introduce DropckOutlives type-op

src/librustc_mir/borrow_check/nll/type_check/liveness.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 use borrow_check::nll::region_infer::Cause;
-use borrow_check::nll::type_check::type_op::CustomTypeOp;
+use borrow_check::nll::type_check::type_op::DropckOutlives;
 use borrow_check::nll::type_check::AtLocation;
 use dataflow::move_paths::{HasMoveData, MoveData};
 use dataflow::MaybeInitializedPlaces;
@@ -17,7 +17,6 @@ use dataflow::{FlowAtLocation, FlowsAtLocation};
 use rustc::infer::region_constraints::RegionConstraintData;
 use rustc::mir::Local;
 use rustc::mir::{BasicBlock, Location, Mir};
-use rustc::traits::ObligationCause;
 use rustc::ty::subst::Kind;
 use rustc::ty::{Ty, TypeFoldable};
 use rustc_data_structures::fx::FxHashMap;
@@ -217,15 +216,11 @@ impl<'gen, 'typeck, 'flow, 'gcx, 'tcx> TypeLivenessGenerator<'gen, 'typeck, 'flo
     ) -> DropData<'tcx> {
         debug!("compute_drop_data(dropped_ty={:?})", dropped_ty,);
 
+        let param_env = cx.param_env;
         let (dropped_kinds, region_constraint_data) =
-            cx.fully_perform_op_and_get_region_constraint_data(CustomTypeOp::new(
-                |cx| {
-                    Ok(cx
-                        .infcx
-                        .at(&ObligationCause::dummy(), cx.param_env)
-                        .dropck_outlives(dropped_ty))
-                },
-                || format!("compute_drop_data(dropped_ty={:?})", dropped_ty),
+            cx.fully_perform_op_and_get_region_constraint_data(DropckOutlives::new(
+                param_env,
+                dropped_ty,
             )).unwrap();
 
         DropData {

src/librustc_mir/borrow_check/nll/type_check/type_op.rs

@@ -13,6 +13,7 @@ use rustc::infer::{InferCtxt, InferOk, InferResult};
 use rustc::traits::query::NoSolution;
 use rustc::traits::{Normalized, Obligation, ObligationCause, PredicateObligation};
 use rustc::ty::fold::TypeFoldable;
+use rustc::ty::subst::Kind;
 use rustc::ty::{ParamEnv, Predicate, Ty};
 use std::fmt;
 
@@ -242,3 +243,32 @@ where
         Ok(InferOk { value, obligations })
     }
 }
+
+#[derive(Debug)]
+pub(super) struct DropckOutlives<'tcx> {
+    param_env: ParamEnv<'tcx>,
+    dropped_ty: Ty<'tcx>,
+}
+
+impl<'tcx> DropckOutlives<'tcx> {
+    pub(super) fn new(
+        param_env: ParamEnv<'tcx>,
+        dropped_ty: Ty<'tcx>,
+    ) -> Self {
+        DropckOutlives { param_env, dropped_ty }
+    }
+}
+
+impl<'gcx, 'tcx> InfcxTypeOp<'gcx, 'tcx> for DropckOutlives<'tcx> {
+    type Output = Vec<Kind<'tcx>>;
+
+    fn trivial_noop(self) -> Result<Self::Output, Self> {
+        Err(self)
+    }
+
+    fn perform(self, infcx: &InferCtxt<'_, 'gcx, 'tcx>) -> InferResult<'tcx, Self::Output> {
+        Ok(infcx
+           .at(&ObligationCause::dummy(), self.param_env)
+           .dropck_outlives(self.dropped_ty))
+    }
+}