pkg/analysis_server/lib/src/services/completion/dart/suggestion_builder.dart - sdk.git - Git at Google

 // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 import 'dart:collection';

 import 'package:analysis_server/src/computer/computer_hover.dart';
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
 import 'package:analysis_server/src/protocol_server.dart'
     hide Element, ElementKind;
 import 'package:analysis_server/src/protocol_server.dart'
     show CompletionSuggestion;
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/services/completion/dart/feature_computer.dart';
 import 'package:analysis_server/src/services/completion/dart/utilities.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/visitor.dart';
 import 'package:analyzer/src/util/comment.dart';
 import 'package:meta/meta.dart';

 /// Return a suggestion based upon the given element or `null` if a suggestion
 /// is not appropriate for the given element.
 CompletionSuggestion createSuggestion(
     DartCompletionRequest request, Element element,
     {String completion,
     CompletionSuggestionKind kind,
     int relevance = DART_RELEVANCE_DEFAULT,
     bool useNewRelevance = false}) {
   if (element == null) {
     return null;
   }
   if (element is ExecutableElement && element.isOperator) {
     // Do not include operators in suggestions
     return null;
   }
   completion ??= element.displayName;
   kind ??= CompletionSuggestionKind.INVOCATION;
   var isDeprecated = element.hasDeprecated;
   if (!useNewRelevance && isDeprecated) {
     relevance = DART_RELEVANCE_LOW;
   }
   var suggestion = CompletionSuggestion(
       kind, relevance, completion, completion.length, 0, isDeprecated, false);

   // Attach docs.
   var doc = DartUnitHoverComputer.computeDocumentation(
       request.dartdocDirectiveInfo, element);
   if (doc != null) {
     suggestion.docComplete = doc;
     suggestion.docSummary = getDartDocSummary(doc);
   }

   suggestion.element = protocol.convertElement(element);
   var enclosingElement = element.enclosingElement;
   if (enclosingElement is ClassElement) {
     suggestion.declaringType = enclosingElement.displayName;
   }
   suggestion.returnType = getReturnTypeString(element);
   if (element is ExecutableElement && element is! PropertyAccessorElement) {
     suggestion.parameterNames = element.parameters
         .map((ParameterElement parameter) => parameter.name)
         .toList();
     suggestion.parameterTypes =
         element.parameters.map((ParameterElement parameter) {
       var paramType = parameter.type;
       // Gracefully degrade if type not resolved yet
       return paramType != null
           ? paramType.getDisplayString(withNullability: false)
           : 'var';
     }).toList();

     var requiredParameters = element.parameters
         .where((ParameterElement param) => param.isRequiredPositional);
     suggestion.requiredParameterCount = requiredParameters.length;

     var namedParameters =
         element.parameters.where((ParameterElement param) => param.isNamed);
     suggestion.hasNamedParameters = namedParameters.isNotEmpty;

     addDefaultArgDetails(
         suggestion, element, requiredParameters, namedParameters);
   }
   return suggestion;
 }

 /// Common mixin for sharing behavior.
 mixin ElementSuggestionBuilder {
   /// A collection of completion suggestions.
   final List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];

   /// A set of existing completions used to prevent duplicate suggestions.
   final Set<String> _completions = <String>{};

   /// A map of element names to suggestions for synthetic getters and setters.
   final Map<String, CompletionSuggestion> _syntheticMap =
       <String, CompletionSuggestion>{};

   /// Return the library in which the completion is requested.
   LibraryElement get containingLibrary;

   /// Return the kind of suggestions that should be built.
   CompletionSuggestionKind get kind;

   /// Return the completion request for which suggestions are being built.
   DartCompletionRequest get request;

   /// Add a suggestion based upon the given element.
   CompletionSuggestion addSuggestion(Element element,
       {String prefix,
       int relevance = DART_RELEVANCE_DEFAULT,
       bool useNewRelevance = false,
       String elementCompletion}) {
     if (element.isPrivate) {
       if (element.library != containingLibrary) {
         return null;
       }
     }
     var completion = elementCompletion ?? element.displayName;
     if (prefix != null && prefix.isNotEmpty) {
       if (completion == null || completion.isEmpty) {
         completion = prefix;
       } else {
         completion = '$prefix.$completion';
       }
     }
     if (completion == null || completion.isEmpty) {
       return null;
     }
     var suggestion = createSuggestion(request, element,
         completion: completion,
         kind: kind,
         relevance: relevance,
         useNewRelevance: useNewRelevance);
     if (suggestion != null) {
       if (element.isSynthetic && element is PropertyAccessorElement) {
         String cacheKey;
         if (element.isGetter) {
           cacheKey = element.name;
         }
         if (element.isSetter) {
           cacheKey = element.name;
           cacheKey = cacheKey.substring(0, cacheKey.length - 1);
         }
         if (cacheKey != null) {
           var existingSuggestion = _syntheticMap[cacheKey];

