Update w/ comments

Removes uses of ty() where a method is implemented on TypeFoldable, and also directly formats
a Term.

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

@@ -905,7 +905,13 @@ pub trait PrettyPrinter<'tcx>:
                 }
 
                 for (assoc_item_def_id, term) in assoc_items {
-                    let ty = if let Term::Ty(ty) = term.skip_binder() { ty } else { continue };
+                    let ty = match term.skip_binder() {
+                        Term::Ty(ty) => ty,
+                        Term::Const(c) => {
+                            p!(print(c));
+                            continue;
+                        }
+                    };
                     if !first {
                         p!(", ");
                     }

compiler/rustc_middle/src/ty/sty.rs

@@ -1580,10 +1580,9 @@ impl<'tcx> ExistentialProjection<'tcx> {
     ) -> Self {
         // Assert there is a Self.
         projection_predicate.projection_ty.substs.type_at(0);
-        let ty = if let Term::Ty(ty) = projection_predicate.term {
+        let ty = match projection_predicate.term {
-            ty
+            Term::Ty(ty) => ty,
-        } else {
+            Term::Const(_c) => unimplemented!(),
-            panic!("Only types are permitted here");
         };
 
         Self {

compiler/rustc_privacy/src/lib.rs

@@ -128,10 +128,7 @@ where
                 polarity: _,
             }) => self.visit_trait(trait_ref),
             ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, term }) => {
-                match term {
+                term.visit_with(self)?;
-                    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)) => {
@@ -1189,10 +1186,7 @@ impl<'tcx> Visitor<'tcx> for TypePrivacyVisitor<'tcx> {
 
             for (poly_predicate, _) in bounds.projection_bounds {
                 let pred = poly_predicate.skip_binder();
-                let poly_pred_term = match pred.term {
+                let poly_pred_term = self.visit(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()
                 {

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -779,8 +779,7 @@ 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.term().skip_binder().ty().map_or(false, |ty| ty.has_infer_types())
+                            if p.term().skip_binder().ty().has_infer_types() {
-                            {
                                 panic!("Unexpected result when selecting {:?} {:?}", ty, obligation)
                             }
                         }

compiler/rustc_typeck/src/check/closure.rs

@@ -709,7 +709,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // does not have any regions in it.
         let output_ty = self.resolve_vars_if_possible(predicate.term);
         debug!("deduce_future_output_from_projection: output_ty={:?}", output_ty);
-        // FIXME(...): How to handle consts here? Will this always be a const?
+        // This is a projection on a Fn trait so will always be a type.
         Some(output_ty.ty().unwrap())
     }
 

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -789,13 +789,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     item_def_id: projection_ty.item_def_id,
                                 };
 
-                                let fmt = match pred.skip_binder().term {
+                                let term = pred.skip_binder().term;
-                                    ty::Term::Ty(ty) => format!("{}", ty),
-                                    ty::Term::Const(c) => format!("{}", c),
-                                };
 
-                                let obligation = format!("{} = {}", projection_ty, fmt);
+                                let obligation = format!("{} = {}", projection_ty, term);
-                                let quiet = format!("{} = {}", quiet_projection_ty, fmt);
+                                let quiet = format!("{} = {}", quiet_projection_ty, term);
 
                                 bound_span_label(projection_ty.self_ty(), &obligation, &quiet);
                                 Some((obligation, projection_ty.self_ty()))

compiler/rustc_typeck/src/check/mod.rs

@@ -694,10 +694,7 @@ fn bounds_from_generic_predicates<'tcx>(
         where_clauses.push(format!(
             "{} = {}",
             tcx.def_path_str(p.projection_ty.item_def_id),
-            match p.term {
+            p.term,
-                ty::Term::Ty(ty) => format!("{}", ty),
-                ty::Term::Const(c) => format!("{}", c),
-            }
         ));
     }
     let where_clauses = if where_clauses.is_empty() {

compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs

@@ -199,7 +199,7 @@ fn unconstrained_parent_impl_substs<'tcx>(
     for (predicate, _) in impl_generic_predicates.predicates.iter() {
         if let ty::PredicateKind::Projection(proj) = predicate.kind().skip_binder() {
             let projection_ty = proj.projection_ty;
-            let projected_ty = proj.term.ty();
+            let projected_ty = proj.term;
 
             let unbound_trait_ref = projection_ty.trait_ref(tcx);
             if Some(unbound_trait_ref) == impl_trait_ref {

src/librustdoc/clean/types.rs

@@ -1309,10 +1309,7 @@ impl FnDecl {
                 GenericBound::TraitBound(PolyTrait { trait_, .. }, ..) => {
                     let bindings = trait_.bindings().unwrap();
                     let ret_ty = bindings[0].term();
-                    let ty = match ret_ty {
+                    let ty = ret_ty.ty().expect("Unexpected constant return term");
-                        Term::Type(ty) => ty,
-                        Term::Constant(_c) => unreachable!(),
-                    };
                     FnRetTy::Return(ty.clone())
                 }
                 _ => panic!("unexpected desugaring of async function"),

src/tools/clippy/clippy_lints/src/methods/mod.rs

@@ -2143,7 +2143,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
                     if let ty::PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
                         let assoc_ty = match projection_predicate.term {
                           ty::Term::Ty(ty) => ty,
-                          ty::Term::Const(c) => c.ty,
+                          ty::Term::Const(_c) => continue,
                         };
                         // walk the associated type and check for Self
                         if let Some(self_adt) = self_ty.ty_adt_def() {