Canonicalize BackendImpact

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

 // Copyright (c) 2015, 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 dart2js.js_helpers.impact;
 
 import '../common/names.dart' show
     Identifiers;
 import '../compiler.dart' show
     Compiler;
@@ skipping 27 matching lines @@
   final Compiler compiler;
 
   BackendImpacts(this.compiler);
 
   JavaScriptBackend get backend => compiler.backend;
 
   BackendHelpers get helpers => backend.helpers;
 
   CoreClasses get coreClasses => compiler.coreClasses;
 
-  BackendImpact get getRuntimeTypeArgument => new BackendImpact(
-      staticUses: [
-        helpers.getRuntimeTypeArgument,
-        helpers.getTypeArgumentByIndex,
-        helpers.copyTypeArguments]);
-
-  BackendImpact get computeSignature => new BackendImpact(
-      staticUses: [
-        helpers.setRuntimeTypeInfo,
-        helpers.getRuntimeTypeInfo,
-        helpers.computeSignature,
-        helpers.getRuntimeTypeArguments],
-      instantiatedClasses: [
-        coreClasses.listClass]);
-
-  BackendImpact get asyncBody => new BackendImpact(
-      staticUses: [
-        helpers.asyncHelper,
-        helpers.syncCompleterConstructor,
-        helpers.streamIteratorConstructor,
-        helpers.wrapBody]);
-
-  BackendImpact get syncStarBody => new BackendImpact(
-      staticUses: [
-        helpers.syncStarIterableConstructor,
-        helpers.endOfIteration,
-        helpers.yieldStar,
-        helpers.syncStarUncaughtError],
-      instantiatedClasses: [
-        helpers.syncStarIterable]);
-
-  BackendImpact get asyncStarBody => new BackendImpact(
-      staticUses: [
-        helpers.asyncStarHelper,
-        helpers.streamOfController,
-        helpers.yieldSingle,
-        helpers.yieldStar,
-        helpers.asyncStarControllerConstructor,
-        helpers.streamIteratorConstructor,
-        helpers.wrapBody],
-      instantiatedClasses: [
-        helpers.asyncStarController]);
-
-  BackendImpact get typeVariableBoundCheck => new BackendImpact(
-      staticUses: [
-        helpers.throwTypeError,
-        helpers.assertIsSubtype]);
-
-  BackendImpact get abstractClassInstantiation => new BackendImpact(
-      staticUses: [
-        helpers.throwAbstractClassInstantiationError],
-      otherImpacts: [
-        needsString('Needed to encode the message.')]);
-
-  BackendImpact get fallThroughError => new BackendImpact(
-      staticUses: [
-        helpers.fallThroughError]);
-
-  BackendImpact get asCheck => new BackendImpact(
-      staticUses: [
-        helpers.throwRuntimeError]);
-
-  BackendImpact get throwNoSuchMethod => new BackendImpact(
-      staticUses: [
-        helpers.throwNoSuchMethod],
-      otherImpacts: [
-        // Also register the types of the arguments passed to this method.
-        needsList(
-            'Needed to encode the arguments for throw NoSuchMethodError.'),
-        needsString(
-            'Needed to encode the name for throw NoSuchMethodError.')]);
-
-  BackendImpact get throwRuntimeError => new BackendImpact(
-      staticUses: [
-        helpers.throwRuntimeError],
-      // Also register the types of the arguments passed to this method.
-      instantiatedClasses: [
-        coreClasses.stringClass]);
-
-  BackendImpact get superNoSuchMethod => new BackendImpact(
-      staticUses: [
-        helpers.createInvocationMirror,
-        coreClasses.objectClass.lookupLocalMember(Identifiers.noSuchMethod_)],
-      otherImpacts: [
-        needsInt(
-            'Needed to encode the invocation kind of super.noSuchMethod.'),
-        needsList(
-            'Needed to encode the arguments of super.noSuchMethod.'),
-        needsString(
-            'Needed to encode the name of super.noSuchMethod.')]);
+  BackendImpact _getRuntimeTypeArgument;
+
+  BackendImpact get getRuntimeTypeArgument {
+    if(_getRuntimeTypeArgument == null) {
+      _getRuntimeTypeArgument = new BackendImpact(

[sigurdm, 2015/11/10 08:07:07]

These could be done with ?= null-aware assignment. Not sure its better though.

[Johnni Winther, 2015/11/10 10:26:37]

It looks strange:

  return _getRuntimeTypeArgument ?= new Backend(...)

