Don't unbox types in ty::is_binopable, do it on typeck side instead

Closes issue #631

Removes ty::strip_boxes entirely, since unboxing is now more complicated
anyway.

Author: marijnh

src/comp/middle/ty.rs

@@ -2897,20 +2897,6 @@ fn ret_ty_of_fn(ctxt cx, ast::node_id id) -> t {
     ret ret_ty_of_fn_ty(cx, node_id_to_type(cx, id));
 }
 
-
-// NB: This function requires that the given type has no variables. So, inside
-// typeck, you should use typeck::do_autoderef() instead.
-fn strip_boxes(&ctxt cx, &ty::t t) -> ty::t {
-    auto t1 = t;
-    while (true) {
-        alt (struct(cx, t1)) {
-            case (ty::ty_box(?inner)) { t1 = inner.ty; }
-            case (_) { ret t1; }
-        }
-    }
-    fail;
-}
-
 fn is_binopable(&ctxt cx, t ty, ast::binop op) -> bool {
 
     const int tycat_other = 0;
@@ -2955,7 +2941,7 @@ fn is_binopable(&ctxt cx, t ty, ast::binop op) -> bool {
     }
 
     fn tycat(&ctxt cx, t ty) -> int {
-        alt (struct(cx, strip_boxes(cx, ty))) {
+        alt (struct(cx, ty)) {
             case (ty_bool) { tycat_bool }
             case (ty_int) { tycat_int }
             case (ty_uint) { tycat_int }

src/comp/middle/typeck.rs

@@ -1620,7 +1620,8 @@ fn check_expr(&@fn_ctxt fcx, &@ast::expr expr) {
             auto rhs_t = expr_ty(fcx.ccx.tcx, rhs);
 
             demand::autoderef(fcx, rhs.span, lhs_t, rhs_t, AUTODEREF_OK);
-            check_binop_type_compat(fcx, expr.span, lhs_t, binop);
+            auto deref_t = do_autoderef(fcx, expr.span, lhs_t);
+            check_binop_type_compat(fcx, expr.span, deref_t, binop);
 
             auto t = alt (binop) {
                 case (ast::eq) { ty::mk_bool(fcx.ccx.tcx) }
@@ -1629,7 +1630,7 @@ fn check_expr(&@fn_ctxt fcx, &@ast::expr expr) {
                 case (ast::ne) { ty::mk_bool(fcx.ccx.tcx) }
                 case (ast::ge) { ty::mk_bool(fcx.ccx.tcx) }
                 case (ast::gt) { ty::mk_bool(fcx.ccx.tcx) }
-                case (_) { do_autoderef(fcx, expr.span, lhs_t) }
+                case (_) { deref_t }
             };
             write::ty_only_fixup(fcx, id, t);
         }