Re-apply "Move the container tracer to the call graph inferrer.".

sdk/lib/_internal/compiler/implementation/inferrer/container_tracer.dart

Index: sdk/lib/_internal/compiler/implementation/inferrer/container_tracer.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/inferrer/container_tracer.dart	(revision 27995)
+++ sdk/lib/_internal/compiler/implementation/inferrer/container_tracer.dart	(working copy)
@@ -2,18 +2,8 @@
 // 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 container_tracer;
+part of type_graph_inferrer;
 
-import '../dart2jslib.dart' hide Selector, TypedSelector;
-import '../elements/elements.dart';
-import '../tree/tree.dart';
-import '../universe/universe.dart';
-import '../util/util.dart' show Link;
-import 'simple_types_inferrer.dart'
-    show InferrerEngine, InferrerVisitor, LocalsHandler, TypeMaskSystem;
-import '../types/types.dart';
-import 'inferrer_visitor.dart';
-
 /**
  * A set of selector names that [List] implements, that we know do not
  * change the element type of the list, or let the list escape to code
@@ -136,672 +126,154 @@
 
 bool _VERBOSE = false;
 
-class InferrerEngineForContainerTracer
-    implements MinimalInferrerEngine<TypeMask> {
+class ContainerTracerVisitor implements TypeInformationVisitor {
+  final ContainerTypeInformation container;
+  final TypeGraphInferrerEngine inferrer;
   final Compiler compiler;
 
-  InferrerEngineForContainerTracer(this.compiler);
+  // The set of [TypeInformation] where the traced container could
+  // flow in, and operations done on them.
+  final Set<TypeInformation> allUsers = new Set<TypeInformation>();
 
-  TypeMask typeOfElement(Element element) {
-    return compiler.typesTask.getGuaranteedTypeOfElement(element);
-  }
+  // The list of found assignments to the container.
+  final List<TypeInformation> assignments = <TypeInformation>[];
 
-  TypeMask returnTypeOfElement(Element element) {
-    return compiler.typesTask.getGuaranteedReturnTypeOfElement(element);
-  }
+  bool enableLengthTracking = true;
+  bool continueAnalyzing = true;
 
-  TypeMask returnTypeOfSelector(Selector selector) {
-    return compiler.typesTask.getGuaranteedTypeOfSelector(selector);
-  }
-
-  TypeMask typeOfNode(Node node) {
-    return compiler.typesTask.getGuaranteedTypeOfNode(null, node);
-  }
-
-  Iterable<Element> getCallersOf(Element element) {
-    return compiler.typesTask.typesInferrer.getCallersOf(element);
-  }
-
-  void recordTypeOfNonFinalField(Node node,
-                                 Element field,
-                                 TypeMask type) {}
-}
-
-/**
- * Global analysis phase that traces container instantiations in order to
- * find their element type.
- */
-class ContainerTracer extends CompilerTask {
-  ContainerTracer(Compiler compiler) : super(compiler);
-
-  String get name => 'List tracer';
-
-  bool analyze() {
-    measure(() {
-      if (compiler.disableTypeInference) return;
-      TypesInferrer inferrer = compiler.typesTask.typesInferrer;
-      InferrerEngineForContainerTracer engine =
-          new InferrerEngineForContainerTracer(compiler);
-
-      // Walk over all created [ContainerTypeMask].
-      inferrer.containerTypes.forEach((ContainerTypeMask mask) {
-        // The element type has already been set for const containers.
-        if (mask.elementType != null) return;
-        new TracerForConcreteContainer(mask, this, compiler, engine).run();
-      });
-    });
-  }
-}
-
-/**
- * A tracer for a specific container.
- */
-class TracerForConcreteContainer {
-  final Compiler compiler;
-  final ContainerTracer tracer;
-  final InferrerEngineForContainerTracer inferrer;
-  final ContainerTypeMask mask;
-
-  final Node analyzedNode;
-  final Element startElement;
-
-  final List<Element> workList = <Element>[];
-
-  /**
-   * A set of elements where this list might escape.
-   */
-  final Set<Element> escapingElements = new Set<Element>();
-
-  /**
-   * A set of selectors that both use and update the list, for example
-   * [: list[0]++; :] or [: list[0] |= 42; :].
-   */
-  final Set<Selector> constraints = new Set<Selector>();
-
-  /**
-   * A cache of setters that were already seen. Caching these
-   * selectors avoid the filtering done in [addSettersToAnalysis].
-   */
-  final Set<Selector> seenSetterSelectors = new Set<Selector>();
-
   static const int MAX_ANALYSIS_COUNT = 11;
+  final Set<Element> analyzedElements = new Set<Element>();
 
