Rollup of 11 pull requests

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -5,13 +5,14 @@ use rustc_infer::infer::canonical::QueryRegionConstraints;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::region_constraints::GenericKind;
 use rustc_infer::infer::{InferCtxt, outlives};
+use rustc_infer::traits::ScrubbedTraitError;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::traits::query::OutlivesBound;
 use rustc_middle::ty::{self, RegionVid, Ty, TypeVisitableExt};
 use rustc_span::{ErrorGuaranteed, Span};
-use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
-use rustc_trait_selection::solve::deeply_normalize;
+use rustc_trait_selection::solve::NoSolution;
+use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOp};
 use tracing::{debug, instrument};
 use type_op::TypeOpOutput;
@@ -229,24 +230,14 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         let mut constraints = vec![];
         let mut known_type_outlives_obligations = vec![];
         for bound in param_env.caller_bounds() {
-            let Some(mut outlives) = bound.as_type_outlives_clause() else { continue };
-
-            // In the new solver, normalize the type-outlives obligation assumptions.
-            if self.infcx.next_trait_solver() {
-                match deeply_normalize(
-                    self.infcx.at(&ObligationCause::misc(span, defining_ty_def_id), param_env),
+            if let Some(outlives) = bound.as_type_outlives_clause() {
+                self.normalize_and_push_type_outlives_obligation(
                     outlives,
-                ) {
-                    Ok(normalized_outlives) => {
-                        outlives = normalized_outlives;
-                    }
-                    Err(e) => {
-                        self.infcx.err_ctxt().report_fulfillment_errors(e);
-                    }
-                }
-            }
-
-            known_type_outlives_obligations.push(outlives);
+                    span,
+                    &mut known_type_outlives_obligations,
+                    &mut constraints,
+                );
+            };
         }
 
         let unnormalized_input_output_tys = self
@@ -356,6 +347,44 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         }
     }
 
+    fn normalize_and_push_type_outlives_obligation(
+        &self,
+        mut outlives: ty::PolyTypeOutlivesPredicate<'tcx>,
+        span: Span,
+        known_type_outlives_obligations: &mut Vec<ty::PolyTypeOutlivesPredicate<'tcx>>,
+        constraints: &mut Vec<&QueryRegionConstraints<'tcx>>,
+    ) {
+        // In the new solver, normalize the type-outlives obligation assumptions.
+        if self.infcx.next_trait_solver() {
+            let Ok(TypeOpOutput {
+                output: normalized_outlives,
+                constraints: constraints_normalize,
+                error_info: _,
+            }) = CustomTypeOp::new(
+                |ocx| {
+                    ocx.deeply_normalize(
+                        &ObligationCause::dummy_with_span(span),
+                        self.param_env,
+                        outlives,
+                    )
+                    .map_err(|_: Vec<ScrubbedTraitError<'tcx>>| NoSolution)
+                },
+                "normalize type outlives obligation",
+            )
+            .fully_perform(self.infcx, span)
+            else {
+                self.infcx.dcx().delayed_bug(format!("could not normalize {outlives:?}"));
+                return;
+            };
+            outlives = normalized_outlives;
+            if let Some(c) = constraints_normalize {
+                constraints.push(c);
+            }
+        }
+
+        known_type_outlives_obligations.push(outlives);
+    }
+
     /// Update the type of a single local, which should represent
     /// either the return type of the MIR or one of its arguments. At
     /// the same time, compute and add any implied bounds that come

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -35,6 +35,12 @@ use crate::errors;
 type QualifResults<'mir, 'tcx, Q> =
     rustc_mir_dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'mir, 'mir, 'tcx, Q>>;
 
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+enum ConstConditionsHold {
+    Yes,
+    No,
+}
+
 #[derive(Default)]
 pub(crate) struct Qualifs<'mir, 'tcx> {
     has_mut_interior: Option<QualifResults<'mir, 'tcx, HasMutInterior>>,
@@ -376,15 +382,15 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         callee: DefId,
         callee_args: ty::GenericArgsRef<'tcx>,
         call_span: Span,
-    ) -> bool {
+    ) -> Option<ConstConditionsHold> {
         let tcx = self.tcx;
         if !tcx.is_conditionally_const(callee) {
-            return false;
+            return None;
         }
 
         let const_conditions = tcx.const_conditions(callee).instantiate(tcx, callee_args);
         if const_conditions.is_empty() {
-            return false;
+            return None;
         }
 
         let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(self.body.typing_env(tcx));
@@ -413,12 +419,13 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
         }));
 
         let errors = ocx.select_all_or_error();
-        if !errors.is_empty() {
+        if errors.is_empty() {
+            Some(ConstConditionsHold::Yes)
+        } else {
             tcx.dcx()
                 .span_delayed_bug(call_span, "this should have reported a ~const error in HIR");
+            Some(ConstConditionsHold::No)
         }
-
-        true
     }
 
     pub fn check_drop_terminator(
@@ -706,7 +713,10 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     trace!("attempting to call a trait method");
                     let trait_is_const = tcx.is_const_trait(trait_did);
 
