gistfile1.txt

pmichaud@kiwi:~/p6/rakudo$ git diff src/core/Range.pm
diff --git a/src/core/Range.pm b/src/core/Range.pm
index f94036a..6c061a6 100644
--- a/src/core/Range.pm
+++ b/src/core/Range.pm
@@ -1,3 +1,5 @@
+my class X::Range::InvalidArg { ... }
+
 class Range is Iterable is Cool does Positional {
     has $.min;
     has $.max;
@@ -23,7 +25,9 @@ class Range is Iterable is Cool does Positional {
     multi method new(Whatever $min, Whatever $max, :$excludes_min, :$excludes_m
         fail "*..* is not a valid range";
     }
-    
+    multi method new($min, Range $max, :$excludes_min, :$excludes_max) {
+        X::Range::InvalidArg.new(got => $max).throw;
+    }
 
     submethod BUILD($min, $max, $excludes_min, $excludes_max) {
         $!min = $min;