A Failure that throws counts as handled.

This means fatalized Failures will not report themselves as leaked.

src/core/Failure.pm

@@ -14,6 +14,12 @@ my class Failure {
     # "Shouldn't happen."  We use note here because the dynamic scope in GC is likely meaningless.
     submethod DESTROY () { if not $!handled { note "WARNING: unhandled Failure detected in DESTROY:\n" ~ self.mess } }
 
+    # Marks the Failure has handled (since we're now fatalizing it) and throws.
+    method !throw() {
+        $!handled = 1;
+        $!exception.throw($!backtrace);
+    }
+
     # Turns out multidimensional lookups are one way to leak unhandled failures, so
     # we'll just propagate the initial failure much as we propagate Nil on methods.
     method AT-POS(|) { self }
@@ -23,28 +29,28 @@ my class Failure {
     # but obscure problems prevent us from making Mu.defined
     # a multi. See http://irclog.perlgeek.de/perl6/2011-06-28#i_4016747
     method defined() {
-        $!handled =1 if nqp::isconcrete(self);
+        $!handled = 1 if nqp::isconcrete(self);
         Bool::False;
     }
     multi method Bool(Failure:D:) { $!handled = 1; Bool::False; }
 
-    method Int(Failure:D:)        { $!handled ?? 0   !! $!exception.throw($!backtrace); }
-    method Num(Failure:D:)        { $!handled ?? 0e0 !! $!exception.throw($!backtrace); }
-    method Numeric(Failure:D:)    { $!handled ?? 0e0 !! $!exception.throw($!backtrace); }
-    multi method Str(Failure:D:)  { $!handled ?? ''  !! $!exception.throw($!backtrace); }
-    multi method gist(Failure:D:) { $!handled ?? $.mess !! $!exception.throw($!backtrace); }
+    method Int(Failure:D:)        { $!handled ?? 0   !! self!throw(); }
+    method Num(Failure:D:)        { $!handled ?? 0e0 !! self!throw(); }
+    method Numeric(Failure:D:)    { $!handled ?? 0e0 !! self!throw(); }
+    multi method Str(Failure:D:)  { $!handled ?? ''  !! self!throw(); }
+    multi method gist(Failure:D:) { $!handled ?? $.mess !! self!throw(); }
     method mess (Failure:D:) {
         self.exception.message ~ "\n" ~ self.backtrace;
     }
 
     method sink() {
-        $!exception.throw($!backtrace) unless $!handled
+        self!throw() unless $!handled
     }
     method CALL-ME(|) {
-        $!exception.throw($!backtrace)
+        self!throw()
     }
     method FALLBACK(*@) {
-        $!exception.throw($!backtrace)
+        self!throw()
     }
 }