Implement generalized function types.

pkg/front_end/lib/src/fasta/parser/identifier_context.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.
 
 /// Information about the parser state which is passed to the listener at the
 /// time an identifier is encountered.
 ///
 /// This can be used by the listener to determine the context in which the
 /// identifier appears; that in turn can help the listener decide how to resolve
 /// the identifier (if the listener is doing resolution).
@@ skipping 95 matching lines @@
   static const classDeclaration = const IdentifierContext._('classDeclaration',
       inDeclaration: true, isBuiltInIdentifierAllowed: false);
 
   /// Identifier is the name of a type variable being declared (e.g. `Foo` in
   /// `class C<Foo extends num> {}`).
   static const typeVariableDeclaration = const IdentifierContext._(
       'typeVariableDeclaration',
       inDeclaration: true,
       isBuiltInIdentifierAllowed: false);
 
+  /// Identifier is the start of a reference to a type that starts with prefix.
+  static const prefixedTypeReference = const IdentifierContext._(
+      'prefixedTypeReference',
+      isScopeReference: true,
+      isBuiltInIdentifierAllowed: true);
+
   /// Identifier is the start of a reference to a type declared elsewhere.
   static const typeReference = const IdentifierContext._('typeReference',
       isScopeReference: true, isBuiltInIdentifierAllowed: false);
 
   /// Identifier is part of a reference to a type declared elsewhere, but it's
   /// not the first identifier of the reference.
   static const typeReferenceContinuation = const IdentifierContext._(
       'typeReferenceContinuation',
       isContinuation: true,
       isBuiltInIdentifierAllowed: false);
@@ skipping 163 matching lines @@
       bool allowedInConstantExpression})
       : this.allowedInConstantExpression =
             // Generally, declarations are legal in constant expressions.  A
             // continuation doesn't affect constant expressions: if what it's
             // continuing is a problem, it has already been reported.
             allowedInConstantExpression ??
                 (inDeclaration || isContinuation || inSymbol);
 
   String toString() => _name;
 }