Propertly summarize LUB function types.

pkg/analyzer/lib/src/summary/idl.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.
 
 /**
  * This file is an "idl" style description of the summary format.  It
  * contains abstract classes which declare the interface for reading data from
  * summaries.  It is parsed and transformed into code that implements the
  * summary format.
  *
@@ skipping 104 matching lines @@
    * If this [EntityRef] is contained within [LinkedUnit.types], slot id (which
    * is unique within the compilation unit) identifying the target of type
    * propagation or type inference with which this [EntityRef] is associated.
    *
    * Otherwise zero.
    */
   @Id(2)
   int get slot;
 
   /**
+   * If this [EntityRef] is a reference to a function type whose
+   * [FunctionElement] is not in any library (e.g. a function type that was
+   * synthesized by a LUB computation), the function parameters.  Otherwise
+   * empty.
+   */
+  @Id(6)
+  List<UnlinkedParam> get syntheticParams;
+
+  /**
+   * If this [EntityRef] is a reference to a function type whose
+   * [FunctionElement] is not in any library (e.g. a function type that was
+   * synthesized by a LUB computation), the return type of the function.
+   * Otherwise `null`.
+   */
+  @Id(5)
+  EntityRef get syntheticReturnType;
+
+  /**
    * If this is an instantiation of a generic type or generic executable, the
    * type arguments used to instantiate it.  Trailing type arguments of type
    * `dynamic` are omitted.
    */
   @Id(1)
   List<EntityRef> get typeArguments;
 }
 
 /**
  * Enum used to indicate the kind of index relation.
@@ skipping 1989 matching lines @@
    */
   @Id(11)
   int get visibleLength;
 
   /**
    * If a local variable, the beginning of the visible range; zero otherwise.
    */
   @Id(12)
   int get visibleOffset;
 }