Move InheritanceManager to its own file.

pkg/analyzer/lib/src/dart/resolver/inheritance_manager.dart

+// Copyright (c) 2016, 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.
+
+import 'dart:collection';
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/src/dart/ast/token.dart';
+import 'package:analyzer/src/dart/element/element.dart';
+import 'package:analyzer/src/dart/element/member.dart';
+import 'package:analyzer/src/dart/element/type.dart';
+import 'package:analyzer/src/generated/error.dart';
+import 'package:analyzer/src/generated/type_system.dart';
+import 'package:analyzer/src/generated/utilities_dart.dart';
+
+/**
+ * Instances of the class `InheritanceManager` manage the knowledge of where class members
+ * (methods, getters & setters) are inherited from.
+ */
+class InheritanceManager {
+  /**
+   * The [LibraryElement] that is managed by this manager.
+   */
+  LibraryElement _library;
+
+  /**
+   * This is a mapping between each [ClassElement] and a map between the [String] member
+   * names and the associated [ExecutableElement] in the mixin and superclass chain.
+   */
+  HashMap<ClassElement, MemberMap> _classLookup;
+
+  /**
+   * This is a mapping between each [ClassElement] and a map between the [String] member
+   * names and the associated [ExecutableElement] in the interface set.
+   */
+  HashMap<ClassElement, MemberMap> _interfaceLookup;
+
+  /**
+   * A map between each visited [ClassElement] and the set of [AnalysisError]s found on
+   * the class element.
+   */
+  HashMap<ClassElement, HashSet<AnalysisError>> _errorsInClassElement =
+      new HashMap<ClassElement, HashSet<AnalysisError>>();
+
+  /**
+   * Initialize a newly created inheritance manager.
+   *
+   * @param library the library element context that the inheritance mappings are being generated
+   */
+  InheritanceManager(LibraryElement library) {
+    this._library = library;
+    _classLookup = new HashMap<ClassElement, MemberMap>();
+    _interfaceLookup = new HashMap<ClassElement, MemberMap>();
+  }
+
+  /**
+   * Set the new library element context.
+   *
+   * @param library the new library element
+   */
+  void set libraryElement(LibraryElement library) {
+    this._library = library;
+  }
+
+  /**
+   * Return the set of [AnalysisError]s found on the passed [ClassElement], or
+   * `null` if there are none.
+   *
+   * @param classElt the class element to query
+   * @return the set of [AnalysisError]s found on the passed [ClassElement], or
+   *         `null` if there are none
+   */
+  HashSet<AnalysisError> getErrors(ClassElement classElt) =>
+      _errorsInClassElement[classElt];
+
+  /**
+   * Get and return a mapping between the set of all string names of the members inherited from the
+   * passed [ClassElement] superclass hierarchy, and the associated [ExecutableElement].
+   *
+   * @param classElt the class element to query
+   * @return a mapping between the set of all members inherited from the passed [ClassElement]
+   *         superclass hierarchy, and the associated [ExecutableElement]
+   */
+  MemberMap getMapOfMembersInheritedFromClasses(ClassElement classElt) =>
+      _computeClassChainLookupMap(classElt, new HashSet<ClassElement>());
+
+  /**
+   * Get and return a mapping between the set of all string names of the members inherited from the
+   * passed [ClassElement] interface hierarchy, and the associated [ExecutableElement].
+   *
+   * @param classElt the class element to query
+   * @return a mapping between the set of all string names of the members inherited from the passed
+   *         [ClassElement] interface hierarchy, and the associated [ExecutableElement].
+   */
+  MemberMap getMapOfMembersInheritedFromInterfaces(ClassElement classElt) =>
+      _computeInterfaceLookupMap(classElt, new HashSet<ClassElement>());
+
+  /**
+   * Given some [ClassElement] and some member name, this returns the
+   * [ExecutableElement] that the class inherits from the mixins,
+   * superclasses or interfaces, that has the member name, if no member is inherited `null` is
+   * returned.
+   *
+   * @param classElt the class element to query
+   * @param memberName the name of the executable element to find and return
+   * @return the inherited executable element with the member name, or `null` if no such
+   *         member exists
+   */
+  ExecutableElement lookupInheritance(
+      ClassElement classElt, String memberName) {
+    if (memberName == null || memberName.isEmpty) {
+      return null;
+    }
+    ExecutableElement executable =
+        _computeClassChainLookupMap(classElt, new HashSet<ClassElement>())
+            .get(memberName);
+    if (executable == null) {
+      return _computeInterfaceLookupMap(classElt, new HashSet<ClassElement>())
+          .get(memberName);
+    }
+    return executable;
+  }
+
+  /**
+   * Given some [ClassElement] and some member name, this returns the
+   * [ExecutableElement] that the class either declares itself, or
+   * inherits, that has the member name, if no member is inherited `null` is returned.
+   *
+   * @param classElt the class element to query
+   * @param memberName the name of the executable element to find and return
+   * @return the inherited executable element with the member name, or `null` if no such
+   *         member exists
+   */
+  ExecutableElement lookupMember(ClassElement classElt, String memberName) {
+    ExecutableElement element = _lookupMemberInClass(classElt, memberName);
+    if (element != null) {
+      return element;
+    }
+    return lookupInheritance(classElt, memberName);
+  }
+
+  /**
+   * Determine the set of methods which is overridden by the given class member. If no member is
+   * inherited, an empty list is returned. If one of the inherited members is a
+   * [MultiplyInheritedExecutableElement], then it is expanded into its constituent inherited
+   * elements.