           // Pair getter/setter by updating the existing suggestion
           if (existingSuggestion != null) {
             var getter = element.isGetter ? suggestion : existingSuggestion;
             var elemKind = element.enclosingElement is ClassElement
                 ? protocol.ElementKind.FIELD
                 : protocol.ElementKind.TOP_LEVEL_VARIABLE;
             existingSuggestion.element = protocol.Element(
                 elemKind,
                 existingSuggestion.element.name,
                 existingSuggestion.element.flags,
                 location: getter.element.location,
                 typeParameters: getter.element.typeParameters,
                 parameters: null,
                 returnType: getter.returnType);
             return existingSuggestion;
           }

           // Cache lone getter/setter so that it can be paired
           _syntheticMap[cacheKey] = suggestion;
         }
       }
       if (_completions.add(suggestion.completion)) {
         suggestions.add(suggestion);
       }
     }
     return suggestion;
   }
 }

 /// This class creates suggestions based on top-level elements.
 class LibraryElementSuggestionBuilder extends SimpleElementVisitor<void>
     with ElementSuggestionBuilder {
   @override
   final DartCompletionRequest request;

   @override
   final CompletionSuggestionKind kind;

   final bool typesOnly;

   final bool instCreation;

   /// Return `true` if the new relevance scores should be produced.
   final bool useNewRelevance;

   LibraryElementSuggestionBuilder(
       this.request, this.kind, this.typesOnly, this.instCreation)
       : useNewRelevance = request.useNewRelevance;

   @override
   LibraryElement get containingLibrary => request.libraryElement;

   @override
   void visitClassElement(ClassElement element) {
     if (instCreation) {
       element.visitChildren(this);
     } else {
       // TODO(brianwilkerson) Determine whether this should be based on features
       //  (such as the kind of the element) or a constant.
       var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
       addSuggestion(element,
           relevance: relevance, useNewRelevance: useNewRelevance);
     }
   }

   @override
   void visitConstructorElement(ConstructorElement element) {
     if (instCreation) {
       var classElem = element.enclosingElement;
       if (classElem != null) {
         var prefix = classElem.name;
         if (prefix != null && prefix.isNotEmpty) {
           // TODO(brianwilkerson) Determine whether this should be based on features
           //  (such as the kind of the element) or a constant.
           var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
           addSuggestion(element,
               prefix: prefix,
               relevance: relevance,
               useNewRelevance: useNewRelevance);
         }
       }
     }
   }

   @override
   void visitExtensionElement(ExtensionElement element) {
     if (!instCreation) {
       // TODO(brianwilkerson) Determine whether this should be based on features
       //  (such as the kind of the element) or a constant.
       var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
       addSuggestion(element,
           relevance: relevance, useNewRelevance: useNewRelevance);
     }
   }

   @override
   void visitFunctionElement(FunctionElement element) {
     if (!typesOnly) {
       int relevance;
       if (useNewRelevance) {
         // TODO(brianwilkerson) Determine whether this should be based on
         //  features (such as the kind of the element) or a constant.
         relevance = element.library == containingLibrary ? 800 : 750;
       } else {
         relevance = element.library == containingLibrary
             ? DART_RELEVANCE_LOCAL_FUNCTION
             : DART_RELEVANCE_DEFAULT;
       }
       addSuggestion(element,
           relevance: relevance, useNewRelevance: useNewRelevance);
     }
   }

   @override
   void visitFunctionTypeAliasElement(FunctionTypeAliasElement element) {
     if (!instCreation) {
       // TODO(brianwilkerson) Determine whether this should be based on features
       //  (such as the kind of the element) or a constant.
       var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
       addSuggestion(element,
           relevance: relevance, useNewRelevance: useNewRelevance);
     }
   }

   @override
   void visitPropertyAccessorElement(PropertyAccessorElement element) {
     if (!typesOnly) {
       var variable = element.variable;
       int relevance;
       if (useNewRelevance) {
         // TODO(brianwilkerson) Determine whether this should be based on
         //  features (such as the kind of the element) or a constant.
         relevance = variable.library == containingLibrary ? 800 : 750;
       } else {
         relevance = variable.library == containingLibrary
             ? DART_RELEVANCE_LOCAL_TOP_LEVEL_VARIABLE
             : DART_RELEVANCE_DEFAULT;
       }
       addSuggestion(variable,
           relevance: relevance, useNewRelevance: useNewRelevance);
     }
   }
 }

 /// This class provides suggestions based upon the visible instance members in
 /// an interface type.
 class MemberSuggestionBuilder {
   /// Enumerated value indicating that we have not generated any completions for
   /// a given identifier yet.
   static const int _COMPLETION_TYPE_NONE = 0;