Maybe me (and my editor) just need to get used to it. Not in this CL though.

[sigurdm, 2015/11/10 12:11:06]

I thought about two lines:
_getRuntimeTypeArgument ?= new Backend(...)
return _getRuntimeTypeArgument;

+          staticUses: [
+            helpers.getRuntimeTypeArgument,
+            helpers.getTypeArgumentByIndex,
+            helpers.copyTypeArguments]);
+    }
+    return _getRuntimeTypeArgument;
+  }
+
+  BackendImpact _computeSignature;
+
+  BackendImpact get computeSignature {
+    if(_computeSignature == null) {
+      _computeSignature = new BackendImpact(
+          staticUses: [
+            helpers.setRuntimeTypeInfo,
+            helpers.getRuntimeTypeInfo,
+            helpers.computeSignature,
+            helpers.getRuntimeTypeArguments],
+          instantiatedClasses: [
+            coreClasses.listClass]);
+    }
+    return _computeSignature;
+  }
+
+  BackendImpact _asyncBody;
+
+  BackendImpact get asyncBody {
+    if(_asyncBody == null) {
+      _asyncBody = new BackendImpact(
+          staticUses: [
+            helpers.asyncHelper,
+            helpers.syncCompleterConstructor,
+            helpers.streamIteratorConstructor,
+            helpers.wrapBody]);
+    }
+    return _asyncBody;
+  }
+
+  BackendImpact _syncStarBody;
+
+  BackendImpact get syncStarBody {
+    if(_syncStarBody == null) {
+      _syncStarBody = new BackendImpact(
+          staticUses: [
+            helpers.syncStarIterableConstructor,
+            helpers.endOfIteration,
+            helpers.yieldStar,
+            helpers.syncStarUncaughtError],
+          instantiatedClasses: [
+            helpers.syncStarIterable]);
+    }
+    return _syncStarBody;
+  }
+
+  BackendImpact _asyncStarBody;
+
+  BackendImpact get asyncStarBody {
+    if(_asyncStarBody == null) {
+      _asyncStarBody = new BackendImpact(
+          staticUses: [
+            helpers.asyncStarHelper,
+            helpers.streamOfController,
+            helpers.yieldSingle,
+            helpers.yieldStar,
+            helpers.asyncStarControllerConstructor,
+            helpers.streamIteratorConstructor,
+            helpers.wrapBody],
+          instantiatedClasses: [
+            helpers.asyncStarController]);
+    }
+    return _asyncStarBody;
+  }
+
+  BackendImpact _typeVariableBoundCheck;
+
+  BackendImpact get typeVariableBoundCheck {
+    if(_typeVariableBoundCheck == null) {
+      _typeVariableBoundCheck = new BackendImpact(
+          staticUses: [
+            helpers.throwTypeError,
+            helpers.assertIsSubtype]);
+    }
+    return _typeVariableBoundCheck;
+  }
+
+  BackendImpact _abstractClassInstantiation;
+
+  BackendImpact get abstractClassInstantiation {
+    if(_abstractClassInstantiation == null) {
+      _abstractClassInstantiation = new BackendImpact(
+          staticUses: [
+            helpers.throwAbstractClassInstantiationError],
+          otherImpacts: [
+            _needsString('Needed to encode the message.')]);
+    }
+    return _abstractClassInstantiation;
+  }
+
+  BackendImpact _fallThroughError;
+
+  BackendImpact get fallThroughError {
+    if(_fallThroughError == null) {
+      _fallThroughError = new BackendImpact(
+          staticUses: [
+            helpers.fallThroughError]);
+    }
+    return _fallThroughError;
+  }
+
+  BackendImpact _asCheck;
+
+  BackendImpact get asCheck {
+    if(_asCheck == null) {
+      _asCheck = new BackendImpact(
+          staticUses: [
+            helpers.throwRuntimeError]);
+    }
+    return _asCheck;
+  }
+
+  BackendImpact _throwNoSuchMethod;
+
+  BackendImpact get throwNoSuchMethod {
+    if(_throwNoSuchMethod == null) {
+      _throwNoSuchMethod = new BackendImpact(
+          staticUses: [
+            helpers.throwNoSuchMethod],
+          otherImpacts: [
+            // Also register the types of the arguments passed to this method.
+            _needsList(
+                'Needed to encode the arguments for throw NoSuchMethodError.'),
+            _needsString(
+                'Needed to encode the name for throw NoSuchMethodError.')]);
+    }
+    return _throwNoSuchMethod;
+  }
+
+  BackendImpact _throwRuntimeError;
+
+  BackendImpact get throwRuntimeError {
+    if(_throwRuntimeError == null) {
+      _throwRuntimeError = new BackendImpact(
+          staticUses: [
+            helpers.throwRuntimeError],
+          // Also register the types of the arguments passed to this method.
+          instantiatedClasses: [
+            coreClasses.stringClass]);
+    }
+    return _throwRuntimeError;
+  }
+
+  BackendImpact _superNoSuchMethod;
+
+  BackendImpact get superNoSuchMethod {
+    if(_superNoSuchMethod == null) {
+      _superNoSuchMethod = new BackendImpact(
+          staticUses: [
+            helpers.createInvocationMirror,
+            coreClasses.objectClass.lookupLocalMember(
+                Identifiers.noSuchMethod_)],
+          otherImpacts: [
+            _needsInt(
+                'Needed to encode the invocation kind of super.noSuchMethod.'),
+            _needsList(
+                'Needed to encode the arguments of super.noSuchMethod.'),
+            _needsString(
+                'Needed to encode the name of super.noSuchMethod.')]);
+    }
+    return _superNoSuchMethod;
+  }
+
+  BackendImpact _constantMapLiteral;
 
