Handle unresolved constructor (issue 29925)

pkg/analyzer_plugin/lib/src/utilities/completion/optype.dart

 // Copyright (c) 2017, 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/standard_resolution_map.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';
@@ skipping 720 matching lines @@
           return relevance;
         }
       };
       optype.includeTypeNameSuggestions = true;
 
       // Check for named parameters in constructor calls.
       AstNode grandparent = node.parent.parent;
       if (grandparent is ConstructorReferenceNode) {
         ConstructorElement element =
             (grandparent as ConstructorReferenceNode).staticElement;
-        List<ParameterElement> parameters = element.parameters;
-        ParameterElement parameterElement = parameters.firstWhere((e) {
-          if (e is DefaultFieldFormalParameterElementImpl) {
-            return e.field.name == node.name.label.name;
+        if (element != null) {
+          List<ParameterElement> parameters = element.parameters;
+          ParameterElement parameterElement = parameters.firstWhere((e) {
+            if (e is DefaultFieldFormalParameterElementImpl) {
+              return e.field.name == node.name.label.name;
+            }
+            return e.parameterKind == ParameterKind.NAMED &&
+                e.name == node.name.label.name;
+          }, orElse: () => null);
+          // Suggest tear-offs.
+          if (parameterElement?.type is FunctionType) {
+            optype.includeVoidReturnSuggestions = true;
           }
-          return e.parameterKind == ParameterKind.NAMED &&
-              e.name == node.name.label.name;
-        }, orElse: () => null);
-        // Suggest tear-offs.
-        if (parameterElement?.type is FunctionType) {
-          optype.includeVoidReturnSuggestions = true;
         }
       }
     }
   }
 
   @override
   void visitNode(AstNode node) {
     // no suggestion by default
   }
 
@@ skipping 213 matching lines @@
   }
 
   bool _isEntityPrevTokenSynthetic() {
     Object entity = this.entity;
     if (entity is AstNode && entity.beginToken.previous?.isSynthetic ?? false) {
       return true;
     }
     return false;
   }
 }