub method method({core::String* s = #C1}) → core::String*;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{self::C::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41210b.dart.strong.transformed.expect

@@ -0,0 +1,62 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210b_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210b_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract member-signature method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method() → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{iss::A::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210b_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210b_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41210b.dart.weak.transformed.expect

@@ -0,0 +1,62 @@
+library;
+import self as self;
+import "dart:core" as core;
+import "issue41210b_lib1.dart" as iss;
+
+import "org-dartlang-testcase:///issue41210b_lib1.dart";
+
+abstract class _C&Object&A extends core::Object implements iss::A /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A*
+    : super core::Object::•()
+    ;
+  method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class _C&Object&A&B extends self::_C&Object&A implements iss::B /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_C&Object&A&B*
+    : super self::_C&Object&A::•()
+    ;
+  abstract member-signature method /* from org-dartlang-testcase:///issue41210b_lib1.dart */ method() → core::String*;
+}
+class C extends self::_C&Object&A&B {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&A&B::•()
+    ;
+}
+static method main() → dynamic {
+  core::print(new self::C::•().{iss::A::method}());
+}
+
+library;
+import self as iss;
+import "dart:core" as core;
+import "issue41210b_lib2.dart" as iss2;
+
+import "org-dartlang-testcase:///issue41210b_lib2.dart";
+
+abstract class A extends core::Object implements iss2::Interface /*isMixinDeclaration*/  {
+  method method({core::String* s = #C1}) → core::String*
+    return s;
+}
+abstract class B extends core::Object implements iss2::Interface {
+  synthetic constructor •() → iss::B*
+    : super core::Object::•()
+    ;
+  abstract member-signature method method() → core::String*;
+}
+static method main() → void {}
+
+library /*isNonNullableByDefault*/;
+import self as iss2;
+import "dart:core" as core;
+
+abstract class Interface extends core::Object {
+  synthetic constructor •() → iss2::Interface
+    : super core::Object::•()
+    ;
+  abstract method method() → core::String;
+}
+
+constants  {
+  #C1 = "hello"
+}

pkg/front_end/testcases/nnbd/issue41273.dart

@@ -0,0 +1,32 @@
+// 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.
+
+void test(var x) {
+  if (x is Never) {
+    Never n1 = x.toString();
+    Never n2 = x.runtimeType;
+    Never n3 = x.someGetter;
+    Never n4 = x.someMethod();
+    Never n5 = x + x;
+    Never n6 = x[x];
+    Never n7 = x();
+    Never n8 = x.runtimeType();
+    Never n9 = x.toString;
+    x.runtimeType = Object;
+    x.toString = () => '';
+    var v1 = x.toString();
+    var v2 = x.runtimeType;
+    var v3 = x.someGetter;
+    var v4 = x.someMethod();
+    var v5 = x + x;
+    var v6 = x[x];
+    var v7 = x();
+    var v8 = x.runtimeType();
+    var v9 = x.toString;
+  }
+}
+
+main() {
+  test(null);
+}

pkg/front_end/testcases/nnbd/issue41273.dart.outline.expect

@@ -0,0 +1,7 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+
+static method test(dynamic x) → void
+  ;
+static method main() → dynamic
+  ;

pkg/front_end/testcases/nnbd/issue41273.dart.strong.expect

@@ -0,0 +1,31 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → void {
+  if(x is{ForNonNullableByDefault} Never) {
+    Never n1 = x{Never}.toString();
+    Never n2 = x{Never}.runtimeType;
+    Never n3 = x{Never}.someGetter;
+    Never n4 = x{Never}.someMethod();
+    Never n5 = x{Never}.+(x{Never});
+    Never n6 = x{Never}.[](x{Never});
+    Never n7 = x{Never}.call();
+    Never n8 = x{Never}.runtimeType();
+    Never n9 = x{Never}.toString;
+    x{Never}.runtimeType = core::Object;
+    x{Never}.toString = () → core::String => "";
+    Never v1 = x{Never}.toString();
+    Never v2 = x{Never}.runtimeType;
+    Never v3 = x{Never}.someGetter;
+    Never v4 = x{Never}.someMethod();
+    Never v5 = x{Never}.+(x{Never});
+    Never v6 = x{Never}.[](x{Never});
+    Never v7 = x{Never}.call();
+    Never v8 = x{Never}.runtimeType();
+    Never v9 = x{Never}.toString;
+  }
+}
+static method main() → dynamic {
+  self::test(null);
+}