   /// Enumerated value indicating that we have generated a completion for a
   /// getter.
   static const int _COMPLETION_TYPE_GETTER = 1;

   /// Enumerated value indicating that we have generated a completion for a
   /// setter.
   static const int _COMPLETION_TYPE_SETTER = 2;

   /// Enumerated value indicating that we have generated a completion for a
   /// field, a method, or a getter/setter pair.
   static const int _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET = 3;

   /// The request for which suggestions are being built.
   final DartCompletionRequest request;

   /// Map indicating, for each possible completion identifier, whether we have
   /// already generated completions for a getter, setter, or both.  The "both"
   /// case also handles the case where have generated a completion for a method
   /// or a field.
   ///
   /// Note: the enumerated values stored in this map are intended to be bitwise
   /// compared.
   final Map<String, int> _completionTypesGenerated = HashMap<String, int>();

   /// A map from a completion identifier to a completion suggestion.
   final Map<String, CompletionSuggestion> _suggestionMap =
       <String, CompletionSuggestion>{};

   MemberSuggestionBuilder(this.request);

   Iterable<CompletionSuggestion> get suggestions => _suggestionMap.values;

   /// Add the given completion [suggestion].
   void addCompletionSuggestion(CompletionSuggestion suggestion) {
     _suggestionMap[suggestion.completion] = suggestion;
   }

   /// Add a suggestion for the given [method].
   CompletionSuggestion addSuggestionForAccessor(
       {@required PropertyAccessorElement accessor,
       String containingMethodName,
       @required double inheritanceDistance}) {
     int oldRelevance() {
       if (accessor.hasDeprecated) {
         return DART_RELEVANCE_LOW;
       }
       var identifier = accessor.displayName;
       if (identifier != null && identifier.startsWith(r'$')) {
         // Decrease relevance of suggestions starting with $
         // https://github.com/dart-lang/sdk/issues/27303
         return DART_RELEVANCE_LOW;
       }
       return DART_RELEVANCE_DEFAULT;
     }

     if (!accessor.isAccessibleIn(request.libraryElement)) {
       // Don't suggest private members from imported libraries.
       return null;
     }
     if (accessor.isSynthetic) {
       // Avoid visiting a field twice. All fields induce a getter, but only
       // non-final fields induce a setter, so we don't add a suggestion for a
       // synthetic setter.
       if (accessor.isGetter) {
         var variable = accessor.variable;
         int relevance;
         var useNewRelevance = request.useNewRelevance;
         if (useNewRelevance) {
           var featureComputer = request.featureComputer;
           var contextType = featureComputer.contextTypeFeature(
               request.contextType, variable.type);
           var hasDeprecated = featureComputer.hasDeprecatedFeature(accessor);
           var startsWithDollar =
               featureComputer.startsWithDollarFeature(accessor.name);
           var superMatches = featureComputer.superMatchesFeature(
               containingMethodName, accessor.name);
           relevance = _computeRelevance(
               contextType: contextType,
               hasDeprecated: hasDeprecated,
               inheritanceDistance: inheritanceDistance,
               startsWithDollar: startsWithDollar,
               superMatches: superMatches);
         } else {
           relevance = oldRelevance();
         }
         return _addSuggestion(variable, relevance, useNewRelevance);
       }
     } else {
       var type =
           accessor.isGetter ? accessor.returnType : accessor.parameters[0].type;
       int relevance;
       var useNewRelevance = request.useNewRelevance;
       if (useNewRelevance) {
         var featureComputer = request.featureComputer;
         var contextType =
             featureComputer.contextTypeFeature(request.contextType, type);
         var hasDeprecated = featureComputer.hasDeprecatedFeature(accessor);
         var startsWithDollar =
             featureComputer.startsWithDollarFeature(accessor.name);
         var superMatches = featureComputer.superMatchesFeature(
             containingMethodName, accessor.name);
         relevance = _computeRelevance(
             contextType: contextType,
             hasDeprecated: hasDeprecated,
             inheritanceDistance: inheritanceDistance,
             startsWithDollar: startsWithDollar,
             superMatches: superMatches);
       } else {
         relevance = oldRelevance();
       }
       return _addSuggestion(accessor, relevance, useNewRelevance);
     }
     return null;
   }

