[dart2js, ddc] Remove support for SNS checks.

Bug: #60327
Change-Id: I38f04fea4e51dcd0fd43dc93ecc7007a0a816f29
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/416120
Reviewed-by: Nate Biggs <[email protected]>
Reviewed-by: Nicholas Shahan <[email protected]>

Author: fishythefish

pkg/compiler/lib/src/dart2js.dart

@@ -553,7 +553,7 @@ Future<api.CompilationResult> compile(
     _OneOption(Flags.experimentToBoolean, passThrough),
     _OneOption(Flags.experimentUnreachableMethodsThrow, passThrough),
     _OneOption(Flags.experimentCallInstrumentation, passThrough),
-    _OneOption(Flags.experimentNullSafetyChecks, passThrough),
+    _OneOption(Flags.experimentNullSafetyChecks, ignoreOption),
     _OneOption(Flags.experimentNewRti, ignoreOption),
     _OneOption('${Flags.mergeFragmentsThreshold}=.+', passThrough),
 

pkg/compiler/lib/src/js_backend/specialized_checks.dart

@@ -32,9 +32,8 @@ class SpecializedChecks {
   static IsTestSpecialization? findIsTestSpecialization(
     DartType dartType,
     MemberEntity compiland,
-    JClosedWorld closedWorld, {
-    required bool experimentNullSafetyChecks,
-  }) {
+    JClosedWorld closedWorld,
+  ) {
     if (dartType is InterfaceType) {
       ClassEntity element = dartType.element;
       JCommonElements commonElements = closedWorld.commonElements;
@@ -90,10 +89,6 @@ class SpecializedChecks {
         return SimpleIsTestSpecialization.isNotNull;
       }
 
-      if (experimentNullSafetyChecks && dartType.typeArguments.isNotEmpty) {
-        return null;
-      }
-
       ClassHierarchy classHierarchy = closedWorld.classHierarchy;
       InterceptorData interceptorData = closedWorld.interceptorData;
       OutputUnitData outputUnitData = closedWorld.outputUnitData;

pkg/compiler/lib/src/kernel/transformations/global/constant_transformer.dart

@@ -4,15 +4,11 @@ import 'package:front_end/src/api_unstable/dart2js.dart'
 import 'package:kernel/ast.dart';
 import 'package:kernel/type_environment.dart';
 
-import '../../../options.dart';
-
 class ConstantTransformer extends Transformer {
   final TryConstantEvaluator constantEvaluator;
   late StaticTypeContext _staticTypeContext;
 
-  final CompilerOptions _options;
-
-  ConstantTransformer(this.constantEvaluator, this._options);
+  ConstantTransformer(this.constantEvaluator);
 
   Constant _evaluate(Expression node) =>
       constantEvaluator.evaluate(_staticTypeContext, node);
@@ -116,18 +112,14 @@ class ConstantTransformer extends Transformer {
   @override
   TreeNode visitIsExpression(IsExpression node) {
     node.transformChildren(this);
-    if (!_options.experimentNullSafetyChecks && _isConstant(node.operand)) {
-      return _evaluateAndWrapOrNode(node);
-    }
+    if (_isConstant(node.operand)) return _evaluateAndWrapOrNode(node);
     return node;
   }
 
   @override
   TreeNode visitAsExpression(AsExpression node) {
     node.transformChildren(this);
-    if (!_options.experimentNullSafetyChecks && _isConstant(node.operand)) {
-      return _evaluateAndWrapOrNode(node);
-    }
+    if (_isConstant(node.operand)) return _evaluateAndWrapOrNode(node);
     return node;
   }
 

pkg/compiler/lib/src/kernel/transformations/global/js_get_flag_lowering.dart

@@ -59,7 +59,6 @@ class JsGetFlagLowering {
       _options.features.useContentSecurityPolicy.isEnabled,
     'VARIANCE' => _options.enableVariance,
     'LEGACY' => _options.useLegacySubtyping,
-    'EXTRA_NULL_SAFETY_CHECKS' => _options.experimentNullSafetyChecks,
     'PRINT_LEGACY_STARS' => _options.printLegacyStars,
     _ => null,
   };

pkg/compiler/lib/src/kernel/transformations/global/transform.dart

@@ -38,7 +38,7 @@ class _GlobalTransformer extends ConstantTransformer {
   _GlobalTransformer(
     super.constantEvaluator,
     CoreTypes coreTypes,
-    super.options,
+    CompilerOptions options,
   ) : _jsGetFlagLowering = JsGetFlagLowering(coreTypes, options);
 
   @override

pkg/compiler/lib/src/options.dart

@@ -656,19 +656,6 @@ class CompilerOptions implements DiagnosticOptions {
   /// called.
   bool experimentCallInstrumentation = false;
 
