Issue 24, drop output slot when not initializing. Un-XFAIL generic-tag.rs. Add test for output slot modes with several broken cases.

src/Makefile

@@ -321,7 +321,6 @@ TEST_XFAILS_X86 :=  test/run-pass/mlist-cycle.rs \
                     test/run-pass/vec-slice.rs \
                     test/run-pass/generic-fn-infer.rs \
                     test/run-pass/generic-recursive-tag.rs \
-                    test/run-pass/generic-tag.rs \
                     test/run-pass/bind-obj-ctor.rs \
                     test/run-pass/task-comm.rs \
                     test/compile-fail/rec-missing-fields.rs \
@@ -391,6 +390,7 @@ TEST_XFAILS_LLVM := $(addprefix test/run-pass/, \
                       obj-dtor.rs \
                       obj-with-vec.rs \
                       opeq.rs \
+                      output-slot-variants.rs \
                       preempt.rs \
                       pred.rs \
                       readalias.rs \

src/boot/me/trans.ml

@@ -3708,7 +3708,7 @@ let trans_visitor
 
 
   and trans_prepare_call
-      ((*initializing*)_:bool)
+      (initializing:bool)
       (logname:(unit -> string))
       (call:call)
       : Il.operand =
@@ -3718,11 +3718,15 @@ let trans_visitor
                (Printf.sprintf "copy args for call to %s" (logname ())));
       copy_fn_args false CLONE_none call;
       iflog (fun _ -> annotate (Printf.sprintf "call %s" (logname ())));
-      (* FIXME (issue #24): we need to actually handle writing to an
-       * already-initialised slot. Currently we blindly assume we're
-       * initializing, overwrite the slot; this is ok if we're writing
-       * to an interior output slot, but we'll leak any exteriors as we
-       * do that.  *)
+      if not initializing
+      then
+        begin
+          match call.call_callee_ty with
+              Ast.TY_fn (tsig, _) ->
+                drop_slot (get_ty_params_of_current_frame()) call.call_output
+                  tsig.Ast.sig_output_slot None;
+            | _ -> bug () "calling non-fn"
+        end;
       callee_fptr
 
   and callee_drop_slot

src/test/run-pass/output-slot-variants.rs

@@ -0,0 +1,58 @@
+fn ret_int_i() -> int {
+  ret 10;
+}
+
+fn ret_ext_i() -> @int {
+  ret 10;
+}
+
+fn ret_int_tup() -> tup(int,int) {
+  ret tup(10, 10);
+}
+
+fn ret_ext_tup() -> @tup(int,int) {
+  ret tup(10, 10);
+}
+
+fn ret_ext_mem() -> tup(@int, @int) {
+  ret tup(@10, @10);
+}
+
+fn ret_ext_ext_mem() -> @tup(@int, @int) {
+  ret tup(@10, @10);
+}
+
+fn main() {
+
+  let int int_i;
+  let @int ext_i;
+  let tup(int,int) int_tup;
+  let @tup(int,int) ext_tup;
+  let tup(@int,@int) ext_mem;
+  let @tup(@int,@int) ext_ext_mem;
+
+  int_i = ret_int_i(); // initializing
+  int_i = ret_int_i(); // non-initializing
+  int_i = ret_int_i(); // non-initializing
+
+  //ext_i = ret_ext_i(); // initializing
+  //ext_i = ret_ext_i(); // non-initializing
+  //ext_i = ret_ext_i(); // non-initializing
+
+  int_tup = ret_int_tup(); // initializing
+  int_tup = ret_int_tup(); // non-initializing
+  int_tup = ret_int_tup(); // non-initializing
+
+  //ext_tup = ret_ext_tup(); // initializing
+  //ext_tup = ret_ext_tup(); // non-initializing
+  //ext_tup = ret_ext_tup(); // non-initializing
+
+  ext_mem = ret_ext_mem(); // initializing
+  ext_mem = ret_ext_mem(); // non-initializing
+  ext_mem = ret_ext_mem(); // non-initializing
+
+  //ext_ext_mem = ret_ext_ext_mem(); // initializing
+  //ext_ext_mem = ret_ext_ext_mem(); // non-initializing
+  //ext_ext_mem = ret_ext_ext_mem(); // non-initializing
+
+}