   BackendImpact get constantMapLiteral {
-
-    ClassElement find(String name) {
-      return helpers.find(helpers.jsHelperLibrary, name);
-    }
-
-    return new BackendImpact(
-      instantiatedClasses: [
-        find(JavaScriptMapConstant.DART_CLASS),
-        find(JavaScriptMapConstant.DART_PROTO_CLASS),
-        find(JavaScriptMapConstant.DART_STRING_CLASS),
-        find(JavaScriptMapConstant.DART_GENERAL_CLASS)]);
-  }
-
-  BackendImpact get symbolConstructor => new BackendImpact(
-      staticUses: [
-        helpers.compiler.symbolValidatedConstructor]);
-
-  BackendImpact get constSymbol => new BackendImpact(
-      instantiatedClasses: [
-        coreClasses.symbolClass],
-      staticUses: [
-        compiler.symbolConstructor.declaration]);
-
-  BackendImpact get incDecOperation =>
-      needsInt('Needed for the `+ 1` or `- 1` operation of ++/--.');
+    if (_constantMapLiteral == null) {
+
+      ClassElement find(String name) {
+        return helpers.find(helpers.jsHelperLibrary, name);
+      }
+
+      _constantMapLiteral = new BackendImpact(
+          instantiatedClasses: [
+            find(JavaScriptMapConstant.DART_CLASS),
+            find(JavaScriptMapConstant.DART_PROTO_CLASS),
+            find(JavaScriptMapConstant.DART_STRING_CLASS),
+            find(JavaScriptMapConstant.DART_GENERAL_CLASS)]);
+    }
+    return _constantMapLiteral;
+  }
+
+  BackendImpact _symbolConstructor;
+
+  BackendImpact get symbolConstructor {
+    if(_symbolConstructor == null) {
+      _symbolConstructor = new BackendImpact(
+        staticUses: [
+          helpers.compiler.symbolValidatedConstructor]);
+    }
+    return _symbolConstructor;
+  }
+
+  BackendImpact _constSymbol;
+
+  BackendImpact get constSymbol {
+    if(_constSymbol == null) {
+      _constSymbol = new BackendImpact(
+        instantiatedClasses: [
+          coreClasses.symbolClass],
+        staticUses: [
+          compiler.symbolConstructor.declaration]);
+    }
+    return _constSymbol;
+  }
+
+  BackendImpact _incDecOperation;
+
+  BackendImpact get incDecOperation {
+    if (_incDecOperation == null) {
+      _incDecOperation =
+          _needsInt('Needed for the `+ 1` or `- 1` operation of ++/--.');
+    }
+    return _incDecOperation;
+  }
 
   /// Helper for registering that `int` is needed.
-  BackendImpact needsInt(String reason) {
+  BackendImpact _needsInt(String reason) {
     // TODO(johnniwinther): Register [reason] for use in dump-info.
     return new BackendImpact(
         instantiatedClasses: [coreClasses.intClass]);
   }
 
   /// Helper for registering that `List` is needed.
-  BackendImpact needsList(String reason) {
+  BackendImpact _needsList(String reason) {
     // TODO(johnniwinther): Register [reason] for use in dump-info.
     return new BackendImpact(
         instantiatedClasses: [coreClasses.listClass]);
   }
 
