pkg/compiler/lib/src/inferrer/node_tracer.dart - sdk.git - Git at Google

 // Copyright (c) 2013, 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 compiler.src.inferrer.node_tracer;

 import '../common/names.dart' show Identifiers;
 import '../elements/entities.dart';
 import '../types/abstract_value_domain.dart';
 import '../util/util.dart' show Setlet;
 import 'debug.dart' as debug;
 import 'inferrer_engine.dart';
 import 'type_graph_nodes.dart';

 // A set of selectors we know do not escape the elements inside the
 // list.
 Set<String> doesNotEscapeListSet = new Set<String>.from(const <String>[
   // From Object.
   '==',
   'hashCode',
   'toString',
   'noSuchMethod',
   'runtimeType',

   // From Iterable.
   'isEmpty',
   'isNotEmpty',
   'length',
   'contains',
   'join',

   // From List.
   'add',
   'addAll',
   'clear',
   'fillRange',
   'indexOf',
   'insert',
   'insertAll',
   'lastIndexOf',
   'remove',
   'removeRange',
   'replaceRange',
   'setAll',
   'setRange',
   'shuffle',
   '[]=',

   // From JSArray.
   'checkMutable',
   'checkGrowable',
 ]);

 Set<String> doesNotEscapeMapSet = new Set<String>.from(const <String>[
   // From Object.
   '==',
   'hashCode',
   'toString',
   'noSuchMethod',
   'runtimeType',
   // from Map.
   'isEmpty',
   'isNotEmpty',
   'length',
   'clear',
   'containsKey',
   'containsValue',
   '[]=',
   // [keys] only allows key values to escape, which we do not track.
   'keys'
 ]);

 /// Common logic to trace a value through the type inference graph nodes.
 abstract class TracerVisitor implements TypeInformationVisitor {
   final TypeInformation tracedType;
   final InferrerEngine inferrer;

   static const int MAX_ANALYSIS_COUNT =
       const int.fromEnvironment('dart2js.tracing.limit', defaultValue: 32);
   final Setlet<MemberEntity> analyzedElements = new Setlet<MemberEntity>();

   TracerVisitor(this.tracedType, this.inferrer);

   // Work list that gets populated with [TypeInformation] that could
   // contain the container.
   final List<TypeInformation> workList = <TypeInformation>[];

   // Work list of lists to analyze after analyzing the users of a
   // [TypeInformation]. We know the [tracedType] has been stored in these
   // lists and we must check how it escapes from these lists.
   final List<ListTypeInformation> listsToAnalyze = <ListTypeInformation>[];
   // Work list of maps to analyze after analyzing the users of a
   // [TypeInformation]. We know the [tracedType] has been stored in these
   // maps and we must check how it escapes from these maps.
   final List<MapTypeInformation> mapsToAnalyze = <MapTypeInformation>[];

   final Setlet<TypeInformation> flowsInto = new Setlet<TypeInformation>();

   // The current [TypeInformation] in the analysis.
   TypeInformation currentUser;
   bool continueAnalyzing = true;

   void addNewEscapeInformation(TypeInformation info) {
     if (flowsInto.contains(info)) return;
     flowsInto.add(info);
     workList.add(info);
   }

   bool _wouldBeTooManyUsers(Set users) {
     int seenSoFar = analyzedElements.length;
     if (seenSoFar + users.length <= MAX_ANALYSIS_COUNT) return false;
     int actualWork = 0;
     for (TypeInformation user in users) {
       if (!analyzedElements.contains(user.owner)) {
         actualWork++;
         if (actualWork > MAX_ANALYSIS_COUNT - seenSoFar) return true;
       }
     }
     return false;
   }

