Rollup merge of rust-lang#60292 - varkor:ty-tuple-substs, r=nikomatsakis

Replace the `&'tcx List<Ty<'tcx>>` in `TyKind::Tuple` with `SubstsRef<'tcx>`

Part of the suggested refactoring for rust-lang#42340. As expected, this is a little messy, because there are many places that the components of tuples are expected to be types, rather than arbitrary kinds. However, it should open up the way for a refactoring of `TyS` itself.

r? @nikomatsakis

src/librustc/mir/tcx.rs

@@ -47,7 +47,7 @@ impl<'a, 'gcx, 'tcx> PlaceTy<'tcx> {
                 let field_def = &variant_def.fields[f.index()];
                 field_def.ty(tcx, substs)
             }
-            ty::Tuple(ref tys) => tys[f.index()],
+            ty::Tuple(ref tys) => tys[f.index()].expect_ty(),
             _ => bug!("extracting field of non-tuple non-adt: {:?}", self),
         };
         debug!("field_ty self: {:?} f: {:?} yields: {:?}", self, f, answer);

src/librustc/traits/error_reporting.rs

@@ -875,7 +875,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 let expected_ty = expected_trait_ref.skip_binder().substs.type_at(1);
                 let expected = match expected_ty.sty {
                     ty::Tuple(ref tys) => tys.iter()
-                        .map(|t| ArgKind::from_expected_ty(t, Some(span))).collect(),
+                        .map(|t| ArgKind::from_expected_ty(t.expect_ty(), Some(span))).collect(),
                     _ => vec![ArgKind::Arg("_".to_owned(), expected_ty.to_string())],
                 };
 
@@ -1247,7 +1247,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             let inputs = trait_ref.substs.type_at(1);
             let sig = if let ty::Tuple(inputs) = inputs.sty {
                 tcx.mk_fn_sig(
-                    inputs.iter().cloned(),
+                    inputs.iter().map(|k| k.expect_ty()),
                     tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
                     false,
                     hir::Unsafety::Normal,

src/librustc/traits/query/dropck_outlives.rs

@@ -217,7 +217,7 @@ pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'_, '_, 'tcx>, ty: Ty<'tcx>) ->
 
         // (T1..Tn) and closures have same properties as T1..Tn --
         // check if *any* of those are trivial.
-        ty::Tuple(ref tys) => tys.iter().all(|t| trivial_dropck_outlives(tcx, t)),
+        ty::Tuple(ref tys) => tys.iter().all(|t| trivial_dropck_outlives(tcx, t.expect_ty())),
         ty::Closure(def_id, ref substs) => substs
             .upvar_tys(def_id, tcx)
             .all(|t| trivial_dropck_outlives(tcx, t)),

src/librustc/traits/select.rs

@@ -2429,7 +2429,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => None,
 
-            ty::Tuple(tys) => Where(ty::Binder::bind(tys.last().into_iter().cloned().collect())),
+            ty::Tuple(tys) => {
+                Where(ty::Binder::bind(tys.last().into_iter().map(|k| k.expect_ty()).collect()))
+            }
 
             ty::Adt(def, substs) => {
                 let sized_crit = def.sized_constraint(self.tcx());
@@ -2503,7 +2505,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::Tuple(tys) => {
                 // (*) binder moved here
-                Where(ty::Binder::bind(tys.to_vec()))
+                Where(ty::Binder::bind(tys.iter().map(|k| k.expect_ty()).collect()))
             }
 
             ty::Closure(def_id, substs) => {
@@ -2590,7 +2592,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::Tuple(ref tys) => {
                 // (T1, ..., Tn) -- meets any bound that all of T1...Tn meet
-                tys.to_vec()
+                tys.iter().map(|k| k.expect_ty()).collect()
             }
 
