fixes #27586, prefer context type in generic inference

pkg/analyzer/lib/src/summary/fasta/summary_builder.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.
 
 /// Logic to build unlinked summaries.
 library summary.src.summary_builder;
 
 import 'package:front_end/src/fasta/parser/class_member_parser.dart';
 import 'package:front_end/src/fasta/parser/identifier_context.dart';
 import 'package:front_end/src/fasta/parser/parser.dart';
@@ skipping 1418 matching lines @@
 
   void handleModifier(Token token) {
     debugEvent("Modifier");
     var modifier = _modifierFlag[token.stringValue];
     if (modifier & _const_flag != 0) inConstContext = true;
     push(modifier);
   }
 
   void handleModifiers(int count) {
     debugEvent("Modifiers");
-    push((popList(count) ?? const []).fold(0, (a, b) => a | b));
+    push((popList(count) ?? const []).fold/*<int>*/(0, (a, b) => a | b));
   }
 
   void handleNoConstructorReferenceContinuationAfterTypeArguments(Token token) {
     debugEvent("NoConstructorReferenceContinuationAfterTypeArguments");
   }
 
   void handleNoFieldInitializer(Token token) {
     debugEvent("NoFieldInitializer");
     push(new _InitializedName(pop(), null));
   }
@@ skipping 140 matching lines @@
 }
 
 /// Internal representation of an initialized name.
 class _InitializedName {
   final String name;
   final UnlinkedExecutableBuilder initializer;
   _InitializedName(this.name, this.initializer);
 
   toString() => "II:" + (initializer != null ? "$name = $initializer" : name);
 }