Update term for use in more places

Replace use of `ty()` on term and use it in more places. This will allow more flexibility in the
future, but slightly worried it allows items which are consts which only accept types.

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -7,7 +7,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::subst::{GenericArgKind, Subst};
-use rustc_middle::ty::{self, OpaqueTypeKey, Term, Ty, TyCtxt, TypeFoldable, TypeVisitor};
+use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeVisitor};
 use rustc_span::Span;
 
 use std::ops::ControlFlow;
@@ -584,13 +584,8 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
             debug!(?predicate);
 
             if let ty::PredicateKind::Projection(projection) = predicate.kind().skip_binder() {
-                if let Term::Ty(ty) = projection.term {
-                    if ty.references_error() {
-                        // No point on adding these obligations since there's a type error involved.
-                        return tcx.ty_error();
-                    }
-                } else {
-                    todo!();
+                if projection.term.references_error() {
+                    return tcx.ty_error();
                 }
             }
 

compiler/rustc_interface/src/util.rs

@@ -742,6 +742,8 @@ impl<'a, 'b> ReplaceBodyWithLoop<'a, 'b> {
                                         ast::AssocConstraintKind::Equality { ref term } => {
                                             match term {
                                                 Term::Ty(ty) => involves_impl_trait(ty),
+                                                // FIXME(...): This should check if the constant
+                                                // involves a trait impl, but for now ignore.
                                                 Term::Const(_) => false,
                                             }
                                         }

compiler/rustc_middle/src/ty/assoc.rs

@@ -152,6 +152,19 @@ impl<'tcx> AssocItems<'tcx> {
             .find(|item| tcx.hygienic_eq(ident, item.ident, parent_def_id))
     }
 
+    /// Returns the associated item with the given name and any of `AssocKind`, if one exists.
+    pub fn find_by_name_and_kinds(
+        &self,
+        tcx: TyCtxt<'_>,
+        ident: Ident,
+        kinds: &[AssocKind],
+        parent_def_id: DefId,
+    ) -> Option<&ty::AssocItem> {
+        self.filter_by_name_unhygienic(ident.name)
+            .filter(|item| kinds.contains(&item.kind))
+            .find(|item| tcx.hygienic_eq(ident, item.ident, parent_def_id))
+    }
+
     /// Returns the associated item with the given name in the given `Namespace`, if one exists.
     pub fn find_by_name_and_namespace(
         &self,

compiler/rustc_middle/src/ty/consts.rs

@@ -86,10 +86,14 @@ impl<'tcx> Const<'tcx> {
         if let Some(lit_input) = lit_input {
             // If an error occurred, ignore that it's a literal and leave reporting the error up to
             // mir.
-            if let Ok(c) = tcx.at(expr.span).lit_to_const(lit_input) {
-                return Some(c);
-            } else {
-                tcx.sess.delay_span_bug(expr.span, "Const::from_anon_const: couldn't lit_to_const");
+            match tcx.at(expr.span).lit_to_const(lit_input) {
+                Ok(c) => return Some(c),
+                Err(e) => {
+                    tcx.sess.delay_span_bug(
+                        expr.span,
+                        &format!("Const::from_anon_const: couldn't lit_to_const {:?}", e),
+                    );
+                }
             }
         }
 

compiler/rustc_middle/src/ty/flags.rs

@@ -245,7 +245,7 @@ impl FlagComputation {
                 self.add_projection_ty(projection_ty);
                 match term {
                     Term::Ty(ty) => self.add_ty(ty),
-                    Term::Const(_c) => todo!(),
+                    Term::Const(c) => self.add_const(c),
                 }
             }
             ty::PredicateKind::WellFormed(arg) => {

compiler/rustc_middle/src/ty/mod.rs

@@ -815,8 +815,8 @@ impl<'tcx> From<&'tcx Const<'tcx>> for Term<'tcx> {
 }
 
 impl<'tcx> Term<'tcx> {
-    pub fn ty(&self) -> Ty<'tcx> {
-        if let Term::Ty(ty) = self { ty } else { panic!("Expected type") }
+    pub fn ty(&self) -> Option<Ty<'tcx>> {
+        if let Term::Ty(ty) = self { Some(ty) } else { None }
     }
 }
 
@@ -861,8 +861,8 @@ impl<'tcx> PolyProjectionPredicate<'tcx> {
         self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
     }
 
-    pub fn ty(&self) -> Binder<'tcx, Ty<'tcx>> {
-        self.map_bound(|predicate| if let Term::Ty(ty) = predicate.term { ty } else { todo!() })
+    pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
+        self.map_bound(|predicate| predicate.term)
     }
 
     /// The `DefId` of the `TraitItem` for the associated type.

