pkg/analyzer_plugin/lib/utilities/navigation/navigation_dart.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 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/ast/extensions.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart' as protocol;
 import 'package:analyzer_plugin/utilities/analyzer_converter.dart';
 import 'package:analyzer_plugin/utilities/navigation/navigation.dart';

 NavigationCollector computeDartNavigation(
     ResourceProvider resourceProvider,
     NavigationCollector collector,
     CompilationUnit unit,
     int? offset,
     int? length) {
   var dartCollector = _DartNavigationCollector(collector, offset, length);
   var visitor = _DartNavigationComputerVisitor(resourceProvider, dartCollector);
   if (offset == null || length == null) {
     unit.accept(visitor);
   } else {
     var node = _getNodeForRange(unit, offset, length);
     node?.accept(visitor);
   }
   return collector;
 }

 AstNode? _getNodeForRange(CompilationUnit unit, int offset, int length) {
   var node = NodeLocator(offset, offset + length).searchWithin(unit);
   for (var n = node; n != null; n = n.parent) {
     if (n is Directive) {
       return n;
     }
   }
   return node;
 }

 /// A Dart specific wrapper around [NavigationCollector].
 class _DartNavigationCollector {
   final NavigationCollector collector;
   final int? requestedOffset;
   final int? requestedLength;

   _DartNavigationCollector(
       this.collector, this.requestedOffset, this.requestedLength);

   void _addRegion(int offset, int length, Element? element) {
     if (element is FieldFormalParameterElement) {
       element = element.field;
     }
     if (element == null || element == DynamicElementImpl.instance) {
       return;
     }
     if (element.location == null) {
       return;
     }
     // Discard elements that don't span the offset/range given (if provided).
     if (requestedOffset != null &&
         (offset > requestedOffset! + (requestedLength ?? 0) ||
             offset + length < requestedOffset!)) {
       return;
     }
     var converter = AnalyzerConverter();
     var kind = converter.convertElementKind(element.kind);
     var location = converter.locationFromElement(element);
     if (location == null) {
       return;
     }

     var codeLocation = collector.collectCodeLocations
         ? _getCodeLocation(element, location, converter)
         : null;

     collector.addRegion(offset, length, kind, location,
         targetCodeLocation: codeLocation);
   }

   void _addRegion_nodeStart_nodeEnd(AstNode a, AstNode b, Element? element) {
     var offset = a.offset;
     var length = b.end - offset;
     _addRegion(offset, length, element);
   }

   void _addRegionForNode(AstNode? node, Element? element) {
     if (node == null) {
       return;
     }
     var offset = node.offset;
     var length = node.length;
     _addRegion(offset, length, element);
   }

   void _addRegionForToken(Token token, Element? element) {
     var offset = token.offset;
     var length = token.length;
     _addRegion(offset, length, element);
   }

   /// Get the location of the code (excluding leading doc comments) for this element.
   protocol.Location? _getCodeLocation(Element element,
       protocol.Location location, AnalyzerConverter converter) {
     var codeElement = element;
     // For synthetic getters created for fields, we need to access the associated
     // variable to get the codeOffset/codeLength.
     if (codeElement.isSynthetic && codeElement is PropertyAccessorElementImpl) {
       final variable = codeElement.variable;
       if (variable is ElementImpl) {
         codeElement = variable as ElementImpl;
       }
     }

     // Read the main codeOffset from the element. This may include doc comments
     // but will give the correct end position.
     int? codeOffset, codeLength;
     if (codeElement is ElementImpl) {
       codeOffset = codeElement.codeOffset;
       codeLength = codeElement.codeLength;
     }

     if (codeOffset == null || codeLength == null) {
       return null;
     }

     // Read the declaration so we can get the offset after the doc comments.
     // TODO(dantup): Skip this for parts (getParsedLibrary will throw), but find
     // a better solution.
     var session = codeElement.session;
     final declaration =
         session != null && !session.getFile(location.file).isPart
             ? session
                 .getParsedLibrary(location.file)
                 .getElementDeclaration(codeElement)
             : null;
     var node = declaration?.node;
     if (node is VariableDeclaration) {
       node = node.parent;
     }
     if (node is AnnotatedNode) {
       var offsetAfterDocs = node.firstTokenAfterCommentAndMetadata.offset;

