Fix VM to accept literal function type as type bound (fixes #29481).

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index c5cc870457d1efca83ec37264fff7e6e32a7a5cb..7309990bcb0eae5e79b48a8ca6f0442027079bb5 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -5626,7 +5626,8 @@ void Parser::ParseTypeParameters(bool parameterizing_class) {
         // i.e. to the class or function currently being parsed.
         // Postpone resolution in order to avoid resolving the owner and its
         // type parameters, as they are not fully parsed yet.
-        type_parameter_bound = ParseType(ClassFinalizer::kDoNotResolve);
+        type_parameter_bound =
+            ParseTypeOrFunctionType(false, ClassFinalizer::kDoNotResolve);
         if (is_lower_bound) {
           // TODO(regis): Handle 'super' differently than 'extends' if lower
           // bounds make it in the final specification and if run time support