Auto merge of rust-lang#110978 - Dylan-DPC:rollup-xclzwax, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - rust-lang#110614 (Clear response values for overflow in new solver)
 - rust-lang#110894 (Bump libffi-sys to 2.3.0)
 - rust-lang#110932 (include source error for LoadLibraryExW)
 - rust-lang#110958 (Make sure that some stdlib method signatures aren't accidental refinements)
 - rust-lang#110962 (Make drop_flags an IndexVec.)
 - rust-lang#110965 (Don't duplicate anonymous lifetimes for async fn in traits)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Cargo.lock

@@ -1956,9 +1956,9 @@ dependencies = [
 
 [[package]]
 name = "libffi-sys"
-version = "2.2.1"
+version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc65067b78c0fc069771e8b9a9e02df71e08858bec92c1f101377c67b9dca7c7"
+checksum = "f36115160c57e8529781b4183c2bb51fdc1f6d6d1ed345591d84be7703befb3c"
 dependencies = [
  "cc",
 ]

compiler/rustc_metadata/src/creader.rs

@@ -27,6 +27,7 @@ use rustc_span::{Span, DUMMY_SP};
 use rustc_target::spec::{PanicStrategy, TargetTriple};
 
 use proc_macro::bridge::client::ProcMacro;
+use std::error::Error;
 use std::ops::Fn;
 use std::path::Path;
 use std::time::Duration;
@@ -1094,5 +1095,12 @@ fn load_dylib(path: &Path, max_attempts: usize) -> Result<libloading::Library, S
     }
 
     debug!("Failed to load proc-macro `{}` even after {} attempts.", path.display(), max_attempts);
-    Err(format!("{} (retried {} times)", last_error.unwrap(), max_attempts))
+
+    let last_error = last_error.unwrap();
+    let message = if let Some(src) = last_error.source() {
+        format!("{last_error} ({src}) (retried {max_attempts} times)")
+    } else {
+        format!("{last_error} (retried {max_attempts} times)")
+    };
+    Err(message)
 }

compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -1,7 +1,7 @@
 use crate::deref_separator::deref_finder;
 use crate::MirPass;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_index::bit_set::BitSet;
+use rustc_index::IndexVec;
 use rustc_middle::mir::patch::MirPatch;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, TyCtxt};
@@ -84,12 +84,13 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops {
 
             let reachable = traversal::reachable_as_bitset(body);
 
+            let drop_flags = IndexVec::from_elem(None, &env.move_data.move_paths);
             ElaborateDropsCtxt {
                 tcx,
                 body,
                 env: &env,
                 init_data: InitializationData { inits, uninits },
-                drop_flags: Default::default(),
+                drop_flags,
                 patch: MirPatch::new(body),
                 un_derefer: un_derefer,
                 reachable,
@@ -293,7 +294,7 @@ struct ElaborateDropsCtxt<'a, 'tcx> {
     body: &'a Body<'tcx>,
     env: &'a MoveDataParamEnv<'tcx>,
     init_data: InitializationData<'a, 'tcx>,
-    drop_flags: FxHashMap<MovePathIndex, Local>,
+    drop_flags: IndexVec<MovePathIndex, Option<Local>>,
     patch: MirPatch<'tcx>,
     un_derefer: UnDerefer<'tcx>,
     reachable: BitSet<BasicBlock>,
@@ -312,11 +313,11 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
         let tcx = self.tcx;
         let patch = &mut self.patch;
         debug!("create_drop_flag({:?})", self.body.span);
-        self.drop_flags.entry(index).or_insert_with(|| patch.new_internal(tcx.types.bool, span));
+        self.drop_flags[index].get_or_insert_with(|| patch.new_internal(tcx.types.bool, span));
     }
 
     fn drop_flag(&mut self, index: MovePathIndex) -> Option<Place<'tcx>> {
-        self.drop_flags.get(&index).map(|t| Place::from(*t))
+        self.drop_flags[index].map(Place::from)
     }
 
