Split ct_err out into CommonConsts

Co-Authored-By: Gabriel Smith <yodaldevoid@users.noreply.github.com>

src/librustc/infer/resolve.rs

@@ -220,7 +220,7 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for FullTypeResolver<'a, 'gcx, 'tcx>
             match c.val {
                 ConstValue::Infer(InferConst::Var(vid)) => {
                     self.err = Some(FixupError::UnresolvedConst(vid));
-                    return self.tcx().types.ct_err;
+                    return self.tcx().consts.err;
                 }
                 ConstValue::Infer(InferConst::Fresh(_)) => {
                     bug!("Unexpected const in full const resolver: {:?}", c);

src/librustc/ty/context.rs

@@ -231,8 +231,10 @@ pub struct CommonLifetimes<'tcx> {
     pub re_empty: Region<'tcx>,
     pub re_static: Region<'tcx>,
     pub re_erased: Region<'tcx>,
+}
 
-    pub ct_err: &'tcx Const<'tcx>,
+pub struct CommonConsts<'tcx> {
+    pub err: &'tcx Const<'tcx>,
 }
 
 pub struct LocalTableInContext<'a, V: 'a> {
@@ -945,7 +947,7 @@ impl<'tcx> CommonTypes<'tcx> {
             bool: mk(Bool),
             char: mk(Char),
             never: mk(Never),
-            err,
+            err: mk(Error),
             isize: mk(Int(ast::IntTy::Isize)),
             i8: mk(Int(ast::IntTy::I8)),
             i16: mk(Int(ast::IntTy::I16)),
@@ -982,6 +984,20 @@ impl<'tcx> CommonLifetimes<'tcx> {
     }
 }
 
+impl<'tcx> CommonConsts<'tcx> {
+    fn new(interners: &CtxtInterners<'tcx>, types: &CommonTypes<'tcx>) -> CommonConsts<'tcx> {
+        let mk_const = |c| {
+            interners.const_.borrow_mut().intern(c, |c| {
+                Interned(interners.arena.alloc(c))
+            }).0
+        };
+
+        CommonConsts {
+            err: mk_const(ty::Const::zero_sized(types.err)),
+        }
+    }
+}
+
 // This struct contains information regarding the `ReFree(FreeRegion)` corresponding to a lifetime
 // conflict.
 #[derive(Debug)]
@@ -1032,6 +1048,9 @@ pub struct GlobalCtxt<'tcx> {
     /// Common lifetimes, pre-interned for your convenience.
     pub lifetimes: CommonLifetimes<'tcx>,
 
+    /// Common consts, pre-interned for your convenience.
+    pub consts: CommonConsts<'tcx>,
+
     /// Map indicating what traits are in scope for places where this
     /// is relevant; generated by resolve.
     trait_map: FxHashMap<DefIndex,
@@ -1231,6 +1250,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         let interners = CtxtInterners::new(&arenas.interner);
         let common_types = CommonTypes::new(&interners);
         let common_lifetimes = CommonLifetimes::new(&interners);
+        let common_consts = CommonConsts::new(&interners, &common_types);
         let dep_graph = hir.dep_graph.clone();
         let max_cnum = cstore.crates_untracked().iter().map(|c| c.as_usize()).max().unwrap_or(0);
         let mut providers = IndexVec::from_elem_n(extern_providers, max_cnum + 1);
@@ -1286,6 +1306,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             dep_graph,
             types: common_types,
             lifetimes: common_lifetimes,
+            consts: common_consts,
             trait_map,
             export_map: resolutions.export_map.into_iter().map(|(k, v)| {
                 let exports: Vec<_> = v.into_iter().map(|e| {

src/librustc_typeck/check/writeback.rs

@@ -594,7 +594,7 @@ impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
                                     ),
                                 )
                                 .emit();
-                            return self.tcx().types.ct_err;
+                            return self.tcx().consts.err;
                         }
                         ct
                     }
@@ -864,7 +864,7 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Resolver<'cx, 'gcx, 'tcx> {
                 );
                 // FIXME: we'd like to use `self.report_error`, but it doesn't yet
                 // accept a &'tcx ty::Const.
-                self.tcx().types.ct_err
+                self.tcx().consts.err
             }
         }
     }