             ty::Closure(def_id, ref substs) => substs.upvar_tys(def_id, self.tcx()).collect(),
@@ -3495,7 +3497,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
                 // Check that the source tuple with the target's
                 // last element is equal to the target.
-                let new_tuple = tcx.mk_tup(a_mid.iter().cloned().chain(iter::once(b_last)));
+                let new_tuple = tcx.mk_tup(
+                    a_mid.iter().map(|k| k.expect_ty()).chain(iter::once(b_last.expect_ty())),
+                );
                 let InferOk { obligations, .. } = self.infcx
                     .at(&obligation.cause, obligation.param_env)
                     .eq(target, new_tuple)
@@ -3508,7 +3512,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                     obligation.cause.clone(),
                     obligation.predicate.def_id(),
                     obligation.recursion_depth + 1,
-                    a_last,
+                    a_last.expect_ty(),
                     &[b_last.into()],
                 ));
             }

src/librustc/ty/context.rs

@@ -2431,7 +2431,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         let converted_sig = sig.map_bound(|s| {
             let params_iter = match s.inputs()[0].sty {
                 ty::Tuple(params) => {
-                    params.into_iter().cloned()
+                    params.into_iter().map(|k| k.expect_ty())
                 }
                 _ => bug!(),
             };
@@ -2573,11 +2573,15 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
     #[inline]
     pub fn intern_tup(self, ts: &[Ty<'tcx>]) -> Ty<'tcx> {
-        self.mk_ty(Tuple(self.intern_type_list(ts)))
+        let kinds: Vec<_> = ts.into_iter().map(|&t| Kind::from(t)).collect();
+        self.mk_ty(Tuple(self.intern_substs(&kinds)))
     }
 
     pub fn mk_tup<I: InternAs<[Ty<'tcx>], Ty<'tcx>>>(self, iter: I) -> I::Output {
-        iter.intern_with(|ts| self.mk_ty(Tuple(self.intern_type_list(ts))))
+        iter.intern_with(|ts| {
+            let kinds: Vec<_> = ts.into_iter().map(|&t| Kind::from(t)).collect();
+            self.mk_ty(Tuple(self.intern_substs(&kinds)))
+        })
     }
 
     #[inline]

src/librustc/ty/flags.rs

@@ -195,8 +195,8 @@ impl FlagComputation {
                 self.add_ty(ty);
             }
 
-            &ty::Tuple(ref ts) => {
-                self.add_tys(&ts[..]);
+            &ty::Tuple(ref substs) => {
+                self.add_substs(substs);
             }
 
             &ty::FnDef(_, substs) => {

src/librustc/ty/inhabitedness/mod.rs

@@ -181,7 +181,7 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
 
             Tuple(ref tys) => {
                 DefIdForest::union(tcx, tys.iter().map(|ty| {
-                    ty.uninhabited_from(tcx)
+                    ty.expect_ty().uninhabited_from(tcx)
                 }))
             }
 

src/librustc/ty/layout.rs

@@ -626,8 +626,9 @@ impl<'a, 'tcx> LayoutCx<'tcx, TyCtxt<'a, 'tcx, 'tcx>> {
                     StructKind::MaybeUnsized
                 };
 
-                univariant(&tys.iter().map(|ty| self.layout_of(ty)).collect::<Result<Vec<_>, _>>()?,
-                           &ReprOptions::default(), kind)?
+                univariant(&tys.iter().map(|k| {
+                    self.layout_of(k.expect_ty())
+                }).collect::<Result<Vec<_>, _>>()?, &ReprOptions::default(), kind)?
             }
 
             // SIMD vector types.
@@ -1723,7 +1724,7 @@ impl<'a, 'tcx, C> TyLayoutMethods<'tcx, C> for Ty<'tcx>
                 substs.field_tys(def_id, tcx).nth(i).unwrap()
             }
 
-            ty::Tuple(tys) => tys[i],
+            ty::Tuple(tys) => tys[i].expect_ty(),
 