-                    if trait_is_const {
+                    // Only consider a trait to be const if the const conditions hold.
+                    // Otherwise, it's really misleading to call something "conditionally"
+                    // const when it's very obviously not conditionally const.
+                    if trait_is_const && has_const_conditions == Some(ConstConditionsHold::Yes) {
                         // Trait calls are always conditionally-const.
                         self.check_op(ops::ConditionallyConstCall {
                             callee,
@@ -730,7 +740,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 }
 
                 // Even if we know the callee, ensure we can use conditionally-const calls.
-                if has_const_conditions {
+                if has_const_conditions.is_some() {
                     self.check_op(ops::ConditionallyConstCall {
                         callee,
                         args: fn_args,

compiler/rustc_hir_analysis/messages.ftl

@@ -135,7 +135,7 @@ hir_analysis_dispatch_from_dyn_multi = implementing the `DispatchFromDyn` trait
 
 hir_analysis_dispatch_from_dyn_repr = structs implementing `DispatchFromDyn` may not have `#[repr(packed)]` or `#[repr(C)]`
 
-hir_analysis_dispatch_from_dyn_zst = the trait `DispatchFromDyn` may only be implemented for structs containing the field being coerced, ZST fields with 1 byte alignment, and nothing else
+hir_analysis_dispatch_from_dyn_zst = the trait `DispatchFromDyn` may only be implemented for structs containing the field being coerced, ZST fields with 1 byte alignment that don't mention type/const generics, and nothing else
     .note = extra field `{$name}` of type `{$ty}` is not allowed
 
 hir_analysis_drop_impl_negative = negative `Drop` impls are not supported

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -259,19 +259,37 @@ fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<()
             let coerced_fields = fields
                 .iter()
                 .filter(|field| {
+                    // Ignore PhantomData fields
+                    let unnormalized_ty = tcx.type_of(field.did).instantiate_identity();
+                    if tcx
+                        .try_normalize_erasing_regions(
+                            ty::TypingEnv::non_body_analysis(tcx, def_a.did()),
+                            unnormalized_ty,
+                        )
+                        .unwrap_or(unnormalized_ty)
+                        .is_phantom_data()
+                    {
+                        return false;
+                    }
+
                     let ty_a = field.ty(tcx, args_a);
                     let ty_b = field.ty(tcx, args_b);
 
-                    if let Ok(layout) =
-                        tcx.layout_of(infcx.typing_env(param_env).as_query_input(ty_a))
-                    {
-                        if layout.is_1zst() {
+                    // FIXME: We could do normalization here, but is it really worth it?
+                    if ty_a == ty_b {
+                        // Allow 1-ZSTs that don't mention type params.
+                        //
+                        // Allowing type params here would allow us to possibly transmute
+                        // between ZSTs, which may be used to create library unsoundness.
+                        if let Ok(layout) =
+                            tcx.layout_of(infcx.typing_env(param_env).as_query_input(ty_a))
+                            && layout.is_1zst()
+                            && !ty_a.has_non_region_param()
+                        {
                             // ignore 1-ZST fields
                             return false;
                         }
-                    }
 
-                    if ty_a == ty_b {
                         res = Err(tcx.dcx().emit_err(errors::DispatchFromDynZST {
                             span,
                             name: field.name,
@@ -460,8 +478,16 @@ pub(crate) fn coerce_unsized_info<'tcx>(
                 .filter_map(|(i, f)| {
                     let (a, b) = (f.ty(tcx, args_a), f.ty(tcx, args_b));
 