+   *
+   * @param classElt the class to query
+   * @param memberName the name of the class member to query
+   * @return a list of overridden methods
+   */
+  List<ExecutableElement> lookupOverrides(
+      ClassElement classElt, String memberName) {
+    List<ExecutableElement> result = new List<ExecutableElement>();
+    if (memberName == null || memberName.isEmpty) {
+      return result;
+    }
+    List<MemberMap> interfaceMaps =
+        _gatherInterfaceLookupMaps(classElt, new HashSet<ClassElement>());
+    if (interfaceMaps != null) {
+      for (MemberMap interfaceMap in interfaceMaps) {
+        ExecutableElement overriddenElement = interfaceMap.get(memberName);
+        if (overriddenElement != null) {
+          if (overriddenElement is MultiplyInheritedExecutableElement) {
+            MultiplyInheritedExecutableElement multiplyInheritedElement =
+                overriddenElement;
+            for (ExecutableElement element
+                in multiplyInheritedElement.inheritedElements) {
+              result.add(element);
+            }
+          } else {
+            result.add(overriddenElement);
+          }
+        }
+      }
+    }
+    return result;
+  }
+
+  /**
+   * This method takes some inherited [FunctionType], and resolves all the parameterized types
+   * in the function type, dependent on the class in which it is being overridden.
+   *
+   * @param baseFunctionType the function type that is being overridden
+   * @param memberName the name of the member, this is used to lookup the inheritance path of the
+   *          override
+   * @param definingType the type that is overriding the member
+   * @return the passed function type with any parameterized types substituted
+   */
+  // TODO(jmesserly): investigate why this is needed in ErrorVerifier's override
+  // checking. There seems to be some rare cases where we get partially
+  // substituted type arguments, and the function types don't compare equally.
+  FunctionType substituteTypeArgumentsInMemberFromInheritance(
+      FunctionType baseFunctionType,
+      String memberName,
+      InterfaceType definingType) {
+    // if the baseFunctionType is null, or does not have any parameters,
+    // return it.
+    if (baseFunctionType == null ||
+        baseFunctionType.typeArguments.length == 0) {
+      return baseFunctionType;
+    }
+    // First, generate the path from the defining type to the overridden member
+    Queue<InterfaceType> inheritancePath = new Queue<InterfaceType>();
+    _computeInheritancePath(inheritancePath, definingType, memberName);
+    if (inheritancePath == null || inheritancePath.isEmpty) {
+      // TODO(jwren) log analysis engine error
+      return baseFunctionType;
+    }
+    FunctionType functionTypeToReturn = baseFunctionType;
+    // loop backward through the list substituting as we go:
+    while (!inheritancePath.isEmpty) {
+      InterfaceType lastType = inheritancePath.removeLast();
+      List<DartType> parameterTypes = lastType.element.type.typeArguments;
+      List<DartType> argumentTypes = lastType.typeArguments;
+      functionTypeToReturn =
+          functionTypeToReturn.substitute2(argumentTypes, parameterTypes);
+    }
+    return functionTypeToReturn;
+  }
+
+  /**
+   * Compute and return a mapping between the set of all string names of the members inherited from
+   * the passed [ClassElement] superclass hierarchy, and the associated
+   * [ExecutableElement].
+   *
+   * @param classElt the class element to query
+   * @param visitedClasses a set of visited classes passed back into this method when it calls
+   *          itself recursively
+   * @return a mapping between the set of all string names of the members inherited from the passed
+   *         [ClassElement] superclass hierarchy, and the associated [ExecutableElement]
+   */
+  MemberMap _computeClassChainLookupMap(
+      ClassElement classElt, HashSet<ClassElement> visitedClasses) {
+    MemberMap resultMap = _classLookup[classElt];
+    if (resultMap != null) {
+      return resultMap;
+    } else {
+      resultMap = new MemberMap();
+    }
+    ClassElement superclassElt = null;
+    InterfaceType supertype = classElt.supertype;
+    if (supertype != null) {
+      superclassElt = supertype.element;
+    } else {
+      // classElt is Object
+      _classLookup[classElt] = resultMap;
+      return resultMap;
+    }
+    if (superclassElt != null) {
+      if (!visitedClasses.contains(superclassElt)) {
+        visitedClasses.add(superclassElt);
+        try {
+          resultMap = new MemberMap.from(
+              _computeClassChainLookupMap(superclassElt, visitedClasses));
+          //
+          // Substitute the super types down the hierarchy.
+          //
+          _substituteTypeParametersDownHierarchy(supertype, resultMap);
+          //
+          // Include the members from the superclass in the resultMap.
+          //
+          _recordMapWithClassMembers(resultMap, supertype, false);
+        } finally {
+          visitedClasses.remove(superclassElt);
+        }
+      } else {
+        // This case happens only when the superclass was previously visited and
+        // not in the lookup, meaning this is meant to shorten the compute for
+        // recursive cases.
+        _classLookup[superclassElt] = resultMap;
+        return resultMap;
+      }
+    }
+    //
+    // Include the members from the mixins in the resultMap.  If there are
+    // multiple mixins, visit them in the order listed so that methods in later
+    // mixins will overwrite identically-named methods in earlier mixins.
+    //
+    List<InterfaceType> mixins = classElt.mixins;
+    for (InterfaceType mixin in mixins) {
+      ClassElement mixinElement = mixin.element;
+      if (mixinElement != null) {
+        if (!visitedClasses.contains(mixinElement)) {
+          visitedClasses.add(mixinElement);
+          try {
+            MemberMap map = new MemberMap.from(
+                _computeClassChainLookupMap(mixinElement, visitedClasses));
+            //
+            // Substitute the super types down the hierarchy.
+            //
+            _substituteTypeParametersDownHierarchy(mixin, map);
+            //
+            // Include the members from the superclass in the resultMap.
+            //
+            _recordMapWithClassMembers(map, mixin, false);
+            //
+            // Add the members from map into result map.