   /// Helper for registering that `String` is needed.
-  BackendImpact needsString(String reason) {
+  BackendImpact _needsString(String reason) {
     // TODO(johnniwinther): Register [reason] for use in dump-info.
     return new BackendImpact(
         instantiatedClasses: [
           coreClasses.stringClass]);
   }
 
-  BackendImpact get assertWithoutMessage => new BackendImpact(
-      staticUses: [
-        helpers.assertHelper]);
-
-  BackendImpact get assertWithMessage => new BackendImpact(
-      staticUses: [
-        helpers.assertTest,
-        helpers.assertThrow]);
-
-  BackendImpact get asyncForIn => new BackendImpact(
-      staticUses: [
-        helpers.streamIteratorConstructor]);
-
-  BackendImpact get stringInterpolation => new BackendImpact(
-      staticUses: [
-        helpers.stringInterpolationHelper]);
-
-  BackendImpact get catchStatement => new BackendImpact(
-      staticUses: [
-        helpers.exceptionUnwrapper],
-      instantiatedClasses: [
-        helpers.jsPlainJavaScriptObjectClass,
-        helpers.jsUnknownJavaScriptObjectClass]);
-
-  BackendImpact get throwExpression => new BackendImpact(
-      // We don't know ahead of time whether we will need the throw in a
-      // statement context or an expression context, so we register both
-      // here, even though we may not need the throwExpression helper.
-      staticUses: [
-        helpers.wrapExceptionHelper,
-        helpers.throwExpressionHelper]);
-
-  BackendImpact get lazyField => new BackendImpact(
-      staticUses: [
-        helpers.cyclicThrowHelper]);
-
-  BackendImpact get typeLiteral => new BackendImpact(
-      instantiatedClasses: [
-        backend.typeImplementation],
-      staticUses: [
-        helpers.createRuntimeType]);
-
-  BackendImpact get stackTraceInCatch => new BackendImpact(
-      instantiatedClasses: [
-        coreClasses.stackTraceClass],
-      staticUses: [
-        helpers.traceFromException]);
-
-  BackendImpact get syncForIn => new BackendImpact(
-      // The SSA builder recognizes certain for-in loops and can generate calls
-      // to throwConcurrentModificationError.
-      staticUses: [
-        helpers.checkConcurrentModificationError]);
-
-  BackendImpact get typeVariableExpression => new BackendImpact(
-      staticUses: [
-        helpers.setRuntimeTypeInfo,
-        helpers.getRuntimeTypeInfo,
-        helpers.runtimeTypeToString,
-        helpers.createRuntimeType],
-      instantiatedClasses: [
-        coreClasses.listClass],
-      otherImpacts: [
-        getRuntimeTypeArgument,
-        needsInt('Needed for accessing a type variable literal on this.')]);
-
-  BackendImpact get typeCheck => new BackendImpact(
-      instantiatedClasses: [
-        coreClasses.boolClass]);
-
-  BackendImpact get checkedModeTypeCheck => new BackendImpact(
-      staticUses: [
-        helpers.throwRuntimeError]);
-
-  BackendImpact get malformedTypeCheck => new BackendImpact(
-      staticUses: [
-        helpers.throwTypeError]);
-
-  BackendImpact get genericTypeCheck => new BackendImpact(
-      staticUses: [
-        helpers.checkSubtype,
-        // TODO(johnniwinther): Investigate why this is needed.
-        helpers.setRuntimeTypeInfo,
-        helpers.getRuntimeTypeInfo],
-      instantiatedClasses: [
-        coreClasses.listClass],
-      otherImpacts: [
-        getRuntimeTypeArgument]);
-
-  BackendImpact get genericIsCheck => new BackendImpact(
-      instantiatedClasses: [
-        coreClasses.listClass]);
-
-  BackendImpact get genericCheckedModeTypeCheck => new BackendImpact(
-      staticUses: [
-        helpers.assertSubtype]);
-
-  BackendImpact get typeVariableTypeCheck => new BackendImpact(
-      staticUses: [
-        helpers.checkSubtypeOfRuntimeType]);
-
-  BackendImpact get typeVariableCheckedModeTypeCheck => new BackendImpact(
-      staticUses: [
-        helpers.assertSubtypeOfRuntimeType]);
-
-  BackendImpact get functionTypeCheck => new BackendImpact(
-      staticUses: [
-        helpers.functionTypeTestMetaHelper]);
