disallow.diff

diff --git a/src/core/traits.pm b/src/core/traits.pm
index c0e961a..e4d70fe 100644
--- a/src/core/traits.pm
+++ b/src/core/traits.pm
@@ -187,6 +187,18 @@ multi sub trait_mod:<is>(Routine $r, :&tighter!) {
     }
     $r.prec<prec> := $r.prec<prec>.subst(/\=/, '@=');
     $r.prec<assoc>:delete;
+    if $r.prec<prec> le 'w=' {
+        my $name := $r.name;
+        if $name.starts-with('prefix:') {
+            die 'Precedence of a prefix must be tighter then any infix'
+        }
+        elsif $name.starts-with('postfix:') {
+            die 'Precedence of a postfix must be tighter then any infix'
+        }
+        elsif $name.starts-with('postcircumfix:') {
+            die 'Precedence of a postcircumfix must be tighter then any infix'
+        }
+    }
 }
 multi sub trait_mod:<is>(Routine $r, :&looser!) {
     die "Routine given to looser does not appear to be an operator"
@@ -196,6 +208,18 @@ multi sub trait_mod:<is>(Routine $r, :&looser!) {
     }
     $r.prec<prec> := $r.prec<prec>.subst(/\=/, ':=');
     $r.prec<assoc>:delete;
+    if $r.prec<prec> le 'w=' {
+        my $name := $r.name;
+        if $name.starts-with('prefix:') {
+            die 'Precedence of a prefix must be tighter then any infix'
+        }
+        elsif $name.starts-with('postfix:') {
+            die 'Precedence of a postfix must be tighter then any infix'
+        }
+        elsif $name.starts-with('postcircumfix:') {
+            die 'Precedence of a postcircumfix must be tighter then any infix'
+        }
+    }
 }
 multi sub trait_mod:<is>(Routine $r, :$assoc!) {
     trait_mod:<is>($r, :prec({ :$assoc }))