   void analyze() {
     // Collect the [TypeInformation] where the list can flow in,
     // as well as the operations done on all these [TypeInformation]s.
     addNewEscapeInformation(tracedType);
     while (!workList.isEmpty) {
       currentUser = workList.removeLast();
       if (_wouldBeTooManyUsers(currentUser.users)) {
         bailout('Too many users');
         break;
       }
       for (TypeInformation info in currentUser.users) {
         analyzedElements.add(info.owner);
         info.accept(this);
       }
       while (!listsToAnalyze.isEmpty) {
         analyzeStoredIntoList(listsToAnalyze.removeLast());
       }
       while (!mapsToAnalyze.isEmpty) {
         analyzeStoredIntoMap(mapsToAnalyze.removeLast());
       }
       if (!continueAnalyzing) break;
     }
   }

   void bailout(String reason) {
     if (debug.VERBOSE) {
       print('Bailing out on $tracedType because: $reason');
     }
     continueAnalyzing = false;
   }

   void visitAwaitTypeInformation(AwaitTypeInformation info) {
     bailout("Passed through await");
   }

   void visitYieldTypeInformation(YieldTypeInformation info) {
     // TODO(29344): The enclosing sync*/async/async* method could have a
     // tracable TypeInformation for the Iterable / Future / Stream with an
     // element TypeInformation. Then YieldTypeInformation could connect the
     // source type information to the tracable element.
     bailout("Passed through yield");
   }

   void visitNarrowTypeInformation(NarrowTypeInformation info) {
     addNewEscapeInformation(info);
   }

   void visitPhiElementTypeInformation(PhiElementTypeInformation info) {
     addNewEscapeInformation(info);
   }

   void visitElementInContainerTypeInformation(
       ElementInContainerTypeInformation info) {
     addNewEscapeInformation(info);
   }

   void visitKeyInMapTypeInformation(KeyInMapTypeInformation info) {
     // We do not track the use of keys from a map, so we have to bail.
     bailout('Used as key in Map');
   }

   void visitValueInMapTypeInformation(ValueInMapTypeInformation info) {
     addNewEscapeInformation(info);
   }

   void visitListTypeInformation(ListTypeInformation info) {
     listsToAnalyze.add(info);
   }

   void visitMapTypeInformation(MapTypeInformation info) {
     mapsToAnalyze.add(info);
   }

   void visitConcreteTypeInformation(ConcreteTypeInformation info) {}

   void visitStringLiteralTypeInformation(StringLiteralTypeInformation info) {}

   void visitBoolLiteralTypeInformation(BoolLiteralTypeInformation info) {}

   void visitClosureTypeInformation(ClosureTypeInformation info) {}

   void visitClosureCallSiteTypeInformation(
       ClosureCallSiteTypeInformation info) {}

   visitStaticCallSiteTypeInformation(StaticCallSiteTypeInformation info) {
     MemberEntity called = info.calledElement;
     TypeInformation inferred = inferrer.types.getInferredTypeOfMember(called);
     if (inferred == currentUser) {
       addNewEscapeInformation(info);
     }
   }

   void analyzeStoredIntoList(ListTypeInformation list) {
     inferrer.analyzeListAndEnqueue(list);
     if (list.bailedOut) {
       bailout('Stored in a list that bailed out');
     } else {
       list.flowsInto.forEach((flow) {
         flow.users.forEach((dynamic user) {
           if (user is! DynamicCallSiteTypeInformation) return;
           if (user.receiver != flow) return;
           if (inferrer.returnsListElementTypeSet.contains(user.selector)) {
             addNewEscapeInformation(user);
           } else if (!doesNotEscapeListSet.contains(user.selector.name)) {
             bailout('Escape from a list via [${user.selector.name}]');
           }
         });
       });
     }
   }

   void analyzeStoredIntoMap(MapTypeInformation map) {
     inferrer.analyzeMapAndEnqueue(map);
     if (map.bailedOut) {
       bailout('Stored in a map that bailed out');
     } else {
       map.flowsInto.forEach((flow) {
         flow.users.forEach((dynamic user) {
           if (user is! DynamicCallSiteTypeInformation) return;
           if (user.receiver != flow) return;
           if (user.selector.isIndex) {
             addNewEscapeInformation(user);
           } else if (!doesNotEscapeMapSet.contains(user.selector.name)) {
             bailout('Escape from a map via [${user.selector.name}]');
           }
         });
       });
     }
   }

