[fasta] Allow const constructors in mixin applications

Closes #33644, closes #33645, closes #32223.

Bug: http://dartbug.com/33644
Bug: http://dartbug.com/33645
Bug: http://dartbug.com/32223
Change-Id: Ia30efb8f450e62bfeb65c8b7fd7e23871ef0e87e
Reviewed-on: https://dart-review.googlesource.com/c/68368
Reviewed-by: Peter von der Ahé <[email protected]>
Reviewed-by: Erik Ernst <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Dmitry Stefantsov <[email protected]>

Author: Dmitry Stefantsov

pkg/front_end/lib/src/fasta/fasta_codes_generated.dart

@@ -922,18 +922,6 @@ const MessageCode messageConstClass = const MessageCode("ConstClass",
     tip:
         r"""Try removing the 'const' keyword. If you're trying to indicate that instances of the class can be constants, place the 'const' keyword on  the class' constructor(s).""");
 
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Null> codeConstConstructorInSubclassOfMixinApplication =
-    messageConstConstructorInSubclassOfMixinApplication;
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const MessageCode messageConstConstructorInSubclassOfMixinApplication =
-    const MessageCode("ConstConstructorInSubclassOfMixinApplication",
-        analyzerCodes: <String>[
-      "CONST_CONSTRUCTOR_IN_SUBCLASS_OF_MIXIN_APPLICATION"
-    ],
-        message: r"""Can't extend a mixin application and be 'const'.""");
-
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeConstConstructorNonFinalField =
     messageConstConstructorNonFinalField;

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

@@ -599,11 +599,6 @@ abstract class BodyBuilder extends ScopeListener<JumpTarget>
     ProcedureBuilder<TypeBuilder> member = this.member;
     scope = member.computeFormalParameterInitializerScope(scope);
     if (member is KernelConstructorBuilder) {
-      if (member.isConst &&
-          (classBuilder.cls.superclass?.isMixinApplication ?? false)) {
-        addProblem(fasta.messageConstConstructorInSubclassOfMixinApplication,
-            member.charOffset, member.name.length);
-      }
       if (member.formals != null) {
         for (KernelFormalParameterBuilder formal in member.formals) {
           if (formal.isInitializingFormal) {

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

@@ -533,7 +533,8 @@ class KernelTarget extends TargetImplementation {
     return new Constructor(function,
         name: constructor.name,
         initializers: <Initializer>[initializer],
-        isSynthetic: true);
+        isSynthetic: true,
+        isConst: constructor.isConst && mixin.fields.isEmpty);
   }
 
   void finishClonedParameters() {

pkg/front_end/messages.yaml

@@ -2665,10 +2665,6 @@ ConstConstructorNonFinalFieldCause:
   template: "Field isn't final, but constructor is 'const'."
   severity: CONTEXT
 
-ConstConstructorInSubclassOfMixinApplication:
-  template: "Can't extend a mixin application and be 'const'."
-  analyzerCode: CONST_CONSTRUCTOR_IN_SUBCLASS_OF_MIXIN_APPLICATION
-
 ConstConstructorRedirectionToNonConst:
   template: "A constant constructor can't call a non-constant constructor."
   script:

pkg/front_end/testcases/bug33099.dart.outline.expect

@@ -14,7 +14,7 @@ class MyTest extends core::Object {
     ;
 }
 abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest {
-  synthetic constructor •() → self::_MyTest2&Object&MyTest
+  const synthetic constructor •() → self::_MyTest2&Object&MyTest
     : super core::Object::•()
     ;
 }

pkg/front_end/testcases/bug33099.dart.strong.expect

@@ -16,7 +16,7 @@ class MyTest extends core::Object {
   method foo() → void {}
 }
 abstract class _MyTest2&Object&MyTest = core::Object with self::MyTest {
-  synthetic constructor •() → self::_MyTest2&Object&MyTest
+  const synthetic constructor •() → self::_MyTest2&Object&MyTest
     : super core::Object::•()
     ;
 }

pkg/front_end/testcases/bug33099.dart.strong.transformed.expect

@@ -16,7 +16,7 @@ class MyTest extends core::Object {
   method foo() → void {}
 }
 abstract class _MyTest2&Object&MyTest extends core::Object implements self::MyTest {
-  synthetic constructor •() → self::_MyTest2&Object&MyTest
+  const synthetic constructor •() → self::_MyTest2&Object&MyTest
     : super core::Object::•()
     ;
   @self::failingTest

pkg/front_end/testcases/bug34511.dart.legacy.expect

@@ -8,7 +8,7 @@ class A<X extends core::Object = dynamic> extends core::Object {
     ;
 }
 abstract class _B&Object&A<Z extends core::Object = dynamic> = core::Object with self::A<() → self::_B&Object&A::Z> {
-  synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
+  const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
     : super core::Object::•()
     ;
 }

pkg/front_end/testcases/bug34511.dart.legacy.transformed.expect

@@ -8,7 +8,7 @@ class A<X extends core::Object = dynamic> extends core::Object {
     ;
 }
 abstract class _B&Object&A<Z extends core::Object = dynamic> extends core::Object implements self::A<() → self::_B&Object&A::Z> {
-  synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
+  const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
     : super core::Object::•()
     ;
 }

pkg/front_end/testcases/bug34511.dart.outline.expect

@@ -7,7 +7,7 @@ class A<X extends core::Object = dynamic> extends core::Object {
     ;
 }
 abstract class _B&Object&A<Z extends core::Object = dynamic> = core::Object with self::A<() → self::_B&Object&A::Z> {
-  synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
+  const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
     : super core::Object::•()
     ;
 }

pkg/front_end/testcases/bug34511.dart.strong.expect

@@ -8,7 +8,7 @@ class A<X extends core::Object = dynamic> extends core::Object {
     ;
 }
 abstract class _B&Object&A<Z extends core::Object = dynamic> = core::Object with self::A<() → self::_B&Object&A::Z> {
-  synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
+  const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
     : super core::Object::•()
     ;
 }

pkg/front_end/testcases/bug34511.dart.strong.transformed.expect

@@ -8,7 +8,7 @@ class A<X extends core::Object = dynamic> extends core::Object {
     ;
 }
 abstract class _B&Object&A<Z extends core::Object = dynamic> extends core::Object implements self::A<() → self::_B&Object&A::Z> {
-  synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
+  const synthetic constructor •() → self::_B&Object&A<self::_B&Object&A::Z>
     : super core::Object::•()
     ;
 }