refactor World.rethrow a bit

you can now throw typed exceptions without file/line information, and have World.ex-handle add them for you
previously only untyped exceptions were supported, and wrapped into X::Comp::AdHoc.
arnsholt++ for poking me

src/Perl6/World.pm

@@ -1964,16 +1964,31 @@ class Perl6::World is HLL::World {
         my $success := 0;
         my $ex_t;
         my $coercer;
-        try { $ex_t := self.find_symbol(['X', 'Comp', 'AdHoc']); $success := 1 };
         try { $coercer := self.find_symbol(['&COMP_EXCEPTION']); ++$success; };
-        $err.rethrow unless $success == 2;
-        my $p6ex    := $coercer($err);
-        nqp::bindattr($p6ex, $ex_t, '$!filename',
+        nqp::rethrow($err) unless $success;
+        my $p6ex := $coercer($err);
+        try {
+            $ex_t := self.find_symbol(['X', 'Comp']);
+            if nqp::istype($p6ex, $err) {
+                $p6ex.SET_FILE_LINE(
+                    nqp::box_s(pir::find_caller_lex__ps('$?FILES'),
+                        self.find_symbol(['Str'])),
+                    nqp::box_i(HLL::Compiler.lineof($/.orig, $/.from),
+                        self.find_symbol(['Int'])),
+                );
+                $success++;
+            }
+        }
+        $p6ex.rethrow if $success == 2;
+        $success := 0;
+        try { $ex_t := self.find_symbol(['X', 'Comp', 'AdHoc']); ++$success };
+        $p6ex.rethrow unless $success;
+        $p6ex.SET_FILE_LINE(
             nqp::box_s(pir::find_caller_lex__ps('$?FILES'),
-                self.find_symbol(['Str'])));
-        nqp::bindattr($p6ex, $ex_t, '$!line',
+                self.find_symbol(['Str'])),
             nqp::box_i(HLL::Compiler.lineof($/.orig, $/.from),
-                self.find_symbol(['Int'])));
+                self.find_symbol(['Int'])),
+        );
         $p6ex.rethrow();
     }
 }

src/core/Exception.pm

@@ -313,6 +313,10 @@ my role X::Comp is Exception {
         }
         $r;
     }
+    method SET_FILE_LINE($file, $line) {
+        $!filename = $file;
+        $!line     = $line;
+    }
 }
 
 # XXX a hack for getting line numbers from exceptions from the metamodel