   /**
    * Checks whether this is a call to a list adding method. The definition of
    * what list adding means has to stay in sync with
    * [isParameterOfListAddingMethod].
    */
   bool mightAddToContainer(DynamicCallSiteTypeInformation info) {
     if (info.arguments == null) return false;
     if (info.arguments.named.isNotEmpty) return false;
     String selectorName = info.selector.name;
     List<TypeInformation> arguments = info.arguments.positional;
     if (arguments.length == 1) {
       return (selectorName == 'add' && currentUser == arguments[0]);
     } else if (arguments.length == 2) {
       return (selectorName == 'insert' && currentUser == arguments[1]);
     }
     return false;
   }

   bool isIndexSetArgument(DynamicCallSiteTypeInformation info, int index) {
     String selectorName = info.selector.name;
     if (selectorName != '[]=') return false;
     assert(info.arguments.length == 2);
     List<TypeInformation> arguments = info.arguments.positional;
     return currentUser == arguments[index];
   }

   /**
    * Checks whether the call site flows the currentUser to the key argument of
    * an indexing setter. This must be kept in sync with
    * [isParameterOfMapAddingMethod].
    */
   bool isIndexSetKey(DynamicCallSiteTypeInformation info) {
     return isIndexSetArgument(info, 0);
   }

   /**
    * Checks whether the call site flows the currentUser to the value argument of
    * an indexing setter. This must be kept in sync with
    * [isParameterOfListAddingMethod] and [isParameterOfMapAddingMethod].
    */
   bool isIndexSetValue(DynamicCallSiteTypeInformation info) {
     return isIndexSetArgument(info, 1);
   }

   void bailoutIfReaches(bool predicate(ParameterTypeInformation e)) {
     for (var user in currentUser.users) {
       if (user is ParameterTypeInformation) {
         if (predicate(user)) {
           bailout('Reached suppressed parameter without precise receiver');
           break;
         }
       }
     }
   }

   void visitDynamicCallSiteTypeInformation(
       DynamicCallSiteTypeInformation info) {
     void addsToContainer(AbstractValue mask) {
       Object allocationNode =
           inferrer.abstractValueDomain.getAllocationNode(mask);
       if (allocationNode != null) {
         ListTypeInformation list =
             inferrer.types.allocatedLists[allocationNode];
         listsToAnalyze.add(list);
       } else {
         // The [mask] is a union of two containers, and we lose track of where
         // these containers have been allocated at this point.
         bailout('Stored in too many containers');
       }
     }

     void addsToMapValue(AbstractValue mask) {
       Object allocationNode =
           inferrer.abstractValueDomain.getAllocationNode(mask);
       if (allocationNode != null) {
         MapTypeInformation map = inferrer.types.allocatedMaps[allocationNode];
         mapsToAnalyze.add(map);
       } else {
         // The [mask] is a union. See comment for [mask] above.
         bailout('Stored in too many maps');
       }
     }

     void addsToMapKey(AbstractValue mask) {
       // We do not track the use of keys from a map, so we have to bail.
       bailout('Used as key in Map');
     }

     // "a[...] = x" could be a list (container) or map assignemnt.
     if (isIndexSetValue(info)) {
       var receiverType = info.receiver.type;
       if (inferrer.abstractValueDomain.isContainer(receiverType)) {
         addsToContainer(receiverType);
       } else if (inferrer.abstractValueDomain.isMap(receiverType)) {
         addsToMapValue(receiverType);
       } else {
         // Not a container or map, so the targets could be any methods. There
         // are edges from the [currentUser] to the parameters of the targets, so
         // tracing will continue into the targets.  Tracing stops at parameters
         // that match the targets corresponding to the receiverTypes above (to
         // prevent imprecise results from tracing the implementation), so we
         // need compensate if one of the targets is in the target set. If there
         // is an edge to a parameter matching [isParameterOfListAddingMethod] or
         // [isParameterOfMapAddingMethod] then the traced value is being stored
         // into an untraced list or map.

