move functional argument check into manager

pkg/analysis_server/lib/src/provisional/completion/dart/completion_target.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 analysis_server.src.provisional.completion.dart.completion_target;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/scanner.dart';
@@ skipping 247 matching lines @@
     }
     if (node is MethodInvocation) {
       return node.isCascaded && offset > node.operator.offset + 1;
     }
     return false;
   }
 
   /**
    * Return `true` if the target is a functional argument in an argument list.
    * The target [AstNode] hierarchy *must* be resolved for this to work.
+   * See [maybeFunctionalArgument].
    */
   bool isFunctionalArgument() {
     if (!maybeFunctionalArgument()) {
       return false;
     }
     AstNode parent = containingNode.parent;
     if (parent is InstanceCreationExpression) {
       DartType instType = parent.bestType;
       if (instType != null) {
         Element intTypeElem = instType.element;
@@ skipping 14 matching lines @@
           return _isFunctionalParameter(methodElem.parameters, argIndex);
         } else if (methodElem is FunctionElement) {
           return _isFunctionalParameter(methodElem.parameters, argIndex);
         }
       }
     }
     return false;
   }
 
   /**
-   * Return `true` if the target is a functional argument in an argument list.
-   * The target [AstNode] hierarchy *must* be resolved for this to work.
+   * Return `true` if the target maybe a functional argument in an argument list.
+   * This is used in determining whether the target [AstNode] hierarchy
+   * needs to be resolved so that [isFunctionalArgument] will work.
    */
   bool maybeFunctionalArgument() {
     if (argIndex == null) {
       return false;
     }
     AstNode argList = containingNode;
     if (argList is! ArgumentList) {
       return false;
     }
     return true;
@@ skipping 100 matching lines @@
       if (param.parameterKind == ParameterKind.NAMED) {
         // TODO(danrubel) handle named parameters
         return false;
       } else {
         return paramType is FunctionType || paramType is FunctionTypeAlias;
       }
     }
     return false;
   }
 }