       // Reduce the length by the difference between the end of docs and the start.
       codeLength -= (offsetAfterDocs - codeOffset);
       codeOffset = offsetAfterDocs;
     }

     return converter.locationFromElement(element,
         offset: codeOffset, length: codeLength);
   }
 }

 class _DartNavigationComputerVisitor extends RecursiveAstVisitor<void> {
   final ResourceProvider resourceProvider;
   final _DartNavigationCollector computer;

   _DartNavigationComputerVisitor(this.resourceProvider, this.computer);

   @override
   void visitAnnotation(Annotation node) {
     var element = node.element;
     if (element is ConstructorElement && element.isSynthetic) {
       element = element.enclosingElement;
     }
     var name = node.name;
     if (name is PrefixedIdentifier) {
       // use constructor in: @PrefixClass.constructorName
       var prefixElement = name.prefix.staticElement;
       if (prefixElement is ClassElement) {
         prefixElement = element;
       }
       computer._addRegionForNode(name.prefix, prefixElement);
       // always constructor
       computer._addRegionForNode(name.identifier, element);
     } else {
       computer._addRegionForNode(name, element);
     }
     computer._addRegionForNode(node.constructorName, element);
     // type arguments
     node.typeArguments?.accept(this);
     // arguments
     node.arguments?.accept(this);
   }

   @override
   void visitAssignmentExpression(AssignmentExpression node) {
     node.leftHandSide.accept(this);
     computer._addRegionForToken(node.operator, node.staticElement);
     node.rightHandSide.accept(this);
   }

   @override
   void visitBinaryExpression(BinaryExpression node) {
     node.leftOperand.accept(this);
     computer._addRegionForToken(node.operator, node.staticElement);
     node.rightOperand.accept(this);
   }

   @override
   void visitCompilationUnit(CompilationUnit unit) {
     // prepare top-level nodes sorted by their offsets
     var nodes = <AstNode>[];
     nodes.addAll(unit.directives);
     nodes.addAll(unit.declarations);
     nodes.sort((a, b) {
       return a.offset - b.offset;
     });
     // visit sorted nodes
     for (var node in nodes) {
       node.accept(this);
     }
   }

   @override
   void visitConfiguration(Configuration node) {
     var source = node.uriSource;
     if (source != null) {
       if (resourceProvider.getResource(source.fullName).exists) {
         // TODO(brianwilkerson) If the analyzer ever resolves the URI to a
         //  library, use that library element to create the region.
         var uriNode = node.uri;
         computer.collector.addRegion(
             uriNode.offset,
             uriNode.length,
             protocol.ElementKind.LIBRARY,
             protocol.Location(source.fullName, 0, 0, 0, 0, 0, 0));
       }
     }
     super.visitConfiguration(node);
   }

   @override
   void visitConstructorDeclaration(ConstructorDeclaration node) {
     // associate constructor with "T" or "T.name"
     {
       AstNode firstNode = node.returnType;
       AstNode? lastNode = node.name;
       lastNode ??= firstNode;
       computer._addRegion_nodeStart_nodeEnd(
           firstNode, lastNode, node.declaredElement);
     }
     super.visitConstructorDeclaration(node);
   }

   @override
   void visitConstructorName(ConstructorName node) {
     var parent = node.parent;
     if (parent is InstanceCreationExpression &&
         parent.constructorName == node) {
       _addConstructorName(parent, node);
     } else if (parent is ConstructorDeclaration &&
         parent.redirectedConstructor == node) {
       _addConstructorName(node, node);
     }
   }

   @override
   void visitDeclaredIdentifier(DeclaredIdentifier node) {
     if (node.type == null) {
       var token = node.keyword;
       if (token != null && token.keyword == Keyword.VAR) {
         var inferredType = node.declaredElement?.type;
         var element = inferredType?.element;
         if (element != null) {
           computer._addRegionForToken(token, element);
         }
       }
     }
     super.visitDeclaredIdentifier(node);
   }

   @override
   void visitExportDirective(ExportDirective node) {
     var exportElement = node.element;
     if (exportElement != null) {
       Element? libraryElement = exportElement.exportedLibrary;
       _addUriDirectiveRegion(node, libraryElement);
     }
     super.visitExportDirective(node);
   }

   @override
   void visitImportDirective(ImportDirective node) {
     var importElement = node.element;
     if (importElement != null) {
       Element? libraryElement = importElement.importedLibrary;
       _addUriDirectiveRegion(node, libraryElement);
     }
     super.visitImportDirective(node);
   }

