Turn new into a multi. Add a candidate that dies if you try to give p…

…ositional arguments. Update bless so it can take * as an initial parameter and create a candidate; inline this rather than calling .CREATE and use it in .new, thus saving a method invocation per .new call.

src/core/Mu.pm

@@ -21,16 +21,25 @@ my class Mu {
         nqp::p6bool(pir::repr_defined__IP(self))
     }
 
-    method new(*%attrinit) {
-        self.bless(self.CREATE(), |%attrinit);
+    proto method new(|$) { * }
+    multi method new(*%attrinit) {
+        self.bless(*, |%attrinit);
+    }
+    multi method new($, *@) {
+        die "Default constructor only takes named arguments";
     }
 
     method CREATE() {
         nqp::create(self)
     }
 
-    method bless(Mu \$candidate, *%attrinit) {
-        $candidate
+    method bless(Mu \$candidate, *@autovivs, *%attrinit) {
+        # If we were passed *, then need to create a candidate.
+        my $cand := nqp::istype($candidate, Whatever) ??
+            nqp::create(self) !!
+            $candidate;
+
+        $cand
     }
 
    proto method Numeric(|$) { * }