add a contains_managed intrinsic

Author: thestinger

src/librustc/middle/trans/foreign.rs

@@ -751,6 +751,12 @@ pub fn trans_intrinsic(ccx: @mut CrateContext,
                   C_bool(ty::type_needs_drop(ccx.tcx, tp_ty)),
                   fcx.llretptr.get());
         }
+        "contains_managed" => {
+            let tp_ty = substs.tys[0];
+            Store(bcx,
+                  C_bool(ty::type_contents(ccx.tcx, tp_ty).contains_managed()),
+                  fcx.llretptr.get());
+        }
         "visit_tydesc" => {
             let td = get_param(decl, first_real_arg);
             let visitor = get_param(decl, first_real_arg + 1u);

src/librustc/middle/trans/type_use.rs

@@ -127,7 +127,7 @@ pub fn type_uses_for(ccx: @mut CrateContext, fn_id: def_id, n_tps: uint)
                     "uninit"   | "init" | "transmute" | "move_val" |
                     "move_val_init" => use_repr,
 
-                    "get_tydesc" | "needs_drop" => use_tydesc,
+                    "get_tydesc" | "needs_drop" | "contains_managed" => use_tydesc,
 
                     "visit_tydesc"  | "forget" | "frame_address" |
                     "morestack_addr" => 0,

src/librustc/middle/typeck/check/mod.rs

@@ -3540,7 +3540,7 @@ pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
                ty::mk_nil())
             }
             "needs_drop" => (1u, ~[], ty::mk_bool()),
-
+            "contains_managed" => (1u, ~[], ty::mk_bool()),
             "atomic_xchg"     | "atomic_xadd"     | "atomic_xsub"     |
             "atomic_xchg_acq" | "atomic_xadd_acq" | "atomic_xsub_acq" |
             "atomic_xchg_rel" | "atomic_xadd_rel" | "atomic_xsub_rel" => {

src/libstd/unstable/intrinsics.rs

@@ -308,6 +308,10 @@ pub extern "rust-intrinsic" {
     /// Returns `true` if a type requires drop glue.
     pub fn needs_drop<T>() -> bool;
 
+    /// Returns `true` if a type is managed (will be allocated on the local heap)
+    #[cfg(not(stage0))]
+    pub fn contains_managed<T>() -> bool;
+
     #[cfg(not(stage0))]
     pub fn visit_tydesc(td: *TyDesc, tv: @TyVisitor);