+            //
+            for (int j = 0; j < map.size; j++) {
+              String key = map.getKey(j);
+              ExecutableElement value = map.getValue(j);
+              if (key != null) {
+                ClassElement definingClass = value
+                    .getAncestor((Element element) => element is ClassElement);
+                if (!definingClass.type.isObject) {
+                  ExecutableElement existingValue = resultMap.get(key);
+                  if (existingValue == null ||
+                      (existingValue != null && !_isAbstract(value))) {
+                    resultMap.put(key, value);
+                  }
+                }
+              }
+            }
+          } finally {
+            visitedClasses.remove(mixinElement);
+          }
+        } else {
+          // This case happens only when the superclass was previously visited
+          // and not in the lookup, meaning this is meant to shorten the compute
+          // for recursive cases.
+          _classLookup[mixinElement] = resultMap;
+          return resultMap;
+        }
+      }
+    }
+    _classLookup[classElt] = resultMap;
+    return resultMap;
+  }
+
+  /**
+   * Compute and return the inheritance path given the context of a type and a member that is
+   * overridden in the inheritance path (for which the type is in the path).
+   *
+   * @param chain the inheritance path that is built up as this method calls itself recursively,
+   *          when this method is called an empty [LinkedList] should be provided
+   * @param currentType the current type in the inheritance path
+   * @param memberName the name of the member that is being looked up the inheritance path
+   */
+  void _computeInheritancePath(Queue<InterfaceType> chain,
+      InterfaceType currentType, String memberName) {
+    // TODO (jwren) create a public version of this method which doesn't require
+    // the initial chain to be provided, then provided tests for this
+    // functionality in InheritanceManagerTest
+    chain.add(currentType);
+    ClassElement classElt = currentType.element;
+    InterfaceType supertype = classElt.supertype;
+    // Base case- reached Object
+    if (supertype == null) {
+      // Looked up the chain all the way to Object, return null.
+      // This should never happen.
+      return;
+    }
+    // If we are done, return the chain
+    // We are not done if this is the first recursive call on this method.
+    if (chain.length != 1) {
+      // We are done however if the member is in this classElt
+      if (_lookupMemberInClass(classElt, memberName) != null) {
+        return;
+      }
+    }
+    // Mixins- note that mixins call lookupMemberInClass, not lookupMember
+    List<InterfaceType> mixins = classElt.mixins;
+    for (int i = mixins.length - 1; i >= 0; i--) {
+      ClassElement mixinElement = mixins[i].element;
+      if (mixinElement != null) {
+        ExecutableElement elt = _lookupMemberInClass(mixinElement, memberName);
+        if (elt != null) {
+          // this is equivalent (but faster than) calling this method
+          // recursively
+          // (return computeInheritancePath(chain, mixins[i], memberName);)
+          chain.add(mixins[i]);
+          return;
+        }
+      }
+    }
+    // Superclass
+    ClassElement superclassElt = supertype.element;
+    if (lookupMember(superclassElt, memberName) != null) {
+      _computeInheritancePath(chain, supertype, memberName);
+      return;
+    }
+    // Interfaces
+    List<InterfaceType> interfaces = classElt.interfaces;
+    for (InterfaceType interfaceType in interfaces) {
+      ClassElement interfaceElement = interfaceType.element;
+      if (interfaceElement != null &&
+          lookupMember(interfaceElement, memberName) != null) {
+        _computeInheritancePath(chain, interfaceType, memberName);
+        return;
+      }
+    }
+  }
+
+  /**
+   * Compute and return a mapping between the set of all string names of the members inherited from
+   * the passed [ClassElement] interface hierarchy, and the associated
+   * [ExecutableElement].
+   *
+   * @param classElt the class element to query
+   * @param visitedInterfaces a set of visited classes passed back into this method when it calls
+   *          itself recursively
+   * @return a mapping between the set of all string names of the members inherited from the passed
+   *         [ClassElement] interface hierarchy, and the associated [ExecutableElement]
+   */
+  MemberMap _computeInterfaceLookupMap(
+      ClassElement classElt, HashSet<ClassElement> visitedInterfaces) {
+    MemberMap resultMap = _interfaceLookup[classElt];
+    if (resultMap != null) {
+      return resultMap;
+    }
+    List<MemberMap> lookupMaps =
+        _gatherInterfaceLookupMaps(classElt, visitedInterfaces);
+    if (lookupMaps == null) {
+      resultMap = new MemberMap();
+    } else {
+      HashMap<String, List<ExecutableElement>> unionMap =
+          _unionInterfaceLookupMaps(lookupMaps);
+      resultMap = _resolveInheritanceLookup(classElt, unionMap);
+    }
+    _interfaceLookup[classElt] = resultMap;
+    return resultMap;
+  }
+
+  /**
+   * Collect a list of interface lookup maps whose elements correspond to all of the classes
+   * directly above [classElt] in the class hierarchy (the direct superclass if any, all
+   * mixins, and all direct superinterfaces). Each item in the list is the interface lookup map
+   * returned by [computeInterfaceLookupMap] for the corresponding super, except with type
+   * parameters appropriately substituted.
+   *
+   * @param classElt the class element to query
+   * @param visitedInterfaces a set of visited classes passed back into this method when it calls
+   *          itself recursively
+   * @return `null` if there was a problem (such as a loop in the class hierarchy) or if there
+   *         are no classes above this one in the class hierarchy. Otherwise, a list of interface
+   *         lookup maps.