   /// Add a suggestion for the given [method].
   CompletionSuggestion addSuggestionForMethod(
       {@required MethodElement method,
       String containingMethodName,
       CompletionSuggestionKind kind,
       @required double inheritanceDistance}) {
     int oldRelevance() {
       if (method.hasDeprecated) {
         return DART_RELEVANCE_LOW;
       } else if (method.name == containingMethodName) {
         // Boost the relevance of a super expression calling a method of the
         // same name as the containing method.
         return DART_RELEVANCE_HIGH;
       }
       var identifier = method.displayName;
       if (identifier != null && identifier.startsWith(r'$')) {
         // Decrease relevance of suggestions starting with $
         // https://github.com/dart-lang/sdk/issues/27303
         return DART_RELEVANCE_LOW;
       }
       return DART_RELEVANCE_DEFAULT;
     }

     if (!method.isAccessibleIn(request.libraryElement)) {
       // Don't suggest private members from imported libraries.
       return null;
     }
     int relevance;
     var useNewRelevance = request.useNewRelevance;
     if (useNewRelevance) {
       var featureComputer = request.featureComputer;
       var contextType = featureComputer.contextTypeFeature(
           request.contextType, method.returnType);
       var hasDeprecated = featureComputer.hasDeprecatedFeature(method);
       var startsWithDollar =
           featureComputer.startsWithDollarFeature(method.name);
       var superMatches = featureComputer.superMatchesFeature(
           containingMethodName, method.name);
       relevance = _computeRelevance(
           contextType: contextType,
           hasDeprecated: hasDeprecated,
           inheritanceDistance: inheritanceDistance,
           startsWithDollar: startsWithDollar,
           superMatches: superMatches);
     } else {
       relevance = oldRelevance();
     }
     return _addSuggestion(method, relevance, useNewRelevance, kind: kind);
   }

   /// Add a suggestion for the given [element] with the given [relevance],
   /// provided that it is not shadowed by a previously added suggestion.
   CompletionSuggestion _addSuggestion(
       Element element, int relevance, bool useNewRelevance,
       {CompletionSuggestionKind kind}) {
     var identifier = element.displayName;

     var alreadyGenerated = _completionTypesGenerated.putIfAbsent(
         identifier, () => _COMPLETION_TYPE_NONE);
     if (element is MethodElement) {
       // Anything shadows a method.
       if (alreadyGenerated != _COMPLETION_TYPE_NONE) {
         return null;
       }
       _completionTypesGenerated[identifier] =
           _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET;
     } else if (element is PropertyAccessorElement) {
       if (element.isGetter) {
         // Getters, fields, and methods shadow a getter.
         if ((alreadyGenerated & _COMPLETION_TYPE_GETTER) != 0) {
           return null;
         }
         _completionTypesGenerated[identifier] |= _COMPLETION_TYPE_GETTER;
       } else {
         // Setters, fields, and methods shadow a setter.
         if ((alreadyGenerated & _COMPLETION_TYPE_SETTER) != 0) {
           return null;
         }
         _completionTypesGenerated[identifier] |= _COMPLETION_TYPE_SETTER;
       }
     } else if (element is FieldElement) {
       // Fields and methods shadow a field.  A getter/setter pair shadows a
       // field, but a getter or setter by itself doesn't.
       if (alreadyGenerated == _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET) {
         return null;
       }
       _completionTypesGenerated[identifier] =
           _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET;
     } else {
       // Unexpected element type; skip it.
       assert(false);
       return null;
     }
     var suggestion = createSuggestion(request, element,
         kind: kind, relevance: relevance, useNewRelevance: useNewRelevance);
     if (suggestion != null) {
       addCompletionSuggestion(suggestion);
     }
     return suggestion;
   }

   /// Compute a relevance value from the given feature scores:
   /// - [contextType] is higher if the type of the element matches the context
   ///   type,
   /// - [hasDeprecated] is higher if the element is not deprecated,
   /// - [inheritanceDistance] is higher if the element is defined closer to the
   ///   target type,
   /// - [startsWithDollar] is higher if the element's name doe _not_ start with
   ///   a dollar sign, and
   /// - [superMatches] is higher if the element is being invoked through `super`
   ///   and the element's name matches the name of the enclosing method.
   int _computeRelevance(
       {@required double contextType,
       @required double hasDeprecated,
       @required double inheritanceDistance,
       @required double startsWithDollar,
       @required double superMatches}) {
     var score = weightedAverage([
       contextType,
       hasDeprecated,
       inheritanceDistance,
       startsWithDollar,
       superMatches
     ], [
       1.0,
       0.5,
       1.0,
       0.5,
       1.0
     ]);
     return toRelevance(score, Relevance.member);
   }
 }

 /// An object used to build a list of suggestions in response to a single
 /// completion request.
 class SuggestionBuilder {
   /// The completion request for which suggestions are being built.
   final DartCompletionRequest request;

   /// A collection of completion suggestions.
   final List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];