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1,6 +1,6 @@
 use crate::mir::interpret::{AllocRange, ConstValue, GlobalAlloc, Pointer, Provenance, Scalar};
 use crate::ty::subst::{GenericArg, GenericArgKind, Subst};
-use crate::ty::{self, ConstInt, DefIdTree, ParamConst, ScalarInt, Ty, TyCtxt, TypeFoldable};
+use crate::ty::{self, ConstInt, DefIdTree, ParamConst, ScalarInt, Term, Ty, TyCtxt, TypeFoldable};
 use rustc_apfloat::ieee::{Double, Single};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sso::SsoHashSet;
@@ -799,7 +799,7 @@ pub trait PrettyPrinter<'tcx>:
                     let trait_ref = proj_ref.required_poly_trait_ref(self.tcx());
 
                     // Projection type entry -- the def-id for naming, and the ty.
-                    let proj_ty = (proj_ref.projection_def_id(), proj_ref.ty());
+                    let proj_ty = (proj_ref.projection_def_id(), proj_ref.term());
 
                     self.insert_trait_and_projection(
                         trait_ref,
@@ -850,8 +850,10 @@ pub trait PrettyPrinter<'tcx>:
                     }
 
                     p!(")");
-                    if !return_ty.skip_binder().is_unit() {
-                        p!("-> ", print(return_ty));
+                    if let Term::Ty(ty) = return_ty.skip_binder() {
+                        if !ty.is_unit() {
+                            p!("-> ", print(return_ty));
+                        }
                     }
                     p!(write("{}", if paren_needed { ")" } else { "" }));
 
@@ -902,14 +904,15 @@ pub trait PrettyPrinter<'tcx>:
                     first = false;
                 }
 
-                for (assoc_item_def_id, ty) in assoc_items {
+                for (assoc_item_def_id, term) in assoc_items {
+                    let ty = if let Term::Ty(ty) = term.skip_binder() { ty } else { continue };
                     if !first {
                         p!(", ");
                     }
                     p!(write("{} = ", self.tcx().associated_item(assoc_item_def_id).ident));
 
                     // Skip printing `<[generator@] as Generator<_>>::Return` from async blocks
-                    match ty.skip_binder().kind() {
+                    match ty.kind() {
                         ty::Projection(ty::ProjectionTy { item_def_id, .. })
                             if Some(*item_def_id) == self.tcx().lang_items().generator_return() =>
                         {
@@ -943,8 +946,11 @@ pub trait PrettyPrinter<'tcx>:
     fn insert_trait_and_projection(
         &mut self,
         trait_ref: ty::PolyTraitRef<'tcx>,
-        proj_ty: Option<(DefId, ty::Binder<'tcx, Ty<'tcx>>)>,
-        traits: &mut BTreeMap<ty::PolyTraitRef<'tcx>, BTreeMap<DefId, ty::Binder<'tcx, Ty<'tcx>>>>,
+        proj_ty: Option<(DefId, ty::Binder<'tcx, Term<'tcx>>)>,
+        traits: &mut BTreeMap<
+            ty::PolyTraitRef<'tcx>,
+            BTreeMap<DefId, ty::Binder<'tcx, Term<'tcx>>>,
+        >,
         fn_traits: &mut BTreeMap<ty::PolyTraitRef<'tcx>, OpaqueFnEntry<'tcx>>,
     ) {
         let trait_def_id = trait_ref.def_id();
@@ -2716,5 +2722,5 @@ pub struct OpaqueFnEntry<'tcx> {
     has_fn_once: bool,
     fn_mut_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
     fn_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
-    return_ty: Option<ty::Binder<'tcx, Ty<'tcx>>>,
+    return_ty: Option<ty::Binder<'tcx, Term<'tcx>>>,
 }

compiler/rustc_middle/src/ty/relate.rs

@@ -833,19 +833,30 @@ impl<'tcx> Relate<'tcx> for ty::TraitPredicate<'tcx> {
     }
 }
 
