Issue 25542. If an element does not have its own documentation, use the documentation from the over…

pkg/analysis_server/lib/src/computer/computer_overrides.dart

Index: pkg/analysis_server/lib/src/computer/computer_overrides.dart
diff --git a/pkg/analysis_server/lib/src/computer/computer_overrides.dart b/pkg/analysis_server/lib/src/computer/computer_overrides.dart
index 8a742125b21e28845847ea3b577d685899296f28..4eb93d1bf22a0d97fcfbd1c2a0576a02f9c2dbae 100644
--- a/pkg/analysis_server/lib/src/computer/computer_overrides.dart
+++ b/pkg/analysis_server/lib/src/computer/computer_overrides.dart
@@ -5,65 +5,42 @@
 library computer.overrides;
 
 import 'package:analysis_server/src/collections.dart';
-import 'package:analysis_server/src/protocol_server.dart';
-import 'package:analyzer/dart/element/element.dart' as engine;
-import 'package:analyzer/dart/element/type.dart' as engine;
+import 'package:analysis_server/src/protocol_server.dart' as proto;
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/generated/ast.dart';
 
 /**
+ * Return the elements that the given [element] overrides.
+ */
+OverriddenElements findOverriddenElements(Element element) {
+  if (element?.enclosingElement is ClassElement) {
+    return new _OverriddenElementsFinder(element).find();
+  }
+  return new OverriddenElements(element, <Element>[], <Element>[]);
+}
+
+/**
  * A computer for class member overrides in a Dart [CompilationUnit].
  */
 class DartUnitOverridesComputer {
-  static const List<ElementKind> FIELD_KINDS = const <ElementKind>[
-    ElementKind.FIELD,
-    ElementKind.GETTER,
-    ElementKind.SETTER
-  ];
-
-  static const List<ElementKind> GETTER_KINDS = const <ElementKind>[
-    ElementKind.FIELD,
-    ElementKind.GETTER
-  ];
-
-  static const List<ElementKind> METHOD_KINDS = const <ElementKind>[
-    ElementKind.METHOD
-  ];
-
-  static const List<ElementKind> SETTER_KINDS = const <ElementKind>[
-    ElementKind.FIELD,
-    ElementKind.SETTER
-  ];
-
   final CompilationUnit _unit;
-
-  final List<Override> _overrides = <Override>[];
-  engine.ClassElement _currentClass;
+  final List<proto.Override> _overrides = <proto.Override>[];
 
   DartUnitOverridesComputer(this._unit);
 
   /**
    * Returns the computed occurrences, not `null`.
    */
-  List<Override> compute() {
+  List<proto.Override> compute() {
     for (CompilationUnitMember unitMember in _unit.declarations) {
       if (unitMember is ClassDeclaration) {
-        _currentClass = unitMember.element;
         for (ClassMember classMember in unitMember.members) {
           if (classMember is MethodDeclaration) {
             if (classMember.isStatic) {
               continue;
             }
-            SimpleIdentifier name = classMember.name;
-            List<ElementKind> kinds;
-            if (classMember.isGetter) {
-              kinds = GETTER_KINDS;
-            } else if (classMember.isSetter) {
-              kinds = SETTER_KINDS;
-            } else {
-              kinds = METHOD_KINDS;
-            }
-            new _SingleOverrideComputer(_currentClass, name, kinds)
-                .addOverrideTo(_overrides);
+            _addOverride(classMember.name);
           }
           if (classMember is FieldDeclaration) {
             if (classMember.isStatic) {
@@ -71,9 +48,7 @@ class DartUnitOverridesComputer {
             }
             List<VariableDeclaration> fields = classMember.fields.variables;
             for (VariableDeclaration field in fields) {
-              SimpleIdentifier name = field.name;
-              new _SingleOverrideComputer(_currentClass, name, FIELD_KINDS)
-                  .addOverrideTo(_overrides);
+              _addOverride(field.name);
             }
           }
         }
@@ -81,105 +56,171 @@ class DartUnitOverridesComputer {
     }
     return _overrides;
   }
-}
-
-/**
- * Computer for [Override] for a single declaration.
- */
-class _SingleOverrideComputer {
-  final engine.LibraryElement currentLibrary;
-  final engine.ClassElement currentClass;
-  final SimpleIdentifier node;
-  final String name;
-  final List<ElementKind> kinds;
-
-  _SingleOverrideComputer(
-      engine.ClassElement currentClass, SimpleIdentifier node, this.kinds)
-      : currentClass = currentClass,
-        currentLibrary = currentClass.library,
-        node = node,
-        name = node.name;
 
