[dart2wasm] Make int, double, bool box fields immutable

Make the `value` fields of `BoxedInt`, `BoxedDouble` and `BoxedBool`
`final`, to generate immutable Wasm fields for them.

Immutable fields can potentially generate better code, as loads from the
same object will always generate the same value.

To allow making the `value` fields `final`, add a constructor.

To allow adding a constructor, "implement` base classes instead of
extending them. With `extends` the front-end wants us to call the
superclass constructors, even though they don't have any constructors.

Implementing `bool` (instead of extending) causes issues in TFA as it
currently assumes bool literals are compiled as the `bool` class. Update
TFA to treat bool literals the same way as `int` and `double` literals.

Tested: existing tests
Change-Id: I3282e188d784fa7a22421edc79ed47f9d85faf19
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/393320
Commit-Queue: Ömer Ağacan <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>

Author: osa1

pkg/dart2wasm/lib/class_info.dart

@@ -311,7 +311,10 @@ class ClassInfoCollector {
       // directly below the public classes they implement.
       // All other classes sit below their superclass.
       ClassInfo superInfo = cls == translator.coreTypes.boolClass ||
-              cls == translator.coreTypes.numClass
+              cls == translator.coreTypes.numClass ||
+              cls == translator.boxedIntClass ||
+              cls == translator.boxedDoubleClass ||
+              cls == translator.boxedBoolClass
           ? topInfo
           : (!translator.options.jsCompatibility &&
                       cls == translator.wasmStringBaseClass) ||

pkg/dart2wasm/lib/target.dart

@@ -112,6 +112,7 @@ class WasmTarget extends Target {
   Class? _closure;
   Class? _boxedInt;
   Class? _boxedDouble;
+  Class? _boxedBool;
   Map<String, Class>? _nativeClasses;
 
   @override
@@ -546,6 +547,10 @@ class WasmTarget extends Target {
       _boxedDouble ??=
           coreTypes.index.getClass("dart:_boxed_double", "BoxedDouble");
 
+  @override
+  Class concreteBoolLiteralClass(CoreTypes coreTypes, bool value) =>
+      _boxedBool ??= coreTypes.index.getClass("dart:_boxed_bool", "BoxedBool");
+
   @override
   DartLibrarySupport get dartLibrarySupport => CustomizedDartLibrarySupport(
       unsupported: {if (!enableExperimentalFfi) 'ffi'});

pkg/dart2wasm/lib/translator.dart

@@ -240,7 +240,7 @@ class Translator with KernelNodes {
   late final Map<Class, Class> valueClasses = {
     boxedIntClass: boxedIntClass,
     boxedDoubleClass: boxedDoubleClass,
-    boxedBoolClass: coreTypes.boolClass,
+    boxedBoolClass: boxedBoolClass,
     if (!options.jsCompatibility) ...{
       oneByteStringClass: stringBaseClass,
       twoByteStringClass: stringBaseClass

pkg/kernel/lib/target/targets.dart

@@ -507,6 +507,7 @@ abstract class Target {
   Class? concreteIntLiteralClass(CoreTypes coreTypes, int value) => null;
   Class? concreteDoubleLiteralClass(CoreTypes coreTypes, double value) => null;
   Class? concreteStringLiteralClass(CoreTypes coreTypes, String value) => null;
+  Class? concreteBoolLiteralClass(CoreTypes coreTypes, bool value) => null;
 
   Class? concreteAsyncResultClass(CoreTypes coreTypes) => null;
   Class? concreteSyncStarResultClass(CoreTypes coreTypes) => null;

pkg/vm/lib/transformations/type_flow/summary_collector.dart

@@ -1425,8 +1425,6 @@ class SummaryCollector extends RecursiveResultVisitor<TypeExpr?> {
 
   Class get _superclass => _staticTypeContext!.thisType!.classNode.superclass!;
 