+   */
+  List<MemberMap> _gatherInterfaceLookupMaps(
+      ClassElement classElt, HashSet<ClassElement> visitedInterfaces) {
+    InterfaceType supertype = classElt.supertype;
+    ClassElement superclassElement =
+        supertype != null ? supertype.element : null;
+    List<InterfaceType> mixins = classElt.mixins;
+    List<InterfaceType> interfaces = classElt.interfaces;
+    // Recursively collect the list of mappings from all of the interface types
+    List<MemberMap> lookupMaps = new List<MemberMap>();
+    //
+    // Superclass element
+    //
+    if (superclassElement != null) {
+      if (!visitedInterfaces.contains(superclassElement)) {
+        try {
+          visitedInterfaces.add(superclassElement);
+          //
+          // Recursively compute the map for the super type.
+          //
+          MemberMap map =
+              _computeInterfaceLookupMap(superclassElement, visitedInterfaces);
+          map = new MemberMap.from(map);
+          //
+          // Substitute the super type down the hierarchy.
+          //
+          _substituteTypeParametersDownHierarchy(supertype, map);
+          //
+          // Add any members from the super type into the map as well.
+          //
+          _recordMapWithClassMembers(map, supertype, true);
+          lookupMaps.add(map);
+        } finally {
+          visitedInterfaces.remove(superclassElement);
+        }
+      } else {
+        return null;
+      }
+    }
+    //
+    // Mixin elements
+    //
+    for (int i = mixins.length - 1; i >= 0; i--) {
+      InterfaceType mixinType = mixins[i];
+      ClassElement mixinElement = mixinType.element;
+      if (mixinElement != null) {
+        if (!visitedInterfaces.contains(mixinElement)) {
+          try {
+            visitedInterfaces.add(mixinElement);
+            //
+            // Recursively compute the map for the mixin.
+            //
+            MemberMap map =
+                _computeInterfaceLookupMap(mixinElement, visitedInterfaces);
+            map = new MemberMap.from(map);
+            //
+            // Substitute the mixin type down the hierarchy.
+            //
+            _substituteTypeParametersDownHierarchy(mixinType, map);
+            //
+            // Add any members from the mixin type into the map as well.
+            //
+            _recordMapWithClassMembers(map, mixinType, true);
+            lookupMaps.add(map);
+          } finally {
+            visitedInterfaces.remove(mixinElement);
+          }
+        } else {
+          return null;
+        }
+      }
+    }
+    //
+    // Interface elements
+    //
+    for (InterfaceType interfaceType in interfaces) {
+      ClassElement interfaceElement = interfaceType.element;
+      if (interfaceElement != null) {
+        if (!visitedInterfaces.contains(interfaceElement)) {
+          try {
+            visitedInterfaces.add(interfaceElement);
+            //
+            // Recursively compute the map for the interfaces.
+            //
+            MemberMap map =
+                _computeInterfaceLookupMap(interfaceElement, visitedInterfaces);
+            map = new MemberMap.from(map);
+            //
+            // Substitute the supertypes down the hierarchy
+            //
+            _substituteTypeParametersDownHierarchy(interfaceType, map);
+            //
+            // And add any members from the interface into the map as well.
+            //
+            _recordMapWithClassMembers(map, interfaceType, true);
+            lookupMaps.add(map);
+          } finally {
+            visitedInterfaces.remove(interfaceElement);
+          }
+        } else {
+          return null;
+        }
+      }
+    }
+    if (lookupMaps.length == 0) {
+      return null;
+    }
+    return lookupMaps;
+  }
+
+  /**
+   * Given some [ClassElement], this method finds and returns the [ExecutableElement] of
+   * the passed name in the class element. Static members, members in super types and members not
+   * accessible from the current library are not considered.
+   *
+   * @param classElt the class element to query
+   * @param memberName the name of the member to lookup in the class
+   * @return the found [ExecutableElement], or `null` if no such member was found
+   */
+  ExecutableElement _lookupMemberInClass(
+      ClassElement classElt, String memberName) {
+    List<MethodElement> methods = classElt.methods;
+    for (MethodElement method in methods) {
+      if (memberName == method.name &&
+          method.isAccessibleIn(_library) &&
+          !method.isStatic) {
+        return method;
+      }
+    }
+    List<PropertyAccessorElement> accessors = classElt.accessors;
+    for (PropertyAccessorElement accessor in accessors) {
+      if (memberName == accessor.name &&
+          accessor.isAccessibleIn(_library) &&
+          !accessor.isStatic) {
+        return accessor;
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Record the passed map with the set of all members (methods, getters and setters) in the type
+   * into the passed map.
+   *
+   * @param map some non-`null` map to put the methods and accessors from the passed
+   *          [ClassElement] into
+   * @param type the type that will be recorded into the passed map
+   * @param doIncludeAbstract `true` if abstract members will be put into the map
+   */
+  void _recordMapWithClassMembers(
+      MemberMap map, InterfaceType type, bool doIncludeAbstract) {
+    List<MethodElement> methods = type.methods;
+    for (MethodElement method in methods) {
+      if (method.isAccessibleIn(_library) &&
+          !method.isStatic &&
+          (doIncludeAbstract || !method.isAbstract)) {
+        map.put(method.name, method);
+      }
+    }
+    List<PropertyAccessorElement> accessors = type.accessors;
+    for (PropertyAccessorElement accessor in accessors) {
+      if (accessor.isAccessibleIn(_library) &&
+          !accessor.isStatic &&
+          (doIncludeAbstract || !accessor.isAbstract)) {
+        map.put(accessor.name, accessor);
+      }
+    }
+  }
+
+  /**
+   * This method is used to report errors on when they are found computing inheritance information.
+   * See [ErrorVerifier.checkForInconsistentMethodInheritance] to see where these generated
+   * error codes are reported back into the analysis engine.