             // SIMD vector types.
             ty::Adt(def, ..) if def.repr.simd() => {

src/librustc/ty/mod.rs

@@ -2501,7 +2501,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
             Tuple(ref tys) => {
                 match tys.last() {
                     None => vec![],
-                    Some(ty) => self.sized_constraint_for_ty(tcx, ty)
+                    Some(ty) => self.sized_constraint_for_ty(tcx, ty.expect_ty()),
                 }
             }
 

src/librustc/ty/print/mod.rs

@@ -264,7 +264,7 @@ pub fn characteristic_def_id_of_type(ty: Ty<'_>) -> Option<DefId> {
         ty::Ref(_, ty, _) => characteristic_def_id_of_type(ty),
 
         ty::Tuple(ref tys) => tys.iter()
-                                   .filter_map(|ty| characteristic_def_id_of_type(ty))
+                                   .filter_map(|ty| characteristic_def_id_of_type(ty.expect_ty()))
                                    .next(),
 
         ty::FnDef(def_id, _) |

src/librustc/ty/print/pretty.rs

@@ -701,7 +701,8 @@ pub trait PrettyPrinter<'gcx: 'tcx, 'tcx>:
                 if let ty::Tuple(ref args) = principal.substs.type_at(0).sty {
                     let mut projections = predicates.projection_bounds();
                     if let (Some(proj), None) = (projections.next(), projections.next()) {
-                        p!(pretty_fn_sig(args, false, proj.ty));
+                        let tys: Vec<_> = args.iter().map(|k| k.expect_ty()).collect();
+                        p!(pretty_fn_sig(&tys, false, proj.ty));
                         resugared = true;
                     }
                 }

src/librustc/ty/relate.rs

@@ -526,7 +526,9 @@ pub fn super_relate_tys<'a, 'gcx, 'tcx, R>(relation: &mut R,
         (&ty::Tuple(as_), &ty::Tuple(bs)) =>
         {
             if as_.len() == bs.len() {
-                Ok(tcx.mk_tup(as_.iter().zip(bs).map(|(a, b)| relation.relate(a, b)))?)
+                Ok(tcx.mk_tup(as_.iter().zip(bs).map(|(a, b)| {
+                    relation.relate(&a.expect_ty(), &b.expect_ty())
+                }))?)
             } else if !(as_.is_empty() || bs.is_empty()) {
                 Err(TypeError::TupleSize(
                     expected_found(relation, &as_.len(), &bs.len())))

src/librustc/ty/sty.rs

@@ -171,7 +171,7 @@ pub enum TyKind<'tcx> {
     Never,
 
     /// A tuple type. For example, `(i32, bool)`.
-    Tuple(&'tcx List<Ty<'tcx>>),
+    Tuple(SubstsRef<'tcx>),
 
     /// The projection of an associated type. For example,
     /// `<T as Trait<..>>::N`.
@@ -1651,7 +1651,9 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
                     })
                 })
             }
-            ty::Tuple(tys) => tys.iter().any(|ty| ty.conservative_is_privately_uninhabited(tcx)),
+            ty::Tuple(tys) => tys.iter().any(|ty| {
+                ty.expect_ty().conservative_is_privately_uninhabited(tcx)
+            }),
             ty::Array(ty, len) => {
                 match len.assert_usize(tcx) {
                     // If the array is definitely non-empty, it's uninhabited if
@@ -2087,8 +2089,9 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
             ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) =>
                 false,
 
-            ty::Tuple(tys) =>
-                tys.iter().all(|ty| ty.is_trivially_sized(tcx)),
+            ty::Tuple(tys) => {
+                tys.iter().all(|ty| ty.expect_ty().is_trivially_sized(tcx))
+            }
 