   /// Initialize a newly created suggestion builder to build suggestions for the
   /// given [request].
   SuggestionBuilder(this.request);
 }
	// Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	import 'dart:collection';

	import 'package:analysis_server/src/computer/computer_hover.dart';
	import 'package:analysis_server/src/protocol_server.dart' as protocol;
	import 'package:analysis_server/src/protocol_server.dart'
	hide Element, ElementKind;
	import 'package:analysis_server/src/protocol_server.dart'
	show CompletionSuggestion;
	import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
	import 'package:analysis_server/src/services/completion/dart/feature_computer.dart';
	import 'package:analysis_server/src/services/completion/dart/utilities.dart';
	import 'package:analyzer/dart/element/element.dart';
	import 'package:analyzer/dart/element/visitor.dart';
	import 'package:analyzer/src/util/comment.dart';
	import 'package:meta/meta.dart';

	/// Return a suggestion based upon the given element or `null` if a suggestion
	/// is not appropriate for the given element.
	CompletionSuggestion createSuggestion(
	DartCompletionRequest request, Element element,
	{String completion,
	CompletionSuggestionKind kind,
	int relevance = DART_RELEVANCE_DEFAULT,
	bool useNewRelevance = false}) {
	if (element == null) {
	return null;
	}
	if (element is ExecutableElement && element.isOperator) {
	// Do not include operators in suggestions
	return null;
	}
	completion ??= element.displayName;
	kind ??= CompletionSuggestionKind.INVOCATION;
	var isDeprecated = element.hasDeprecated;
	if (!useNewRelevance && isDeprecated) {
	relevance = DART_RELEVANCE_LOW;
	}
	var suggestion = CompletionSuggestion(
	kind, relevance, completion, completion.length, 0, isDeprecated, false);

	// Attach docs.
	var doc = DartUnitHoverComputer.computeDocumentation(
	request.dartdocDirectiveInfo, element);
	if (doc != null) {
	suggestion.docComplete = doc;
	suggestion.docSummary = getDartDocSummary(doc);
	}

	suggestion.element = protocol.convertElement(element);
	var enclosingElement = element.enclosingElement;
	if (enclosingElement is ClassElement) {
	suggestion.declaringType = enclosingElement.displayName;
	}
	suggestion.returnType = getReturnTypeString(element);
	if (element is ExecutableElement && element is! PropertyAccessorElement) {
	suggestion.parameterNames = element.parameters
	.map((ParameterElement parameter) => parameter.name)
	.toList();
	suggestion.parameterTypes =
	element.parameters.map((ParameterElement parameter) {
	var paramType = parameter.type;
	// Gracefully degrade if type not resolved yet
	return paramType != null
	? paramType.getDisplayString(withNullability: false)
	: 'var';
	}).toList();

	var requiredParameters = element.parameters
	.where((ParameterElement param) => param.isRequiredPositional);
	suggestion.requiredParameterCount = requiredParameters.length;

	var namedParameters =
	element.parameters.where((ParameterElement param) => param.isNamed);
	suggestion.hasNamedParameters = namedParameters.isNotEmpty;

	addDefaultArgDetails(
	suggestion, element, requiredParameters, namedParameters);
	}
	return suggestion;
	}

	/// Common mixin for sharing behavior.
	mixin ElementSuggestionBuilder {
	/// A collection of completion suggestions.
	final List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];

	/// A set of existing completions used to prevent duplicate suggestions.
	final Set<String> _completions = <String>{};

	/// A map of element names to suggestions for synthetic getters and setters.
	final Map<String, CompletionSuggestion> _syntheticMap =
	<String, CompletionSuggestion>{};

	/// Return the library in which the completion is requested.
	LibraryElement get containingLibrary;

	/// Return the kind of suggestions that should be built.
	CompletionSuggestionKind get kind;

	/// Return the completion request for which suggestions are being built.
	DartCompletionRequest get request;

	/// Add a suggestion based upon the given element.
	CompletionSuggestion addSuggestion(Element element,
	{String prefix,
	int relevance = DART_RELEVANCE_DEFAULT,
	bool useNewRelevance = false,
	String elementCompletion}) {
	if (element.isPrivate) {
	if (element.library != containingLibrary) {
	return null;
	}
	}
	var completion = elementCompletion ?? element.displayName;
	if (prefix != null && prefix.isNotEmpty) {
	if (completion == null \|\| completion.isEmpty) {
	completion = prefix;
	} else {
	completion = '$prefix.$completion';
	}
	}
	if (completion == null \|\| completion.isEmpty) {
	return null;
	}
	var suggestion = createSuggestion(request, element,
	completion: completion,
	kind: kind,
	relevance: relevance,
	useNewRelevance: useNewRelevance);
	if (suggestion != null) {
	if (element.isSynthetic && element is PropertyAccessorElement) {
	String cacheKey;
	if (element.isGetter) {
	cacheKey = element.name;
	}
	if (element.isSetter) {
	cacheKey = element.name;
	cacheKey = cacheKey.substring(0, cacheKey.length - 1);
	}
	if (cacheKey != null) {
	var existingSuggestion = _syntheticMap[cacheKey];