         // TODO(sra): It would be more precise to specifically match the `value'
         // parameters of "operator []=".
         bailoutIfReaches(isParameterOfListAddingMethod);
         bailoutIfReaches(isParameterOfMapAddingMethod);
       }
     }

     // Could be:  m[x] = ...;
     if (isIndexSetKey(info)) {
       var receiverType = info.receiver.type;
       if (inferrer.abstractValueDomain.isMap(receiverType)) {
         addsToMapKey(receiverType);
       } else {
         bailoutIfReaches(isParameterOfListAddingMethod);
         bailoutIfReaches(isParameterOfMapAddingMethod);
       }
     }

     if (mightAddToContainer(info)) {
       var receiverType = info.receiver.type;
       if (inferrer.abstractValueDomain.isContainer(receiverType)) {
         addsToContainer(receiverType);
       } else {
         // Not a container, see note above.
         bailoutIfReaches(isParameterOfListAddingMethod);
       }
     }

     if (info.targetsIncludeComplexNoSuchMethod(inferrer) &&
         info.arguments != null &&
         info.arguments.contains(currentUser)) {
       bailout('Passed to noSuchMethod');
     }

     Iterable<TypeInformation> inferredTargetTypes =
         info.concreteTargets.map((MemberEntity entity) {
       return inferrer.types.getInferredTypeOfMember(entity);
     });
     if (inferredTargetTypes.any((user) => user == currentUser)) {
       addNewEscapeInformation(info);
     }
   }

   /**
    * Check whether element is the parameter of a list adding method.
    * The definition of what a list adding method is has to stay in sync with
    * [mightAddToContainer].
    */
   bool isParameterOfListAddingMethod(ParameterTypeInformation parameterInfo) {
     if (!parameterInfo.isRegularParameter) return false;
     if (parameterInfo.method.enclosingClass !=
         inferrer.closedWorld.commonElements.jsArrayClass) {
       return false;
     }
     String name = parameterInfo.method.name;
     return (name == '[]=') || (name == 'add') || (name == 'insert');
   }

   /**
    * Check whether element is the parameter of a list adding method.
    * The definition of what a list adding method is has to stay in sync with
    * [isIndexSetKey] and [isIndexSetValue].
    */
   bool isParameterOfMapAddingMethod(ParameterTypeInformation parameterInfo) {
     if (!parameterInfo.isRegularParameter) return false;
     if (parameterInfo.method.enclosingClass !=
         inferrer.closedWorld.commonElements.mapLiteralClass) {
       return false;
     }
     String name = parameterInfo.method.name;
     return (name == '[]=');
   }

   bool isClosure(MemberEntity element) {
     if (!element.isFunction) return false;

     /// Creating an instance of a class that implements [Function] also
     /// closurizes the corresponding [call] member. We do not currently
     /// track these, thus the check for [isClosurized] on such a method will
     /// return false. Instead we catch that case here for now.
     // TODO(herhut): Handle creation of closures from instances of Function.
     if (element.isInstanceMember && element.name == Identifiers.call) {
       return true;
     }
     ClassEntity cls = element.enclosingClass;
     return cls != null && cls.isClosure;
   }

   void visitMemberTypeInformation(MemberTypeInformation info) {
     if (info.isClosurized) {
       bailout('Returned from a closurized method');
     }
     if (isClosure(info.member)) {
       bailout('Returned from a closure');
     }
     if (info.member.isField &&
         !inferrer.canFieldBeUsedForGlobalOptimizations(info.member)) {
       bailout('Escape to code that has special backend treatment');
     }
     addNewEscapeInformation(info);
   }

   void visitParameterTypeInformation(ParameterTypeInformation info) {
     if (inferrer.closedWorld.nativeData.isNativeMember(info.method)) {
       bailout('Passed to a native method');
     }
     if (!inferrer
         .canFunctionParametersBeUsedForGlobalOptimizations(info.method)) {
       bailout('Escape to code that has special backend treatment');
     }
     if (isParameterOfListAddingMethod(info) ||
         isParameterOfMapAddingMethod(info)) {
       // These elements are being handled in
       // [visitDynamicCallSiteTypeInformation].
       return;
     }
     addNewEscapeInformation(info);
   }
 }
	// Copyright (c) 2013, 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 compiler.src.inferrer.node_tracer;

	import '../common/names.dart' show Identifiers;
	import '../elements/entities.dart';
	import '../types/abstract_value_domain.dart';
	import '../util/util.dart' show Setlet;
	import 'debug.dart' as debug;
	import 'inferrer_engine.dart';
	import 'type_graph_nodes.dart';