+   *
+   * @param classElt the location of the source for which the exception occurred
+   * @param offset the offset of the location of the error
+   * @param length the length of the location of the error
+   * @param errorCode the error code to be associated with this error
+   * @param arguments the arguments used to build the error message
+   */
+  void _reportError(ClassElement classElt, int offset, int length,
+      ErrorCode errorCode, List<Object> arguments) {
+    HashSet<AnalysisError> errorSet = _errorsInClassElement[classElt];
+    if (errorSet == null) {
+      errorSet = new HashSet<AnalysisError>();
+      _errorsInClassElement[classElt] = errorSet;
+    }
+    errorSet.add(new AnalysisError(
+        classElt.source, offset, length, errorCode, arguments));
+  }
+
+  /**
+   * Given the set of methods defined by classes above [classElt] in the class hierarchy,
+   * apply the appropriate inheritance rules to determine those methods inherited by or overridden
+   * by [classElt]. Also report static warnings
+   * [StaticTypeWarningCode.INCONSISTENT_METHOD_INHERITANCE] and
+   * [StaticWarningCode.INCONSISTENT_METHOD_INHERITANCE_GETTER_AND_METHOD] if appropriate.
+   *
+   * @param classElt the class element to query.
+   * @param unionMap a mapping from method name to the set of unique (in terms of signature) methods
+   *          defined in superclasses of [classElt].
+   * @return the inheritance lookup map for [classElt].
+   */
+  MemberMap _resolveInheritanceLookup(ClassElement classElt,
+      HashMap<String, List<ExecutableElement>> unionMap) {
+    MemberMap resultMap = new MemberMap();
+    unionMap.forEach((String key, List<ExecutableElement> list) {
+      int numOfEltsWithMatchingNames = list.length;
+      if (numOfEltsWithMatchingNames == 1) {
+        //
+        // Example: class A inherits only 1 method named 'm'.
+        // Since it is the only such method, it is inherited.
+        // Another example: class A inherits 2 methods named 'm' from 2
+        // different interfaces, but they both have the same signature, so it is
+        // the method inherited.
+        //
+        resultMap.put(key, list[0]);
+      } else {
+        //
+        // Then numOfEltsWithMatchingNames > 1, check for the warning cases.
+        //
+        bool allMethods = true;
+        bool allSetters = true;
+        bool allGetters = true;
+        for (ExecutableElement executableElement in list) {
+          if (executableElement is PropertyAccessorElement) {
+            allMethods = false;
+            if (executableElement.isSetter) {
+              allGetters = false;
+            } else {
+              allSetters = false;
+            }
+          } else {
+            allGetters = false;
+            allSetters = false;
+          }
+        }
+        //
+        // If there isn't a mixture of methods with getters, then continue,
+        // otherwise create a warning.
+        //
+        if (allMethods || allGetters || allSetters) {
+          //
+          // Compute the element whose type is the subtype of all of the other
+          // types.
+          //
+          List<ExecutableElement> elements = new List.from(list);
+          List<FunctionType> executableElementTypes =
+              new List<FunctionType>(numOfEltsWithMatchingNames);
+          for (int i = 0; i < numOfEltsWithMatchingNames; i++) {
+            executableElementTypes[i] = elements[i].type;
+          }
+          List<int> subtypesOfAllOtherTypesIndexes = new List<int>();
+          for (int i = 0; i < numOfEltsWithMatchingNames; i++) {
+            FunctionType subtype = executableElementTypes[i];
+            if (subtype == null) {
+              continue;
+            }
+            bool subtypeOfAllTypes = true;
+            TypeSystem typeSystem = _library.context.typeSystem;
+            for (int j = 0;
+                j < numOfEltsWithMatchingNames && subtypeOfAllTypes;
+                j++) {
+              if (i != j) {
+                if (!typeSystem.isSubtypeOf(
+                    subtype, executableElementTypes[j])) {
+                  subtypeOfAllTypes = false;
+                  break;
+                }
+              }
+            }
+            if (subtypeOfAllTypes) {
+              subtypesOfAllOtherTypesIndexes.add(i);
+            }
+          }
+          //
+          // The following is split into three cases determined by the number of
+          // elements in subtypesOfAllOtherTypes
+          //
+          if (subtypesOfAllOtherTypesIndexes.length == 1) {
+            //
+            // Example: class A inherited only 2 method named 'm'.
+            // One has the function type '() -> dynamic' and one has the
+            // function type '([int]) -> dynamic'. Since the second method is a
+            // subtype of all the others, it is the inherited method.
+            // Tests: InheritanceManagerTest.
+            // test_getMapOfMembersInheritedFromInterfaces_union_oneSubtype_*
+            //
+            resultMap.put(key, elements[subtypesOfAllOtherTypesIndexes[0]]);
+          } else {
+            if (subtypesOfAllOtherTypesIndexes.isEmpty) {
+              //
+              // Determine if the current class has a method or accessor with
+              // the member name, if it does then then this class does not
+              // "inherit" from any of the supertypes. See issue 16134.
+              //
+              bool classHasMember = false;
+              if (allMethods) {
+                classHasMember = classElt.getMethod(key) != null;
+              } else {
+                List<PropertyAccessorElement> accessors = classElt.accessors;
+                for (int i = 0; i < accessors.length; i++) {
+                  if (accessors[i].name == key) {
+                    classHasMember = true;
+                  }
+                }
+              }
+              //
+              // Example: class A inherited only 2 method named 'm'.
+              // One has the function type '() -> int' and one has the function
+              // type '() -> String'. Since neither is a subtype of the other,
+              // we create a warning, and have this class inherit nothing.
+              //
+              if (!classHasMember) {
+                String firstTwoFuntionTypesStr =
+                    "${executableElementTypes[0]}, ${executableElementTypes[1]}";
+                _reportError(
+                    classElt,
+                    classElt.nameOffset,
+                    classElt.nameLength,
+                    StaticTypeWarningCode.INCONSISTENT_METHOD_INHERITANCE,
+                    [key, firstTwoFuntionTypesStr]);
+              }
+            } else {
+              //
+              // Example: class A inherits 2 methods named 'm'.