	// Pair getter/setter by updating the existing suggestion
	if (existingSuggestion != null) {
	var getter = element.isGetter ? suggestion : existingSuggestion;
	var elemKind = element.enclosingElement is ClassElement
	? protocol.ElementKind.FIELD
	: protocol.ElementKind.TOP_LEVEL_VARIABLE;
	existingSuggestion.element = protocol.Element(
	elemKind,
	existingSuggestion.element.name,
	existingSuggestion.element.flags,
	location: getter.element.location,
	typeParameters: getter.element.typeParameters,
	parameters: null,
	returnType: getter.returnType);
	return existingSuggestion;
	}

	// Cache lone getter/setter so that it can be paired
	_syntheticMap[cacheKey] = suggestion;
	}
	}
	if (_completions.add(suggestion.completion)) {
	suggestions.add(suggestion);
	}
	}
	return suggestion;
	}
	}

	/// This class creates suggestions based on top-level elements.
	class LibraryElementSuggestionBuilder extends SimpleElementVisitor<void>
	with ElementSuggestionBuilder {
	@override
	final DartCompletionRequest request;

	@override
	final CompletionSuggestionKind kind;

	final bool typesOnly;

	final bool instCreation;

	/// Return `true` if the new relevance scores should be produced.
	final bool useNewRelevance;

	LibraryElementSuggestionBuilder(
	this.request, this.kind, this.typesOnly, this.instCreation)
	: useNewRelevance = request.useNewRelevance;

	@override
	LibraryElement get containingLibrary => request.libraryElement;

	@override
	void visitClassElement(ClassElement element) {
	if (instCreation) {
	element.visitChildren(this);
	} else {
	// TODO(brianwilkerson) Determine whether this should be based on features
	// (such as the kind of the element) or a constant.
	var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
	addSuggestion(element,
	relevance: relevance, useNewRelevance: useNewRelevance);
	}
	}

	@override
	void visitConstructorElement(ConstructorElement element) {
	if (instCreation) {
	var classElem = element.enclosingElement;
	if (classElem != null) {
	var prefix = classElem.name;
	if (prefix != null && prefix.isNotEmpty) {
	// TODO(brianwilkerson) Determine whether this should be based on features
	// (such as the kind of the element) or a constant.
	var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
	addSuggestion(element,
	prefix: prefix,
	relevance: relevance,
	useNewRelevance: useNewRelevance);
	}
	}
	}
	}

	@override
	void visitExtensionElement(ExtensionElement element) {
	if (!instCreation) {
	// TODO(brianwilkerson) Determine whether this should be based on features
	// (such as the kind of the element) or a constant.
	var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
	addSuggestion(element,
	relevance: relevance, useNewRelevance: useNewRelevance);
	}
	}

	@override
	void visitFunctionElement(FunctionElement element) {
	if (!typesOnly) {
	int relevance;
	if (useNewRelevance) {
	// TODO(brianwilkerson) Determine whether this should be based on
	// features (such as the kind of the element) or a constant.
	relevance = element.library == containingLibrary ? 800 : 750;
	} else {
	relevance = element.library == containingLibrary
	? DART_RELEVANCE_LOCAL_FUNCTION
	: DART_RELEVANCE_DEFAULT;
	}
	addSuggestion(element,
	relevance: relevance, useNewRelevance: useNewRelevance);
	}
	}

	@override
	void visitFunctionTypeAliasElement(FunctionTypeAliasElement element) {
	if (!instCreation) {
	// TODO(brianwilkerson) Determine whether this should be based on features
	// (such as the kind of the element) or a constant.
	var relevance = useNewRelevance ? 750 : DART_RELEVANCE_DEFAULT;
	addSuggestion(element,
	relevance: relevance, useNewRelevance: useNewRelevance);
	}
	}

	@override
	void visitPropertyAccessorElement(PropertyAccessorElement element) {
	if (!typesOnly) {
	var variable = element.variable;
	int relevance;
	if (useNewRelevance) {
	// TODO(brianwilkerson) Determine whether this should be based on
	// features (such as the kind of the element) or a constant.
	relevance = variable.library == containingLibrary ? 800 : 750;
	} else {
	relevance = variable.library == containingLibrary
	? DART_RELEVANCE_LOCAL_TOP_LEVEL_VARIABLE
	: DART_RELEVANCE_DEFAULT;
	}
	addSuggestion(variable,
	relevance: relevance, useNewRelevance: useNewRelevance);
	}
	}
	}

