make rustc_target usable outside of rustc

compiler/rustc_middle/src/arena.rs

@@ -6,7 +6,7 @@
 macro_rules! arena_types {
     ($macro:path) => (
         $macro!([
-            [] layout: rustc_target::abi::LayoutS<'tcx>,
+            [] layout: rustc_target::abi::LayoutS<rustc_target::abi::VariantIdx>,
             [] fn_abi: rustc_target::abi::call::FnAbi<'tcx, rustc_middle::ty::Ty<'tcx>>,
             // AdtDef are interned and compared by address
             [decode] adt_def: rustc_middle::ty::AdtDefData,

compiler/rustc_middle/src/ty/context.rs

@@ -148,7 +148,7 @@ pub struct CtxtInterners<'tcx> {
     const_: InternedSet<'tcx, ConstS<'tcx>>,
     const_allocation: InternedSet<'tcx, Allocation>,
     bound_variable_kinds: InternedSet<'tcx, List<ty::BoundVariableKind>>,
-    layout: InternedSet<'tcx, LayoutS<'tcx>>,
+    layout: InternedSet<'tcx, LayoutS<VariantIdx>>,
     adt_def: InternedSet<'tcx, AdtDefData>,
 }
 
@@ -2244,7 +2244,7 @@ direct_interners! {
     region: mk_region(RegionKind<'tcx>): Region -> Region<'tcx>,
     const_: mk_const_internal(ConstS<'tcx>): Const -> Const<'tcx>,
     const_allocation: intern_const_alloc(Allocation): ConstAllocation -> ConstAllocation<'tcx>,
-    layout: intern_layout(LayoutS<'tcx>): Layout -> Layout<'tcx>,
+    layout: intern_layout(LayoutS<VariantIdx>): Layout -> Layout<'tcx>,
     adt_def: intern_adt_def(AdtDefData): AdtDef -> AdtDef<'tcx>,
 }
 

compiler/rustc_middle/src/ty/layout.rs

@@ -610,7 +610,7 @@ where
                 })
             }
 
-            Variants::Multiple { ref variants, .. } => variants[variant_index],
+            Variants::Multiple { ref variants, .. } => cx.tcx().intern_layout(variants[variant_index].clone()),
         };
 
         assert_eq!(*layout.variants(), Variants::Single { index: variant_index });