   @override
   void visitIndexExpression(IndexExpression node) {
     super.visitIndexExpression(node);
     var element = node.writeOrReadElement;
     computer._addRegionForToken(node.leftBracket, element);
     computer._addRegionForToken(node.rightBracket, element);
   }

   @override
   void visitLibraryDirective(LibraryDirective node) {
     computer._addRegionForNode(node.name, node.element);
   }

   @override
   void visitPartDirective(PartDirective node) {
     _addUriDirectiveRegion(node, node.element);
     super.visitPartDirective(node);
   }

   @override
   void visitPartOfDirective(PartOfDirective node) {
     computer._addRegionForNode(node.libraryName, node.element);
     super.visitPartOfDirective(node);
   }

   @override
   void visitPostfixExpression(PostfixExpression node) {
     super.visitPostfixExpression(node);
     computer._addRegionForToken(node.operator, node.staticElement);
   }

   @override
   void visitPrefixExpression(PrefixExpression node) {
     computer._addRegionForToken(node.operator, node.staticElement);
     super.visitPrefixExpression(node);
   }

   @override
   void visitRedirectingConstructorInvocation(
       RedirectingConstructorInvocation node) {
     Element? element = node.staticElement;
     if (element != null && element.isSynthetic) {
       element = element.enclosingElement;
     }
     // add region
     computer._addRegionForToken(node.thisKeyword, element);
     computer._addRegionForNode(node.constructorName, element);
     // process arguments
     node.argumentList.accept(this);
   }

   @override
   void visitSimpleIdentifier(SimpleIdentifier node) {
     if (node.parent is ConstructorDeclaration) {
       return;
     }
     var element = node.writeOrReadElement;
     computer._addRegionForNode(node, element);
   }

   @override
   void visitSuperConstructorInvocation(SuperConstructorInvocation node) {
     Element? element = node.staticElement;
     if (element != null && element.isSynthetic) {
       element = element.enclosingElement;
     }
     // add region
     computer._addRegionForToken(node.superKeyword, element);
     computer._addRegionForNode(node.constructorName, element);
     // process arguments
     node.argumentList.accept(this);
   }

   @override
   void visitVariableDeclarationList(VariableDeclarationList node) {
     /// Return the element for the type inferred for each of the variables in
     /// the given list of [variables], or `null` if not all variable have the
     /// same inferred type.
     Element? getCommonElement(List<VariableDeclaration> variables) {
       var firstElement = variables[0].declaredElement?.type.element;
       if (firstElement == null) {
         return null;
       }
       for (var i = 1; i < variables.length; i++) {
         var element = variables[1].declaredElement?.type.element;
         if (element != firstElement) {
           return null;
         }
       }
       return firstElement;
     }

     if (node.type == null) {
       var token = node.keyword;
       if (token?.keyword == Keyword.VAR) {
         var element = getCommonElement(node.variables);
         if (element != null) {
           computer._addRegionForToken(token!, element);
         }
       }
     }
     super.visitVariableDeclarationList(node);
   }

   void _addConstructorName(AstNode parent, ConstructorName node) {
     Element? element = node.staticElement;
     if (element == null) {
       return;
     }
     // if a synthetic constructor, navigate to the class
     if (element.isSynthetic) {
       element = element.enclosingElement;
     }
     // add regions
     var typeName = node.type;
     // [prefix].ClassName
     {
       var name = typeName.name;
       var className = name;
       if (name is PrefixedIdentifier) {
         name.prefix.accept(this);
         className = name.identifier;
       }
       computer._addRegionForNode(className, element);
     }
     // <TypeA, TypeB>
     var typeArguments = typeName.typeArguments;
     if (typeArguments != null) {
       typeArguments.accept(this);
     }
     // optional "name"
     if (node.name != null) {
       computer._addRegionForNode(node.name, element);
     }
   }

   /// If the source of the given [element] (referenced by the [node]) exists,
   /// then add the navigation region from the [node] to the [element].
   void _addUriDirectiveRegion(UriBasedDirective node, Element? element) {
     var source = element?.source;
     if (source != null) {
       if (resourceProvider.getResource(source.fullName).exists) {
         computer._addRegionForNode(node.uri, element);
       }
     }
   }
 }
	// 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 'package:analyzer/dart/ast/ast.dart';
	import 'package:analyzer/dart/ast/token.dart';
	import 'package:analyzer/dart/ast/visitor.dart';
	import 'package:analyzer/dart/element/element.dart';
	import 'package:analyzer/file_system/file_system.dart';
	import 'package:analyzer/src/dart/ast/extensions.dart';
	import 'package:analyzer/src/dart/ast/utilities.dart';
	import 'package:analyzer/src/dart/element/element.dart';
	import 'package:analyzer_plugin/protocol/protocol_common.dart' as protocol;
	import 'package:analyzer_plugin/utilities/analyzer_converter.dart';
	import 'package:analyzer_plugin/utilities/navigation/navigation.dart';