-  TypeMask potentialType;
-  int potentialLength;
-  bool isLengthTrackingDisabled = false;
-  bool continueAnalyzing = true;
+  ContainerTracerVisitor(this.container, inferrer)
+      : this.inferrer = inferrer, this.compiler = inferrer.compiler;
 
-  TracerForConcreteContainer(ContainerTypeMask mask,
-                             this.tracer,
-                             this.compiler,
-                             this.inferrer)
-      : analyzedNode = mask.allocationNode,
-        startElement = mask.allocationElement,
-        this.mask = mask;
-
   void run() {
-    int analysisCount = 0;
-    workList.add(startElement);
+    // Add the assignments found at allocation site.
+    assignments.addAll(container.elementType.assignments);
+
+    // Collect the [TypeInformation] where the container can flow in,
+    // as well as the operations done on all these [TypeInformation]s.
+    List<TypeInformation> workList = <TypeInformation>[];
+    allUsers.add(container);
+    workList.add(container);
     while (!workList.isEmpty) {
-      if (workList.length + analysisCount > MAX_ANALYSIS_COUNT) {
+      TypeInformation user = workList.removeLast();
+      user.users.forEach((TypeInformation info) {
+        if (allUsers.contains(info)) return;
+        allUsers.add(info);
+        analyzedElements.add(info.owner);
+        if (info.reachedBy(user, inferrer)) {
+          workList.add(info);
+        }
+      });
+      if (analyzedElements.length > MAX_ANALYSIS_COUNT) {
         bailout('Too many users');
         break;
       }
-      Element currentElement = workList.removeLast().implementation;
-      new ContainerTracerVisitor(currentElement, this).run();
-      if (!continueAnalyzing) break;
-      analysisCount++;
     }
 
-    if (!continueAnalyzing) {
-      if (mask.forwardTo == compiler.typesTask.fixedListType) {
-        mask.length = potentialLength;
+    if (continueAnalyzing) {
+      for (TypeInformation info in allUsers) {
+        info.accept(this);
+        if (!continueAnalyzing) break;
       }
-      mask.elementType = compiler.typesTask.dynamicType;
-      return;
     }
 
-    // [potentialType] can be null if we did not find any instruction
-    // that adds elements to the list.
-    if (potentialType == null) {
-      if (_VERBOSE) {
-        print('Found empty type for $analyzedNode $startElement');
-      }
-      mask.elementType = new TypeMask.nonNullEmpty();
-      return;
+    ContainerTypeMask mask = container.type;
+    if (!enableLengthTracking
+        && (mask.forwardTo != compiler.typesTask.fixedListType)) {
+      mask.length = null;
     }
 
-    // Walk over the found constraints and update the type according
-    // to the selectors of these constraints.
-    for (Selector constraint in constraints) {
-      assert(constraint.isOperator());
-      constraint = new TypedSelector(potentialType, constraint);
-      potentialType = potentialType.union(
-          inferrer.returnTypeOfSelector(constraint), compiler);
-    }
+    TypeMask result = continueAnalyzing
+      ? inferrer.types.computeTypeMask(assignments)
+      : inferrer.types.dynamicType.type;
+
+    mask.elementType = result;
     if (_VERBOSE) {
-      print('$potentialType and $potentialLength '
-            'for $analyzedNode $startElement');
+      print('$result and ${mask.length} '
+            'for ${mask.allocationNode} ${mask.allocationElement}');
     }
-    mask.elementType = potentialType;
-    mask.length = potentialLength;
   }
 
