Rollup merge of #162942 - nnethercote:rm-StashKey-AssociatedTypeSuggestion, r=davidtwco

Remove `StashKey::AssociatedTypeSuggestion`

Currently it's used in a really hacky way: a diagnostic with an empty message and some suggestions is stashed. Later on it might be retrieved and its suggestions extracted. It uses `Level::Allow` so that it isn't printed by `emit_stashed_diagnostics` at shutdown if it hasn't been retrieved.

This isn't a normal stashed diagnostic, more just a case of "save some information that might be useful for diagnostics later". We can record the information more simply and directly.

This commit adds `paths_matching_assoc_types` fields to `Resolver` and `ResolverGlobalCtxt`. These store the spans of the paths of interest. The new subdiagnostic `AssocTypeWithSameName` is used to construct the relevant suggestions when they are needed. Much nicer. The old approach removed the stashed diagnostic and the new approach doesn't remove the set entry, so a single span could conceivably match more than once, presumably a good thing, though this doesn't show up in the test suite.

r? @davidtwco

Author: JonathanBrouwer

compiler/rustc_errors/src/lib.rs

@@ -384,7 +384,6 @@ pub enum StashKey {
     /// FRU syntax
     MaybeFruTypo,
     CallAssocMethod,
-    AssociatedTypeSuggestion,
     UndeterminedMacroResolution,
     /// Used by `Parser::maybe_recover_trailing_expr`
     ExprInPat,

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs

@@ -2,10 +2,7 @@ use rustc_ast::TraitObjectSyntax;
 use rustc_attr_ir::lang_items::LangItem;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::codes::*;
-use rustc_errors::{
-    Applicability, Diag, DiagCtxtHandle, Diagnostic, Level, StashKey, Suggestions,
-    struct_span_code_err,
-};
+use rustc_errors::{Applicability, Diag, DiagCtxtHandle, Diagnostic, Level, struct_span_code_err};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{self as hir, HirId};
@@ -17,6 +14,7 @@ use rustc_middle::ty::{
 };
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::{ErrorGuaranteed, Span};
+use rustc_trait_selection::diagnostics::AssocTypeWithSameName;
 use rustc_trait_selection::error_reporting::traits::report_dyn_incompatibility;
 use rustc_trait_selection::error_reporting::traits::suggestions::NextTypeParamName;
 use rustc_trait_selection::traits;
@@ -655,15 +653,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 poly_trait_ref.trait_ref.trait_def_id(),
                 &mut diag,
             );
-            // In case there is an associated type with the same name
-            // Add the suggestion to this error
-            if let Some(mut sugg) =
-                self.dcx().steal_non_err(span, StashKey::AssociatedTypeSuggestion)
-                && let Suggestions::Enabled(ref mut s1) = diag.suggestions
-                && let Suggestions::Enabled(ref mut s2) = sugg.suggestions
+            // If there is an associated type with the same name, add the suggestion to this error.
+            if self
+                .tcx()
+                .resolutions(())
+                .paths_matching_assoc_types
+                .contains(&span.with_parent(None))
             {
-                s1.append(s2);
-                sugg.cancel();
+                diag.subdiagnostic(AssocTypeWithSameName { span: span.shrink_to_lo() });
             }
             Some(diag.emit_err())
         } else {

compiler/rustc_middle/src/middle/resolve.rs

@@ -180,6 +180,9 @@ pub struct ResolverGlobalCtxt {
     /// A list of proc macro LocalDefIds, written out in the order in which
     /// they are declared in the static array generated by proc_macro_harness.
     pub proc_macros: Vec<LocalDefId>,
+    /// Path spans where the ident matches an associated type for an enclosing trait. Used to
+    /// improve certain error messages.
+    pub paths_matching_assoc_types: UnordSet<Span>,
     /// Mapping from ident span to path span for paths that don't exist as written, but that
     /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
     pub confused_type_with_std_module: FxIndexMap<Span, Span>,