+              // One has the function type '(int) -> dynamic' and one has the
+              // function type '(num) -> dynamic'. Since they are both a subtype
+              // of the other, a synthetic function '(dynamic) -> dynamic' is
+              // inherited.
+              // Tests: test_getMapOfMembersInheritedFromInterfaces_
+              // union_multipleSubtypes_*
+              //
+              List<ExecutableElement> elementArrayToMerge =
+                  new List<ExecutableElement>(
+                      subtypesOfAllOtherTypesIndexes.length);
+              for (int i = 0; i < elementArrayToMerge.length; i++) {
+                elementArrayToMerge[i] =
+                    elements[subtypesOfAllOtherTypesIndexes[i]];
+              }
+              ExecutableElement mergedExecutableElement =
+                  _computeMergedExecutableElement(elementArrayToMerge);
+              resultMap.put(key, mergedExecutableElement);
+            }
+          }
+        } else {
+          _reportError(
+              classElt,
+              classElt.nameOffset,
+              classElt.nameLength,
+              StaticWarningCode
+                  .INCONSISTENT_METHOD_INHERITANCE_GETTER_AND_METHOD,
+              [key]);
+        }
+      }
+    });
+    return resultMap;
+  }
+
+  /**
+   * Loop through all of the members in some [MemberMap], performing type parameter
+   * substitutions using a passed supertype.
+   *
+   * @param superType the supertype to substitute into the members of the [MemberMap]
+   * @param map the MemberMap to perform the substitutions on
+   */
+  void _substituteTypeParametersDownHierarchy(
+      InterfaceType superType, MemberMap map) {
+    for (int i = 0; i < map.size; i++) {
+      ExecutableElement executableElement = map.getValue(i);
+      if (executableElement is MethodMember) {
+        executableElement =
+            MethodMember.from(executableElement as MethodMember, superType);
+        map.setValue(i, executableElement);
+      } else if (executableElement is PropertyAccessorMember) {
+        executableElement = PropertyAccessorMember.from(
+            executableElement as PropertyAccessorMember, superType);
+        map.setValue(i, executableElement);
+      }
+    }
+  }
+
+  /**
+   * Union all of the [lookupMaps] together into a single map, grouping the ExecutableElements
+   * into a list where none of the elements are equal where equality is determined by having equal
+   * function types. (We also take note too of the kind of the element: ()->int and () -> int may
+   * not be equal if one is a getter and the other is a method.)
+   *
+   * @param lookupMaps the maps to be unioned together.
+   * @return the resulting union map.
+   */
+  HashMap<String, List<ExecutableElement>> _unionInterfaceLookupMaps(
+      List<MemberMap> lookupMaps) {
+    HashMap<String, List<ExecutableElement>> unionMap =
+        new HashMap<String, List<ExecutableElement>>();
+    for (MemberMap lookupMap in lookupMaps) {
+      int lookupMapSize = lookupMap.size;
+      for (int i = 0; i < lookupMapSize; i++) {
+        // Get the string key, if null, break.
+        String key = lookupMap.getKey(i);
+        if (key == null) {
+          break;
+        }
+        // Get the list value out of the unionMap
+        List<ExecutableElement> list = unionMap[key];
+        // If we haven't created such a map for this key yet, do create it and
+        // put the list entry into the unionMap.
+        if (list == null) {
+          list = new List<ExecutableElement>();
+          unionMap[key] = list;
+        }
+        // Fetch the entry out of this lookupMap
+        ExecutableElement newExecutableElementEntry = lookupMap.getValue(i);
+        if (list.isEmpty) {
+          // If the list is empty, just the new value
+          list.add(newExecutableElementEntry);
+        } else {
+          // Otherwise, only add the newExecutableElementEntry if it isn't
+          // already in the list, this covers situation where a class inherits
+          // two methods (or two getters) that are identical.
+          bool alreadyInList = false;
+          bool isMethod1 = newExecutableElementEntry is MethodElement;
+          for (ExecutableElement executableElementInList in list) {
+            bool isMethod2 = executableElementInList is MethodElement;
+            if (isMethod1 == isMethod2 &&
+                executableElementInList.type ==
+                    newExecutableElementEntry.type) {
+              alreadyInList = true;
+              break;
+            }
+          }
+          if (!alreadyInList) {
+            list.add(newExecutableElementEntry);
+          }
+        }
+      }
+    }
+    return unionMap;
+  }
+
+  /**
+   * Given some array of [ExecutableElement]s, this method creates a synthetic element as
+   * described in 8.1.1:
+   *
+   * Let <i>numberOfPositionals</i>(<i>f</i>) denote the number of positional parameters of a
+   * function <i>f</i>, and let <i>numberOfRequiredParams</i>(<i>f</i>) denote the number of
+   * required parameters of a function <i>f</i>. Furthermore, let <i>s</i> denote the set of all
+   * named parameters of the <i>m<sub>1</sub>, &hellip;, m<sub>k</sub></i>. Then let
+   * * <i>h = max(numberOfPositionals(m<sub>i</sub>)),</i>
+   * * <i>r = min(numberOfRequiredParams(m<sub>i</sub>)), for all <i>i</i>, 1 <= i <= k.</i>
+   * Then <i>I</i> has a method named <i>n</i>, with <i>r</i> required parameters of type
+   * <b>dynamic</b>, <i>h</i> positional parameters of type <b>dynamic</b>, named parameters
+   * <i>s</i> of type <b>dynamic</b> and return type <b>dynamic</b>.