-  void disableLengthTracking() {
-    if (mask.forwardTo == compiler.typesTask.fixedListType) {
-      // Bogus update to a fixed list.
-      return;
-    }
-    isLengthTrackingDisabled = true;
-    potentialLength = null;
-  }
-
-  void setPotentialLength(int value) {
-    if (isLengthTrackingDisabled) return;
-    potentialLength = value;
-  }
-
-  void unionPotentialTypeWith(TypeMask newType) {
-    assert(newType != null);
-    potentialType = potentialType == null
-        ? newType
-        : newType.union(potentialType, compiler);
-    if (potentialType == compiler.typesTask.dynamicType) {
-      bailout('Moved to dynamic');
-    }
-  }
-
-  void addEscapingElement(element) {
-    element = element.implementation;
-    if (escapingElements.contains(element)) return;
-    escapingElements.add(element);
-    if (element.isField() || element.isGetter() || element.isFunction()) {
-      for (Element e in inferrer.getCallersOf(element)) {
-        addElementToAnalysis(e);
-      }
-    } else if (element.isParameter()) {
-      addElementToAnalysis(element.enclosingElement);
-    } else if (element.isFieldParameter()) {
-      addEscapingElement(element.fieldElement);
-    }
-  }
-
-  void addSettersToAnalysis(Selector selector) {
-    assert(selector.isSetter());
-    if (seenSetterSelectors.contains(selector)) return;
-    seenSetterSelectors.add(selector);
-    for (var e in compiler.world.allFunctions.filter(selector)) {
-      e = e.implementation;
-      if (e.isField()) {
-        addEscapingElement(e);
-      } else {
-        FunctionSignature signature = e.computeSignature(compiler);
-        signature.forEachRequiredParameter((Element e) {
-          addEscapingElement(e);
-        });
-      }
-    }
-  }
-
-  void addElementToAnalysis(Element element) {
-    workList.add(element);
-  }
-
-  TypeMask bailout(String reason) {
+  void bailout(String reason) {
     if (_VERBOSE) {
-      print('Bailout on $analyzedNode $startElement because of $reason');
+      ContainerTypeMask mask = container.type;
+      print('Bailing out on ${mask.allocationNode} ${mask.allocationElement} '
+            'because: $reason');
     }
     continueAnalyzing = false;
-    return compiler.typesTask.dynamicType;
+    enableLengthTracking = false;
   }
 
-  bool couldBeTheList(resolved) {
-    if (resolved is Selector) {
-      return escapingElements.any((e) {
-        return e.isInstanceMember() && resolved.applies(e, compiler);
-      });
-    } else if (resolved is Node) {
-      return analyzedNode == resolved;
-    } else {
-      assert(resolved is Element);
-      return escapingElements.contains(resolved);
-    }
-  }
+  visitNarrowTypeInformation(NarrowTypeInformation info) {}
+  visitPhiElementTypeInformation(PhiElementTypeInformation info) {}
+  visitElementInContainerTypeInformation(
+      ElementInContainerTypeInformation info) {}
+  visitContainerTypeInformation(ContainerTypeInformation info) {}
+  visitConcreteTypeInformation(ConcreteTypeInformation info) {}
 
-  void recordConstraint(Selector selector) {
-    constraints.add(selector);
+  visitClosureCallSiteTypeInformation(ClosureCallSiteTypeInformation info) {
+    bailout('Passed to a closure');
   }
-}
 
