fix tidy, small cleanup

compiler/rustc_feature/src/active.rs

@@ -586,7 +586,7 @@ declare_features! (
  (active, if_let_guard, "1.47.0", Some(51114), None),
 
  /// Allows non trivial generic constants which have to be manually propageted upwards.
- (active, const_evaluatable_checked, "1.48.0", Some(0), None),
+ (active, const_evaluatable_checked, "1.48.0", Some(76560), None),
 
  // -------------------------------------------------------------------------
  // feature-group-end: actual feature gates

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -73,10 +73,6 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
  }
  }
 
- if concrete.is_ok() {
- debug!("is_const_evaluatable: concrete ~~> ok");
- } else {
- debug!("is_const_evaluatable: concrete ~~> err");
- }
+ debug!(?concrete, "is_const_evaluatable");
  concrete.map(drop)
 }

compiler/rustc_typeck/src/collect.rs

@@ -1678,13 +1678,8 @@ fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicate
 
  if tcx.features().const_evaluatable_checked {
  let const_evaluatable = const_evaluatable_predicates_of(tcx, def_id, &result);
- if result.predicates.is_empty() {
- result.predicates = tcx.arena.alloc_from_iter(const_evaluatable);
- } else {
- result.predicates = tcx
- .arena
- .alloc_from_iter(result.predicates.iter().copied().chain(const_evaluatable));
- }
+ result.predicates =
+ tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(const_evaluatable));
  }
 
  debug!("predicates_defined_on({:?}) = {:?}", def_id, result);

src/test/ui/const-generics/const_evaluatable_checked/feature-gate-const_evaluatable_checked.rs

@@ -0,0 +1,14 @@
+#![feature(const_generics)]
+#![allow(incomplete_features)]
+
+type Arr<const N: usize> = [u8; N - 1];
+
+fn test<const N: usize>() -> Arr<N> where Arr<N>: Default {
+ //~^ ERROR constant expression depends
+ Default::default()
+}
+
+fn main() {
+ let x = test::<33>();
+ assert_eq!(x, [0; 32]);
+}

src/test/ui/const-generics/const_evaluatable_checked/feature-gate-const_evaluatable_checked.stderr

@@ -0,0 +1,10 @@
+error: constant expression depends on a generic parameter
+ --> $DIR/feature-gate-const_evaluatable_checked.rs:6:30
+ |
+LL | fn test<const N: usize>() -> Arr<N> where Arr<N>: Default {
+ | ^^^^^^
+ |
+ = note: this may fail depending on what value the parameter takes
+
+error: aborting due to previous error
+