-
-  BackendImpact get nativeTypeCheck => new BackendImpact(
-      staticUses: [
-        // We will neeed to add the "$is" and "$as" properties on the
-        // JavaScript object prototype, so we make sure
-        // [:defineProperty:] is compiled.
-        helpers.defineProperty]);
-
-  BackendImpact get closure => new BackendImpact(
-      instantiatedClasses: [
-        coreClasses.functionClass]);
+  BackendImpact _assertWithoutMessage;
+
+  BackendImpact get assertWithoutMessage {
+    if(_assertWithoutMessage == null) {
+      _assertWithoutMessage = new BackendImpact(
+          staticUses: [
+            helpers.assertHelper]);
+    }
+    return _assertWithoutMessage;
+  }
+
+  BackendImpact _assertWithMessage;
+
+  BackendImpact get assertWithMessage {
+    if(_assertWithMessage == null) {
+      _assertWithMessage = new BackendImpact(
+          staticUses: [
+            helpers.assertTest,
+            helpers.assertThrow]);
+    }
+    return _assertWithMessage;
+  }
+
+  BackendImpact _asyncForIn;
+
+  BackendImpact get asyncForIn {
+    if(_asyncForIn == null) {
+      _asyncForIn = new BackendImpact(
+          staticUses: [
+            helpers.streamIteratorConstructor]);
+    }
+    return _asyncForIn;
+  }
+
+  BackendImpact _stringInterpolation;
+
+  BackendImpact get stringInterpolation {
+    if(_stringInterpolation == null) {
+      _stringInterpolation = new BackendImpact(
+          staticUses: [
+            helpers.stringInterpolationHelper]);
+    }
+    return _stringInterpolation;
+  }
+
+  BackendImpact _catchStatement;
+
+  BackendImpact get catchStatement {
+    if(_catchStatement == null) {
+      _catchStatement = new BackendImpact(
+          staticUses: [
+            helpers.exceptionUnwrapper],
+          instantiatedClasses: [
+            helpers.jsPlainJavaScriptObjectClass,
+            helpers.jsUnknownJavaScriptObjectClass]);
+    }
+    return _catchStatement;
+  }
+
+  BackendImpact _throwExpression;
+
+  BackendImpact get throwExpression {
+    if(_throwExpression == null) {
+      _throwExpression = new BackendImpact(
+          // We don't know ahead of time whether we will need the throw in a
+          // statement context or an expression context, so we register both
+          // here, even though we may not need the throwExpression helper.
+          staticUses: [
+            helpers.wrapExceptionHelper,
+            helpers.throwExpressionHelper]);
+    }
+    return _throwExpression;
+  }
+
+  BackendImpact _lazyField;
+
+  BackendImpact get lazyField {
+    if(_lazyField == null) {
+      _lazyField = new BackendImpact(
+          staticUses: [
+            helpers.cyclicThrowHelper]);
+    }
+    return _lazyField;
+  }
+
+  BackendImpact _typeLiteral;
+
+  BackendImpact get typeLiteral {
+    if(_typeLiteral == null) {
+      _typeLiteral = new BackendImpact(
+          instantiatedClasses: [
+            backend.typeImplementation],
+          staticUses: [
+            helpers.createRuntimeType]);
+    }
+    return _typeLiteral;
+  }
+
+  BackendImpact _stackTraceInCatch;
+
+  BackendImpact get stackTraceInCatch {
+    if(_stackTraceInCatch == null) {
+      _stackTraceInCatch = new BackendImpact(
+          instantiatedClasses: [
+            coreClasses.stackTraceClass],
+          staticUses: [
+            helpers.traceFromException]);
+    }
+    return _stackTraceInCatch;
+  }
+
+  BackendImpact _syncForIn;
+
+  BackendImpact get syncForIn {
+    if(_syncForIn == null) {
+      _syncForIn = new BackendImpact(
+          // The SSA builder recognizes certain for-in loops and can generate
+          // calls to throwConcurrentModificationError.
+          staticUses: [
+            helpers.checkConcurrentModificationError]);
+    }
+    return _syncForIn;
+  }
+
+  BackendImpact _typeVariableExpression;
+
+  BackendImpact get typeVariableExpression {
+    if(_typeVariableExpression == null) {
+      _typeVariableExpression = new BackendImpact(
+          staticUses: [
