More support for generic function types

pkg/analyzer/lib/src/generated/error_verifier.dart

Index: pkg/analyzer/lib/src/generated/error_verifier.dart
diff --git a/pkg/analyzer/lib/src/generated/error_verifier.dart b/pkg/analyzer/lib/src/generated/error_verifier.dart
index adc6f11aaf184b71a80c82c019de5033fc8447a3..c9bcf4350f783862dabd312a0e328b48b4b93350 100644
--- a/pkg/analyzer/lib/src/generated/error_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -1403,7 +1403,12 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
   void _checkDuplicateDefinitionInParameterList(FormalParameterList node) {
     Map<String, Element> definedNames = new HashMap<String, Element>();
     for (FormalParameter parameter in node.parameters) {
-      _checkDuplicateIdentifier(definedNames, parameter.identifier);
+      SimpleIdentifier identifier = parameter.identifier;
+      if (identifier != null) {
+        // The identifier can be null if this is a parameter list for a generic
+        // function type.
+        _checkDuplicateIdentifier(definedNames, identifier);
+      }
     }
   }