   /**
-   * Add a new [Override] for this declaration to the given [overrides].
+   * Add a new [Override] for the declaration with the given name [node].
    */
-  void addOverrideTo(List<Override> overrides) {
-    // super
-    engine.Element superEngineElement;
-    {
-      engine.InterfaceType superType = currentClass.supertype;
-      if (superType != null) {
-        superEngineElement = _lookupMember(superType.element);
-      }
-    }
-    // interfaces
-    Set<engine.Element> interfaceEngineElements = new Set<engine.Element>();
-    _addInterfaceOverrides(interfaceEngineElements, currentClass.type, false,
-        new Set<engine.InterfaceType>());
-    interfaceEngineElements.remove(superEngineElement);
-    // is there any override?
-    if (superEngineElement != null || interfaceEngineElements.isNotEmpty) {
-      OverriddenMember superMember = superEngineElement != null
-          ? newOverriddenMember_fromEngine(superEngineElement)
+  void _addOverride(SimpleIdentifier node) {
+    Element element = node.staticElement;
+    OverriddenElements overridesResult =
+        new _OverriddenElementsFinder(element).find();
+    List<Element> superElements = overridesResult.superElements;
+    List<Element> interfaceElements = overridesResult.interfaceElements;
+    if (superElements.isNotEmpty || interfaceElements.isNotEmpty) {
+      proto.OverriddenMember superMember = superElements.isNotEmpty
+          ? proto.newOverriddenMember_fromEngine(superElements.first)
           : null;
-      List<OverriddenMember> interfaceMembers = interfaceEngineElements
-          .map((member) => newOverriddenMember_fromEngine(member))
+      List<proto.OverriddenMember> interfaceMembers = interfaceElements
+          .map((member) => proto.newOverriddenMember_fromEngine(member))
           .toList();
-      overrides.add(new Override(node.offset, node.length,
+      _overrides.add(new proto.Override(node.offset, node.length,
           superclassMember: superMember,
           interfaceMembers: nullIfEmpty(interfaceMembers)));
     }
   }
+}
 