	// A set of selectors we know do not escape the elements inside the
	// list.
	Set<String> doesNotEscapeListSet = new Set<String>.from(const <String>[
	// From Object.
	'==',
	'hashCode',
	'toString',
	'noSuchMethod',
	'runtimeType',

	// From Iterable.
	'isEmpty',
	'isNotEmpty',
	'length',
	'contains',
	'join',

	// From List.
	'add',
	'addAll',
	'clear',
	'fillRange',
	'indexOf',
	'insert',
	'insertAll',
	'lastIndexOf',
	'remove',
	'removeRange',
	'replaceRange',
	'setAll',
	'setRange',
	'shuffle',
	'[]=',

	// From JSArray.
	'checkMutable',
	'checkGrowable',
	]);

	Set<String> doesNotEscapeMapSet = new Set<String>.from(const <String>[
	// From Object.
	'==',
	'hashCode',
	'toString',
	'noSuchMethod',
	'runtimeType',
	// from Map.
	'isEmpty',
	'isNotEmpty',
	'length',
	'clear',
	'containsKey',
	'containsValue',
	'[]=',
	// [keys] only allows key values to escape, which we do not track.
	'keys'
	]);

	/// Common logic to trace a value through the type inference graph nodes.
	abstract class TracerVisitor implements TypeInformationVisitor {
	final TypeInformation tracedType;
	final InferrerEngine inferrer;

	static const int MAX_ANALYSIS_COUNT =
	const int.fromEnvironment('dart2js.tracing.limit', defaultValue: 32);
	final Setlet<MemberEntity> analyzedElements = new Setlet<MemberEntity>();

	TracerVisitor(this.tracedType, this.inferrer);

	// Work list that gets populated with [TypeInformation] that could
	// contain the container.
	final List<TypeInformation> workList = <TypeInformation>[];

	// Work list of lists to analyze after analyzing the users of a
	// [TypeInformation]. We know the [tracedType] has been stored in these
	// lists and we must check how it escapes from these lists.
	final List<ListTypeInformation> listsToAnalyze = <ListTypeInformation>[];
	// Work list of maps to analyze after analyzing the users of a
	// [TypeInformation]. We know the [tracedType] has been stored in these
	// maps and we must check how it escapes from these maps.
	final List<MapTypeInformation> mapsToAnalyze = <MapTypeInformation>[];

	final Setlet<TypeInformation> flowsInto = new Setlet<TypeInformation>();

	// The current [TypeInformation] in the analysis.
	TypeInformation currentUser;
	bool continueAnalyzing = true;

	void addNewEscapeInformation(TypeInformation info) {
	if (flowsInto.contains(info)) return;
	flowsInto.add(info);
	workList.add(info);
	}

	bool _wouldBeTooManyUsers(Set users) {
	int seenSoFar = analyzedElements.length;
	if (seenSoFar + users.length <= MAX_ANALYSIS_COUNT) return false;
	int actualWork = 0;
	for (TypeInformation user in users) {
	if (!analyzedElements.contains(user.owner)) {
	actualWork++;
	if (actualWork > MAX_ANALYSIS_COUNT - seenSoFar) return true;
	}
	}
	return false;
	}

	void analyze() {
	// Collect the [TypeInformation] where the list can flow in,
	// as well as the operations done on all these [TypeInformation]s.
	addNewEscapeInformation(tracedType);
	while (!workList.isEmpty) {
	currentUser = workList.removeLast();
	if (_wouldBeTooManyUsers(currentUser.users)) {
	bailout('Too many users');
	break;
	}
	for (TypeInformation info in currentUser.users) {
	analyzedElements.add(info.owner);
	info.accept(this);
	}
	while (!listsToAnalyze.isEmpty) {
	analyzeStoredIntoList(listsToAnalyze.removeLast());
	}
	while (!mapsToAnalyze.isEmpty) {
	analyzeStoredIntoMap(mapsToAnalyze.removeLast());
	}
	if (!continueAnalyzing) break;
	}
	}

