Properly suggest E::assoc when we encounter E::Variant::assoc

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -459,7 +459,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             return (err, Vec::new());
         }
 
-        let (found, mut candidates) = self.try_lookup_name_relaxed(
+        let (found, suggested_candidates, mut candidates) = self.try_lookup_name_relaxed(
             &mut err,
             source,
             path,
@@ -478,7 +478,15 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         }
 
         let mut fallback = self.suggest_trait_and_bounds(&mut err, source, res, span, &base_error);
-        fallback |= self.suggest_typo(&mut err, source, path, following_seg, span, &base_error);
+        fallback |= self.suggest_typo(
+            &mut err,
+            source,
+            path,
+            following_seg,
+            span,
+            &base_error,
+            suggested_candidates,
+        );
 
         if fallback {
             // Fallback label.
@@ -589,7 +597,16 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         span: Span,
         res: Option<Res>,
         base_error: &BaseError,
-    ) -> (bool, Vec<ImportSuggestion>) {
+    ) -> (bool, FxHashSet<String>, Vec<ImportSuggestion>) {
+        let span = match following_seg {
+            Some(_) if path[0].ident.span.eq_ctxt(path[path.len() - 1].ident.span) => {
+                // The path `span` that comes in includes any following segments, which we don't
+                // want to replace in the suggestions.
+                path[0].ident.span.to(path[path.len() - 1].ident.span)
+            }
+            _ => span,
+        };
+        let mut suggested_candidates = FxHashSet::default();
         // Try to lookup name in more relaxed fashion for better error reporting.
         let ident = path.last().unwrap().ident;
         let is_expected = &|res| source.is_expected(res);
@@ -646,6 +663,11 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 };
                 let msg = format!("{preamble}try using the variant's enum");
 
+                suggested_candidates.extend(
+                    enum_candidates
+                        .iter()
+                        .map(|(_variant_path, enum_ty_path)| enum_ty_path.clone()),
+                );
                 err.span_suggestions(
                     span,
                     msg,
@@ -658,7 +680,8 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         // Try finding a suitable replacement.
         let typo_sugg = self
             .lookup_typo_candidate(path, following_seg, source.namespace(), is_expected)
-            .to_opt_suggestion();
+            .to_opt_suggestion()
+            .filter(|sugg| !suggested_candidates.contains(sugg.candidate.as_str()));
         if let [segment] = path
             && !matches!(source, PathSource::Delegation)
             && self.self_type_is_available()
@@ -719,7 +742,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     }
                 }
                 self.r.add_typo_suggestion(err, typo_sugg, ident_span);
-                return (true, candidates);
+                return (true, suggested_candidates, candidates);
             }
 
             // If the first argument in call is `self` suggest calling a method.
@@ -737,7 +760,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     format!("self.{path_str}({args_snippet})"),
                     Applicability::MachineApplicable,
                 );
-                return (true, candidates);
+                return (true, suggested_candidates, candidates);
             }
         }
 
@@ -754,7 +777,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             ) {
                 // We do this to avoid losing a secondary span when we override the main error span.
                 self.r.add_typo_suggestion(err, typo_sugg, ident_span);
-                return (true, candidates);
+                return (true, suggested_candidates, candidates);
             }
         }
 
@@ -772,7 +795,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                         ident.span,
                         format!("the binding `{path_str}` is available in a different scope in the same function"),
                     );
-                    return (true, candidates);
+                    return (true, suggested_candidates, candidates);
                 }
             }
         }
@@ -781,7 +804,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             candidates = self.smart_resolve_partial_mod_path_errors(path, following_seg);
         }
 
-        (false, candidates)
+        (false, suggested_candidates, candidates)
     }
 
     fn suggest_trait_and_bounds(
@@ -869,13 +892,16 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
         following_seg: Option<&Segment>,
         span: Span,
         base_error: &BaseError,
+        suggested_candidates: FxHashSet<String>,
     ) -> bool {
         let is_expected = &|res| source.is_expected(res);
         let ident_span = path.last().map_or(span, |ident| ident.ident.span);
         let typo_sugg =
             self.lookup_typo_candidate(path, following_seg, source.namespace(), is_expected);
         let mut fallback = false;
-        let typo_sugg = typo_sugg.to_opt_suggestion();
+        let typo_sugg = typo_sugg
+            .to_opt_suggestion()
+            .filter(|sugg| !suggested_candidates.contains(sugg.candidate.as_str()));
         if !self.r.add_typo_suggestion(err, typo_sugg, ident_span) {
             fallback = true;
             match self.diag_metadata.current_let_binding {

tests/ui/enum/assoc-fn-call-on-variant.rs

@@ -0,0 +1,15 @@
+#[derive(Default)]
+enum E {
+    A {},
+    B {},
+    #[default]
+    C,
+}
+
+impl E {
+    fn f() {}
+}
+
+fn main() {
+    E::A::f(); //~ ERROR failed to resolve: `A` is a variant, not a module
+}

tests/ui/enum/assoc-fn-call-on-variant.stderr

@@ -0,0 +1,14 @@
+error[E0433]: failed to resolve: `A` is a variant, not a module
+  --> $DIR/assoc-fn-call-on-variant.rs:14:8
+   |
+LL |     E::A::f();
+   |        ^ `A` is a variant, not a module
+   |
+help: there is an enum variant `E::A`; try using the variant's enum
+   |
+LL |     E::f();
+   |     ~
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0433`.

tests/ui/resolve/resolve-variant-assoc-item.stderr

@@ -6,7 +6,7 @@ LL |     E::V::associated_item;
    |
 help: there is an enum variant `E::V`; try using the variant's enum
    |
-LL |     E;
+LL |     E::associated_item;
    |     ~
 
 error[E0433]: failed to resolve: `V` is a variant, not a module
@@ -17,10 +17,6 @@ LL |     V::associated_item;
    |
 help: there is an enum variant `E::V`; try using the variant's enum
    |
-LL |     E;
-   |     ~
-help: an enum with a similar name exists
-   |
 LL |     E::associated_item;
    |     ~