-class ContainerTracerVisitor
-    extends InferrerVisitor<TypeMask, InferrerEngineForContainerTracer> {
-  final Element analyzedElement;
-  final TracerForConcreteContainer tracer;
-  final bool visitingClosure;
-
-  ContainerTracerVisitor(element, tracer, [LocalsHandler<TypeMask> locals])
-      : super(element, tracer.inferrer, new TypeMaskSystem(tracer.compiler),
-              tracer.compiler, locals),
-        this.analyzedElement = element,
-        this.tracer = tracer,
-        visitingClosure = locals != null;
-
-  bool escaping = false;
-  bool visitingInitializers = false;
-
-  void run() {
-    compiler.withCurrentElement(analyzedElement, () {
-      visit(analyzedElement.parseNode(compiler));
-    });
-  }
-
-  /**
-   * Executes [f] and returns whether it triggered the list to escape.
-   */
-  bool visitAndCatchEscaping(Function f) {
-    bool oldEscaping = escaping;
-    escaping = false;
-    f();
-    bool foundEscaping = escaping;
-    escaping = oldEscaping;
-    return foundEscaping;
-  }
-
-  /**
-   * Visits the [arguments] of [callee], and records the parameters
-   * that could hold the container as escaping.
-   *
-   * Returns whether the container escaped.
-   */
-  bool visitArguments(Link<Node> arguments, /* Element or Selector */ callee) {
-    List<int> indices = [];
-    int index = 0;
-    for (Node node in arguments) {
-      if (visitAndCatchEscaping(() { visit(node); })) {
-        indices.add(index);
-      }
-      index++;
+  visitStaticCallSiteTypeInformation(StaticCallSiteTypeInformation info) {
+    analyzedElements.add(info.caller);
+    Element called = info.calledElement;
+    if (called.isForeign(compiler) && called.name == const SourceString('JS')) {
+      bailout('Used in JS ${info.call}');
     }
-    if (!indices.isEmpty) {
-      Iterable<Element> callees;
-      if (callee is Element) {
-        // No need to go further, we know the call will throw.
-        if (callee.isErroneous()) return false;
-        callees = [callee];
-      } else {
-        assert(callee is Selector);
-        callees = compiler.world.allFunctions.filter(callee);
-      }
-      for (var e in callees) {
-        e = e.implementation;
-        if (e.isField()) {
-          tracer.bailout('Passed to a closure');
-          break;
-        }
-        FunctionSignature signature = e.computeSignature(compiler);
-        index = 0;
-        int parameterIndex = 0;
-        signature.forEachRequiredParameter((Element parameter) {
-          if (index < indices.length && indices[index] == parameterIndex) {
-            tracer.addEscapingElement(parameter);
-            index++;
-          }
-          parameterIndex++;
-        });
-        if (index != indices.length) {
-          tracer.bailout('Used in a named parameter or closure');
-        }
-      }
-      return true;
-    } else {
-      return false;
-    }
   }
 