-  /// Experiment to add additional runtime checks to detect code whose semantics
-  /// will change when sound null safety is enabled.
-  ///
-  /// In particular, runtime subtype checks (including those via `is` and `as`)
-  /// will produce diagnostics when they would provide different results in
-  /// sound vs. unsound mode. Note that this adds overhead, both to perform the
-  /// extra checks and because some checks that may have been optimized away
-  /// will be emitted.
-  ///
-  /// We assume this option will only be provided when all files have been
-  /// migrated to null safety (but before sound null safety is enabled).
-  bool experimentNullSafetyChecks = false;
-
   /// Whether to use legacy subtype semantics rather than null-safe semantics.
   /// This is `true` if unsound null-safety semantics are being used, since
   /// dart2js does not emit warnings for unsound null-safety.
@@ -944,10 +931,6 @@ class CompilerOptions implements DiagnosticOptions {
         options,
         Flags.experimentCallInstrumentation,
       )
-      ..experimentNullSafetyChecks = _hasOption(
-        options,
-        Flags.experimentNullSafetyChecks,
-      )
       ..generateSourceMap = !_hasOption(options, Flags.noSourceMaps)
       .._outputUri = _extractUriOption(options, '--out=')
       ..platformBinaries = platformBinaries
@@ -1085,12 +1068,6 @@ class CompilerOptions implements DiagnosticOptions {
         "'${Flags.noInteropNullAssertions}'",
       );
     }
-    if (experimentNullSafetyChecks) {
-      throw ArgumentError(
-        '${Flags.experimentNullSafetyChecks} is incompatible '
-        'with sound null safety.',
-      );
-    }
   }
 
   void deriveOptions() {

pkg/compiler/lib/src/phase/load_kernel.dart

@@ -20,7 +20,6 @@ import 'package:kernel/type_environment.dart' as ir;
 import 'package:kernel/verifier.dart';
 
 import '../../compiler_api.dart' as api;
-import '../commandline_options.dart';
 import '../common.dart';
 import '../diagnostics/diagnostic_listener.dart';
 import '../environment.dart';
@@ -300,16 +299,6 @@ Future<_LoadFromSourceResult> _loadFromSource(
         ..verbosity = verbosity;
   Uri resolvedUri = options.compilationTarget;
   bool isLegacy = await fe.uriUsesLegacyLanguageVersion(resolvedUri, feOptions);
-  if (isLegacy && options.experimentNullSafetyChecks) {
-    reporter.reportErrorMessage(noLocationSpannable, MessageKind.generic, {
-      'text':
-          'The ${Flags.experimentNullSafetyChecks} option may be used '
-          'only after all libraries have been migrated to null safety. Some '
-          'libraries reached from $resolvedUri are still opted out of null '
-          'safety. Please migrate these libraries before passing '
-          '${Flags.experimentNullSafetyChecks}.',
-    });
-  }
   if (isLegacy) {
     reporter.reportErrorMessage(noLocationSpannable, MessageKind.generic, {
       'text':

pkg/compiler/lib/src/ssa/builder.dart

@@ -3314,7 +3314,7 @@ class KernelSsaGraphBuilder extends ir.VisitorDefault<void>
 
     final operandType = _getStaticType(operand);
     DartType type = _elementMap.getDartType(node.type);
-    if (!options.experimentNullSafetyChecks && !node.isCovarianceCheck) {
+    if (!node.isCovarianceCheck) {
       if (_elementMap.types.isSubtype(operandType, type)) {
         // Skip unneeded casts.
         return;

pkg/compiler/lib/src/ssa/nodes.dart

@@ -4599,10 +4599,6 @@ AbstractBool _typeTest(
   CompilerOptions options, {
   required bool isCast,
 }) {
-  // The null safety mode may affect the result of a type test, so defer to
-  // runtime.
-  if (options.experimentNullSafetyChecks) return AbstractBool.maybe;
-
   JCommonElements commonElements = closedWorld.commonElements;
   DartTypes dartTypes = closedWorld.dartTypes;
   AbstractValueDomain abstractValueDomain = closedWorld.abstractValueDomain;

pkg/compiler/lib/src/ssa/optimize.dart

@@ -1237,16 +1237,10 @@ class SsaInstructionSimplifier extends HBaseVisitor<HInstruction>
         );
         if (_closedWorld.dartTypes.isNonNullableIfSound(type.returnType)) {
           node.block!.addBefore(node, invocation);
-          final replacementType =
-              _options.experimentNullSafetyChecks
-                  ? invocation.instructionType
-                  : _abstractValueDomain.excludeNull(
-                    invocation.instructionType,
-                  );
           replacement = HInvokeStatic(
             commonElements.interopNullAssertion,
             [invocation],
-            replacementType,
+            _abstractValueDomain.excludeNull(invocation.instructionType),
             const <DartType>[],
           );
         }
@@ -2666,7 +2660,6 @@ class SsaInstructionSimplifier extends HBaseVisitor<HInstruction>
       node.dartType,
       _graph.element,
       _closedWorld,
-      experimentNullSafetyChecks: _options.experimentNullSafetyChecks,
     );
 
     if (specialization == SimpleIsTestSpecialization.isNull ||