compiler/rustc_resolve/src/late.rs

@@ -22,7 +22,7 @@ use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagArgValue, Diagnostic, ErrorGuaranteed, IntoDiagArg, MultiSpan,
-    StashKey, Suggestions, elided_lifetime_in_path_suggestion, pluralize,
+    Suggestions, elided_lifetime_in_path_suggestion, pluralize,
 };
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{CtorKind, DefKind, NonMacroAttrKind, PerNS};
@@ -4823,7 +4823,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             source,
         ) {
             Ok(Some(partial_res)) if let Some(res) = partial_res.full_res() => {
-                // if we also have an associated type that matches the ident, stash a suggestion
+                // If we also have an associated type that matches the ident, record that.
                 if let Some(items) = self.diag_metadata.current_trait_assoc_items
                     && let [Segment { ident, .. }] = path
                     && items.iter().any(|item| {
@@ -4836,14 +4836,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         }
                     })
                 {
-                    let mut diag = self.r.tcx.dcx().struct_allow("");
-                    diag.span_suggestion_verbose(
-                        path_span.shrink_to_lo(),
-                        "there is an associated type with the same name",
-                        "Self::",
-                        Applicability::MaybeIncorrect,
-                    );
-                    diag.stash(path_span, StashKey::AssociatedTypeSuggestion);
+                    self.r.paths_matching_assoc_types.insert(path_span.with_parent(None));
                 }
 
                 if source.is_expected(res) || res == Res::Err {

compiler/rustc_resolve/src/lib.rs

@@ -1529,6 +1529,7 @@ pub struct Resolver<'ra, 'tcx> {
     /// A list of proc macro LocalDefIds, written out in the order in which
     /// they are declared in the static array generated by proc_macro_harness.
     proc_macros: Vec<LocalDefId> = Vec::new(),
+    paths_matching_assoc_types: UnordSet<Span>,
     confused_type_with_std_module: FxIndexMap<Span, Span>,
 
     /// Names of items that were stripped out via cfg with their corresponding cfg meta item.
@@ -1892,6 +1893,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             invocation_parents,
             trait_impls: Default::default(),
             confused_type_with_std_module: Default::default(),
+            paths_matching_assoc_types: Default::default(),
             stripped_cfg_items: Default::default(),
             effective_visibilities: Default::default(),
             macro_reachable_adts: Default::default(),
@@ -1970,6 +1972,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let glob_map = self.glob_map;
         let main_def = self.main_def;
         let confused_type_with_std_module = self.confused_type_with_std_module;
+        let paths_matching_assoc_types = self.paths_matching_assoc_types;
         let effective_visibilities = self.effective_visibilities;
 
         let stripped_cfg_items = self
@@ -2000,6 +2003,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             trait_impls: self.trait_impls,
             proc_macros,
             confused_type_with_std_module,
+            paths_matching_assoc_types,
             doc_link_resolutions: self.doc_link_resolutions,
             doc_link_traits_in_scope: self.doc_link_traits_in_scope,
             all_macro_rules: self.all_macro_rules,

compiler/rustc_trait_selection/src/diagnostics.rs

@@ -2083,3 +2083,15 @@ pub(crate) struct NonGenericOpaqueTypeParam<'a, 'tcx> {
     }")]
     pub param_span: Span,
 }
+
+#[derive(Subdiagnostic)]
+#[suggestion(
+    "there is an associated type with the same name",
+    style = "verbose",
+    code = "Self::",
+    applicability = "maybe-incorrect"
+)]
+pub struct AssocTypeWithSameName {
+    #[primary_span]
+    pub span: Span,
+}

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -13,8 +13,8 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
 use rustc_errors::{
-    Applicability, Diag, ErrorGuaranteed, MultiSpan, StashKey, StringPart, Sublevel, Suggestions,
-    msg, pluralize, struct_span_code_err,
+    Applicability, Diag, ErrorGuaranteed, MultiSpan, StringPart, Sublevel, msg, pluralize,
+    struct_span_code_err,
 };
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::intravisit::Visitor;
@@ -42,7 +42,8 @@ use tracing::{debug, instrument};
 use super::suggestions::get_explanation_based_on_obligation;
 use super::{ArgKind, CandidateSimilarity, GetSafeTransmuteErrorAndReason, ImplCandidate};
 use crate::diagnostics::{
-    ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch, CoroClosureNotFn,
+    AssocTypeWithSameName, ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch,
+    CoroClosureNotFn,
 };
 use crate::error_reporting::TypeErrCtxt;
 use crate::error_reporting::infer::TyCategory;
@@ -3107,13 +3108,13 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             );
             self.suggest_unsized_bound_if_applicable(err, obligation);
             if let Some(span) = err.span.primary_span()
-                && let Some(mut diag) =
-                    self.dcx().steal_non_err(span, StashKey::AssociatedTypeSuggestion)
-                && let Suggestions::Enabled(ref mut s1) = err.suggestions
-                && let Suggestions::Enabled(ref mut s2) = diag.suggestions
+                && self
+                    .tcx
+                    .resolutions(())
+                    .paths_matching_assoc_types
+                    .contains(&span.with_parent(None))
             {
-                s1.append(s2);
-                diag.cancel()
+                err.subdiagnostic(AssocTypeWithSameName { span: span.shrink_to_lo() });
             }
         }
     }