	void bailout(String reason) {
	if (debug.VERBOSE) {
	print('Bailing out on $tracedType because: $reason');
	}
	continueAnalyzing = false;
	}

	void visitAwaitTypeInformation(AwaitTypeInformation info) {
	bailout("Passed through await");
	}

	void visitYieldTypeInformation(YieldTypeInformation info) {
	// TODO(29344): The enclosing sync/async/async method could have a
	// tracable TypeInformation for the Iterable / Future / Stream with an
	// element TypeInformation. Then YieldTypeInformation could connect the
	// source type information to the tracable element.
	bailout("Passed through yield");
	}

	void visitNarrowTypeInformation(NarrowTypeInformation info) {
	addNewEscapeInformation(info);
	}

	void visitPhiElementTypeInformation(PhiElementTypeInformation info) {
	addNewEscapeInformation(info);
	}

	void visitElementInContainerTypeInformation(
	ElementInContainerTypeInformation info) {
	addNewEscapeInformation(info);
	}

	void visitKeyInMapTypeInformation(KeyInMapTypeInformation info) {
	// We do not track the use of keys from a map, so we have to bail.
	bailout('Used as key in Map');
	}

	void visitValueInMapTypeInformation(ValueInMapTypeInformation info) {
	addNewEscapeInformation(info);
	}

	void visitListTypeInformation(ListTypeInformation info) {
	listsToAnalyze.add(info);
	}

	void visitMapTypeInformation(MapTypeInformation info) {
	mapsToAnalyze.add(info);
	}

	void visitConcreteTypeInformation(ConcreteTypeInformation info) {}

	void visitStringLiteralTypeInformation(StringLiteralTypeInformation info) {}

	void visitBoolLiteralTypeInformation(BoolLiteralTypeInformation info) {}

	void visitClosureTypeInformation(ClosureTypeInformation info) {}

	void visitClosureCallSiteTypeInformation(
	ClosureCallSiteTypeInformation info) {}

	visitStaticCallSiteTypeInformation(StaticCallSiteTypeInformation info) {
	MemberEntity called = info.calledElement;
	TypeInformation inferred = inferrer.types.getInferredTypeOfMember(called);
	if (inferred == currentUser) {
	addNewEscapeInformation(info);
	}
	}

	void analyzeStoredIntoList(ListTypeInformation list) {
	inferrer.analyzeListAndEnqueue(list);
	if (list.bailedOut) {
	bailout('Stored in a list that bailed out');
	} else {
	list.flowsInto.forEach((flow) {
	flow.users.forEach((dynamic user) {
	if (user is! DynamicCallSiteTypeInformation) return;
	if (user.receiver != flow) return;
	if (inferrer.returnsListElementTypeSet.contains(user.selector)) {
	addNewEscapeInformation(user);
	} else if (!doesNotEscapeListSet.contains(user.selector.name)) {
	bailout('Escape from a list via [${user.selector.name}]');
	}
	});
	});
	}
	}

	void analyzeStoredIntoMap(MapTypeInformation map) {
	inferrer.analyzeMapAndEnqueue(map);
	if (map.bailedOut) {
	bailout('Stored in a map that bailed out');
	} else {
	map.flowsInto.forEach((flow) {
	flow.users.forEach((dynamic user) {
	if (user is! DynamicCallSiteTypeInformation) return;
	if (user.receiver != flow) return;
	if (user.selector.isIndex) {
	addNewEscapeInformation(user);
	} else if (!doesNotEscapeMapSet.contains(user.selector.name)) {
	bailout('Escape from a map via [${user.selector.name}]');
	}
	});
	});
	}
	}