	/// This class provides suggestions based upon the visible instance members in
	/// an interface type.
	class MemberSuggestionBuilder {
	/// Enumerated value indicating that we have not generated any completions for
	/// a given identifier yet.
	static const int _COMPLETION_TYPE_NONE = 0;

	/// Enumerated value indicating that we have generated a completion for a
	/// getter.
	static const int _COMPLETION_TYPE_GETTER = 1;

	/// Enumerated value indicating that we have generated a completion for a
	/// setter.
	static const int _COMPLETION_TYPE_SETTER = 2;

	/// Enumerated value indicating that we have generated a completion for a
	/// field, a method, or a getter/setter pair.
	static const int _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET = 3;

	/// The request for which suggestions are being built.
	final DartCompletionRequest request;

	/// Map indicating, for each possible completion identifier, whether we have
	/// already generated completions for a getter, setter, or both. The "both"
	/// case also handles the case where have generated a completion for a method
	/// or a field.
	///
	/// Note: the enumerated values stored in this map are intended to be bitwise
	/// compared.
	final Map<String, int> _completionTypesGenerated = HashMap<String, int>();

	/// A map from a completion identifier to a completion suggestion.
	final Map<String, CompletionSuggestion> _suggestionMap =
	<String, CompletionSuggestion>{};

	MemberSuggestionBuilder(this.request);

	Iterable<CompletionSuggestion> get suggestions => _suggestionMap.values;

	/// Add the given completion [suggestion].
	void addCompletionSuggestion(CompletionSuggestion suggestion) {
	_suggestionMap[suggestion.completion] = suggestion;
	}

	/// Add a suggestion for the given [method].
	CompletionSuggestion addSuggestionForAccessor(
	{@required PropertyAccessorElement accessor,
	String containingMethodName,
	@required double inheritanceDistance}) {
	int oldRelevance() {
	if (accessor.hasDeprecated) {
	return DART_RELEVANCE_LOW;
	}
	var identifier = accessor.displayName;
	if (identifier != null && identifier.startsWith(r'$')) {
	// Decrease relevance of suggestions starting with $
	// https://github.com/dart-lang/sdk/issues/27303
	return DART_RELEVANCE_LOW;
	}
	return DART_RELEVANCE_DEFAULT;
	}

	if (!accessor.isAccessibleIn(request.libraryElement)) {
	// Don't suggest private members from imported libraries.
	return null;
	}
	if (accessor.isSynthetic) {
	// Avoid visiting a field twice. All fields induce a getter, but only
	// non-final fields induce a setter, so we don't add a suggestion for a
	// synthetic setter.
	if (accessor.isGetter) {
	var variable = accessor.variable;
	int relevance;
	var useNewRelevance = request.useNewRelevance;
	if (useNewRelevance) {
	var featureComputer = request.featureComputer;
	var contextType = featureComputer.contextTypeFeature(
	request.contextType, variable.type);
	var hasDeprecated = featureComputer.hasDeprecatedFeature(accessor);
	var startsWithDollar =
	featureComputer.startsWithDollarFeature(accessor.name);
	var superMatches = featureComputer.superMatchesFeature(
	containingMethodName, accessor.name);
	relevance = _computeRelevance(
	contextType: contextType,
	hasDeprecated: hasDeprecated,
	inheritanceDistance: inheritanceDistance,
	startsWithDollar: startsWithDollar,
	superMatches: superMatches);
	} else {
	relevance = oldRelevance();
	}
	return _addSuggestion(variable, relevance, useNewRelevance);
	}
	} else {
	var type =
	accessor.isGetter ? accessor.returnType : accessor.parameters[0].type;
	int relevance;
	var useNewRelevance = request.useNewRelevance;
	if (useNewRelevance) {
	var featureComputer = request.featureComputer;
	var contextType =
	featureComputer.contextTypeFeature(request.contextType, type);
	var hasDeprecated = featureComputer.hasDeprecatedFeature(accessor);
	var startsWithDollar =
	featureComputer.startsWithDollarFeature(accessor.name);
	var superMatches = featureComputer.superMatchesFeature(
	containingMethodName, accessor.name);
	relevance = _computeRelevance(
	contextType: contextType,
	hasDeprecated: hasDeprecated,
	inheritanceDistance: inheritanceDistance,
	startsWithDollar: startsWithDollar,
	superMatches: superMatches);
	} else {
	relevance = oldRelevance();
	}
	return _addSuggestion(accessor, relevance, useNewRelevance);
	}
	return null;
	}