             ty::Adt(def, _substs) =>
                 def.sized_constraint(tcx).is_empty(),

src/librustc/ty/subst.rs

@@ -123,6 +123,16 @@ impl<'tcx> Kind<'tcx> {
             }
         }
     }
+
+    /// Unpack the `Kind` as a type when it is known certainly to be a type.
+    /// This is true in cases where `Substs` is used in places where the kinds are known
+    /// to be limited (e.g. in tuples, where the only parameters are type parameters).
+    pub fn expect_ty(self) -> Ty<'tcx> {
+        match self.unpack() {
+            UnpackedKind::Type(ty) => ty,
+            _ => bug!("expected a type, but found another kind"),
+        }
+    }
 }
 
 impl<'a, 'tcx> Lift<'tcx> for Kind<'a> {
@@ -174,8 +184,7 @@ pub type SubstsRef<'tcx> = &'tcx InternalSubsts<'tcx>;
 
 impl<'a, 'gcx, 'tcx> InternalSubsts<'tcx> {
     /// Creates a `InternalSubsts` that maps each generic parameter to itself.
-    pub fn identity_for_item(tcx: TyCtxt<'a, 'gcx, 'tcx>, def_id: DefId)
-                             -> SubstsRef<'tcx> {
+    pub fn identity_for_item(tcx: TyCtxt<'a, 'gcx, 'tcx>, def_id: DefId) -> SubstsRef<'tcx> {
         Self::for_item(tcx, def_id, |param, _| {
             tcx.mk_param_from_def(param)
         })

src/librustc/ty/util.rs

@@ -278,7 +278,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
                 ty::Tuple(tys) => {
                     if let Some((&last_ty, _)) = tys.split_last() {
-                        ty = last_ty;
+                        ty = last_ty.expect_ty();
                     } else {
                         break;
                     }
@@ -316,8 +316,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 (&Tuple(a_tys), &Tuple(b_tys))
                         if a_tys.len() == b_tys.len() => {
                     if let Some(a_last) = a_tys.last() {
-                        a = a_last;
-                        b = b_tys.last().unwrap();
+                        a = a_last.expect_ty();
+                        b = b_tys.last().unwrap().expect_ty();
                     } else {
                         break;
                     }
@@ -795,7 +795,13 @@ impl<'a, 'tcx> ty::TyS<'tcx> {
                 Tuple(ref ts) => {
                     // Find non representable
                     fold_repr(ts.iter().map(|ty| {
-                        is_type_structurally_recursive(tcx, sp, seen, representable_cache, ty)
+                        is_type_structurally_recursive(
+                            tcx,
+                            sp,
+                            seen,
+                            representable_cache,
+                            ty.expect_ty(),
+                        )
                     }))
                 }
                 // Fixed-length vectors.
@@ -1048,7 +1054,7 @@ fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // state transformation pass
         ty::Generator(..) => true,
 
-        ty::Tuple(ref tys) => tys.iter().cloned().any(needs_drop),
+        ty::Tuple(ref tys) => tys.iter().map(|k| k.expect_ty()).any(needs_drop),
 
         // unions don't have destructors because of the child types,
         // only if they manually implement `Drop` (handled above).

src/librustc/ty/walk.rs

@@ -120,7 +120,7 @@ fn push_subtypes<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent_ty: Ty<'tcx>) {
             stack.extend(ts.skip_binder().iter().cloned().rev());
         }
         ty::Tuple(ts) => {
-            stack.extend(ts.iter().cloned().rev());
+            stack.extend(ts.iter().map(|k| k.expect_ty()).rev());
         }
         ty::FnDef(_, substs) => {
             stack.extend(substs.types().rev());

src/librustc/ty/wf.rs

@@ -265,7 +265,7 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
                 ty::Tuple(ref tys) => {
                     if let Some((_last, rest)) = tys.split_last() {
                         for elem in rest {
-                            self.require_sized(elem, traits::TupleElem);
+                            self.require_sized(elem.expect_ty(), traits::TupleElem);
                         }
                     }
                 }

src/librustc_codegen_llvm/abi.rs

@@ -426,9 +426,9 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
             assert!(!sig.c_variadic && extra_args.is_empty());
 
