Add constness to ParamEnv

This now causes a lot of queries to be executed twice, as reveal_all forces NotConst

Author: oli-obk

compiler/rustc_middle/src/hir/map/mod.rs

@@ -454,18 +454,30 @@ impl<'hir> Map<'hir> {
     ///
     /// Panics if `LocalDefId` does not have an associated body.
     pub fn body_owner_kind(&self, id: HirId) -> BodyOwnerKind {
+        match self.opt_body_owner_kind(id) {
+            Ok(kind) => kind,
+            Err(node) => bug!("{:#?} is not a body node", node),
+        }
+    }
+
+    /// Returns the `BodyOwnerKind` of this `LocalDefId`.
+    ///
+    /// Returns the `Node` if `LocalDefId` does not have an associated body.
+    pub fn opt_body_owner_kind(&self, id: HirId) -> Result<BodyOwnerKind, Node<'_>> {
         match self.get(id) {
             Node::Item(&Item { kind: ItemKind::Const(..), .. })
             | Node::TraitItem(&TraitItem { kind: TraitItemKind::Const(..), .. })
             | Node::ImplItem(&ImplItem { kind: ImplItemKind::Const(..), .. })
-            | Node::AnonConst(_) => BodyOwnerKind::Const,
+            | Node::AnonConst(_) => Ok(BodyOwnerKind::Const),
             Node::Ctor(..)
             | Node::Item(&Item { kind: ItemKind::Fn(..), .. })
             | Node::TraitItem(&TraitItem { kind: TraitItemKind::Fn(..), .. })
-            | Node::ImplItem(&ImplItem { kind: ImplItemKind::Fn(..), .. }) => BodyOwnerKind::Fn,
-            Node::Item(&Item { kind: ItemKind::Static(_, m, _), .. }) => BodyOwnerKind::Static(m),
-            Node::Expr(&Expr { kind: ExprKind::Closure(..), .. }) => BodyOwnerKind::Closure,
-            node => bug!("{:#?} is not a body node", node),
+            | Node::ImplItem(&ImplItem { kind: ImplItemKind::Fn(..), .. }) => Ok(BodyOwnerKind::Fn),
+            Node::Item(&Item { kind: ItemKind::Static(_, m, _), .. }) => {
+                Ok(BodyOwnerKind::Static(m))
+            }
+            Node::Expr(&Expr { kind: ExprKind::Closure(..), .. }) => Ok(BodyOwnerKind::Closure),
+            node => Err(node),
         }
     }
 
@@ -474,7 +486,8 @@ impl<'hir> Map<'hir> {
     /// Panics if `LocalDefId` does not have an associated body.
     ///
     /// This should only be used for determining the context of a body, a return
-    /// value of `Some` does not always suggest that the owner of the body is `const`.
+    /// value of `Some` does not always suggest that the owner of the body is `const`,
+    /// just that it has to be checked as if it were.
     pub fn body_const_context(&self, did: LocalDefId) -> Option<ConstContext> {
         let hir_id = self.local_def_id_to_hir_id(did);
         let ccx = match self.body_owner_kind(hir_id) {

compiler/rustc_middle/src/ty/mod.rs

@@ -1227,22 +1227,27 @@ pub struct ParamEnv<'tcx> {
 #[derive(Copy, Clone)]
 struct ParamTag {
     reveal: traits::Reveal,
+    constness: hir::Constness,
 }
 
 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
-    const BITS: usize = 1;
+    const BITS: usize = 2;
     #[inline]
     fn into_usize(self) -> usize {
         match self {
-            Self { reveal: traits::Reveal::UserFacing } => 0,
-            Self { reveal: traits::Reveal::All } => 1,
+            Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
+            Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
+            Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
+            Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
         }
     }
     #[inline]
     unsafe fn from_usize(ptr: usize) -> Self {
         match ptr {
-            0 => Self { reveal: traits::Reveal::UserFacing },
-            1 => Self { reveal: traits::Reveal::All },
+            0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
+            1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
+            2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
+            3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
             _ => std::hint::unreachable_unchecked(),
         }
     }
@@ -1253,6 +1258,7 @@ impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
         f.debug_struct("ParamEnv")
             .field("caller_bounds", &self.caller_bounds())
             .field("reveal", &self.reveal())
+            .field("constness", &self.constness())
             .finish()
     }
 }
@@ -1261,20 +1267,23 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
         self.caller_bounds().hash_stable(hcx, hasher);
         self.reveal().hash_stable(hcx, hasher);
+        self.constness().hash_stable(hcx, hasher);
     }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
-    fn super_fold_with<F: ty::fold::TypeFolder<'tcx>>(
-        self,
-        folder: &mut F,
-    ) -> Result<Self, F::Error> {
-        Ok(ParamEnv::new(self.caller_bounds().fold_with(folder)?, self.reveal().fold_with(folder)?))
+    fn super_fold_with<F: ty::fold::TypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+        ParamEnv::new(
+            self.caller_bounds().fold_with(folder)?,
+            self.reveal().fold_with(folder)?,
+            self.constness().fold_with(folder)?,
+        )
     }
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
         self.caller_bounds().visit_with(visitor)?;
-        self.reveal().visit_with(visitor)
+        self.reveal().visit_with(visitor)?;
+        self.constness().visit_with(visitor)
     }
 }
 