	NavigationCollector computeDartNavigation(
	ResourceProvider resourceProvider,
	NavigationCollector collector,
	CompilationUnit unit,
	int? offset,
	int? length) {
	var dartCollector = _DartNavigationCollector(collector, offset, length);
	var visitor = _DartNavigationComputerVisitor(resourceProvider, dartCollector);
	if (offset == null \|\| length == null) {
	unit.accept(visitor);
	} else {
	var node = _getNodeForRange(unit, offset, length);
	node?.accept(visitor);
	}
	return collector;
	}

	AstNode? _getNodeForRange(CompilationUnit unit, int offset, int length) {
	var node = NodeLocator(offset, offset + length).searchWithin(unit);
	for (var n = node; n != null; n = n.parent) {
	if (n is Directive) {
	return n;
	}
	}
	return node;
	}

	/// A Dart specific wrapper around [NavigationCollector].
	class _DartNavigationCollector {
	final NavigationCollector collector;
	final int? requestedOffset;
	final int? requestedLength;

	_DartNavigationCollector(
	this.collector, this.requestedOffset, this.requestedLength);

	void _addRegion(int offset, int length, Element? element) {
	if (element is FieldFormalParameterElement) {
	element = element.field;
	}
	if (element == null \|\| element == DynamicElementImpl.instance) {
	return;
	}
	if (element.location == null) {
	return;
	}
	// Discard elements that don't span the offset/range given (if provided).
	if (requestedOffset != null &&
	(offset > requestedOffset! + (requestedLength ?? 0) \|\|
	offset + length < requestedOffset!)) {
	return;
	}
	var converter = AnalyzerConverter();
	var kind = converter.convertElementKind(element.kind);
	var location = converter.locationFromElement(element);
	if (location == null) {
	return;
	}

	var codeLocation = collector.collectCodeLocations
	? _getCodeLocation(element, location, converter)
	: null;

	collector.addRegion(offset, length, kind, location,
	targetCodeLocation: codeLocation);
	}

	void _addRegion_nodeStart_nodeEnd(AstNode a, AstNode b, Element? element) {
	var offset = a.offset;
	var length = b.end - offset;
	_addRegion(offset, length, element);
	}

	void _addRegionForNode(AstNode? node, Element? element) {
	if (node == null) {
	return;
	}
	var offset = node.offset;
	var length = node.length;
	_addRegion(offset, length, element);
	}

	void _addRegionForToken(Token token, Element? element) {
	var offset = token.offset;
	var length = token.length;
	_addRegion(offset, length, element);
	}

	/// Get the location of the code (excluding leading doc comments) for this element.
	protocol.Location? _getCodeLocation(Element element,
	protocol.Location location, AnalyzerConverter converter) {
	var codeElement = element;
	// For synthetic getters created for fields, we need to access the associated
	// variable to get the codeOffset/codeLength.
	if (codeElement.isSynthetic && codeElement is PropertyAccessorElementImpl) {
	final variable = codeElement.variable;
	if (variable is ElementImpl) {
	codeElement = variable as ElementImpl;
	}
	}

	// Read the main codeOffset from the element. This may include doc comments
	// but will give the correct end position.
	int? codeOffset, codeLength;
	if (codeElement is ElementImpl) {
	codeOffset = codeElement.codeOffset;
	codeLength = codeElement.codeLength;
	}

	if (codeOffset == null \|\| codeLength == null) {
	return null;
	}

	// Read the declaration so we can get the offset after the doc comments.
	// TODO(dantup): Skip this for parts (getParsedLibrary will throw), but find
	// a better solution.
	var session = codeElement.session;
	final declaration =
	session != null && !session.getFile(location.file).isPart
	? session
	.getParsedLibrary(location.file)
	.getElementDeclaration(codeElement)
	: null;
	var node = declaration?.node;
	if (node is VariableDeclaration) {
	node = node.parent;
	}
	if (node is AnnotatedNode) {
	var offsetAfterDocs = node.firstTokenAfterCommentAndMetadata.offset;

