Rollup merge of #139858 - oli-obk:new-const-traits-syntax, r=fee1-dead

New const traits syntax

This PR only affects the AST and doesn't actually change anything semantically.

All occurrences of `~const` outside of libcore have been replaced by `[const]`. Within libcore we have to wait for rustfmt to be bumped in the bootstrap compiler. This will happen "automatically" (when rustfmt is run) during the bootstrap bump, as rustfmt converts `~const` into `[const]`. After this we can remove the `~const` support from the parser

Caveat discovered during impl: there is no legacy bare trait object recovery for `[const] Trait` as that snippet in type position goes down the slice /array parsing code and will error

r? ``@fee1-dead``

cc ``@nikomatsakis`` ``@traviscross`` ``@compiler-errors``

3 files changed, 8 insertions, 8 deletions

diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index c151e8acf92..c1d91f98957 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -421,7 +421,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
             Some(ConstConditionsHold::Yes)
         } else {
             tcx.dcx()
-                .span_delayed_bug(call_span, "this should have reported a ~const error in HIR");
+                .span_delayed_bug(call_span, "this should have reported a [const] error in HIR");
             Some(ConstConditionsHold::No)
         }
     }
diff --git a/compiler/rustc_const_eval/src/check_consts/ops.rs b/compiler/rustc_const_eval/src/check_consts/ops.rs
index 02edff8f632..b1e0ffd46c5 100644
--- a/compiler/rustc_const_eval/src/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/check_consts/ops.rs
@@ -149,7 +149,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                         debug!(?param_ty);
                         if let Some(generics) = tcx.hir_node_by_def_id(caller).generics() {
                             let constraint = with_no_trimmed_paths!(format!(
-                                "~const {}",
+                                "[const] {}",
                                 trait_ref.print_trait_sugared(),
                             ));
                             suggest_constraining_type_param(
diff --git a/compiler/rustc_const_eval/src/check_consts/qualifs.rs b/compiler/rustc_const_eval/src/check_consts/qualifs.rs
index c1a37ab6a83..166491b47a1 100644
--- a/compiler/rustc_const_eval/src/check_consts/qualifs.rs
+++ b/compiler/rustc_const_eval/src/check_consts/qualifs.rs
@@ -170,14 +170,14 @@ impl Qualif for NeedsNonConstDrop {
 
     #[instrument(level = "trace", skip(cx), ret)]
     fn in_any_value_of_ty<'tcx>(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> bool {
-        // If this doesn't need drop at all, then don't select `~const Destruct`.
+        // If this doesn't need drop at all, then don't select `[const] Destruct`.
         if !ty.needs_drop(cx.tcx, cx.typing_env) {
             return false;
         }
 
-        // We check that the type is `~const Destruct` since that will verify that
-        // the type is both `~const Drop` (if a drop impl exists for the adt), *and*
-        // that the components of this type are also `~const Destruct`. This
+        // We check that the type is `[const] Destruct` since that will verify that
+        // the type is both `[const] Drop` (if a drop impl exists for the adt), *and*
+        // that the components of this type are also `[const] Destruct`. This
         // amounts to verifying that there are no values in this ADT that may have
         // a non-const drop.
         let destruct_def_id = cx.tcx.require_lang_item(LangItem::Destruct, cx.body.span);
@@ -203,9 +203,9 @@ impl Qualif for NeedsNonConstDrop {
     fn is_structural_in_adt_value<'tcx>(cx: &ConstCx<'_, 'tcx>, adt: AdtDef<'tcx>) -> bool {
         // As soon as an ADT has a destructor, then the drop becomes non-structural
         // in its value since:
-        // 1. The destructor may have `~const` bounds which are not present on the type.
+        // 1. The destructor may have `[const]` bounds which are not present on the type.
         //   Someone needs to check that those are satisfied.
-        //   While this could be instead satisfied by checking that the `~const Drop`
+        //   While this could be instead satisfied by checking that the `[const] Drop`
         //   impl holds (i.e. replicating part of the `in_any_value_of_ty` logic above),
         //   even in this case, we have another problem, which is,
         // 2. The destructor may *modify* the operand being dropped, so even if we