-  TypeMask visitFunctionExpression(FunctionExpression node) {
-    FunctionElement function = elements[node];
-    if (function != analyzedElement) {
-      // Visiting a closure.
-      LocalsHandler closureLocals = new LocalsHandler<TypeMask>.from(
-          locals, node, useOtherTryBlock: false);
-      new ContainerTracerVisitor(function, tracer, closureLocals).run();
-      return types.functionType;
-    } else {
-      // Visiting [analyzedElement].
-      FunctionSignature signature = function.computeSignature(compiler);
-      signature.forEachParameter((element) {
-        locals.update(element, inferrer.typeOfElement(element), node);
-      });
-      visitingInitializers = true;
-      visit(node.initializers);
-      visitingInitializers = false;
-      visit(node.body);
-      return null;
-    }
-  }
-
-  TypeMask visitLiteralList(LiteralList node) {
-    if (node.isConst()) {
-      return inferrer.typeOfNode(node);
-    }
-    if (tracer.couldBeTheList(node)) {
-      escaping = true;
-      int length = 0;
-      for (Node element in node.elements.nodes) {
-        tracer.unionPotentialTypeWith(visit(element));
-        length++;
-      }
-      tracer.setPotentialLength(length);
-    } else {
-      node.visitChildren(this);
-    }
-    return types.growableListType;
-  }
-
-  TypeMask visitSendSet(SendSet node) {
-    bool isReceiver = visitAndCatchEscaping(() {
-      visit(node.receiver);
-    });
-    return handleSendSet(node, isReceiver);
-  }
-
-  TypeMask handleSendSet(SendSet node, bool isReceiver) {
-    TypeMask rhsType;
-    TypeMask indexType;
-
-    Selector getterSelector =
-        elements.getGetterSelectorInComplexSendSet(node);
-    Selector operatorSelector =
-        elements.getOperatorSelectorInComplexSendSet(node);
-    Selector setterSelector = elements.getSelector(node);
-
-    String op = node.assignmentOperator.source.stringValue;
-    bool isIncrementOrDecrement = op == '++' || op == '--';
-    bool isIndexEscaping = false;
-    bool isValueEscaping = false;
-    if (isIncrementOrDecrement) {
-      rhsType = types.intType;
-      if (node.isIndex) {
-        isIndexEscaping = visitAndCatchEscaping(() {
-          indexType = visit(node.arguments.head);
-        });
-      }
-    } else if (node.isIndex) {
-      isIndexEscaping = visitAndCatchEscaping(() {
-        indexType = visit(node.arguments.head);
-      });
-      isValueEscaping = visitAndCatchEscaping(() {
-        rhsType = visit(node.arguments.tail.head);
-      });
-    } else {
-      isValueEscaping = visitAndCatchEscaping(() {
-        rhsType = visit(node.arguments.head);
-      });
-    }
-
-    Element element = elements[node];
-
-    if (node.isIndex) {
-      if (isReceiver) {
-        if (op == '=') {
-          tracer.unionPotentialTypeWith(rhsType);
-        } else {
-          tracer.recordConstraint(operatorSelector);
-        }
-      } else if (isIndexEscaping || isValueEscaping) {
-        // If the index or value is escaping, iterate over all
-        // potential targets, and mark their parameter as escaping.
-        for (var e in compiler.world.allFunctions.filter(setterSelector)) {
-          e = e.implementation;
-          FunctionSignature signature = e.computeSignature(compiler);
-          int index = 0;
-          signature.forEachRequiredParameter((Element parameter) {
-            if (index == 0 && isIndexEscaping) {
-              tracer.addEscapingElement(parameter);
+  visitDynamicCallSiteTypeInformation(DynamicCallSiteTypeInformation info) {
+    Selector selector = info.selector;
+    String selectorName = selector.name.slowToString();
+    if (allUsers.contains(info.receiver)) {
+      if (!okSelectorsSet.contains(selectorName)) {
+        if (selector.isCall()) {
+          int positionalLength = info.arguments.positional.length;
+          if (selectorName == 'add') {
+            if (positionalLength == 1) {
+              assignments.add(info.arguments.positional[0]);
             }
-            if (index == 1 && isValueEscaping) {
-              tracer.addEscapingElement(parameter);
+          } else if (selectorName == 'insert') {
+            if (positionalLength == 2) {
+              assignments.add(info.arguments.positional[1]);
             }
-            index++;
-          });
+          } else {
+            bailout('Used in a not-ok selector');
+            return;
+          }
+        } else if (selector.isIndexSet()) {
+          assignments.add(info.arguments.positional[1]);
+        } else if (!selector.isIndex()) {
+          bailout('Used in a not-ok selector');
+          return;
         }
       }
-    } else if (isReceiver) {
-      if (setterSelector.name == const SourceString('length')) {
-        tracer.disableLengthTracking();
-        tracer.unionPotentialTypeWith(compiler.typesTask.nullType);
+      if (!doNotChangeLengthSelectorsSet.contains(selectorName)) {
+        enableLengthTracking = false;
       }
-    } else if (isValueEscaping) {
-      if (element != null
-          && element.isField()
-          && setterSelector == null
-          && !visitingInitializers) {
-        // Initializer at declaration of a field.
-        assert(analyzedElement.isField());
-        tracer.addEscapingElement(analyzedElement);
-      } else if (element != null
-                  && (!element.isInstanceMember() || visitingInitializers)) {
-        // A local, a static element, or a field in an initializer.
-        tracer.addEscapingElement(element);
-      } else {
-        tracer.addSettersToAnalysis(setterSelector);
+      if (selectorName == 'length' && selector.isSetter()) {
+        enableLengthTracking = false;
+        assignments.add(inferrer.types.nullType);
       }
+    } else if (selector.isCall()
+               && !info.targets.every((element) => element.isFunction())) {
+      bailout('Passed to a closure');
+      return;
     }
-
-    TypeMask result;
-    if (node.isPostfix) {
-      // We don't check if [getterSelector] could be the container because
-      // a list++ will always throw.
-      result = inferrer.returnTypeOfSelector(getterSelector);
-    } else if (op != '=') {
-      // We don't check if [getterSelector] could be the container because
-      // a list += 42 will always throw.
-      result = inferrer.returnTypeOfSelector(operatorSelector);
-    } else {
-      if (isValueEscaping) {
-        escaping = true;
-      }
-      result = rhsType;
-    }
-
-    if (Elements.isLocal(element)) {
-      locals.update(element, result, node);
-    }
-
-    return result;
   }
 
