Introduce ParameterStructure

pkg/compiler/lib/src/elements/entities.dart

 // Copyright (c) 2016, 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 entities;
 
 import '../common.dart';
 
 /// Abstract interface for entities.
 ///
@@ skipping 101 matching lines @@
 abstract class FieldEntity extends MemberEntity {}
 
 /// Stripped down super interface for function like entities.
 ///
 /// Currently only [MethodElement] but later also kernel based Dart constructors
 /// and methods and/or Dart-in-JS function-like properties.
 abstract class FunctionEntity extends MemberEntity {
   /// Whether this function is external, i.e. the body is not defined in terms
   /// of Dart code.
   bool get isExternal;
+
+  /// The structure of the function parameters.
+  ParameterStructure get parameterStructure;
 }
 
 /// Stripped down super interface for constructor like entities.
 ///
 /// Currently only [ConstructorElement] but later also kernel based Dart
 /// constructors and/or Dart-in-JS constructor-like properties.
 // TODO(johnniwinther): Remove factory constructors from the set of
 // constructors.
 abstract class ConstructorEntity extends FunctionEntity {
   /// Whether this is a generative constructor, possibly redirecting.
@@ skipping 19 matching lines @@
   Entity get executableContext;
 
   /// The outermost member that contains this element.
   ///
   /// For top level, static or instance members, the member context is the
   /// element itself. For parameters, local variables and nested closures, the
   /// member context is the top level, static or instance member in which it is
   /// defined.
   MemberEntity get memberContext;
 }
+
+/// The structure of function parameters.
+class ParameterStructure {
+  /// The number of required (positional) parameters.
+  final int requiredParameters;
+
+  /// The number of positional parameters.
+  final int positionalParameters;
+
+  /// The named parameters sorted alphabetically.
+  final List<String> namedParameters;
+
+  const ParameterStructure(
+      this.requiredParameters, this.positionalParameters, this.namedParameters);
+
+  const ParameterStructure.getter() : this(0, 0, const <String>[]);
+
+  const ParameterStructure.setter() : this(1, 1, const <String>[]);
+
+  /// The number of optional parameters (positional or named).
+  int get optionalParameters =>
+      positionalParameters - requiredParameters + namedParameters.length;
+}