	/**
	* Checks whether this is a call to a list adding method. The definition of
	* what list adding means has to stay in sync with
	* [isParameterOfListAddingMethod].
	*/
	bool mightAddToContainer(DynamicCallSiteTypeInformation info) {
	if (info.arguments == null) return false;
	if (info.arguments.named.isNotEmpty) return false;
	String selectorName = info.selector.name;
	List<TypeInformation> arguments = info.arguments.positional;
	if (arguments.length == 1) {
	return (selectorName == 'add' && currentUser == arguments[0]);
	} else if (arguments.length == 2) {
	return (selectorName == 'insert' && currentUser == arguments[1]);
	}
	return false;
	}

	bool isIndexSetArgument(DynamicCallSiteTypeInformation info, int index) {
	String selectorName = info.selector.name;
	if (selectorName != '[]=') return false;
	assert(info.arguments.length == 2);
	List<TypeInformation> arguments = info.arguments.positional;
	return currentUser == arguments[index];
	}

	/**
	* Checks whether the call site flows the currentUser to the key argument of
	* an indexing setter. This must be kept in sync with
	* [isParameterOfMapAddingMethod].
	*/
	bool isIndexSetKey(DynamicCallSiteTypeInformation info) {
	return isIndexSetArgument(info, 0);
	}

	/**
	* Checks whether the call site flows the currentUser to the value argument of
	* an indexing setter. This must be kept in sync with
	* [isParameterOfListAddingMethod] and [isParameterOfMapAddingMethod].
	*/
	bool isIndexSetValue(DynamicCallSiteTypeInformation info) {
	return isIndexSetArgument(info, 1);
	}

	void bailoutIfReaches(bool predicate(ParameterTypeInformation e)) {
	for (var user in currentUser.users) {
	if (user is ParameterTypeInformation) {
	if (predicate(user)) {
	bailout('Reached suppressed parameter without precise receiver');
	break;
	}
	}
	}
	}

	void visitDynamicCallSiteTypeInformation(
	DynamicCallSiteTypeInformation info) {
	void addsToContainer(AbstractValue mask) {
	Object allocationNode =
	inferrer.abstractValueDomain.getAllocationNode(mask);
	if (allocationNode != null) {
	ListTypeInformation list =
	inferrer.types.allocatedLists[allocationNode];
	listsToAnalyze.add(list);
	} else {
	// The [mask] is a union of two containers, and we lose track of where
	// these containers have been allocated at this point.
	bailout('Stored in too many containers');
	}
	}

	void addsToMapValue(AbstractValue mask) {
	Object allocationNode =
	inferrer.abstractValueDomain.getAllocationNode(mask);
	if (allocationNode != null) {
	MapTypeInformation map = inferrer.types.allocatedMaps[allocationNode];
	mapsToAnalyze.add(map);
	} else {
	// The [mask] is a union. See comment for [mask] above.
	bailout('Stored in too many maps');
	}
	}

	void addsToMapKey(AbstractValue mask) {
	// We do not track the use of keys from a map, so we have to bail.
	bailout('Used as key in Map');
	}

	// "a[...] = x" could be a list (container) or map assignemnt.
	if (isIndexSetValue(info)) {
	var receiverType = info.receiver.type;
	if (inferrer.abstractValueDomain.isContainer(receiverType)) {
	addsToContainer(receiverType);
	} else if (inferrer.abstractValueDomain.isMap(receiverType)) {
	addsToMapValue(receiverType);
	} else {
	// Not a container or map, so the targets could be any methods. There
	// are edges from the [currentUser] to the parameters of the targets, so
	// tracing will continue into the targets. Tracing stops at parameters
	// that match the targets corresponding to the receiverTypes above (to
	// prevent imprecise results from tracing the implementation), so we
	// need compensate if one of the targets is in the target set. If there
	// is an edge to a parameter matching [isParameterOfListAddingMethod] or
	// [isParameterOfMapAddingMethod] then the traced value is being stored
	// into an untraced list or map.

