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_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,
                                             }
                                         }