+   *
+   */
+  static ExecutableElement _computeMergedExecutableElement(
+      List<ExecutableElement> elementArrayToMerge) {
+    int h = _getNumOfPositionalParameters(elementArrayToMerge[0]);
+    int r = _getNumOfRequiredParameters(elementArrayToMerge[0]);
+    Set<String> namedParametersList = new HashSet<String>();
+    for (int i = 1; i < elementArrayToMerge.length; i++) {
+      ExecutableElement element = elementArrayToMerge[i];
+      int numOfPositionalParams = _getNumOfPositionalParameters(element);
+      if (h < numOfPositionalParams) {
+        h = numOfPositionalParams;
+      }
+      int numOfRequiredParams = _getNumOfRequiredParameters(element);
+      if (r > numOfRequiredParams) {
+        r = numOfRequiredParams;
+      }
+      namedParametersList.addAll(_getNamedParameterNames(element));
+    }
+    return _createSyntheticExecutableElement(
+        elementArrayToMerge,
+        elementArrayToMerge[0].displayName,
+        r,
+        h - r,
+        new List.from(namedParametersList));
+  }
+
+  /**
+   * Used by [computeMergedExecutableElement] to actually create the
+   * synthetic element.
+   *
+   * @param elementArrayToMerge the array used to create the synthetic element
+   * @param name the name of the method, getter or setter
+   * @param numOfRequiredParameters the number of required parameters
+   * @param numOfPositionalParameters the number of positional parameters
+   * @param namedParameters the list of [String]s that are the named parameters
+   * @return the created synthetic element
+   */
+  static ExecutableElement _createSyntheticExecutableElement(
+      List<ExecutableElement> elementArrayToMerge,
+      String name,
+      int numOfRequiredParameters,
+      int numOfPositionalParameters,
+      List<String> namedParameters) {
+    DynamicTypeImpl dynamicType = DynamicTypeImpl.instance;
+    SimpleIdentifier nameIdentifier =
+        new SimpleIdentifier(new StringToken(TokenType.IDENTIFIER, name, 0));
+    ExecutableElementImpl executable;
+    if (elementArrayToMerge[0] is MethodElement) {
+      MultiplyInheritedMethodElementImpl unionedMethod =
+          new MultiplyInheritedMethodElementImpl(nameIdentifier);
+      unionedMethod.inheritedElements = elementArrayToMerge;
+      executable = unionedMethod;
+    } else {
+      MultiplyInheritedPropertyAccessorElementImpl unionedPropertyAccessor =
+          new MultiplyInheritedPropertyAccessorElementImpl(nameIdentifier);
+      unionedPropertyAccessor.getter =
+          (elementArrayToMerge[0] as PropertyAccessorElement).isGetter;
+      unionedPropertyAccessor.setter =
+          (elementArrayToMerge[0] as PropertyAccessorElement).isSetter;
+      unionedPropertyAccessor.inheritedElements = elementArrayToMerge;
+      executable = unionedPropertyAccessor;
+    }
+    int numOfParameters = numOfRequiredParameters +
+        numOfPositionalParameters +
+        namedParameters.length;
+    List<ParameterElement> parameters =
+        new List<ParameterElement>(numOfParameters);
+    int i = 0;
+    for (int j = 0; j < numOfRequiredParameters; j++, i++) {
+      ParameterElementImpl parameter = new ParameterElementImpl("", 0);
+      parameter.type = dynamicType;
+      parameter.parameterKind = ParameterKind.REQUIRED;
+      parameters[i] = parameter;
+    }
+    for (int k = 0; k < numOfPositionalParameters; k++, i++) {
+      ParameterElementImpl parameter = new ParameterElementImpl("", 0);
+      parameter.type = dynamicType;
+      parameter.parameterKind = ParameterKind.POSITIONAL;
+      parameters[i] = parameter;
+    }
+    for (int m = 0; m < namedParameters.length; m++, i++) {
+      ParameterElementImpl parameter =
+          new ParameterElementImpl(namedParameters[m], 0);
+      parameter.type = dynamicType;
+      parameter.parameterKind = ParameterKind.NAMED;
+      parameters[i] = parameter;
+    }
+    executable.returnType = dynamicType;
+    executable.parameters = parameters;
+    FunctionTypeImpl methodType = new FunctionTypeImpl(executable);
+    executable.type = methodType;
+    return executable;
+  }
+
+  /**
+   * Given some [ExecutableElement], return the list of named parameters.
+   */
+  static List<String> _getNamedParameterNames(
+      ExecutableElement executableElement) {
+    List<String> namedParameterNames = new List<String>();
+    List<ParameterElement> parameters = executableElement.parameters;
+    for (int i = 0; i < parameters.length; i++) {
+      ParameterElement parameterElement = parameters[i];
+      if (parameterElement.parameterKind == ParameterKind.NAMED) {
+        namedParameterNames.add(parameterElement.name);
+      }
+    }
+    return namedParameterNames;
+  }
+
+  /**
+   * Given some [ExecutableElement] return the number of parameters of the specified kind.
+   */
+  static int _getNumOfParameters(
+      ExecutableElement executableElement, ParameterKind parameterKind) {
+    int parameterCount = 0;
+    List<ParameterElement> parameters = executableElement.parameters;
+    for (int i = 0; i < parameters.length; i++) {
+      ParameterElement parameterElement = parameters[i];
+      if (parameterElement.parameterKind == parameterKind) {
+        parameterCount++;
+      }
+    }
+    return parameterCount;
+  }
+
+  /**
+   * Given some [ExecutableElement] return the number of positional parameters.
+   *
+   * Note: by positional we mean [ParameterKind.REQUIRED] or [ParameterKind.POSITIONAL].