	// TODO(sra): It would be more precise to specifically match the `value'
	// parameters of "operator []=".
	bailoutIfReaches(isParameterOfListAddingMethod);
	bailoutIfReaches(isParameterOfMapAddingMethod);
	}
	}

	// Could be: m[x] = ...;
	if (isIndexSetKey(info)) {
	var receiverType = info.receiver.type;
	if (inferrer.abstractValueDomain.isMap(receiverType)) {
	addsToMapKey(receiverType);
	} else {
	bailoutIfReaches(isParameterOfListAddingMethod);
	bailoutIfReaches(isParameterOfMapAddingMethod);
	}
	}

	if (mightAddToContainer(info)) {
	var receiverType = info.receiver.type;
	if (inferrer.abstractValueDomain.isContainer(receiverType)) {
	addsToContainer(receiverType);
	} else {
	// Not a container, see note above.
	bailoutIfReaches(isParameterOfListAddingMethod);
	}
	}

	if (info.targetsIncludeComplexNoSuchMethod(inferrer) &&
	info.arguments != null &&
	info.arguments.contains(currentUser)) {
	bailout('Passed to noSuchMethod');
	}

	Iterable<TypeInformation> inferredTargetTypes =
	info.concreteTargets.map((MemberEntity entity) {
	return inferrer.types.getInferredTypeOfMember(entity);
	});
	if (inferredTargetTypes.any((user) => user == currentUser)) {
	addNewEscapeInformation(info);
	}
	}

	/**
	* Check whether element is the parameter of a list adding method.
	* The definition of what a list adding method is has to stay in sync with
	* [mightAddToContainer].
	*/
	bool isParameterOfListAddingMethod(ParameterTypeInformation parameterInfo) {
	if (!parameterInfo.isRegularParameter) return false;
	if (parameterInfo.method.enclosingClass !=
	inferrer.closedWorld.commonElements.jsArrayClass) {
	return false;
	}
	String name = parameterInfo.method.name;
	return (name == '[]=') \|\| (name == 'add') \|\| (name == 'insert');
	}

	/**
	* Check whether element is the parameter of a list adding method.
	* The definition of what a list adding method is has to stay in sync with
	* [isIndexSetKey] and [isIndexSetValue].
	*/
	bool isParameterOfMapAddingMethod(ParameterTypeInformation parameterInfo) {
	if (!parameterInfo.isRegularParameter) return false;
	if (parameterInfo.method.enclosingClass !=
	inferrer.closedWorld.commonElements.mapLiteralClass) {
	return false;
	}
	String name = parameterInfo.method.name;
	return (name == '[]=');
	}

	bool isClosure(MemberEntity element) {
	if (!element.isFunction) return false;

	/// Creating an instance of a class that implements [Function] also
	/// closurizes the corresponding [call] member. We do not currently
	/// track these, thus the check for [isClosurized] on such a method will
	/// return false. Instead we catch that case here for now.
	// TODO(herhut): Handle creation of closures from instances of Function.
	if (element.isInstanceMember && element.name == Identifiers.call) {
	return true;
	}
	ClassEntity cls = element.enclosingClass;
	return cls != null && cls.isClosure;
	}

	void visitMemberTypeInformation(MemberTypeInformation info) {
	if (info.isClosurized) {
	bailout('Returned from a closurized method');
	}
	if (isClosure(info.member)) {
	bailout('Returned from a closure');
	}
	if (info.member.isField &&
	!inferrer.canFieldBeUsedForGlobalOptimizations(info.member)) {
	bailout('Escape to code that has special backend treatment');
	}
	addNewEscapeInformation(info);
	}

	void visitParameterTypeInformation(ParameterTypeInformation info) {
	if (inferrer.closedWorld.nativeData.isNativeMember(info.method)) {
	bailout('Passed to a native method');
	}
	if (!inferrer
	.canFunctionParametersBeUsedForGlobalOptimizations(info.method)) {
	bailout('Escape to code that has special backend treatment');
	}
	if (isParameterOfListAddingMethod(info) \|\|
	isParameterOfMapAddingMethod(info)) {
	// These elements are being handled in
	// [visitDynamicCallSiteTypeInformation].
	return;
	}
	addNewEscapeInformation(info);
	}
	}