-  TypeMask visitSuperSend(Send node) {
-    Element element = elements[node];
-    if (!node.isPropertyAccess) {
-      visitArguments(node.arguments, element);
-    }
-
-    if (tracer.couldBeTheList(element)) {
-      escaping = true;
-    }
-
-    if (element.isField()) {
-      return inferrer.typeOfElement(element);
-    } else if (element.isFunction()) {
-      return inferrer.returnTypeOfElement(element);
-    } else {
-      return types.dynamicType;
-    }
+  bool isClosure(Element element) {
+    if (!element.isFunction()) return false;
+    Element outermost = element.getOutermostEnclosingMemberOrTopLevel();
+    return outermost.declaration != element.declaration;
   }
 
-  TypeMask visitStaticSend(Send node) {
-    Element element = elements[node];
-
-    if (Elements.isGrowableListConstructorCall(element, node, compiler)) {
-      visitArguments(node.arguments, element);
-      if (tracer.couldBeTheList(node)) {
-        escaping = true;
-      }
-      return inferrer.typeOfNode(node);
-    } else if (Elements.isFixedListConstructorCall(element, node, compiler)) {
-      visitArguments(node.arguments, element);
-      if (tracer.couldBeTheList(node)) {
-        tracer.unionPotentialTypeWith(types.nullType);
-        escaping = true;
-        LiteralInt length = node.arguments.head.asLiteralInt();
-        if (length != null) {
-          tracer.setPotentialLength(length.value);
-        }
-      }
-      return inferrer.typeOfNode(node);
-    } else if (Elements.isFilledListConstructorCall(element, node, compiler)) {
-      if (tracer.couldBeTheList(node)) {
-        escaping = true;
-        visit(node.arguments.head);
-        TypeMask fillWithType = visit(node.arguments.tail.head);
-        tracer.unionPotentialTypeWith(fillWithType);
-        LiteralInt length = node.arguments.head.asLiteralInt();
-        if (length != null) {
-          tracer.setPotentialLength(length.value);
-        }
-      } else {
-        visitArguments(node.arguments, element);
-      }
-      return inferrer.typeOfNode(node);
+  visitElementTypeInformation(ElementTypeInformation info) {
+    if (isClosure(info.element)) {
+      bailout('Returned from a closure');
     }
-
-    bool isEscaping = visitArguments(node.arguments, element);
-
-    if (element.isForeign(compiler)) {
-      if (isEscaping) return tracer.bailout('Used in a JS');
-    }
-
-    if (tracer.couldBeTheList(element)) {
-      escaping = true;
-    }
-
-    if (element.isFunction() || element.isConstructor()) {
-      return inferrer.returnTypeOfElement(element);
-    } else {
-      // Closure call or unresolved.
-      return types.dynamicType;
-    }
   }
-
-  TypeMask visitGetterSend(Send node) {
-    Element element = elements[node];
-    Selector selector = elements.getSelector(node);
-    if (Elements.isStaticOrTopLevelField(element)) {
-      if (tracer.couldBeTheList(element)) {
-        escaping = true;
-      }
-      return inferrer.typeOfElement(element);
-    } else if (Elements.isInstanceSend(node, elements)) {
-      return visitDynamicSend(node);
-    } else if (Elements.isStaticOrTopLevelFunction(element)) {
-      return types.functionType;
-    } else if (Elements.isErroneousElement(element)) {
-      return types.dynamicType;
-    } else if (Elements.isLocal(element)) {
