Rollup merge of #99095 - rhysd:issue-99092, r=compiler-errors

Remove duplicate notes from error on inter-crate ambiguous impl of traits

Fixes #99092

4 files changed, 12 insertions, 12 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index f933f1c3c94..52ca23c4b30 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -13,7 +13,7 @@ use crate::traits::{
     self, FulfillmentContext, Normalized, Obligation, ObligationCause, PredicateObligation,
     PredicateObligations, SelectionContext,
 };
-//use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::Diagnostic;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
@@ -44,7 +44,7 @@ pub enum Conflict {
 
 pub struct OverlapResult<'tcx> {
     pub impl_header: ty::ImplHeader<'tcx>,
-    pub intercrate_ambiguity_causes: Vec<IntercrateAmbiguityCause>,
+    pub intercrate_ambiguity_causes: FxIndexSet<IntercrateAmbiguityCause>,
 
     /// `true` if the overlap might've been permitted before the shift
     /// to universes.
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 21e14eae0ee..96d83deeeb7 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -110,7 +110,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             IntercrateAmbiguityCause::DownstreamCrate { trait_desc, self_desc }
                         };
                         debug!(?cause, "evaluate_stack: pushing cause");
-                        self.intercrate_ambiguity_causes.as_mut().unwrap().push(cause);
+                        self.intercrate_ambiguity_causes.as_mut().unwrap().insert(cause);
                     }
                 }
             }
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index b205ca8fa11..2bb53a466ca 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -24,7 +24,7 @@ use crate::traits::error_reporting::InferCtxtExt;
 use crate::traits::project::ProjectAndUnifyResult;
 use crate::traits::project::ProjectionCacheKeyExt;
 use crate::traits::ProjectionCacheKey;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::{Diagnostic, ErrorGuaranteed};
 use rustc_hir as hir;
@@ -52,7 +52,7 @@ pub use rustc_middle::traits::select::*;
 mod candidate_assembly;
 mod confirmation;
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
 pub enum IntercrateAmbiguityCause {
     DownstreamCrate { trait_desc: String, self_desc: Option<String> },
     UpstreamCrateUpdate { trait_desc: String, self_desc: Option<String> },
@@ -128,7 +128,7 @@ pub struct SelectionContext<'cx, 'tcx> {
     /// We don't do his until we detect a coherence error because it can
     /// lead to false overflow results (#47139) and because always
     /// computing it may negatively impact performance.
-    intercrate_ambiguity_causes: Option<Vec<IntercrateAmbiguityCause>>,
+    intercrate_ambiguity_causes: Option<FxIndexSet<IntercrateAmbiguityCause>>,
 
     /// The mode that trait queries run in, which informs our error handling
     /// policy. In essence, canonicalized queries need their errors propagated
@@ -254,14 +254,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     pub fn enable_tracking_intercrate_ambiguity_causes(&mut self) {
         assert!(self.intercrate);
         assert!(self.intercrate_ambiguity_causes.is_none());
-        self.intercrate_ambiguity_causes = Some(vec![]);
+        self.intercrate_ambiguity_causes = Some(FxIndexSet::default());
         debug!("selcx: enable_tracking_intercrate_ambiguity_causes");
     }
 
     /// Gets the intercrate ambiguity causes collected since tracking
     /// was enabled and disables tracking at the same time. If
     /// tracking is not enabled, just returns an empty vector.
-    pub fn take_intercrate_ambiguity_causes(&mut self) -> Vec<IntercrateAmbiguityCause> {
+    pub fn take_intercrate_ambiguity_causes(&mut self) -> FxIndexSet<IntercrateAmbiguityCause> {
         assert!(self.intercrate);
         self.intercrate_ambiguity_causes.take().unwrap_or_default()
     }
@@ -960,7 +960,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                             });
 
                             debug!(?cause, "evaluate_stack: pushing cause");
-                            self.intercrate_ambiguity_causes.as_mut().unwrap().push(cause);
+                            self.intercrate_ambiguity_causes.as_mut().unwrap().insert(cause);
                         }
                     }
                 }
@@ -1252,7 +1252,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                                  reservation impl ambiguity on {:?}",
                             def_id
                         );
-                        intercrate_ambiguity_clauses.push(
+                        intercrate_ambiguity_clauses.insert(
                             IntercrateAmbiguityCause::ReservationImpl {
                                 message: value.to_string(),
                             },
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 13848d37890..2c4a453aefc 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -15,7 +15,7 @@ use specialization_graph::GraphExt;
 use crate::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use crate::traits::select::IntercrateAmbiguityCause;
 use crate::traits::{self, coherence, FutureCompatOverlapErrorKind, ObligationCause, TraitEngine};
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_errors::{struct_span_err, EmissionGuarantee, LintDiagnosticBuilder};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
@@ -33,7 +33,7 @@ pub struct OverlapError {
     pub with_impl: DefId,
     pub trait_desc: String,
     pub self_desc: Option<String>,
-    pub intercrate_ambiguity_causes: Vec<IntercrateAmbiguityCause>,
+    pub intercrate_ambiguity_causes: FxIndexSet<IntercrateAmbiguityCause>,
     pub involves_placeholder: bool,
 }