-                    if tcx.type_of(f.did).instantiate_identity().is_phantom_data() {
-                        // Ignore PhantomData fields
+                    // Ignore PhantomData fields
+                    let unnormalized_ty = tcx.type_of(f.did).instantiate_identity();
+                    if tcx
+                        .try_normalize_erasing_regions(
+                            ty::TypingEnv::non_body_analysis(tcx, def_a.did()),
+                            unnormalized_ty,
+                        )
+                        .unwrap_or(unnormalized_ty)
+                        .is_phantom_data()
+                    {
                         return None;
                     }
 

compiler/rustc_middle/src/middle/stability.rs

@@ -30,6 +30,14 @@ pub enum StabilityLevel {
     Stable,
 }
 
+#[derive(Copy, Clone)]
+pub enum UnstableKind {
+    /// Enforcing regular stability of an item
+    Regular,
+    /// Enforcing const stability of an item
+    Const(Span),
+}
+
 /// An entry in the `depr_map`.
 #[derive(Copy, Clone, HashStable, Debug, Encodable, Decodable)]
 pub struct DeprecationEntry {
@@ -108,10 +116,16 @@ pub fn report_unstable(
     is_soft: bool,
     span: Span,
     soft_handler: impl FnOnce(&'static Lint, Span, String),
+    kind: UnstableKind,
 ) {
+    let qual = match kind {
+        UnstableKind::Regular => "",
+        UnstableKind::Const(_) => " const",
+    };
+
     let msg = match reason {
-        Some(r) => format!("use of unstable library feature `{feature}`: {r}"),
-        None => format!("use of unstable library feature `{feature}`"),
+        Some(r) => format!("use of unstable{qual} library feature `{feature}`: {r}"),
+        None => format!("use of unstable{qual} library feature `{feature}`"),
     };
 
     if is_soft {
@@ -121,6 +135,9 @@ pub fn report_unstable(
         if let Some((inner_types, msg, sugg, applicability)) = suggestion {
             err.span_suggestion(inner_types, msg, sugg, applicability);
         }
+        if let UnstableKind::Const(kw) = kind {
+            err.span_label(kw, "trait is not stable as const yet");
+        }
         err.emit();
     }
 }
@@ -587,13 +604,81 @@ impl<'tcx> TyCtxt<'tcx> {
                 is_soft,
                 span,
                 soft_handler,
+                UnstableKind::Regular,
             ),
             EvalResult::Unmarked => unmarked(span, def_id),
         }
 
         is_allowed
     }
 
+    /// This function is analogous to `check_optional_stability` but with the logic in
+    /// `eval_stability_allow_unstable` inlined, and which operating on const stability
+    /// instead of regular stability.
+    ///
+    /// This enforces *syntactical* const stability of const traits. In other words,
+    /// it enforces the ability to name `~const`/`const` traits in trait bounds in various
+    /// syntax positions in HIR (including in the trait of an impl header).
+    pub fn check_const_stability(self, def_id: DefId, span: Span, const_kw_span: Span) {
+        let is_staged_api = self.lookup_stability(def_id.krate.as_def_id()).is_some();
+        if !is_staged_api {
+            return;
+        }
+
+        // Only the cross-crate scenario matters when checking unstable APIs
+        let cross_crate = !def_id.is_local();
+        if !cross_crate {
+            return;
+        }
+
+        let stability = self.lookup_const_stability(def_id);
+        debug!(
+            "stability: \
+                inspecting def_id={:?} span={:?} of stability={:?}",
+            def_id, span, stability
+        );
+
+        match stability {
+            Some(ConstStability {
+                level: attr::StabilityLevel::Unstable { reason, issue, is_soft, implied_by, .. },
+                feature,
+                ..
+            }) => {
+                assert!(!is_soft);
+
+                if span.allows_unstable(feature) {
+                    debug!("body stability: skipping span={:?} since it is internal", span);
+                    return;
+                }
+                if self.features().enabled(feature) {
+                    return;
+                }
+
+                // If this item was previously part of a now-stabilized feature which is still
+                // enabled (i.e. the user hasn't removed the attribute for the stabilized feature
+                // yet) then allow use of this item.
+                if let Some(implied_by) = implied_by
+                    && self.features().enabled(implied_by)
+                {
+                    return;
+                }
+
+                report_unstable(
+                    self.sess,
+                    feature,
+                    reason.to_opt_reason(),
+                    issue,
+                    None,
+                    false,
+                    span,
+                    |_, _, _| {},
+                    UnstableKind::Const(const_kw_span),
+                );
+            }
+            Some(_) | None => {}
+        }
+    }
+
     pub fn lookup_deprecation(self, id: DefId) -> Option<Deprecation> {
         self.lookup_deprecation_entry(id).map(|depr| depr.attr)
     }