Rollup merge of #99704 - fee1-dead-contrib:add_self_tilde_const_trait, r=oli-obk

Add `Self: ~const Trait` to traits with `#[const_trait]`

r? `@oli-obk`

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -23,8 +23,8 @@ use rustc_trait_selection::traits::SelectionContext;
 
 use super::ConstCx;
 use crate::errors::{
-    MutDerefErr, NonConstOpErr, PanicNonStrErr, RawPtrComparisonErr, RawPtrToIntErr,
-    StaticAccessErr, TransientMutBorrowErr, TransientMutBorrowErrRaw,
+    MutDerefErr, NonConstOpErr, PanicNonStrErr, RawPtrToIntErr, StaticAccessErr,
+    TransientMutBorrowErr, TransientMutBorrowErrRaw,
 };
 use crate::util::{call_kind, CallDesugaringKind, CallKind};
 
@@ -654,10 +654,10 @@ pub struct RawPtrComparison;
 impl<'tcx> NonConstOp<'tcx> for RawPtrComparison {
     fn build_error(
         &self,
-        ccx: &ConstCx<'_, 'tcx>,
+        _: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        ccx.tcx.sess.create_err(RawPtrComparisonErr { span })
+        span_bug!(span, "raw ptr comparison should already be caught in the trait system");
     }
 }
 

compiler/rustc_middle/src/ty/mod.rs

@@ -829,6 +829,14 @@ impl<'tcx> TraitPredicate<'tcx> {
     pub fn is_const_if_const(self) -> bool {
         self.constness == BoundConstness::ConstIfConst
     }
+
+    pub fn is_constness_satisfied_by(self, constness: hir::Constness) -> bool {
+        match (self.constness, constness) {
+            (BoundConstness::NotConst, _)
+            | (BoundConstness::ConstIfConst, hir::Constness::Const) => true,
+            (BoundConstness::ConstIfConst, hir::Constness::NotConst) => false,
+        }
+    }
 }
 
 impl<'tcx> PolyTraitPredicate<'tcx> {

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

@@ -2556,7 +2556,7 @@ define_print_and_forward_display! {
 
     ty::TraitPredicate<'tcx> {
         p!(print(self.trait_ref.self_ty()), ": ");
-        if let ty::BoundConstness::ConstIfConst = self.constness {
+        if let ty::BoundConstness::ConstIfConst = self.constness && cx.tcx().features().const_trait_impl {
             p!("~const ");
         }
         p!(print(self.trait_ref.print_only_trait_path()))

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

@@ -666,7 +666,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             );
                         } else if !suggested {
                             // Can't show anything else useful, try to find similar impls.
-                            let impl_candidates = self.find_similar_impl_candidates(trait_ref);
+                            let impl_candidates = self.find_similar_impl_candidates(trait_predicate);
                             if !self.report_similar_impl_candidates(
                                 impl_candidates,
                                 trait_ref,
@@ -701,7 +701,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                                 {
                                     let trait_ref = trait_pred.to_poly_trait_ref();
                                     let impl_candidates =
-                                        self.find_similar_impl_candidates(trait_ref);
+                                        self.find_similar_impl_candidates(trait_pred);
                                     self.report_similar_impl_candidates(
                                         impl_candidates,
                                         trait_ref,
@@ -1325,7 +1325,7 @@ trait InferCtxtPrivExt<'hir, 'tcx> {
 
     fn find_similar_impl_candidates(
         &self,
-        trait_ref: ty::PolyTraitRef<'tcx>,
+        trait_pred: ty::PolyTraitPredicate<'tcx>,
     ) -> Vec<ImplCandidate<'tcx>>;
 
     fn report_similar_impl_candidates(
@@ -1694,18 +1694,22 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
 
     fn find_similar_impl_candidates(
         &self,
-        trait_ref: ty::PolyTraitRef<'tcx>,
+        trait_pred: ty::PolyTraitPredicate<'tcx>,
     ) -> Vec<ImplCandidate<'tcx>> {
         self.tcx
-            .all_impls(trait_ref.def_id())
+            .all_impls(trait_pred.def_id())
             .filter_map(|def_id| {
-                if self.tcx.impl_polarity(def_id) == ty::ImplPolarity::Negative {
+                if self.tcx.impl_polarity(def_id) == ty::ImplPolarity::Negative
+                    || !trait_pred
+                        .skip_binder()
+                        .is_constness_satisfied_by(self.tcx.constness(def_id))
+                {
                     return None;
                 }
 
                 let imp = self.tcx.impl_trait_ref(def_id).unwrap();
 
-                self.fuzzy_match_tys(trait_ref.skip_binder().self_ty(), imp.self_ty(), false)
+                self.fuzzy_match_tys(trait_pred.skip_binder().self_ty(), imp.self_ty(), false)
                     .map(|similarity| ImplCandidate { trait_ref: imp, similarity })
             })
             .collect()

compiler/rustc_typeck/src/collect.rs

@@ -2090,10 +2090,17 @@ fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
         // from the trait itself that *shouldn't* be shown as the source of
         // an obligation and instead be skipped. Otherwise we'd use
         // `tcx.def_span(def_id);`
+
+        let constness = if tcx.has_attr(def_id, sym::const_trait) {
+            ty::BoundConstness::ConstIfConst
+        } else {
+            ty::BoundConstness::NotConst
+        };
+
         let span = rustc_span::DUMMY_SP;
         result.predicates =
             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
-                ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
+                ty::TraitRef::identity(tcx, def_id).with_constness(constness).to_predicate(tcx),
                 span,
             ))));
     }