[cfe] Handle Object* in NNBD_TOP_MERGE

Closes flutter#40481

Change-Id: I5f1060b137e9855106873b2173930d3ebed69930
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/137921
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Dmitry Stefantsov <dmitryas@google.com>

Author: johnniwinther

pkg/_fe_analyzer_shared/test/inheritance/data/issue40481.dart

@@ -0,0 +1,26 @@
+// 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<T>,Object*/
+class A<T> {}
+
+/*class: A_Object:A<Object?>,A_Object,Object*/
+class A_Object implements A<Object?> {}
+
+/*class: A_dynamic:A<dynamic>,A_dynamic,Object*/
+class A_dynamic implements A<dynamic> {}
+
+/*class: A_void:A<void>,A_void,Object*/
+class A_void implements A<void> {}
+
+/*class: B1:A<Object?>,A_Object,A_dynamic,B1,Object*/
+class B1 extends A_Object implements A_dynamic {}
+
+/*cfe|cfe:builder.class: B2:A<void>,A_Object,A_void,B2,Object*/
+/*analyzer.class: B2:A<Object?>,A_Object,A_void,B2,Object*/
+class B2 extends A_Object implements A_void {}
+
+main() {}

pkg/_fe_analyzer_shared/test/inheritance/data/issue40481/main.dart

@@ -0,0 +1,23 @@
+// 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*/
+
+import "opt_out.dart";
+
+/*class: A_dynamic:A<dynamic>,A_dynamic,Object*/
+class A_dynamic implements A<dynamic> {}
+
+/*class: A_void:A<void>,A_void,Object*/
+class A_void implements A<void> {}
+
+/*cfe|cfe:builder.class: B1:A<Object?>,A_Object,A_dynamic,B1,Object*/
+/*analyzer.class: B1:A<Object*>,A_Object,A_dynamic,B1,Object*/
+class B1 extends A_Object implements A_dynamic {}
+
+/*cfe|cfe:builder.class: B2:A<void>,A_Object,A_void,B2,Object*/
+/*analyzer.class: B2:A<Object*>,A_Object,A_void,B2,Object*/
+class B2 extends A_Object implements A_void {}
+
+main() {}

pkg/_fe_analyzer_shared/test/inheritance/data/issue40481/opt_out.dart

@@ -0,0 +1,13 @@
+// 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*/
+
+/*class: A:A<T*>,Object*/
+class A<T> {}
+
+/*class: A_Object:A<Object*>,A_Object,Object*/
+class A_Object implements A<Object> {}

pkg/kernel/lib/src/nnbd_top_merge.dart

@@ -61,6 +61,14 @@ class NnbdTopMergeVisitor extends MergeVisitor {
         // NNBD_TOP_MERGE(Object?, Object?) = Object?
         return coreTypes.objectNullableRawType;
       }
+    } else if (a == coreTypes.objectLegacyRawType) {
+      if (b is DynamicType) {
+        // NNBD_TOP_MERGE(Object*, dynamic) = Object?
+        return coreTypes.objectNullableRawType;
+      } else if (b is VoidType) {
+        // NNBD_TOP_MERGE(Object*, void) = void
+        return const VoidType();
+      }
     } else if (a == coreTypes.nullType &&
         b is NeverType &&
         b.nullability == Nullability.legacy) {
@@ -81,6 +89,9 @@ class NnbdTopMergeVisitor extends MergeVisitor {
     } else if (b == coreTypes.objectNullableRawType) {
       // NNBD_TOP_MERGE(void, Object?) = void
       return const VoidType();
+    } else if (b == coreTypes.objectLegacyRawType) {
+      // NNBD_TOP_MERGE(void, Object*) = void
+      return const VoidType();
     }
     return null;
   }
@@ -94,7 +105,10 @@ class NnbdTopMergeVisitor extends MergeVisitor {
       // NNBD_TOP_MERGE(dynamic, void) = void
       return const VoidType();
     } else if (b == coreTypes.objectNullableRawType) {
-      // NNBD_TOP_MERGE(Object?, dynamic) = Object?
+      // NNBD_TOP_MERGE(dynamic, Object?) = Object?
+      return coreTypes.objectNullableRawType;
+    } else if (b == coreTypes.objectLegacyRawType) {
+      // NNBD_TOP_MERGE(dynamic, Object*) = Object?
       return coreTypes.objectNullableRawType;
     }
     return null;

pkg/kernel/test/nnbd_top_merge_test.dart

@@ -13,15 +13,16 @@ const Map<String, dynamic> data = {
   'Object* vs Object?': 'Object?',
   'Object vs Object?': null,
   'Object* vs Object': 'Object',
+  'Object* vs Object*': 'Object*',
   'Object vs Object': 'Object',
   'dynamic vs dynamic': 'dynamic',
   'void vs void': 'void',
   'Object? vs void': 'void',
-  'Object* vs void': null,
+  'Object* vs void': 'void',
   'Object vs void': null,
   'dynamic vs void': 'void',
   'Object? vs dynamic': 'Object?',
-  'Object* vs dynamic': null,
+  'Object* vs dynamic': 'Object?',
   'Object vs dynamic': null,
   'Never? vs Null': null,
   'Never* vs Null': 'Null',
@@ -32,6 +33,24 @@ const Map<String, dynamic> data = {
   'int* vs int': 'int',
   'int vs int': 'int',
   'int? vs int': null,
+  'List<Object?> vs List<Object?>': 'List<Object?>',
+  'List<Object*> vs List<Object?>': 'List<Object?>',
+  'List<Object*> vs List<Object*>': 'List<Object*>',
+  'List<Object> vs List<Object?>': null,
+  'List<Object*> vs List<Object>': 'List<Object>',
+  'List<Object> vs List<Object>': 'List<Object>',
+  'List<dynamic> vs List<dynamic>': 'List<dynamic>',
+  'List<void> vs List<void>': 'List<void>',
+  'List<Object?> vs List<void>': 'List<void>',
+  'List<Object*> vs List<void>': 'List<void>',
+  'List<Object> vs List<void>': null,
+  'List<dynamic> vs List<void>': 'List<void>',
+  'List<Object?> vs List<dynamic>': 'List<Object?>',
+  'List<Object*> vs List<dynamic>': 'List<Object?>',
+  'List<Object> vs List<dynamic>': null,
+  'List<Never?> vs List<Null>': null,
+  'List<Never*> vs List<Null>': 'List<Null>',
+  'List<Never> vs List<Null>': null,
   'List<int?> vs List<int?>': 'List<int?>',
   'List<int?> vs List<int*>': 'List<int?>',
   'List<int*> vs List<int*>': 'List<int*>',