-  Type _boolLiteralType(bool value) => value ? _boolTrue : _boolFalse;
-
   Type _intLiteralType(int value, Constant? constant) {
     final Class? concreteClass =
         target.concreteIntLiteralClass(_environment.coreTypes, value);
@@ -1466,6 +1464,19 @@ class SummaryCollector extends RecursiveResultVisitor<TypeExpr?> {
     return _stringType;
   }
 
+  Type _boolLiteralType(bool value, Constant? constant) {
+    final Class? concreteClass =
+        target.concreteBoolLiteralClass(_environment.coreTypes, value);
+    if (concreteClass != null) {
+      constant ??= BoolConstant(value);
+      return _entryPointsListener
+          .addAllocatedClass(concreteClass)
+          .cls
+          .constantConcreteType(constant);
+    }
+    return value ? _boolTrue : _boolFalse;
+  }
+
   TypeExpr _closureType(LocalFunction node) {
     final Class? concreteClass =
         target.concreteClosureClass(_environment.coreTypes);
@@ -1682,7 +1693,7 @@ class SummaryCollector extends RecursiveResultVisitor<TypeExpr?> {
 
   @override
   TypeExpr visitBoolLiteral(BoolLiteral node) {
-    return _boolLiteralType(node.value);
+    return _boolLiteralType(node.value, null);
   }
 
   @override
@@ -2845,7 +2856,7 @@ class ConstantAllocationCollector implements ConstantVisitor<Type> {
 
   @override
   Type visitBoolConstant(BoolConstant constant) {
-    return summaryCollector._boolLiteralType(constant.value);
+    return summaryCollector._boolLiteralType(constant.value, constant);
   }
 
   @override

sdk/lib/_internal/wasm/lib/boxed_bool.dart

@@ -3,13 +3,19 @@
 // BSD-style license that can be found in the LICENSE file.
 
 @pragma("wasm:entry-point")
-final class BoxedBool extends bool {
+final class BoxedBool implements bool {
   // A boxed bool contains an unboxed bool.
   @pragma("wasm:entry-point")
-  bool value = false;
+  final bool value;
 
-  /// Dummy factory to silence error about missing superclass constructor.
-  external factory BoxedBool();
+  @pragma("wasm:entry-point")
+  BoxedBool._(this.value);
+
+  @override
+  int get hashCode => this ? 1231 : 1237;
+
+  @override
+  String toString() => this ? "true" : "false";
 
   @override
   bool operator ==(Object other) {
@@ -18,7 +24,12 @@ final class BoxedBool extends bool {
         : false;
   }
 
+  @override
   bool operator &(bool other) => this & other; // Intrinsic &
+
+  @override
   bool operator ^(bool other) => this ^ other; // Intrinsic ^
+
+  @override
   bool operator |(bool other) => this | other; // Intrinsic |
 }

sdk/lib/_internal/wasm/lib/boxed_double.dart

@@ -9,13 +9,13 @@ import 'dart:_string';
 import 'dart:_wasm';
 
 @pragma("wasm:entry-point")
-final class BoxedDouble extends double {
+final class BoxedDouble implements double {
   // A boxed double contains an unboxed double.
   @pragma("wasm:entry-point")
-  double value = 0.0;
+  final double value;
 
-  /// Dummy factory to silence error about missing superclass constructor.
-  external factory BoxedDouble();
+  @pragma("wasm:entry-point")
+  BoxedDouble._(this.value);
 
   static const int _mantissaBits = 52;
   static const int _exponentBits = 11;

sdk/lib/_internal/wasm/lib/boxed_int.dart

@@ -7,13 +7,13 @@ import 'dart:_internal';
 import 'dart:_wasm';
 
 @pragma("wasm:entry-point")
-final class BoxedInt extends int {
+final class BoxedInt implements int {
   // A boxed int contains an unboxed int.
   @pragma("wasm:entry-point")
-  int value = 0;
+  final int value;
 
-  /// Dummy factory to silence error about missing superclass constructor.
-  external factory BoxedInt();
+  @pragma("wasm:entry-point")
+  BoxedInt._(this.value);
 
   external num operator +(num other);
   external num operator -(num other);