More likely to get a mismatch on named/unnamed

Than it is to get one on sub signature/no sub signature.  So let's
test the named part first.

src/core/Parameter.pm

@@ -196,19 +196,6 @@ my class Parameter { # declared in BOOTSTRAP
             return False;
         }
 
-        # we have sub sig and not the same
-        my $osub_signature := nqp::getattr(o,Parameter,'$!sub_signature');
-        if $!sub_signature {
-            return False
-              unless $osub_signature
-              && $!sub_signature.ACCEPTS($osub_signature);
-        }
-
-        # no sub sig, but other has one
-        elsif $osub_signature {
-            return False;
-        }
-
         # have nameds here
         my $onamed_names := nqp::getattr(o,Parameter,'$!named_names');
         if $!named_names {
@@ -241,6 +228,19 @@ my class Parameter { # declared in BOOTSTRAP
             return False;
         }
 
+        # we have sub sig and not the same
+        my $osub_signature := nqp::getattr(o,Parameter,'$!sub_signature');
+        if $!sub_signature {
+            return False
+              unless $osub_signature
+              && $!sub_signature.ACCEPTS($osub_signature);
+        }
+
+        # no sub sig, but other has one
+        elsif $osub_signature {
+            return False;
+        }
+
         # we have a post constraint
         if nqp::islist($!post_constraints) {