-  void _addInterfaceOverrides(
-      Set<engine.Element> elements,
-      engine.InterfaceType type,
-      bool checkType,
-      Set<engine.InterfaceType> visited) {
+/**
+ * The container with elements that a class member overrides.
+ */
+class OverriddenElements {
+  /**
+   * The element that overrides other class members.
+   */
+  final Element element;
+
+  /**
+   * The elements that [element] overrides and which is defined in a class that
+   * is a superclass of the class that defines [element].
+   */
+  final List<Element> superElements;
+
+  /**
+   * The elements that [element] overrides and which is defined in a class that
+   * which is implemented by the class that defines [element].
+   */
+  final List<Element> interfaceElements;
+
+  OverriddenElements(this.element, this.superElements, this.interfaceElements);
+}
+
+class _OverriddenElementsFinder {
+  static const List<ElementKind> FIELD_KINDS = const <ElementKind>[
+    ElementKind.FIELD,
+    ElementKind.GETTER,
+    ElementKind.SETTER
+  ];
+
+  static const List<ElementKind> GETTER_KINDS = const <ElementKind>[
+    ElementKind.FIELD,
+    ElementKind.GETTER
+  ];
+
+  static const List<ElementKind> METHOD_KINDS = const <ElementKind>[
+    ElementKind.METHOD
+  ];
+
+  static const List<ElementKind> SETTER_KINDS = const <ElementKind>[
+    ElementKind.FIELD,
+    ElementKind.SETTER
+  ];
+
+  Element _seed;
+  LibraryElement _library;
+  ClassElement _class;
+  String _name;
+  List<ElementKind> _kinds;
+
+  List<Element> _superElements = <Element>[];
+  List<Element> _interfaceElements = <Element>[];
+  Set<InterfaceType> _visited = new Set<InterfaceType>();
+
+  _OverriddenElementsFinder(Element seed) {
+    _seed = seed;
+    _class = seed.enclosingElement;
+    _library = _class.library;
+    _name = seed.displayName;
+    if (seed is MethodElement) {
+      _kinds = METHOD_KINDS;
+    } else if (seed is PropertyAccessorElement) {
+      _kinds = seed.isGetter ? GETTER_KINDS : SETTER_KINDS;
+    } else {
+      _kinds = FIELD_KINDS;
+    }
+  }
+
+  /**
+   * Add the [OverriddenElements] for this element.
+   */
+  OverriddenElements find() {
+    _visited.clear();
+    _addSuperOverrides(_class.supertype);
+    _visited.clear();
+    _addInterfaceOverrides(_class.type, false);
+    _superElements.forEach(_interfaceElements.remove);
+    return new OverriddenElements(_seed, _superElements, _interfaceElements);
+  }
+
+  void _addInterfaceOverrides(InterfaceType type, bool checkType) {
     if (type == null) {
       return;
     }
-    if (!visited.add(type)) {
+    if (!_visited.add(type)) {
       return;
     }
-    // check type
+    // this type
     if (checkType) {
-      engine.Element element = _lookupMember(type.element);
-      if (element != null) {
-        elements.add(element);
-        return;
+      Element element = _lookupMember(type.element);
+      if (element != null && !_interfaceElements.contains(element)) {
+        _interfaceElements.add(element);
       }
     }
-    // check interfaces
-    for (engine.InterfaceType interfaceType in type.interfaces) {
-      _addInterfaceOverrides(elements, interfaceType, true, visited);
+    // interfaces
+    for (InterfaceType interfaceType in type.interfaces) {
+      _addInterfaceOverrides(interfaceType, true);
     }
-    // check super
-    _addInterfaceOverrides(elements, type.superclass, checkType, visited);
+    // super
+    _addInterfaceOverrides(type.superclass, checkType);
+  }
+
+  void _addSuperOverrides(InterfaceType type) {
+    if (type == null) {
+      return;
+    }
+    if (!_visited.add(type)) {
+      return;
+    }
+    // this type
+    Element element = _lookupMember(type.element);
+    if (element != null && !_superElements.contains(element)) {
+      _superElements.add(element);
+    }
+    // super
+    _addSuperOverrides(type.superclass);
   }
 
-  engine.Element _lookupMember(engine.ClassElement classElement) {
+  Element _lookupMember(ClassElement classElement) {
     if (classElement == null) {
       return null;
     }
-    engine.Element member;
+    Element member;
     // method
-    if (kinds.contains(ElementKind.METHOD)) {
-      member = classElement.lookUpMethod(name, currentLibrary);
+    if (_kinds.contains(ElementKind.METHOD)) {
+      member = classElement.lookUpMethod(_name, _library);
       if (member != null) {
         return member;
       }
     }
     // getter
-    if (kinds.contains(ElementKind.GETTER)) {
-      member = classElement.lookUpGetter(name, currentLibrary);
+    if (_kinds.contains(ElementKind.GETTER)) {
+      member = classElement.lookUpGetter(_name, _library);
       if (member != null) {
         return member;
       }
     }
     // setter
-    if (kinds.contains(ElementKind.SETTER)) {
-      member = classElement.lookUpSetter(name + '=', currentLibrary);
+    if (_kinds.contains(ElementKind.SETTER)) {
+      member = classElement.lookUpSetter(_name + '=', _library);
       if (member != null) {
         return member;
       }