@@ -1285,7 +1294,7 @@ impl<'tcx> ParamEnv<'tcx> {
     /// type-checking.
     #[inline]
     pub fn empty() -> Self {
-        Self::new(List::empty(), Reveal::UserFacing)
+        Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
     }
 
     #[inline]
@@ -1298,6 +1307,11 @@ impl<'tcx> ParamEnv<'tcx> {
         self.packed.tag().reveal
     }
 
+    #[inline]
+    pub fn constness(self) -> hir::Constness {
+        self.packed.tag().constness
+    }
+
     /// Construct a trait environment with no where-clauses in scope
     /// where the values of all `impl Trait` and other hidden types
     /// are revealed. This is suitable for monomorphized, post-typeck
@@ -1307,13 +1321,17 @@ impl<'tcx> ParamEnv<'tcx> {
     /// or invoke `param_env.with_reveal_all()`.
     #[inline]
     pub fn reveal_all() -> Self {
-        Self::new(List::empty(), Reveal::All)
+        Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
     }
 
     /// Construct a trait environment with the given set of predicates.
     #[inline]
-    pub fn new(caller_bounds: &'tcx List<Predicate<'tcx>>, reveal: Reveal) -> Self {
-        ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal }) }
+    pub fn new(
+        caller_bounds: &'tcx List<Predicate<'tcx>>,
+        reveal: Reveal,
+        constness: hir::Constness,
+    ) -> Self {
+        ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
     }
 
     pub fn with_user_facing(mut self) -> Self {
@@ -1335,13 +1353,17 @@ impl<'tcx> ParamEnv<'tcx> {
             return self;
         }
 
-        ParamEnv::new(tcx.normalize_opaque_types(self.caller_bounds()), Reveal::All)
+        ParamEnv::new(
+            tcx.normalize_opaque_types(self.caller_bounds()),
+            Reveal::All,
+            self.constness(),
+        )
     }
 
     /// Returns this same environment but with no caller bounds.
     #[inline]
     pub fn without_caller_bounds(self) -> Self {
-        Self::new(List::empty(), self.reveal())
+        Self::new(List::empty(), self.reveal(), self.constness())
     }
 
     /// Creates a suitable environment in which to perform trait

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -480,7 +480,7 @@ impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
     type Lifted = ty::ParamEnv<'tcx>;
     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
         tcx.lift(self.caller_bounds())
-            .map(|caller_bounds| ty::ParamEnv::new(caller_bounds, self.reveal()))
+            .map(|caller_bounds| ty::ParamEnv::new(caller_bounds, self.reveal(), self.constness()))
     }
 }
 

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -370,12 +370,17 @@ impl AutoTraitFinder<'tcx> {
                 computed_preds.clone().chain(user_computed_preds.iter().cloned()),
             )
             .map(|o| o.predicate);
-            new_env = ty::ParamEnv::new(tcx.mk_predicates(normalized_preds), param_env.reveal());
+            new_env = ty::ParamEnv::new(
+                tcx.mk_predicates(normalized_preds),
+                param_env.reveal(),
+                param_env.constness(),
+            );
         }
 
         let final_user_env = ty::ParamEnv::new(
             tcx.mk_predicates(user_computed_preds.into_iter()),
             user_env.reveal(),
+            user_env.constness(),
         );
         debug!(
             "evaluate_nested_obligations(ty={:?}, trait_did={:?}): succeeded with '{:?}' \

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -307,8 +307,11 @@ pub fn normalize_param_env_or_error<'tcx>(
 
     debug!("normalize_param_env_or_error: elaborated-predicates={:?}", predicates);
 
-    let elaborated_env =
-        ty::ParamEnv::new(tcx.intern_predicates(&predicates), unnormalized_env.reveal());
+    let elaborated_env = ty::ParamEnv::new(
+        tcx.intern_predicates(&predicates),
+        unnormalized_env.reveal(),
+        unnormalized_env.constness(),
+    );
 
     // HACK: we are trying to normalize the param-env inside *itself*. The problem is that
     // normalization expects its param-env to be already normalized, which means we have
@@ -360,8 +363,11 @@ pub fn normalize_param_env_or_error<'tcx>(
     // predicates here anyway. Keeping them here anyway because it seems safer.
     let outlives_env: Vec<_> =
         non_outlives_predicates.iter().chain(&outlives_predicates).cloned().collect();
-    let outlives_env =
-        ty::ParamEnv::new(tcx.intern_predicates(&outlives_env), unnormalized_env.reveal());
+    let outlives_env = ty::ParamEnv::new(
+        tcx.intern_predicates(&outlives_env),
+        unnormalized_env.reveal(),
+        unnormalized_env.constness(),
+    );
     let outlives_predicates = match do_normalize_predicates(
         tcx,
         region_context,
@@ -381,7 +387,11 @@ pub fn normalize_param_env_or_error<'tcx>(
     let mut predicates = non_outlives_predicates;
     predicates.extend(outlives_predicates);
     debug!("normalize_param_env_or_error: final predicates={:?}", predicates);
-    ty::ParamEnv::new(tcx.intern_predicates(&predicates), unnormalized_env.reveal())
+    ty::ParamEnv::new(
+        tcx.intern_predicates(&predicates),
+        unnormalized_env.reveal(),
+        unnormalized_env.constness(),
+    )
 }
 