+   */
+  static int _getNumOfPositionalParameters(
+          ExecutableElement executableElement) =>
+      _getNumOfParameters(executableElement, ParameterKind.REQUIRED) +
+      _getNumOfParameters(executableElement, ParameterKind.POSITIONAL);
+
+  /**
+   * Given some [ExecutableElement] return the number of required parameters.
+   */
+  static int _getNumOfRequiredParameters(ExecutableElement executableElement) =>
+      _getNumOfParameters(executableElement, ParameterKind.REQUIRED);
+
+  /**
+   * Given some [ExecutableElement] returns `true` if it is an abstract member of a
+   * class.
+   *
+   * @param executableElement some [ExecutableElement] to evaluate
+   * @return `true` if the given element is an abstract member of a class
+   */
+  static bool _isAbstract(ExecutableElement executableElement) {
+    if (executableElement is MethodElement) {
+      return executableElement.isAbstract;
+    } else if (executableElement is PropertyAccessorElement) {
+      return executableElement.isAbstract;
+    }
+    return false;
+  }
+}
+
+/**
+ * This class is used to replace uses of `HashMap<String, ExecutableElement>`
+ * which are not as performant as this class.
+ */
+class MemberMap {
+  /**
+   * The current size of this map.
+   */
+  int _size = 0;
+
+  /**
+   * The array of keys.
+   */
+  List<String> _keys;
+
+  /**
+   * The array of ExecutableElement values.
+   */
+  List<ExecutableElement> _values;
+
+  /**
+   * Initialize a newly created member map to have the given [initialCapacity].
+   * The map will grow if needed.
+   */
+  MemberMap([int initialCapacity = 10]) {
+    _initArrays(initialCapacity);
+  }
+
+  /**
+   * Initialize a newly created member map to contain the same members as the
+   * given [memberMap].
+   */
+  MemberMap.from(MemberMap memberMap) {
+    _initArrays(memberMap._size + 5);
+    for (int i = 0; i < memberMap._size; i++) {
+      _keys[i] = memberMap._keys[i];
+      _values[i] = memberMap._values[i];
+    }
+    _size = memberMap._size;
+  }
+
+  /**
+   * The size of the map.
+   *
+   * @return the size of the map.
+   */
+  int get size => _size;
+
+  /**
+   * Given some key, return the ExecutableElement value from the map, if the key does not exist in
+   * the map, `null` is returned.
+   *
+   * @param key some key to look up in the map
+   * @return the associated ExecutableElement value from the map, if the key does not exist in the
+   *         map, `null` is returned
+   */
+  ExecutableElement get(String key) {
+    for (int i = 0; i < _size; i++) {
+      if (_keys[i] != null && _keys[i] == key) {
+        return _values[i];
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Get and return the key at the specified location. If the key/value pair has been removed from
+   * the set, then `null` is returned.
+   *
+   * @param i some non-zero value less than size
+   * @return the key at the passed index
+   * @throw ArrayIndexOutOfBoundsException this exception is thrown if the passed index is less than
+   *        zero or greater than or equal to the capacity of the arrays
+   */
+  String getKey(int i) => _keys[i];
+
+  /**
+   * Get and return the ExecutableElement at the specified location. If the key/value pair has been
+   * removed from the set, then then `null` is returned.
+   *
+   * @param i some non-zero value less than size
+   * @return the key at the passed index
+   * @throw ArrayIndexOutOfBoundsException this exception is thrown if the passed index is less than
+   *        zero or greater than or equal to the capacity of the arrays
+   */
+  ExecutableElement getValue(int i) => _values[i];
+
+  /**
+   * Given some key/value pair, store the pair in the map. If the key exists already, then the new
+   * value overrides the old value.
+   *
+   * @param key the key to store in the map
+   * @param value the ExecutableElement value to store in the map
+   */
+  void put(String key, ExecutableElement value) {
+    // If we already have a value with this key, override the value
+    for (int i = 0; i < _size; i++) {
+      if (_keys[i] != null && _keys[i] == key) {
+        _values[i] = value;
+        return;
+      }
+    }
+    // If needed, double the size of our arrays and copy values over in both
+    // arrays
+    if (_size == _keys.length) {
+      int newArrayLength = _size * 2;
+      List<String> keys_new_array = new List<String>(newArrayLength);
+      List<ExecutableElement> values_new_array =
+          new List<ExecutableElement>(newArrayLength);
+      for (int i = 0; i < _size; i++) {
+        keys_new_array[i] = _keys[i];
+      }
+      for (int i = 0; i < _size; i++) {
+        values_new_array[i] = _values[i];
+      }
+      _keys = keys_new_array;
+      _values = values_new_array;
+    }
+    // Put new value at end of array
+    _keys[_size] = key;
+    _values[_size] = value;
+    _size++;
+  }
+
+  /**
+   * Given some [String] key, this method replaces the associated key and value pair with
+   * `null`. The size is not decremented with this call, instead it is expected that the users
+   * check for `null`.
+   *
+   * @param key the key of the key/value pair to remove from the map
+   */
+  void remove(String key) {
+    for (int i = 0; i < _size; i++) {
+      if (_keys[i] == key) {
+        _keys[i] = null;
+        _values[i] = null;
+        return;
+      }
+    }
+  }
+
+  /**
+   * Sets the ExecutableElement at the specified location.
+   *
+   * @param i some non-zero value less than size
+   * @param value the ExecutableElement value to store in the map
+   */
+  void setValue(int i, ExecutableElement value) {
+    _values[i] = value;
+  }
+
+  /**
+   * Initializes [keys] and [values].
+   */
+  void _initArrays(int initialCapacity) {
+    _keys = new List<String>(initialCapacity);
+    _values = new List<ExecutableElement>(initialCapacity);
+  }
+}