runtime: move turns discard into UVar (fix #30)

LPCIC · Aug 19, 2019 · 3016e45 · 3016e45
1 parent 6c45d05
commit 3016e45
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Showing 3 changed files with 14 additions and 1 deletion.
diff --git a/src/runtime.ml b/src/runtime.ml
@@ -731,7 +731,9 @@ let rec move ~adepth:argsdepth e ?avoid ?(depth=0) ~from ~to_ t =
        let tl' = maux e depth tl in
        if hd == hd' && tl == tl' then x else Cons(hd',tl')
     | Nil -> x
-    | Discard -> x
+    | Discard ->
+       let r = oref C.dummy in
+       UVar(r,to_,0)
 
     (* fast path with no deref... *)
     | UVar _ when delta == 0 && avoid == None -> x

diff --git a/tests/sources/heap_discard.elpi b/tests/sources/heap_discard.elpi
@@ -0,0 +1,4 @@
+main :-
+  X = [_,2],
+  X = [1,2],
+  not(X = [2,2]).
diff --git a/tests/suite/elpi_specific.ml b/tests/suite/elpi_specific.ml
@@ -184,3 +184,10 @@ let () = declare "list_comma"
   ~typecheck:true
   ~expectation:Test.Success
   ()
+
+let () = declare "heap_discard"
+  ~source_elpi:"heap_discard.elpi"
+  ~description:"heapification of _"
+  ~typecheck:true
+  ~expectation:Test.Success
+  ()