	/// Add a suggestion for the given [method].
	CompletionSuggestion addSuggestionForMethod(
	{@required MethodElement method,
	String containingMethodName,
	CompletionSuggestionKind kind,
	@required double inheritanceDistance}) {
	int oldRelevance() {
	if (method.hasDeprecated) {
	return DART_RELEVANCE_LOW;
	} else if (method.name == containingMethodName) {
	// Boost the relevance of a super expression calling a method of the
	// same name as the containing method.
	return DART_RELEVANCE_HIGH;
	}
	var identifier = method.displayName;
	if (identifier != null && identifier.startsWith(r'$')) {
	// Decrease relevance of suggestions starting with $
	// https://github.com/dart-lang/sdk/issues/27303
	return DART_RELEVANCE_LOW;
	}
	return DART_RELEVANCE_DEFAULT;
	}

	if (!method.isAccessibleIn(request.libraryElement)) {
	// Don't suggest private members from imported libraries.
	return null;
	}
	int relevance;
	var useNewRelevance = request.useNewRelevance;
	if (useNewRelevance) {
	var featureComputer = request.featureComputer;
	var contextType = featureComputer.contextTypeFeature(
	request.contextType, method.returnType);
	var hasDeprecated = featureComputer.hasDeprecatedFeature(method);
	var startsWithDollar =
	featureComputer.startsWithDollarFeature(method.name);
	var superMatches = featureComputer.superMatchesFeature(
	containingMethodName, method.name);
	relevance = _computeRelevance(
	contextType: contextType,
	hasDeprecated: hasDeprecated,
	inheritanceDistance: inheritanceDistance,
	startsWithDollar: startsWithDollar,
	superMatches: superMatches);
	} else {
	relevance = oldRelevance();
	}
	return _addSuggestion(method, relevance, useNewRelevance, kind: kind);
	}

	/// Add a suggestion for the given [element] with the given [relevance],
	/// provided that it is not shadowed by a previously added suggestion.
	CompletionSuggestion _addSuggestion(
	Element element, int relevance, bool useNewRelevance,
	{CompletionSuggestionKind kind}) {
	var identifier = element.displayName;

	var alreadyGenerated = _completionTypesGenerated.putIfAbsent(
	identifier, () => _COMPLETION_TYPE_NONE);
	if (element is MethodElement) {
	// Anything shadows a method.
	if (alreadyGenerated != _COMPLETION_TYPE_NONE) {
	return null;
	}
	_completionTypesGenerated[identifier] =
	_COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET;
	} else if (element is PropertyAccessorElement) {
	if (element.isGetter) {
	// Getters, fields, and methods shadow a getter.
	if ((alreadyGenerated & _COMPLETION_TYPE_GETTER) != 0) {
	return null;
	}
	_completionTypesGenerated[identifier] \|= _COMPLETION_TYPE_GETTER;
	} else {
	// Setters, fields, and methods shadow a setter.
	if ((alreadyGenerated & _COMPLETION_TYPE_SETTER) != 0) {
	return null;
	}
	_completionTypesGenerated[identifier] \|= _COMPLETION_TYPE_SETTER;
	}
	} else if (element is FieldElement) {
	// Fields and methods shadow a field. A getter/setter pair shadows a
	// field, but a getter or setter by itself doesn't.
	if (alreadyGenerated == _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET) {
	return null;
	}
	_completionTypesGenerated[identifier] =
	_COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET;
	} else {
	// Unexpected element type; skip it.
	assert(false);
	return null;
	}
	var suggestion = createSuggestion(request, element,
	kind: kind, relevance: relevance, useNewRelevance: useNewRelevance);
	if (suggestion != null) {
	addCompletionSuggestion(suggestion);
	}
	return suggestion;
	}

	/// Compute a relevance value from the given feature scores:
	/// - [contextType] is higher if the type of the element matches the context
	/// type,
	/// - [hasDeprecated] is higher if the element is not deprecated,
	/// - [inheritanceDistance] is higher if the element is defined closer to the
	/// target type,
	/// - [startsWithDollar] is higher if the element's name doe _not_ start with
	/// a dollar sign, and
	/// - [superMatches] is higher if the element is being invoked through `super`
	/// and the element's name matches the name of the enclosing method.
	int _computeRelevance(
	{@required double contextType,
	@required double hasDeprecated,
	@required double inheritanceDistance,
	@required double startsWithDollar,
	@required double superMatches}) {
	var score = weightedAverage([
	contextType,
	hasDeprecated,
	inheritanceDistance,
	startsWithDollar,
	superMatches
	], [
	1.0,
	0.5,
	1.0,
	0.5,
	1.0
	]);
	return toRelevance(score, Relevance.member);
	}
	}

	/// An object used to build a list of suggestions in response to a single
	/// completion request.
	class SuggestionBuilder {
	/// The completion request for which suggestions are being built.
	final DartCompletionRequest request;

	/// A collection of completion suggestions.
	final List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];

	/// Initialize a newly created suggestion builder to build suggestions for the
	/// given [request].
	SuggestionBuilder(this.request);
	}