Add infrastructure #[rustc_confusables] attribute to allow targeted

"no method" errors on standard library types

The standard library developer can annotate methods on e.g.
`BTreeSet::push` with `#[rustc_confusables("insert")]`. When the user
mistypes `btreeset.push()`, `BTreeSet::insert` will be suggested if
there are no other candidates to suggest.

compiler/rustc_passes/messages.ftl

@@ -98,6 +98,9 @@ passes_collapse_debuginfo =
     `collapse_debuginfo` attribute should be applied to macro definitions
     .label = not a macro definition
 
+passes_confusables = attribute should be applied to an inherent method
+    .label = not an inherent method
+
 passes_const_impl_const_trait =
     const `impl`s must be for traits marked with `#[const_trait]`
     .note = this trait must be annotated with `#[const_trait]`
@@ -266,6 +269,9 @@ passes_duplicate_lang_item_crate_depends =
     .first_definition_path = first definition in `{$orig_crate_name}` loaded from {$orig_path}
     .second_definition_path = second definition in `{$crate_name}` loaded from {$path}
 
+passes_empty_confusables =
+    expected at least one confusable name
+
 passes_export_name =
     attribute should be applied to a free function, impl method or static
     .label = not a free function, impl method or static
@@ -326,6 +332,9 @@ passes_implied_feature_not_exist =
 passes_incorrect_do_not_recommend_location =
     `#[do_not_recommend]` can only be placed on trait implementations
 
+passes_incorrect_meta_item = expected a quoted string literal
+passes_incorrect_meta_item_suggestion = consider surrounding this with quotes
+
 passes_incorrect_target =
     `{$name}` language item must be applied to a {$kind} with {$at_least ->
         [true] at least {$num}

compiler/rustc_passes/src/check_attr.rs

@@ -183,6 +183,7 @@ impl CheckAttrVisitor<'_> {
                 | sym::rustc_allowed_through_unstable_modules
                 | sym::rustc_promotable => self.check_stability_promotable(&attr, span, target),
                 sym::link_ordinal => self.check_link_ordinal(&attr, span, target),
+                sym::rustc_confusables => self.check_confusables(&attr, target),
                 _ => true,
             };
 
@@ -1985,6 +1986,46 @@ impl CheckAttrVisitor<'_> {
         }
     }
 
+    fn check_confusables(&self, attr: &Attribute, target: Target) -> bool {
+        match target {
+            Target::Method(MethodKind::Inherent) => {
+                let Some(meta) = attr.meta() else {
+                    return false;
+                };
+                let ast::MetaItem { kind: MetaItemKind::List(ref metas), .. } = meta else {
+                    return false;
+                };
+
+                let mut candidates = Vec::new();
+
+                for meta in metas {
+                    let NestedMetaItem::Lit(meta_lit) = meta else {
+                        self.tcx.sess.emit_err(errors::IncorrectMetaItem {
+                            span: meta.span(),
+                            suggestion: errors::IncorrectMetaItemSuggestion {
+                                lo: meta.span().shrink_to_lo(),
+                                hi: meta.span().shrink_to_hi(),
+                            },
+                        });
+                        return false;
+                    };
+                    candidates.push(meta_lit.symbol);
+                }
+
+                if candidates.is_empty() {
+                    self.tcx.sess.emit_err(errors::EmptyConfusables { span: attr.span });
+                    return false;
+                }
+
+                true
+            }
+            _ => {
+                self.tcx.sess.emit_err(errors::Confusables { attr_span: attr.span });
+                false
+            }
+        }
+    }
+
     fn check_deprecated(&self, hir_id: HirId, attr: &Attribute, _span: Span, target: Target) {
         match target {
             Target::Closure | Target::Expression | Target::Statement | Target::Arm => {

compiler/rustc_passes/src/errors.rs

@@ -617,6 +617,38 @@ pub struct LinkOrdinal {
     pub attr_span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(passes_confusables)]
+pub struct Confusables {
+    #[primary_span]
+    pub attr_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(passes_empty_confusables)]
+pub(crate) struct EmptyConfusables {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(passes_incorrect_meta_item, code = "E0539")]
+pub(crate) struct IncorrectMetaItem {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub suggestion: IncorrectMetaItemSuggestion,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(passes_incorrect_meta_item_suggestion, applicability = "maybe-incorrect")]
+pub(crate) struct IncorrectMetaItemSuggestion {
+    #[suggestion_part(code = "\"")]
+    pub lo: Span,
+    #[suggestion_part(code = "\"")]
+    pub hi: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(passes_stability_promotable)]
 pub struct StabilityPromotable {