	// Reduce the length by the difference between the end of docs and the start.
	codeLength -= (offsetAfterDocs - codeOffset);
	codeOffset = offsetAfterDocs;
	}

	return converter.locationFromElement(element,
	offset: codeOffset, length: codeLength);
	}
	}

	class _DartNavigationComputerVisitor extends RecursiveAstVisitor<void> {
	final ResourceProvider resourceProvider;
	final _DartNavigationCollector computer;

	_DartNavigationComputerVisitor(this.resourceProvider, this.computer);

	@override
	void visitAnnotation(Annotation node) {
	var element = node.element;
	if (element is ConstructorElement && element.isSynthetic) {
	element = element.enclosingElement;
	}
	var name = node.name;
	if (name is PrefixedIdentifier) {
	// use constructor in: @PrefixClass.constructorName
	var prefixElement = name.prefix.staticElement;
	if (prefixElement is ClassElement) {
	prefixElement = element;
	}
	computer._addRegionForNode(name.prefix, prefixElement);
	// always constructor
	computer._addRegionForNode(name.identifier, element);
	} else {
	computer._addRegionForNode(name, element);
	}
	computer._addRegionForNode(node.constructorName, element);
	// type arguments
	node.typeArguments?.accept(this);
	// arguments
	node.arguments?.accept(this);
	}

	@override
	void visitAssignmentExpression(AssignmentExpression node) {
	node.leftHandSide.accept(this);
	computer._addRegionForToken(node.operator, node.staticElement);
	node.rightHandSide.accept(this);
	}

	@override
	void visitBinaryExpression(BinaryExpression node) {
	node.leftOperand.accept(this);
	computer._addRegionForToken(node.operator, node.staticElement);
	node.rightOperand.accept(this);
	}

	@override
	void visitCompilationUnit(CompilationUnit unit) {
	// prepare top-level nodes sorted by their offsets
	var nodes = <AstNode>[];
	nodes.addAll(unit.directives);
	nodes.addAll(unit.declarations);
	nodes.sort((a, b) {
	return a.offset - b.offset;
	});
	// visit sorted nodes
	for (var node in nodes) {
	node.accept(this);
	}
	}

	@override
	void visitConfiguration(Configuration node) {
	var source = node.uriSource;
	if (source != null) {
	if (resourceProvider.getResource(source.fullName).exists) {
	// TODO(brianwilkerson) If the analyzer ever resolves the URI to a
	// library, use that library element to create the region.
	var uriNode = node.uri;
	computer.collector.addRegion(
	uriNode.offset,
	uriNode.length,
	protocol.ElementKind.LIBRARY,
	protocol.Location(source.fullName, 0, 0, 0, 0, 0, 0));
	}
	}
	super.visitConfiguration(node);
	}

	@override
	void visitConstructorDeclaration(ConstructorDeclaration node) {
	// associate constructor with "T" or "T.name"
	{
	AstNode firstNode = node.returnType;
	AstNode? lastNode = node.name;
	lastNode ??= firstNode;
	computer._addRegion_nodeStart_nodeEnd(
	firstNode, lastNode, node.declaredElement);
	}
	super.visitConstructorDeclaration(node);
	}

	@override
	void visitConstructorName(ConstructorName node) {
	var parent = node.parent;
	if (parent is InstanceCreationExpression &&
	parent.constructorName == node) {
	_addConstructorName(parent, node);
	} else if (parent is ConstructorDeclaration &&
	parent.redirectedConstructor == node) {
	_addConstructorName(node, node);
	}
	}

	@override
	void visitDeclaredIdentifier(DeclaredIdentifier node) {
	if (node.type == null) {
	var token = node.keyword;
	if (token != null && token.keyword == Keyword.VAR) {
	var inferredType = node.declaredElement?.type;
	var element = inferredType?.element;
	if (element != null) {
	computer._addRegionForToken(token, element);
	}
	}
	}
	super.visitDeclaredIdentifier(node);
	}

	@override
	void visitExportDirective(ExportDirective node) {
	var exportElement = node.element;
	if (exportElement != null) {
	Element? libraryElement = exportElement.exportedLibrary;
	_addUriDirectiveRegion(node, libraryElement);
	}
	super.visitExportDirective(node);
	}