             match sig.inputs().last().unwrap().sty {
-                ty::Tuple(ref tupled_arguments) => {
+                ty::Tuple(tupled_arguments) => {
                     inputs = &sig.inputs()[0..sig.inputs().len() - 1];
-                    tupled_arguments
+                    tupled_arguments.iter().map(|k| k.expect_ty()).collect()
                 }
                 _ => {
                     bug!("argument to function with \"rust-call\" ABI \
@@ -437,7 +437,7 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
             }
         } else {
             assert!(sig.c_variadic || extra_args.is_empty());
-            extra_args
+            extra_args.to_vec()
         };
 
         let target = &cx.sess().target.target;
@@ -587,7 +587,7 @@ impl<'tcx> FnTypeExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
 
         let mut fn_ty = FnType {
             ret: arg_of(sig.output(), None),
-            args: inputs.iter().chain(extra_args).enumerate().map(|(i, ty)| {
+            args: inputs.iter().cloned().chain(extra_args).enumerate().map(|(i, ty)| {
                 arg_of(ty, Some(i))
             }).collect(),
             c_variadic: sig.c_variadic,

src/librustc_codegen_llvm/debuginfo/metadata.rs

@@ -722,9 +722,10 @@ pub fn type_metadata(
             }
         },
         ty::Tuple(ref elements) => {
+            let tys: Vec<_> = elements.iter().map(|k| k.expect_ty()).collect();
             prepare_tuple_metadata(cx,
                                    t,
-                                   &elements[..],
+                                   &tys,
                                    unique_type_id,
                                    usage_site_span).finalize(cx)
         }

src/librustc_codegen_llvm/debuginfo/mod.rs

@@ -392,7 +392,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 if let ty::Tuple(args) = sig.inputs()[sig.inputs().len() - 1].sty {
                     signature.extend(
                         args.iter().map(|argument_type| {
-                            Some(type_metadata(cx, argument_type, syntax_pos::DUMMY_SP))
+                            Some(type_metadata(cx, argument_type.expect_ty(), syntax_pos::DUMMY_SP))
                         })
                     );
                 }

src/librustc_codegen_ssa/debuginfo/type_names.rs

@@ -46,7 +46,7 @@ pub fn push_debuginfo_type_name<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         ty::Tuple(component_types) => {
             output.push('(');
             for &component_type in component_types {
-                push_debuginfo_type_name(tcx, component_type, true, output, visited);
+                push_debuginfo_type_name(tcx, component_type.expect_ty(), true, output, visited);
                 output.push_str(", ");
             }
             if !component_types.is_empty() {

src/librustc_mir/borrow_check/error_reporting.rs

@@ -2213,7 +2213,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                 // Closure arguments are wrapped in a tuple, so we need to get the first
                 // from that.
                 if let ty::Tuple(elems) = argument_ty.sty {
-                    let argument_ty = elems.first()?;
+                    let argument_ty = elems.first()?.expect_ty();
                     if let ty::Ref(_, _, _) = argument_ty.sty {
                         return Some(AnnotatedBorrowFnSignature::Closure {
                             argument_ty,

src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs

@@ -515,7 +515,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 // just worry about trying to match up the rustc type
                 // with the HIR types:
                 (ty::Tuple(elem_tys), hir::TyKind::Tup(elem_hir_tys)) => {
-                    search_stack.extend(elem_tys.iter().cloned().zip(elem_hir_tys));
+                    search_stack.extend(elem_tys.iter().map(|k| k.expect_ty()).zip(elem_hir_tys));
                 }
 
                 (ty::Slice(elem_ty), hir::TyKind::Slice(elem_hir_ty))

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

@@ -779,7 +779,7 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
                 }
                 ty::Tuple(tys) => {
                     return match tys.get(field.index()) {
-                        Some(&ty) => Ok(ty),
+                        Some(&ty) => Ok(ty.expect_ty()),
                         None => Err(FieldAccessError::OutOfRange {
                             field_count: tys.len(),
                         }),