Prepare for decoupling analyzer ASTs from element model.

pkg/analysis_server/lib/src/services/completion/dart/optype.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/optype.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/optype.dart b/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
index 132c8235799d3a2aaba80375d8be4d4030f90615..59a7c7498453a12ff167299d54805c136f566672 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
@@ -8,6 +8,7 @@ import 'package:analysis_server/src/protocol_server.dart' hide Element;
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/resolution_accessors.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ -567,7 +568,8 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
         if (node.parent is VariableDeclaration) {
           VariableDeclaration varDeclaration =
               node.parent as VariableDeclaration;
-          localTypeAssertion = varDeclaration.element?.type;
+          localTypeAssertion =
+              elementForVariableDeclaration(varDeclaration)?.type;
         } else if (node.parent is AssignmentExpression) {
           AssignmentExpression assignmentExpression =
               node.parent as AssignmentExpression;
@@ -653,7 +655,7 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
     if (identical(entity, node.expression)) {
       optype.includeReturnValueSuggestions = true;
       optype.returnValueSuggestionsFilter = (DartType dartType, int relevance) {
-        DartType type = node.element?.type;
+        DartType type = elementForNamedExpression(node)?.type;
         bool isEnum = type != null &&
             type.element is ClassElement &&
             (type.element as ClassElement).isEnum;