	@override
	void visitImportDirective(ImportDirective node) {
	var importElement = node.element;
	if (importElement != null) {
	Element? libraryElement = importElement.importedLibrary;
	_addUriDirectiveRegion(node, libraryElement);
	}
	super.visitImportDirective(node);
	}

	@override
	void visitIndexExpression(IndexExpression node) {
	super.visitIndexExpression(node);
	var element = node.writeOrReadElement;
	computer._addRegionForToken(node.leftBracket, element);
	computer._addRegionForToken(node.rightBracket, element);
	}

	@override
	void visitLibraryDirective(LibraryDirective node) {
	computer._addRegionForNode(node.name, node.element);
	}

	@override
	void visitPartDirective(PartDirective node) {
	_addUriDirectiveRegion(node, node.element);
	super.visitPartDirective(node);
	}

	@override
	void visitPartOfDirective(PartOfDirective node) {
	computer._addRegionForNode(node.libraryName, node.element);
	super.visitPartOfDirective(node);
	}

	@override
	void visitPostfixExpression(PostfixExpression node) {
	super.visitPostfixExpression(node);
	computer._addRegionForToken(node.operator, node.staticElement);
	}

	@override
	void visitPrefixExpression(PrefixExpression node) {
	computer._addRegionForToken(node.operator, node.staticElement);
	super.visitPrefixExpression(node);
	}

	@override
	void visitRedirectingConstructorInvocation(
	RedirectingConstructorInvocation node) {
	Element? element = node.staticElement;
	if (element != null && element.isSynthetic) {
	element = element.enclosingElement;
	}
	// add region
	computer._addRegionForToken(node.thisKeyword, element);
	computer._addRegionForNode(node.constructorName, element);
	// process arguments
	node.argumentList.accept(this);
	}

	@override
	void visitSimpleIdentifier(SimpleIdentifier node) {
	if (node.parent is ConstructorDeclaration) {
	return;
	}
	var element = node.writeOrReadElement;
	computer._addRegionForNode(node, element);
	}

	@override
	void visitSuperConstructorInvocation(SuperConstructorInvocation node) {
	Element? element = node.staticElement;
	if (element != null && element.isSynthetic) {
	element = element.enclosingElement;
	}
	// add region
	computer._addRegionForToken(node.superKeyword, element);
	computer._addRegionForNode(node.constructorName, element);
	// process arguments
	node.argumentList.accept(this);
	}

	@override
	void visitVariableDeclarationList(VariableDeclarationList node) {
	/// Return the element for the type inferred for each of the variables in
	/// the given list of [variables], or `null` if not all variable have the
	/// same inferred type.
	Element? getCommonElement(List<VariableDeclaration> variables) {
	var firstElement = variables[0].declaredElement?.type.element;
	if (firstElement == null) {
	return null;
	}
	for (var i = 1; i < variables.length; i++) {
	var element = variables[1].declaredElement?.type.element;
	if (element != firstElement) {
	return null;
	}
	}
	return firstElement;
	}

	if (node.type == null) {
	var token = node.keyword;
	if (token?.keyword == Keyword.VAR) {
	var element = getCommonElement(node.variables);
	if (element != null) {
	computer._addRegionForToken(token!, element);
	}
	}
	}
	super.visitVariableDeclarationList(node);
	}

	void _addConstructorName(AstNode parent, ConstructorName node) {
	Element? element = node.staticElement;
	if (element == null) {
	return;
	}
	// if a synthetic constructor, navigate to the class
	if (element.isSynthetic) {
	element = element.enclosingElement;
	}
	// add regions
	var typeName = node.type;
	// [prefix].ClassName
	{
	var name = typeName.name;
	var className = name;
	if (name is PrefixedIdentifier) {
	name.prefix.accept(this);
	className = name.identifier;
	}
	computer._addRegionForNode(className, element);
	}
	// <TypeA, TypeB>
	var typeArguments = typeName.typeArguments;
	if (typeArguments != null) {
	typeArguments.accept(this);
	}
	// optional "name"
	if (node.name != null) {
	computer._addRegionForNode(node.name, element);
	}
	}

	/// If the source of the given [element] (referenced by the [node]) exists,
	/// then add the navigation region from the [node] to the [element].
	void _addUriDirectiveRegion(UriBasedDirective node, Element? element) {
	var source = element?.source;
	if (source != null) {
	if (resourceProvider.getResource(source.fullName).exists) {
	computer._addRegionForNode(node.uri, element);
	}
	}
	}
	}