 pub fn fully_normalize<'a, 'tcx, T>(

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -698,7 +698,11 @@ fn receiver_is_dispatchable<'tcx>(
             .chain(array::IntoIter::new([unsize_predicate, trait_predicate]))
             .collect();
 
-        ty::ParamEnv::new(tcx.intern_predicates(&caller_bounds), param_env.reveal())
+        ty::ParamEnv::new(
+            tcx.intern_predicates(&caller_bounds),
+            param_env.reveal(),
+            param_env.constness(),
+        )
     };
 
     // Receiver: DispatchFromDyn<Receiver[Self => U]>

compiler/rustc_ty_utils/src/ty.rs

@@ -285,16 +285,33 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
     // issue #89334
     predicates = tcx.expose_default_const_substs(predicates);
 
-    let unnormalized_env =
-        ty::ParamEnv::new(tcx.intern_predicates(&predicates), traits::Reveal::UserFacing);
-
-    debug!("unnormalized_env caller bounds: {:?}", unnormalized_env.caller_bounds());
-    let body_id = def_id
-        .as_local()
-        .map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
-        .map_or(hir::CRATE_HIR_ID, |id| {
-            tcx.hir().maybe_body_owned_by(id).map_or(id, |body| body.hir_id)
-        });
+    let local_did = def_id.as_local();
+    let hir_id = local_did.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id));
+
+    let constness = match hir_id {
+        Some(hir_id) => match tcx.hir().opt_body_owner_kind(hir_id) {
+            Err(hir::Node::Item(&hir::Item {
+                kind: hir::ItemKind::Impl(hir::Impl { constness, .. }),
+                ..
+            })) => constness,
+            Err(_) => hir::Constness::NotConst,
+            Ok(_) => match tcx.hir().body_const_context(local_did.unwrap()) {
+                Some(_) => hir::Constness::Const,
+                None => hir::Constness::NotConst,
+            },
+        },
+        None => hir::Constness::NotConst,
+    };
+
+    let unnormalized_env = ty::ParamEnv::new(
+        tcx.intern_predicates(&predicates),
+        traits::Reveal::UserFacing,
+        constness,
+    );
+
+    let body_id = hir_id.map_or(hir::CRATE_HIR_ID, |id| {
+        tcx.hir().maybe_body_owned_by(id).map_or(id, |body| body.hir_id)
+    });
     let cause = traits::ObligationCause::misc(tcx.def_span(def_id), body_id);
     traits::normalize_param_env_or_error(tcx, def_id, unnormalized_env, cause)
 }

compiler/rustc_typeck/src/check/compare_method.rs

@@ -208,8 +208,11 @@ fn compare_predicate_entailment<'tcx>(
     // The key step here is to update the caller_bounds's predicates to be
     // the new hybrid bounds we computed.
     let normalize_cause = traits::ObligationCause::misc(impl_m_span, impl_m_hir_id);
-    let param_env =
-        ty::ParamEnv::new(tcx.intern_predicates(&hybrid_preds.predicates), Reveal::UserFacing);
+    let param_env = ty::ParamEnv::new(
+        tcx.intern_predicates(&hybrid_preds.predicates),
+        Reveal::UserFacing,
+        hir::Constness::NotConst,
+    );
     let param_env =
         traits::normalize_param_env_or_error(tcx, impl_m.def_id, param_env, normalize_cause);
 
@@ -1183,8 +1186,11 @@ fn compare_type_predicate_entailment<'tcx>(
     debug!("compare_type_predicate_entailment: bounds={:?}", hybrid_preds);
 
     let normalize_cause = traits::ObligationCause::misc(impl_ty_span, impl_ty_hir_id);
-    let param_env =
-        ty::ParamEnv::new(tcx.intern_predicates(&hybrid_preds.predicates), Reveal::UserFacing);
+    let param_env = ty::ParamEnv::new(
+        tcx.intern_predicates(&hybrid_preds.predicates),
+        Reveal::UserFacing,
+        hir::Constness::NotConst,
+    );
     let param_env = traits::normalize_param_env_or_error(
         tcx,
         impl_ty.def_id,
@@ -1369,7 +1375,11 @@ pub fn check_type_bounds<'tcx>(
                 .to_predicate(tcx),
             ),
         };
-        ty::ParamEnv::new(tcx.intern_predicates(&predicates), Reveal::UserFacing)
+        ty::ParamEnv::new(
+            tcx.intern_predicates(&predicates),
+            Reveal::UserFacing,
+            param_env.constness(),
+        )
     };
     debug!(?normalize_param_env);