+impl<'tcx> Relate<'tcx> for ty::Term<'tcx> {
+    fn relate<R: TypeRelation<'tcx>>(
+        relation: &mut R,
+        a: Self,
+        b: Self,
+    ) -> RelateResult<'tcx, Self> {
+        Ok(match (a, b) {
+            (Term::Ty(a), Term::Ty(b)) => relation.relate(a, b)?.into(),
+            (Term::Const(a), Term::Const(b)) => relation.relate(a, b)?.into(),
+            _ => return Err(TypeError::Mismatch),
+        })
+    }
+}
+
 impl<'tcx> Relate<'tcx> for ty::ProjectionPredicate<'tcx> {
     fn relate<R: TypeRelation<'tcx>>(
         relation: &mut R,
         a: ty::ProjectionPredicate<'tcx>,
         b: ty::ProjectionPredicate<'tcx>,
     ) -> RelateResult<'tcx, ty::ProjectionPredicate<'tcx>> {
-        match (a.term, b.term) {
-            (Term::Ty(a_ty), Term::Ty(b_ty)) => Ok(ty::ProjectionPredicate {
-                projection_ty: relation.relate(a.projection_ty, b.projection_ty)?,
-                term: relation.relate(a_ty, b_ty)?.into(),
-            }),
-            _ => todo!(),
-        }
+        Ok(ty::ProjectionPredicate {
+            projection_ty: relation.relate(a.projection_ty, b.projection_ty)?,
+            term: relation.relate(a.term, b.term)?.into(),
+        })
     }
 }
 

compiler/rustc_middle/src/ty/sty.rs

@@ -1583,7 +1583,7 @@ impl<'tcx> ExistentialProjection<'tcx> {
         let ty = if let Term::Ty(ty) = projection_predicate.term {
             ty
         } else {
-            todo!();
+            panic!("Only types are permitted here");
         };
 
         Self {

compiler/rustc_privacy/src/lib.rs

@@ -128,8 +128,10 @@ where
                 polarity: _,
             }) => self.visit_trait(trait_ref),
             ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, term }) => {
-                let ty = term.ty();
-                ty.visit_with(self)?;
+                match term {
+                    ty::Term::Ty(ty) => ty.visit_with(self)?,
+                    ty::Term::Const(ct) => ct.visit_with(self)?,
+                }
                 self.visit_projection_ty(projection_ty)
             }
             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(ty, _region)) => {
@@ -1186,10 +1188,13 @@ impl<'tcx> Visitor<'tcx> for TypePrivacyVisitor<'tcx> {
             }
 
             for (poly_predicate, _) in bounds.projection_bounds {
-                if self.visit(poly_predicate.skip_binder().term.ty()).is_break()
-                    || self
-                        .visit_projection_ty(poly_predicate.skip_binder().projection_ty)
-                        .is_break()
+                let pred = poly_predicate.skip_binder();
+                let poly_pred_term = match pred.term {
+                    ty::Term::Ty(ty) => self.visit(ty),
+                    ty::Term::Const(ct) => self.visit(ct),
+                };
+                if poly_pred_term.is_break()
+                    || self.visit_projection_ty(pred.projection_ty).is_break()
                 {
                     return;
                 }

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -6,7 +6,7 @@ use super::*;
 use crate::infer::region_constraints::{Constraint, RegionConstraintData};
 use crate::infer::InferCtxt;
 use rustc_middle::ty::fold::TypeFolder;
-use rustc_middle::ty::{Region, RegionVid};
+use rustc_middle::ty::{Region, RegionVid, Term};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 
@@ -606,7 +606,11 @@ impl<'tcx> AutoTraitFinder<'tcx> {
     }
 
     fn is_self_referential_projection(&self, p: ty::PolyProjectionPredicate<'_>) -> bool {
-        matches!(*p.ty().skip_binder().kind(), ty::Projection(proj) if proj == p.skip_binder().projection_ty)
+        if let Term::Ty(ty) = p.term().skip_binder() {
+            matches!(ty.kind(), ty::Projection(proj) if proj == &p.skip_binder().projection_ty)
+        } else {
+            false
+        }
     }
 
     fn evaluate_nested_obligations(
@@ -663,7 +667,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                     // Additionally, we check if we've seen this predicate before,
                     // to avoid rendering duplicate bounds to the user.
                     if self.is_param_no_infer(p.skip_binder().projection_ty.substs)
-                        && !p.ty().skip_binder().has_infer_types()
+                        && !p.term().skip_binder().has_infer_types()
                         && is_new_pred
                     {
                         debug!(
@@ -752,7 +756,8 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                             // when we started out trying to unify
                             // some inference variables. See the comment above
                             // for more infomration
-                            if p.ty().skip_binder().has_infer_types() {
+                            if p.term().skip_binder().ty().map_or(false, |ty| ty.has_infer_types())
+                            {
                                 if !self.evaluate_nested_obligations(
                                     ty,
                                     v.into_iter(),
@@ -774,7 +779,8 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                             // However, we should always make progress (either by generating
                             // subobligations or getting an error) when we started off with
                             // inference variables
-                            if p.ty().skip_binder().has_infer_types() {
+                            if p.term().skip_binder().ty().map_or(false, |ty| ty.has_infer_types())
+                            {
                                 panic!("Unexpected result when selecting {:?} {:?}", ty, obligation)
                             }
                         }