-      if (tracer.couldBeTheList(element)) {
-        escaping = true;
-      }
-      return locals.use(element);
-    } else {
-      node.visitChildren(this);
-      return types.dynamicType;
-    }
-  }
-
-  TypeMask visitClosureSend(Send node) {
-    assert(node.receiver == null);
-    visit(node.selector);
-    bool isEscaping =
-        visitArguments(node.arguments, elements.getSelector(node));
-
-    if (isEscaping) return tracer.bailout('Passed to a closure');
-    return types.dynamicType;
-  }
-
-  TypeMask visitDynamicSend(Send node) {
-    bool isReceiver = visitAndCatchEscaping(() {
-      visit(node.receiver);
-    });
-    return handleDynamicSend(node, isReceiver);
-  }
-
-  TypeMask handleDynamicSend(Send node, bool isReceiver) {
-    Selector selector = elements.getSelector(node);
-    String selectorName = selector.name.slowToString();
-    if (isReceiver && !okSelectorsSet.contains(selectorName)) {
-      if (selector.isCall()
-          && (selectorName == 'add' || selectorName == 'insert')) {
-        TypeMask argumentType;
-        if (node.arguments.isEmpty
-            || (selectorName == 'insert' && node.arguments.tail.isEmpty)) {
-          return tracer.bailout('Invalid "add" or "insert" call on a list');
-        }
-        bool isEscaping = visitAndCatchEscaping(() {
-          argumentType = visit(node.arguments.head);
-          if (selectorName == 'insert') {
-            argumentType = visit(node.arguments.tail.head);
-          }
-        });
-        if (isEscaping) {
-          return tracer.bailout('List containing itself');
-        }
-        tracer.unionPotentialTypeWith(argumentType);
-      } else {
-        return tracer.bailout('Send with the node as receiver $node');
-      }
-    } else if (!node.isPropertyAccess) {
-      visitArguments(node.arguments, selector);
-    }
-    if (isReceiver && !doNotChangeLengthSelectorsSet.contains(selectorName)) {
-      tracer.disableLengthTracking();
-    }
-    if (tracer.couldBeTheList(selector)) {
-      escaping = true;
-    }
-    return inferrer.returnTypeOfSelector(selector);
-  }
-
-  TypeMask visitReturn(Return node) {
-    if (node.expression == null) {
-      return types.nullType;
-    }
-
-    TypeMask type;
-    bool isEscaping = visitAndCatchEscaping(() {
-      type = visit(node.expression);
-    });
-
-    if (isEscaping) {
-      if (visitingClosure) {
-        tracer.bailout('Return from closure');
-      } else {
-        tracer.addEscapingElement(analyzedElement);
-      }
-    }
-    return type;
-  }
-
-  TypeMask visitForIn(ForIn node) {
-    visit(node.expression);
-    Selector iteratorSelector = elements.getIteratorSelector(node);
-    Selector currentSelector = elements.getCurrentSelector(node);
-
-    TypeMask iteratorType = inferrer.returnTypeOfSelector(iteratorSelector);
-    TypeMask currentType = inferrer.returnTypeOfSelector(currentSelector);
-
-    // We nullify the type in case there is no element in the
-    // iterable.
-    currentType = currentType.nullable();
-
-    Node identifier = node.declaredIdentifier;
-    Element element = elements[identifier];
-    if (Elements.isLocal(element)) {
-      locals.update(element, currentType, node);
-    }
-
-    return handleLoop(node, () {
-      visit(node.body);
-    });
-  }
 }