[cfe] Handle mixing in Function

Closes #35477
Closes #35573

Change-Id: I0612641108caf1fa08da1aae7684e7f33dfe3b46
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/140402
Reviewed-by: Jens Johansen <jensj@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

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

@@ -12,8 +12,13 @@ class A implements Function {}
 /*analyzer.class: B:B,Function,Object*/
 class B extends Function {}
 
-/*class: C:C,Function,Object*/
-class C extends Object with Function {
-  /*cfe|cfe:builder.member: C.hashCode:int**/
-  /*cfe|cfe:builder.member: C.==:bool* Function(Object*)**/
-}
+/*cfe|cfe:builder.class: C:C,Object,_C&Object&Function*/
+/*analyzer.class: C:C,Function,Object*/
+class C extends Object with Function {}
+
+// CFE hides that this is a mixin declaration since its mixed in type has been
+// removed.
+/*cfe|cfe:builder.class: _C&Object&Function:Object,_C&Object&Function*/
+
+/*cfe|cfe:builder.class: D:D,Object*/
+class D = Object with Function;

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

@@ -77,6 +77,7 @@ import '../fasta_codes.dart'
         noLength,
         messageExtendFunction,
         messageImplementFunction,
+        messageMixinFunction,
         templateConflictsWithConstructor,
         templateConflictsWithFactory,
         templateConflictsWithMember,
@@ -245,13 +246,24 @@ class SourceClassBuilder extends ClassBuilderImpl
     actualCls.supertype = supertype;
 
     mixedInTypeBuilder = checkSupertype(mixedInTypeBuilder);
-    actualCls.mixedInType =
+    Supertype mixedInType =
         mixedInTypeBuilder?.buildMixedInType(library, charOffset, fileUri);
-    if (actualCls.mixedInType == null &&
-        mixedInTypeBuilder is! NamedTypeBuilder) {
+    if (mixedInType != null) {
+      Class superclass = mixedInType.classNode;
+      if (superclass.name == 'Function' &&
+          superclass.enclosingLibrary == coreLibrary.library) {
+        library.addProblem(messageMixinFunction, charOffset, noLength, fileUri);
+        mixedInType = null;
+        mixedInTypeBuilder = null;
+        actualCls.isAnonymousMixin = false;
+        isMixinDeclaration = false;
+      }
+    }
+    if (mixedInType == null && mixedInTypeBuilder is! NamedTypeBuilder) {
       mixedInTypeBuilder = null;
     }
     actualCls.isMixinDeclaration = isMixinDeclaration;
+    actualCls.mixedInType = mixedInType;
 
     // TODO(ahe): If `cls.supertype` is null, and this isn't Object, report a
     // compile-time error.

pkg/front_end/messages.status

@@ -459,7 +459,7 @@ MissingPartOf/part_wrapped_script: Fail # Using 'part' in the (now) part.
 MissingPrefixInDeferredImport/example: Fail
 MixinDeclaresConstructor/example: Fail
 MixinFunction/part_wrapped_script: Fail
-MixinFunction/script: Fail # TODO(johnniwinther): Handle mixing in Function
+MixinFunction/script: Fail # TODO(johnniwinther): This message is currently ignored.
 MixinInferenceNoMatchingClass/example: Fail
 ModifierOutOfOrder/part_wrapped_script1: Fail
 ModifierOutOfOrder/script1: Fail

pkg/front_end/testcases/general/inherit_function.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.
+
+class A implements Function {}
+
+class B extends Function {}
+
+class C extends Object with Function {}
+
+class D = Object with Function;
+
+main() {}

pkg/front_end/testcases/general/inherit_function.dart.outline.expect

@@ -0,0 +1,26 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → self::A*
+    ;
+}
+class B extends core::Object {
+  synthetic constructor •() → self::B*
+    ;
+}
+abstract class _C&Object&Function extends core::Object {
+  synthetic constructor •() → self::_C&Object&Function*
+    ;
+}
+class C extends self::_C&Object&Function {
+  synthetic constructor •() → self::C*
+    ;
+}
+class D extends core::Object {
+  synthetic constructor •() → self::D*
+    ;
+}
+static method main() → dynamic
+  ;

pkg/front_end/testcases/general/inherit_function.dart.strong.expect

@@ -0,0 +1,30 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → self::A*
+    : super core::Object::•()
+    ;
+}
+class B extends core::Object {
+  synthetic constructor •() → self::B*
+    : super core::Object::•()
+    ;
+}
+abstract class _C&Object&Function extends core::Object {
+  synthetic constructor •() → self::_C&Object&Function*
+    : super core::Object::•()
+    ;
+}
+class C extends self::_C&Object&Function {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&Function::•()
+    ;
+}
+class D extends core::Object {
+  synthetic constructor •() → self::D*
+    : super core::Object::•()
+    ;
+}
+static method main() → dynamic {}

pkg/front_end/testcases/general/inherit_function.dart.strong.transformed.expect

@@ -0,0 +1,30 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  synthetic constructor •() → self::A*
+    : super core::Object::•()
+    ;
+}
+class B extends core::Object {
+  synthetic constructor •() → self::B*
+    : super core::Object::•()
+    ;
+}
+abstract class _C&Object&Function extends core::Object {
+  synthetic constructor •() → self::_C&Object&Function*
+    : super core::Object::•()
+    ;
+}
+class C extends self::_C&Object&Function {
+  synthetic constructor •() → self::C*
+    : super self::_C&Object&Function::•()
+    ;
+}
+class D extends core::Object {
+  synthetic constructor •() → self::D*
+    : super core::Object::•()
+    ;
+}
+static method main() → dynamic {}

pkg/front_end/testcases/text_serialization.status

@@ -218,6 +218,7 @@ general/infer_field_from_multiple: TypeCheckError
 general/infer_field_type: TextSerializationFailure
 general/infer_fixed_generic_return_type: TextSerializationFailure
 general/infer_map_literal_with_closure: TextSerializationFailure
+general/inherit_function: TextSerializationFailure
 general/interface_conflict: TextSerializationFailure
 general/interface_contravariant_from_class: TextSerializationFailure
 general/interface_covariantImpl_from_class: TextSerializationFailure