A very first-cut implementation of lastcall, which just trims the can…

…didate list such that nextsame and friends will find nothing else to defer to.

src/builtins/control.pir

@@ -517,6 +517,21 @@ on error.
 .end
 
 
+=item lastcall
+
+Trims the candidate list so that nextsame/nextwith/callsame/callwith will
+find nothing more to call.
+
+=cut
+
+.sub 'lastcall'
+    # Find candidate list and trim it.
+    .local pmc clist
+    get_next_candidate_info clist, $P0, $P1
+    clist.'trim_candidate_list'()
+.end
+
+
 =item !get_original_args
 
 Helper for callsame and nextsame that uses the signature and lexpad of a

src/pmc/p6invocation.pmc

@@ -249,4 +249,14 @@ pmclass P6Invocation need_ext dynpmc group perl6_group {
         PMC *result = VTABLE_shift_pmc(interp, SELF);
         RETURN(PMC *result);
     }
+
+    METHOD void trim_candidate_list() {
+        /* Just blank out everything we could use to find another
+         * method. */
+        SETATTR_P6Invocation_candidate_list(interp, SELF, PMCNULL);
+        SETATTR_P6Invocation_position(interp, SELF, 0);
+        SETATTR_P6Invocation_name(interp, SELF, NULL);
+        SETATTR_P6Invocation_search_list(interp, SELF, PMCNULL);
+        SETATTR_P6Invocation_resume_point(interp, SELF, 0);
+    }
 }