Add support for the new function-type syntax.

pkg/compiler/lib/src/diagnostics/messages.dart

Index: pkg/compiler/lib/src/diagnostics/messages.dart
diff --git a/pkg/compiler/lib/src/diagnostics/messages.dart b/pkg/compiler/lib/src/diagnostics/messages.dart
index d9785c64cca93be434ed7b0bd0a89e4293362269..14c6961d5953c8c5c472d665d73b063ce26f6c8d 100644
--- a/pkg/compiler/lib/src/diagnostics/messages.dart
+++ b/pkg/compiler/lib/src/diagnostics/messages.dart
@@ -275,6 +275,7 @@ enum MessageKind {
   INVALID_RECEIVER_IN_INITIALIZER,
   INVALID_SOURCE_FILE_LOCATION,
   INVALID_SYMBOL,
+  INVALID_INLINE_FUNCTION_TYPE,
   INVALID_SYNC_MODIFIER,
   INVALID_TYPE_VARIABLE_BOUND,
   INVALID_UNNAMED_CONSTRUCTOR_NAME,
@@ -3319,6 +3320,15 @@ Please include the following information:
           " require a preamble file located in:\n"
           "  <sdk>/lib/_internal/js_runtime/lib/preambles."),
 
+      MessageKind.INVALID_INLINE_FUNCTION_TYPE: const MessageTemplate(
+          MessageKind.INVALID_INLINE_FUNCTION_TYPE,
+          "Invalid inline function type.",
+          howToFix: "Try changing the inline function type (as in 'int f()') to"
+             " a prefixed function type using the `Function` keyword (as in "
+             "'int Function() f').",
+          examples: const ["typedef F = Function(int f(String x))"],
+      ),
+
       MessageKind.INVALID_SYNC_MODIFIER: const MessageTemplate(
           MessageKind.INVALID_SYNC_MODIFIER, "Invalid modifier 'sync'.",
           howToFix: "Try replacing 'sync' with 'sync*'.",