+            helpers.setRuntimeTypeInfo,
+            helpers.getRuntimeTypeInfo,
+            helpers.runtimeTypeToString,
+            helpers.createRuntimeType],
+          instantiatedClasses: [
+            coreClasses.listClass],
+          otherImpacts: [
+            getRuntimeTypeArgument,
+            _needsInt('Needed for accessing a type variable literal on this.')
+          ]);
+    }
+    return _typeVariableExpression;
+  }
+
+  BackendImpact _typeCheck;
+
+  BackendImpact get typeCheck {
+    if(_typeCheck == null) {
+      _typeCheck = new BackendImpact(
+          instantiatedClasses: [
+            coreClasses.boolClass]);
+    }
+    return _typeCheck;
+  }
+
+  BackendImpact _checkedModeTypeCheck;
+
+  BackendImpact get checkedModeTypeCheck {
+    if(_checkedModeTypeCheck == null) {
+      _checkedModeTypeCheck = new BackendImpact(
+          staticUses: [
+            helpers.throwRuntimeError]);
+    }
+    return _checkedModeTypeCheck;
+  }
+
+  BackendImpact _malformedTypeCheck;
+
+  BackendImpact get malformedTypeCheck {
+    if(_malformedTypeCheck == null) {
+      _malformedTypeCheck = new BackendImpact(
+          staticUses: [
+            helpers.throwTypeError]);
+    }
+    return _malformedTypeCheck;
+  }
+
+  BackendImpact _genericTypeCheck;
+
+  BackendImpact get genericTypeCheck {
+    if(_genericTypeCheck == null) {
+      _genericTypeCheck = new BackendImpact(
+          staticUses: [
+            helpers.checkSubtype,
+            // TODO(johnniwinther): Investigate why this is needed.
+            helpers.setRuntimeTypeInfo,
+            helpers.getRuntimeTypeInfo],
+          instantiatedClasses: [
+            coreClasses.listClass],
+          otherImpacts: [
+            getRuntimeTypeArgument]);
+    }
+    return _genericTypeCheck;
+  }
+
+  BackendImpact _genericIsCheck;
+
+  BackendImpact get genericIsCheck {
+    if(_genericIsCheck == null) {
+      _genericIsCheck = new BackendImpact(
+          instantiatedClasses: [
+            coreClasses.listClass]);
+    }
+    return _genericIsCheck;
+  }
+
+  BackendImpact _genericCheckedModeTypeCheck;
+
+  BackendImpact get genericCheckedModeTypeCheck {
+    if(_genericCheckedModeTypeCheck == null) {
+      _genericCheckedModeTypeCheck = new BackendImpact(
+          staticUses: [
+            helpers.assertSubtype]);
+    }
+    return _genericCheckedModeTypeCheck;
+  }
+
+  BackendImpact _typeVariableTypeCheck;
+
+  BackendImpact get typeVariableTypeCheck {
+    if(_typeVariableTypeCheck == null) {
+      _typeVariableTypeCheck = new BackendImpact(
+          staticUses: [
+            helpers.checkSubtypeOfRuntimeType]);
+    }
+    return _typeVariableTypeCheck;
+  }
+
+  BackendImpact _typeVariableCheckedModeTypeCheck;
+
+  BackendImpact get typeVariableCheckedModeTypeCheck {
+    if(_typeVariableCheckedModeTypeCheck == null) {
+      _typeVariableCheckedModeTypeCheck = new BackendImpact(
+        staticUses: [
+          helpers.assertSubtypeOfRuntimeType]);
+    }
+    return _typeVariableCheckedModeTypeCheck;
+  }
+
+  BackendImpact _functionTypeCheck;
+
+  BackendImpact get functionTypeCheck {
+    if(_functionTypeCheck == null) {
+      _functionTypeCheck = new BackendImpact(
+          staticUses: [
+            helpers.functionTypeTestMetaHelper]);
+    }
+    return _functionTypeCheck;
+  }
+
+  BackendImpact _nativeTypeCheck;
+
+  BackendImpact get nativeTypeCheck {
+    if(_nativeTypeCheck == null) {
+      _nativeTypeCheck = new BackendImpact(
+          staticUses: [
+            // We will neeed to add the "$is" and "$as" properties on the
+            // JavaScript object prototype, so we make sure
+            // [:defineProperty:] is compiled.
+            helpers.defineProperty]);
+    }
+    return _nativeTypeCheck;
+  }
+
+  BackendImpact _closure;
+
+  BackendImpact get closure {
+    if(_closure == null) {
+      _closure = new BackendImpact(
+          instantiatedClasses: [
+            coreClasses.functionClass]);
+    }
+    return _closure;
+  }
 }