Support multiple optional parameters.

pkg/front_end/lib/src/fasta/analyzer/ast_builder.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 fasta.analyzer.ast_builder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' as analyzer show Token;
@@ skipping 469 matching lines @@
 
   void endThrowExpression(Token throwToken, Token endToken) {
     debugEvent("ThrowExpression");
     push(ast.throwExpression(toAnalyzerToken(throwToken), pop()));
   }
 
   @override
   void endOptionalFormalParameters(
       int count, Token beginToken, Token endToken) {
     debugEvent("OptionalFormalParameters");
+    push(new _OptionalFormalParameters(popList(count), beginToken, endToken));
   }
 
   void handleValuedFormalParameter(Token equals, Token token) {
     debugEvent("ValuedFormalParameter");
     Expression value = pop();
     push(new _ParameterDefaultValue(equals, value));
   }
 
   void handleFormalParameterWithoutValue(Token token) {
     debugEvent("FormalParameterWithoutValue");
@@ skipping 38 matching lines @@
       node = ast.defaultFormalParameter(node, _toAnalyzerParameterKind(kind),
           toAnalyzerToken(defaultValue.separator), defaultValue.value);
     }
 
     scope[name.name] = name.staticElement = new AnalyzerParameterElement(node);
     push(node);
   }
 
   void endFormalParameters(int count, Token beginToken, Token endToken) {
     debugEvent("FormalParameters");
-    List<FormalParameter> parameters = popList(count) ?? <FormalParameter>[];
-    push(ast.formalParameterList(toAnalyzerToken(beginToken), parameters, null,
-        null, toAnalyzerToken(endToken)));
+    List rawParameters = popList(count) ?? const <Object>[];
+    List<FormalParameter> parameters = <FormalParameter>[];
+    Token leftDelimiter;
+    Token rightDelimiter;
+    for (Object raw in rawParameters) {
+      if (raw is _OptionalFormalParameters) {
+        parameters.addAll(raw.parameters);
+        leftDelimiter = raw.leftDelimiter;
+        rightDelimiter = raw.rightDelimiter;
+      } else {
+        parameters.add(raw as FormalParameter);
+      }
+    }
+    push(ast.formalParameterList(
+        toAnalyzerToken(beginToken),
+        parameters,
+        toAnalyzerToken(leftDelimiter),
+        toAnalyzerToken(rightDelimiter),
+        toAnalyzerToken(endToken)));
   }
 
   void handleCatchBlock(Token onKeyword, Token catchKeyword) {
     debugEvent("CatchBlock");
     Block body = pop();
     FormalParameterList catchParameters = popIfNotNull(catchKeyword);
     if (catchKeyword != null) {
       exitLocalScope();
     }
     TypeName type = popIfNotNull(onKeyword);
@@ skipping 700 matching lines @@
 }
 
 /// Data structure placed on the stack to represent the default parameter
 /// value with the separator token.
 class _ParameterDefaultValue {
   final Token separator;
   final Expression value;
 
   _ParameterDefaultValue(this.separator, this.value);
 }
+
+/// Data structure placed on the stack as a container for optional parameters.
+class _OptionalFormalParameters {
+  final List<FormalParameter> parameters;
+  final Token leftDelimiter;
+  final Token rightDelimiter;
+
+  _OptionalFormalParameters(
+      this.parameters, this.leftDelimiter, this.rightDelimiter);
+}