Allow navigation from var when there is an inferred type (issue 29091)

pkg/analysis_server/lib/src/domains/analysis/navigation_dart.dart

 // 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.
 
 library domains.analysis.navigation_dart;
 
 import 'package:analysis_server/plugin/analysis/navigation/navigation_core.dart';
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
 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/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 NavigationCollector computeDartNavigation(NavigationCollector collector,
     CompilationUnit unit, int offset, int length) {
   _DartNavigationCollector dartCollector =
       new _DartNavigationCollector(collector);
   _DartNavigationComputerVisitor visitor =
@@ skipping 164 matching lines @@
     if (parent is InstanceCreationExpression &&
         parent.constructorName == node) {
       _addConstructorName(parent, node);
     } else if (parent is ConstructorDeclaration &&
         parent.redirectedConstructor == node) {
       _addConstructorName(node, node);
     }
   }
 
   @override
+  visitDeclaredIdentifier(DeclaredIdentifier node) {
+    if (node.type == null) {
+      Token token = node.keyword;
+      if (token?.keyword == Keyword.VAR) {
+        DartType inferredType = node.identifier?.bestType;
+        Element element = inferredType?.element;
+        if (element != null) {
+          computer._addRegionForToken(token, element);
+        }
+      }
+    }
+    super.visitDeclaredIdentifier(node);
+  }
+
+  @override
   visitExportDirective(ExportDirective node) {
     ExportElement exportElement = node.element;
     if (exportElement != null) {
       Element libraryElement = exportElement.exportedLibrary;
       _addUriDirectiveRegion(node, libraryElement);
     }
     super.visitExportDirective(node);
   }
 
   @override
@@ skipping 71 matching lines @@
     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
+  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) {
+      Element firstElement = variables[0].name?.bestType?.element;
+      if (firstElement == null) {
+        return null;
+      }
+      for (int i = 1; i < variables.length; i++) {
+        Element element = variables[1].name?.bestType?.element;

[scheglov, 2017/03/23 00:05:34]

variables[i]

+        if (element != firstElement) {
+          return null;
+        }
+      }
+      return firstElement;
+    }
+
+    if (node.type == null) {
+      Token token = node.keyword;
+      if (token?.keyword == Keyword.VAR) {

[scheglov, 2017/03/23 00:05:34]

final and const too?

+        Element 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
@@ skipping 25 matching lines @@
    */
   void _addUriDirectiveRegion(UriBasedDirective node, Element element) {
     if (element != null) {
       Source source = element.source;
       if (element.context.exists(source)) {
         computer._addRegionForNode(node.uri, element);
       }
     }
   }
 }