Dont use span as key when collecting missing associated types from dyn

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs

@@ -1,9 +1,8 @@
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_errors::codes::*;
 use rustc_errors::struct_span_code_err;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::def_id::DefId;
 use rustc_lint_defs::builtin::UNUSED_ASSOCIATED_TYPE_BOUNDS;
 use rustc_middle::span_bug;
 use rustc_middle::ty::fold::BottomUpFolder;
@@ -11,7 +10,7 @@ use rustc_middle::ty::{
     self, DynKind, ExistentialPredicateStableCmpExt as _, Ty, TyCtxt, TypeFoldable,
     TypeVisitableExt, Upcast,
 };
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
 use rustc_trait_selection::error_reporting::traits::report_dyn_incompatibility;
 use rustc_trait_selection::traits::{self, hir_ty_lowering_dyn_compatibility_violations};
 use rustc_type_ir::elaborate::ClauseWithSupertraitSpan;
@@ -128,8 +127,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
         }
 
-        let mut associated_types: FxIndexMap<Span, FxIndexSet<DefId>> = FxIndexMap::default();
+        let mut needed_associated_types = FxIndexSet::default();
 
+        let principal_span = regular_traits.first().map_or(DUMMY_SP, |info| info.bottom().1);
         let regular_traits_refs_spans = trait_bounds
             .into_iter()
             .filter(|(trait_ref, _)| !tcx.trait_is_auto(trait_ref.def_id()));
@@ -146,11 +146,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 match bound_predicate.skip_binder() {
                     ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => {
                         let pred = bound_predicate.rebind(pred);
-                        associated_types.entry(original_span).or_default().extend(
+                        needed_associated_types.extend(
                             tcx.associated_items(pred.def_id())
                                 .in_definition_order()
                                 .filter(|item| item.kind == ty::AssocKind::Type)
                                 .filter(|item| !item.is_impl_trait_in_trait())
+                                // If the associated type has a `where Self: Sized` bound,
+                                // we do not need to constrain the associated type.
+                                .filter(|item| !tcx.generics_require_sized_self(item.def_id))
                                 .map(|item| item.def_id),
                         );
                     }
@@ -201,10 +204,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // So every `Projection` clause is an `Assoc = Foo` bound. `associated_types` contains all associated
         // types's `DefId`, so the following loop removes all the `DefIds` of the associated types that have a
         // corresponding `Projection` clause
-        for def_ids in associated_types.values_mut() {
         for (projection_bound, span) in &projection_bounds {
             let def_id = projection_bound.item_def_id();
-                def_ids.swap_remove(&def_id);
+            needed_associated_types.swap_remove(&def_id);
             if tcx.generics_require_sized_self(def_id) {
                 tcx.emit_node_span_lint(
                     UNUSED_ASSOCIATED_TYPE_BOUNDS,
@@ -214,13 +216,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 );
             }
         }
-            // If the associated type has a `where Self: Sized` bound, we do not need to constrain the associated
-            // type in the `dyn Trait`.
-            def_ids.retain(|def_id| !tcx.generics_require_sized_self(def_id));
-        }
 
         if let Err(guar) = self.check_for_required_assoc_tys(
-            associated_types,
+            principal_span,
+            needed_associated_types,
             potential_assoc_types,
             hir_trait_bounds,
         ) {

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -722,35 +722,25 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// emit a generic note suggesting using a `where` clause to constraint instead.
     pub(crate) fn check_for_required_assoc_tys(
         &self,
-        associated_types: FxIndexMap<Span, FxIndexSet<DefId>>,
+        principal_span: Span,
+        missing_assoc_types: FxIndexSet<DefId>,
         potential_assoc_types: Vec<usize>,
         trait_bounds: &[hir::PolyTraitRef<'_>],
     ) -> Result<(), ErrorGuaranteed> {
-        if associated_types.values().all(|v| v.is_empty()) {
+        if missing_assoc_types.is_empty() {
             return Ok(());
         }
 
         let tcx = self.tcx();
-        // FIXME: Marked `mut` so that we can replace the spans further below with a more
+        let missing_assoc_types: Vec<_> =
-        // appropriate one, but this should be handled earlier in the span assignment.
+            missing_assoc_types.into_iter().map(|def_id| tcx.associated_item(def_id)).collect();
-        let associated_types: FxIndexMap<Span, Vec<_>> = associated_types
-            .into_iter()
-            .map(|(span, def_ids)| {
-                (span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect())
-            })
-            .collect();
         let mut names: FxIndexMap<String, Vec<Symbol>> = Default::default();
         let mut names_len = 0;
 
         // Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
         // `issue-22560.rs`.
-        let mut trait_bound_spans: Vec<Span> = vec![];
         let mut dyn_compatibility_violations = Ok(());
-        for (span, items) in &associated_types {
+        for assoc_item in &missing_assoc_types {
-            if !items.is_empty() {
-                trait_bound_spans.push(*span);
-            }
-            for assoc_item in items {
             let trait_def_id = assoc_item.container_id(tcx);
             names.entry(tcx.def_path_str(trait_def_id)).or_default().push(assoc_item.name);
             names_len += 1;
@@ -760,7 +750,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             if !violations.is_empty() {
                 dyn_compatibility_violations = Err(report_dyn_incompatibility(
                     tcx,
-                        *span,
+                    principal_span,
                     None,
                     trait_def_id,
                     &violations,
@@ -768,7 +758,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 .emit());
             }
         }
-        }
 
         if let Err(guar) = dyn_compatibility_violations {
             return Err(guar);
@@ -827,10 +816,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         names.sort();
         let names = names.join(", ");
 
-        trait_bound_spans.sort();
         let mut err = struct_span_code_err!(
             self.dcx(),
-            trait_bound_spans,
+            principal_span,
             E0191,
             "the value of the associated type{} {} must be specified",
             pluralize!(names_len),
@@ -840,20 +828,20 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let mut types_count = 0;
         let mut where_constraints = vec![];
         let mut already_has_generics_args_suggestion = false;
-        for (span, assoc_items) in &associated_types {
+
         let mut names: UnordMap<_, usize> = Default::default();
-            for item in assoc_items {
+        for item in &missing_assoc_types {
             types_count += 1;
             *names.entry(item.name).or_insert(0) += 1;
         }
         let mut dupes = false;
         let mut shadows = false;
-            for item in assoc_items {
+        for item in &missing_assoc_types {
             let prefix = if names[&item.name] > 1 {
                 let trait_def_id = item.container_id(tcx);
                 dupes = true;
                 format!("{}::", tcx.def_path_str(trait_def_id))
-                } else if bound_names.get(&item.name).is_some_and(|x| x != &item) {
+            } else if bound_names.get(&item.name).is_some_and(|x| *x != item) {
                 let trait_def_id = item.container_id(tcx);
                 shadows = true;
                 format!("{}::", tcx.def_path_str(trait_def_id))
@@ -864,7 +852,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             let mut is_shadowed = false;
 
             if let Some(assoc_item) = bound_names.get(&item.name)
-                    && assoc_item != &item
+                && *assoc_item != item
             {
                 is_shadowed = true;
 
@@ -885,16 +873,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 );
             }
         }
-            if potential_assoc_types.len() == assoc_items.len() {
+        if potential_assoc_types.len() == missing_assoc_types.len() {
             // When the amount of missing associated types equals the number of
             // extra type arguments present. A suggesting to replace the generic args with
             // associated types is already emitted.
             already_has_generics_args_suggestion = true;
         } else if let (Ok(snippet), false, false) =
-                (tcx.sess.source_map().span_to_snippet(*span), dupes, shadows)
+            (tcx.sess.source_map().span_to_snippet(principal_span), dupes, shadows)
         {
             let types: Vec<_> =
-                    assoc_items.iter().map(|item| format!("{} = Type", item.name)).collect();
+                missing_assoc_types.iter().map(|item| format!("{} = Type", item.name)).collect();
             let code = if snippet.ends_with('>') {
                 // The user wrote `Trait<'a>` or similar and we don't have a type we can
                 // suggest, but at least we can clue them to the correct syntax
@@ -910,11 +898,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 // least we can clue them to the correct syntax `Iterator<Item = Type>`.
                 format!("{}<{}>", snippet, types.join(", "))
             };
-                suggestions.push((*span, code));
+            suggestions.push((principal_span, code));
         } else if dupes {
-                where_constraints.push(*span);
+            where_constraints.push(principal_span);
-            }
         }
+
         let where_msg = "consider introducing a new type parameter, adding `where` constraints \
                          using the fully-qualified path to the associated types";
         if !where_constraints.is_empty() && suggestions.is_empty() {
@@ -925,14 +913,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         }
         if suggestions.len() != 1 || already_has_generics_args_suggestion {
             // We don't need this label if there's an inline suggestion, show otherwise.
-            for (span, assoc_items) in &associated_types {
             let mut names: FxIndexMap<_, usize> = FxIndexMap::default();
-                for item in assoc_items {
+            for item in &missing_assoc_types {
                 types_count += 1;
                 *names.entry(item.name).or_insert(0) += 1;
             }
             let mut label = vec![];
-                for item in assoc_items {
+            for item in &missing_assoc_types {
                 let postfix = if names[&item.name] > 1 {
                     let trait_def_id = item.container_id(tcx);
                     format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id))
@@ -943,7 +930,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
             if !label.is_empty() {
                 err.span_label(
-                        *span,
+                    principal_span,
                     format!(
                         "associated type{} {} must be specified",
                         pluralize!(label.len()),
@@ -952,7 +939,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 );
             }
         }
-        }
         suggestions.sort_by_key(|&(span, _)| span);
         // There are cases where one bound points to a span within another bound's span, like when
         // you have code like the following (#115019), so we skip providing a suggestion in those