suggest "this." local fields in constructor param

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

Index: pkg/analysis_server/lib/src/services/completion/prefixed_element_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/prefixed_element_contributor.dart b/pkg/analysis_server/lib/src/services/completion/prefixed_element_contributor.dart
index cb6ccf42fd1604791458245f2087cc2ae03cedd4..b878cb663f3da2f8a5f029dc6948eaa3627cd7ff 100644
--- a/pkg/analysis_server/lib/src/services/completion/prefixed_element_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/prefixed_element_contributor.dart
@@ -8,14 +8,15 @@ import 'dart:async';
 
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analysis_server/src/services/completion/local_declaration_visitor.dart';
+import 'package:analysis_server/src/services/completion/local_suggestion_builder.dart';
 import 'package:analysis_server/src/services/completion/optype.dart';
 import 'package:analysis_server/src/services/completion/suggestion_builder.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 
-import '../../protocol_server.dart' as protocol;
 import '../../protocol_server.dart'
     show CompletionSuggestion, CompletionSuggestionKind;
+import '../../protocol_server.dart' as protocol;
 
 /**
  * A contributor for calculating invocation / access suggestions
@@ -80,6 +81,72 @@ class _ExpressionSuggestionBuilder implements SuggestionBuilder {
 }
 
 /**
+ * A suggestion builder for 'this.' constructor arguments.
+ */
+class _FieldFormalSuggestionBuilder implements SuggestionBuilder {
+  final DartCompletionRequest request;
+
+  _FieldFormalSuggestionBuilder(this.request);
+
+  @override
+  bool computeFast(AstNode node) {
+    if (node is FieldFormalParameter) {
+
+      // Compute fields already referenced
+      ConstructorDeclaration constructorDecl =
+          node.getAncestor((p) => p is ConstructorDeclaration);
+      List<String> referencedFields = new List<String>();
+      for (FormalParameter param in constructorDecl.parameters.parameters) {
+        if (param is FieldFormalParameter) {
+          SimpleIdentifier fieldId = param.identifier;
+          if (fieldId != null && fieldId != request.target.entity) {
+            String fieldName = fieldId.name;
+            if (fieldName != null && fieldName.length > 0) {
+              referencedFields.add(fieldName);
+            }
+          }
+        }
+      }
+
+      // Add suggestions for fields that are not already referenced
+      ClassDeclaration classDecl =
+          constructorDecl.getAncestor((p) => p is ClassDeclaration);
+      for (ClassMember member in classDecl.members) {
+        if (member is FieldDeclaration) {
+          for (VariableDeclaration varDecl in member.fields.variables) {
+            SimpleIdentifier fieldId = varDecl.name;
+            if (fieldId != null) {
+              String fieldName = fieldId.name;
+              if (fieldName != null && fieldName.length > 0) {
+                if (!referencedFields.contains(fieldName)) {
+                  CompletionSuggestion suggestion =
+                      createFieldSuggestion(member, varDecl);
+                  if (suggestion != null) {
+                    request.addSuggestion(suggestion);
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    } else {
+      // This should never be called with a case not handled above.
+      assert(false);
+    }
+    return true;
+  }
+
+  @override
+  Future<bool> computeFull(AstNode node) {
+    // This should never be called; we should always be able to compute
+    // suggestions and return true in computeFast method.
+    assert(false);
+    return null;
+  }
+}
+
+/**
  * An [AstNode] vistor for determining which suggestion builder
  * should be used to build invocation/access suggestions.
  */
@@ -96,6 +163,11 @@ class _InvocationAstVisitor extends GeneralizingAstVisitor<SuggestionBuilder> {
   }
 
   @override
+  SuggestionBuilder visitFieldFormalParameter(FieldFormalParameter node) {
+    return new _FieldFormalSuggestionBuilder(request);
+  }
+
+  @override
   SuggestionBuilder visitMethodInvocation(MethodInvocation node) {
     return new _ExpressionSuggestionBuilder(request);
   }