Parse optional and named parameters.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 7b8635ea37df82a656c7e6c05e3d68939fdf1723..2bdb4dc61e15d29ccb9acf4a9dbde209f25bd6cc 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -1275,7 +1275,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   @override
-  void endFormalParameter(Token thisKeyword) {
+  void endFormalParameter(Token thisKeyword, FormalParameterType kind) {
     debugEvent("FormalParameter");
     // TODO(ahe): Need beginToken here.
     int charOffset = thisKeyword?.charOffset;
@@ -1362,6 +1362,11 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   @override
+  void handleFormalParameterWithoutValue(Token token) {
+    debugEvent("FormalParameterWithoutValue");
+  }
+
+  @override
   void endFormalParameters(int count, Token beginToken, Token endToken) {
     debugEvent("FormalParameters");
     OptionalFormals optional;