     /// create a patch that elaborates all drops in the input
@@ -463,7 +464,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
     }
 
     fn set_drop_flag(&mut self, loc: Location, path: MovePathIndex, val: DropFlagState) {
-        if let Some(&flag) = self.drop_flags.get(&path) {
+        if let Some(flag) = self.drop_flags[path] {
             let span = self.patch.source_info_for_location(self.body, loc).span;
             let val = self.constant_bool(span, val.value());
             self.patch.add_assign(loc, Place::from(flag), val);
@@ -474,7 +475,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
         let loc = Location::START;
         let span = self.patch.source_info_for_location(self.body, loc).span;
         let false_ = self.constant_bool(span, false);
-        for flag in self.drop_flags.values() {
+        for flag in self.drop_flags.iter().flatten() {
             self.patch.add_assign(loc, Place::from(*flag), false_.clone());
         }
     }

compiler/rustc_resolve/src/late.rs

@@ -859,13 +859,9 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
                             sig.decl.inputs.iter().map(|Param { ty, .. }| (None, &**ty)),
                             &sig.decl.output,
                         );
-
-                        this.record_lifetime_params_for_async(
-                            fn_id,
-                            sig.header.asyncness.opt_return_id(),
-                        );
                     },
                 );
+                self.record_lifetime_params_for_async(fn_id, sig.header.asyncness.opt_return_id());
                 return;
             }
             FnKind::Fn(..) => {

compiler/rustc_trait_selection/src/solve/eval_ctxt.rs

@@ -3,7 +3,8 @@ use rustc_infer::infer::at::ToTrace;
 use rustc_infer::infer::canonical::CanonicalVarValues;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::{
-    DefineOpaqueTypes, InferCtxt, InferOk, LateBoundRegionConversionTime, TyCtxtInferExt,
+    DefineOpaqueTypes, InferCtxt, InferOk, LateBoundRegionConversionTime, RegionVariableOrigin,
+    TyCtxtInferExt,
 };
 use rustc_infer::traits::query::NoSolution;
 use rustc_infer::traits::ObligationCause;
@@ -223,18 +224,20 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
         {
             debug!("rerunning goal to check result is stable");
             let (_orig_values, canonical_goal) = self.canonicalize_goal(goal);
-            let canonical_response =
+            let new_canonical_response =
                 EvalCtxt::evaluate_canonical_goal(self.tcx(), self.search_graph, canonical_goal)?;
-            if !canonical_response.value.var_values.is_identity() {
+            if !new_canonical_response.value.var_values.is_identity() {
                 bug!(
                     "unstable result: re-canonicalized goal={canonical_goal:#?} \
-                     response={canonical_response:#?}"
+                    first_response={canonical_response:#?} \
+                    second_response={new_canonical_response:#?}"
                 );
             }
-            if certainty != canonical_response.value.certainty {
+            if certainty != new_canonical_response.value.certainty {
                 bug!(
                     "unstable certainty: {certainty:#?} re-canonicalized goal={canonical_goal:#?} \
-                     response={canonical_response:#?}"
+                     first_response={canonical_response:#?} \
+                     second_response={new_canonical_response:#?}"
                 );
             }
         }
@@ -434,6 +437,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         })
     }
 
+    pub(super) fn next_region_infer(&self) -> ty::Region<'tcx> {
+        self.infcx.next_region_var(RegionVariableOrigin::MiscVariable(DUMMY_SP))
+    }
+
     pub(super) fn next_const_infer(&self, ty: Ty<'tcx>) -> ty::Const<'tcx> {
         self.infcx.next_const_var(
             ty,

compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs

@@ -16,7 +16,7 @@ use rustc_infer::infer::canonical::query_response::make_query_region_constraints
 use rustc_infer::infer::canonical::CanonicalVarValues;
 use rustc_infer::infer::canonical::{CanonicalExt, QueryRegionConstraints};
 use rustc_middle::traits::query::NoSolution;
-use rustc_middle::traits::solve::{ExternalConstraints, ExternalConstraintsData};
+use rustc_middle::traits::solve::{ExternalConstraints, ExternalConstraintsData, MaybeCause};
 use rustc_middle::ty::{self, BoundVar, GenericArgKind};
 use rustc_span::DUMMY_SP;
 use std::iter;
@@ -60,9 +60,27 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 
         let certainty = certainty.unify_with(goals_certainty);
 
-        let external_constraints = self.compute_external_query_constraints()?;
+        let response = match certainty {
+            Certainty::Yes | Certainty::Maybe(MaybeCause::Ambiguity) => {
+                let external_constraints = self.compute_external_query_constraints()?;
+                Response { var_values: self.var_values, external_constraints, certainty }
+            }
+            Certainty::Maybe(MaybeCause::Overflow) => {
+                // If we have overflow, it's probable that we're substituting a type
+                // into itself infinitely and any partial substitutions in the query
+                // response are probably not useful anyways, so just return an empty
+                // query response.
+                //
+                // This may prevent us from potentially useful inference, e.g.
+                // 2 candidates, one ambiguous and one overflow, which both
+                // have the same inference constraints.
+                //
+                // Changing this to retain some constraints in the future
+                // won't be a breaking change, so this is good enough for now.
+                return Ok(self.make_ambiguous_response_no_constraints(MaybeCause::Overflow));
+            }
+        };
 
