Fix some parser issues related to generic functin types

pkg/analyzer/lib/src/dart/error/syntactic_errors.dart

Index: pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
diff --git a/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart b/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
index f4f53485f9bd1a03699f87bd7baded38bcd994db..c4b6f316e6d2ac3b6f9a7112290a5e506d8b0f20 100644
--- a/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
+++ b/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
@@ -455,6 +455,12 @@ class ParserErrorCode extends ErrorCode {
       "The keyword '{0}' cannot be used to name a constructor.",
       "Try giving the constructor a different name.");
 
+  static const ParserErrorCode INVALID_GENERIC_FUNCTION_TYPE =
+      const ParserErrorCode(
+          'INVALID_GENERIC_FUNCTION_TYPE',
+          "Invalid generic function type.",
+          "Try using a generic function type (returnType 'Function(' parameters ')').");
+
   static const ParserErrorCode INVALID_HEX_ESCAPE = const ParserErrorCode(
       'INVALID_HEX_ESCAPE',
       "An escape sequence starting with '\\x' must be followed by 2 hexidecimal digits.");