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -1304,8 +1304,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
 
                 debug!(
                     "report_projection_error normalized_ty={:?} data.ty={:?}",
-                    normalized_ty,
-                    data.term.ty()
+                    normalized_ty, data.term,
                 );
 
                 let is_normalized_ty_expected = !matches!(
@@ -1315,16 +1314,17 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                         | ObligationCauseCode::ObjectCastObligation(_)
                         | ObligationCauseCode::OpaqueType
                 );
-
+                // FIXME(...): Handle Consts here
+                let data_ty = data.term.ty().unwrap();
                 if let Err(error) = self.at(&obligation.cause, obligation.param_env).eq_exp(
                     is_normalized_ty_expected,
                     normalized_ty,
-                    data.term.ty(),
+                    data_ty,
                 ) {
                     values = Some(infer::ValuePairs::Types(ExpectedFound::new(
                         is_normalized_ty_expected,
                         normalized_ty,
-                        data.term.ty(),
+                        data_ty,
                     )));
 
                     err_buf = error;

compiler/rustc_trait_selection/src/traits/project.rs

@@ -212,10 +212,9 @@ fn project_and_unify_type<'cx, 'tcx>(
     debug!(?normalized_ty, ?obligations, "project_and_unify_type result");
 
     let infcx = selcx.infcx();
-    match infcx
-        .at(&obligation.cause, obligation.param_env)
-        .eq(normalized_ty, obligation.predicate.term.ty())
-    {
+    // FIXME(...): Handle consts here as well as types.
+    let obligation_pred_ty = obligation.predicate.term.ty().unwrap();
+    match infcx.at(&obligation.cause, obligation.param_env).eq(normalized_ty, obligation_pred_ty) {
         Ok(InferOk { obligations: inferred_obligations, value: () }) => {
             obligations.extend(inferred_obligations);
             Ok(Ok(Some(obligations)))
@@ -1803,7 +1802,9 @@ fn confirm_param_env_candidate<'cx, 'tcx>(
         Ok(InferOk { value: _, obligations }) => {
             nested_obligations.extend(obligations);
             assoc_ty_own_obligations(selcx, obligation, &mut nested_obligations);
-            Progress { ty: cache_entry.term.ty(), obligations: nested_obligations }
+            // FIXME(...): Handle consts here as well? Maybe this progress type should just take
+            // a term instead.
+            Progress { ty: cache_entry.term.ty().unwrap(), obligations: nested_obligations }
         }
         Err(e) => {
             let msg = format!(

compiler/rustc_trait_selection/src/traits/relationships.rs

@@ -62,7 +62,7 @@ pub(crate) fn update<'tcx, T>(
     if let ty::PredicateKind::Projection(predicate) = obligation.predicate.kind().skip_binder() {
         // If the projection predicate (Foo::Bar == X) has X as a non-TyVid,
         // we need to make it into one.
-        if let Some(vid) = predicate.term.ty().ty_vid() {
+        if let Some(vid) = predicate.term.ty().and_then(|ty| ty.ty_vid()) {
             debug!("relationship: {:?}.output = true", vid);
             engine.relationships().entry(vid).or_default().output = true;
         }

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -116,7 +116,10 @@ pub fn predicate_obligations<'a, 'tcx>(
         }
         ty::PredicateKind::Projection(t) => {
             wf.compute_projection(t.projection_ty);
-            wf.compute(t.term.ty().into());
+            wf.compute(match t.term {
+                ty::Term::Ty(ty) => ty.into(),
+                ty::Term::Const(c) => c.into(),
+            })
         }
         ty::PredicateKind::WellFormed(arg) => {
             wf.compute(arg);
@@ -219,7 +222,7 @@ fn extend_cause_with_original_assoc_item_obligation<'tcx>(
             // projection coming from another associated type. See
             // `src/test/ui/associated-types/point-at-type-on-obligation-failure.rs` and
             // `traits-assoc-type-in-supertrait-bad.rs`.
-            if let ty::Projection(projection_ty) = proj.term.ty().kind() {
+            if let Some(ty::Projection(projection_ty)) = proj.term.ty().map(|ty| ty.kind()) {
                 if let Some(&impl_item_id) =
                     tcx.impl_item_implementor_ids(impl_def_id).get(&projection_ty.item_def_id)
                 {