-        let response = Response { var_values: self.var_values, external_constraints, certainty };
         let canonical = Canonicalizer::canonicalize(
             self.infcx,
             CanonicalizeMode::Response { max_input_universe: self.max_input_universe },
@@ -72,6 +90,40 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         Ok(canonical)
     }
 
+    /// Constructs a totally unconstrained, ambiguous response to a goal.
+    ///
+    /// Take care when using this, since often it's useful to respond with
+    /// ambiguity but return constrained variables to guide inference.
+    pub(in crate::solve) fn make_ambiguous_response_no_constraints(
+        &self,
+        maybe_cause: MaybeCause,
+    ) -> CanonicalResponse<'tcx> {
+        let unconstrained_response = Response {
+            var_values: CanonicalVarValues {
+                var_values: self.tcx().mk_substs_from_iter(self.var_values.var_values.iter().map(
+                    |arg| -> ty::GenericArg<'tcx> {
+                        match arg.unpack() {
+                            GenericArgKind::Lifetime(_) => self.next_region_infer().into(),
+                            GenericArgKind::Type(_) => self.next_ty_infer().into(),
+                            GenericArgKind::Const(ct) => self.next_const_infer(ct.ty()).into(),
+                        }
+                    },
+                )),
+            },
+            external_constraints: self
+                .tcx()
+                .mk_external_constraints(ExternalConstraintsData::default()),
+            certainty: Certainty::Maybe(maybe_cause),
+        };
+
+        Canonicalizer::canonicalize(
+            self.infcx,
+            CanonicalizeMode::Response { max_input_universe: self.max_input_universe },
+            &mut Default::default(),
+            unconstrained_response,
+        )
+    }
+
     #[instrument(level = "debug", skip(self), ret)]
     fn compute_external_query_constraints(&self) -> Result<ExternalConstraints<'tcx>, NoSolution> {
         // Cannot use `take_registered_region_obligations` as we may compute the response

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -340,17 +340,17 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         if responses.is_empty() {
             return Err(NoSolution);
         }
-        let certainty = responses.iter().fold(Certainty::AMBIGUOUS, |certainty, response| {
-            certainty.unify_with(response.value.certainty)
-        });
-
-        let response = self.evaluate_added_goals_and_make_canonical_response(certainty);
-        if let Ok(response) = response {
-            assert!(response.has_no_inference_or_external_constraints());
-            Ok(response)
-        } else {
-            bug!("failed to make floundered response: {responses:?}");
-        }
+
+        let Certainty::Maybe(maybe_cause) = responses.iter().fold(
+            Certainty::AMBIGUOUS,
+            |certainty, response| {
+                certainty.unify_with(response.value.certainty)
+            },
+        ) else {
+            bug!("expected flounder response to be ambiguous")
+        };
+
+        Ok(self.make_ambiguous_response_no_constraints(maybe_cause))
     }
 }
 

library/alloc/src/collections/btree/map.rs

@@ -1543,11 +1543,17 @@ impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a V)> {
+    fn min(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a V)> {
+    fn max(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next_back()
     }
 }
@@ -1612,11 +1618,17 @@ impl<'a, K, V> Iterator for IterMut<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn min(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn max(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next_back()
     }
 }
@@ -1779,11 +1791,17 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<&'a K> {
+    fn min(mut self) -> Option<&'a K>
+    where
+        &'a K: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<&'a K> {
+    fn max(mut self) -> Option<&'a K>
+    where
+        &'a K: Ord,
+    {
         self.next_back()
     }
 }
@@ -2008,11 +2026,17 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a V)> {
+    fn min(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a V)> {
+    fn max(mut self) -> Option<(&'a K, &'a V)>
+    where
+        (&'a K, &'a V): Ord,
+    {
         self.next_back()
     }
 }
@@ -2081,11 +2105,17 @@ impl<K, V, A: Allocator + Clone> Iterator for IntoKeys<K, V, A> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<K> {
+    fn min(mut self) -> Option<K>
+    where
+        K: Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<K> {
+    fn max(mut self) -> Option<K>
+    where
+        K: Ord,
+    {
         self.next_back()
     }
 }
@@ -2204,11 +2234,17 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
         self.next_back()
     }
 
-    fn min(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn min(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next()
     }
 
-    fn max(mut self) -> Option<(&'a K, &'a mut V)> {
+    fn max(mut self) -> Option<(&'a K, &'a mut V)>
+    where
+        (&'a K, &'a mut V): Ord,
+    {
         self.next_back()
     }
 }