move Debug bounds onto Lift

Just for convenience.

src/librustc/infer/canonical/mod.rs

@@ -348,7 +348,6 @@ impl<'tcx> Index<CanonicalVar> for CanonicalVarValues<'tcx> {
 impl<'gcx: 'tcx, 'tcx, T> Canonicalize<'gcx, 'tcx> for QueryResult<'tcx, T>
 where
     T: TypeFoldable<'tcx> + Lift<'gcx>,
-    T::Lifted: Debug,
 {
     // we ought to intern this, but I'm too lazy just now
     type Canonicalized = Lrc<Canonical<'gcx, QueryResult<'gcx, T::Lifted>>>;

src/librustc/infer/canonical/query_result.rs

@@ -63,7 +63,6 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
     ) -> Result<CanonicalizedQueryResult<'gcx, T>, NoSolution>
     where
         T: Debug + Lift<'gcx> + TypeFoldable<'tcx>,
-        T::Lifted: Debug,
     {
         let query_result = self.make_query_result(inference_vars, answer, fulfill_cx)?;
         let (canonical_result, _) = self.canonicalize_response(&query_result);

src/librustc/ty/context.rs

@@ -64,6 +64,7 @@ use std::borrow::Borrow;
 use std::cmp::Ordering;
 use std::collections::hash_map::{self, Entry};
 use std::hash::{Hash, Hasher};
+use std::fmt::Debug;
 use std::mem;
 use std::ops::Deref;
 use std::iter;
@@ -1503,8 +1504,8 @@ impl<'gcx: 'tcx, 'tcx> GlobalCtxt<'gcx> {
 /// contain the TypeVariants key or if the address of the interned
 /// pointer differs. The latter case is possible if a primitive type,
 /// e.g. `()` or `u8`, was interned in a different context.
-pub trait Lift<'tcx> {
-    type Lifted: 'tcx;
+pub trait Lift<'tcx>: Debug {
+    type Lifted: Debug + 'tcx;
     fn lift_to_tcx<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Option<Self::Lifted>;
 }