src/librustdoc/core.rs

   1 use rustc_ast::NodeId;
   2 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   3 use rustc_data_structures::sync::{self, Lrc};
   4 use rustc_errors::emitter::{Emitter, EmitterWriter};
   5 use rustc_errors::json::JsonEmitter;
   6 use rustc_feature::UnstableFeatures;
   7 use rustc_hir::def::{Namespace, Res};
   8 use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
   9 use rustc_hir::intravisit::{self, Visitor};
  10 use rustc_hir::{HirId, Path, TraitCandidate};
  11 use rustc_interface::interface;
  12 use rustc_middle::hir::nested_filter;
  13 use rustc_middle::middle::privacy::AccessLevels;
  14 use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
  15 use rustc_resolve as resolve;
  16 use rustc_session::config::{self, CrateType, ErrorOutputType};
  17 use rustc_session::lint;
  18 use rustc_session::DiagnosticOutput;
  19 use rustc_session::Session;
  20 use rustc_span::symbol::sym;
  21 use rustc_span::{source_map, Span, Symbol};
  22
  23 use std::cell::RefCell;
  24 use std::mem;
  25 use std::rc::Rc;
  26 use std::sync::LazyLock;
  27
  28 use crate::clean::inline::build_external_trait;
  29 use crate::clean::{self, ItemId, TraitWithExtraInfo};
  30 use crate::config::{Options as RustdocOptions, OutputFormat, RenderOptions};
  31 use crate::formats::cache::Cache;
  32 use crate::passes::collect_intra_doc_links::PreprocessedMarkdownLink;
  33 use crate::passes::{self, Condition::*};
  34
  35 pub(crate) use rustc_session::config::{DebuggingOptions, Input, Options};
  36
  37 pub(crate) struct ResolverCaches {
  38     pub(crate) markdown_links: Option<FxHashMap<String, Vec<PreprocessedMarkdownLink>>>,
  39     pub(crate) doc_link_resolutions: FxHashMap<(Symbol, Namespace, DefId), Option<Res<NodeId>>>,
  40     /// Traits in scope for a given module.
  41     /// See `collect_intra_doc_links::traits_implemented_by` for more details.
  42     pub(crate) traits_in_scope: DefIdMap<Vec<TraitCandidate>>,
  43     pub(crate) all_traits: Option<Vec<DefId>>,
  44     pub(crate) all_trait_impls: Option<Vec<DefId>>,
  45     pub(crate) all_macro_rules: FxHashMap<Symbol, Res<NodeId>>,
  46 }
  47
  48 pub(crate) struct DocContext<'tcx> {
  49     pub(crate) tcx: TyCtxt<'tcx>,
  50     /// Name resolver. Used for intra-doc links.
  51     ///
  52     /// The `Rc<RefCell<...>>` wrapping is needed because that is what's returned by
  53     /// [`rustc_interface::Queries::expansion()`].
  54     // FIXME: see if we can get rid of this RefCell somehow
  55     pub(crate) resolver: Rc<RefCell<interface::BoxedResolver>>,
  56     pub(crate) resolver_caches: ResolverCaches,
  57     /// Used for normalization.
  58     ///
  59     /// Most of this logic is copied from rustc_lint::late.
  60     pub(crate) param_env: ParamEnv<'tcx>,
  61     /// Later on moved through `clean::Crate` into `cache`
  62     pub(crate) external_traits: Rc<RefCell<FxHashMap<DefId, clean::TraitWithExtraInfo>>>,
  63     /// Used while populating `external_traits` to ensure we don't process the same trait twice at
  64     /// the same time.
  65     pub(crate) active_extern_traits: FxHashSet<DefId>,
  66     // The current set of parameter substitutions,
  67     // for expanding type aliases at the HIR level:
  68     /// Table `DefId` of type, lifetime, or const parameter -> substituted type, lifetime, or const
  69     pub(crate) substs: FxHashMap<DefId, clean::SubstParam>,
  70     /// Table synthetic type parameter for `impl Trait` in argument position -> bounds
  71     pub(crate) impl_trait_bounds: FxHashMap<ImplTraitParam, Vec<clean::GenericBound>>,
  72     /// Auto-trait or blanket impls processed so far, as `(self_ty, trait_def_id)`.
  73     // FIXME(eddyb) make this a `ty::TraitRef<'tcx>` set.
  74     pub(crate) generated_synthetics: FxHashSet<(Ty<'tcx>, DefId)>,
  75     pub(crate) auto_traits: Vec<DefId>,
  76     /// The options given to rustdoc that could be relevant to a pass.
  77     pub(crate) render_options: RenderOptions,
  78     /// This same cache is used throughout rustdoc, including in [`crate::html::render`].
  79     pub(crate) cache: Cache,
  80     /// Used by [`clean::inline`] to tell if an item has already been inlined.
  81     pub(crate) inlined: FxHashSet<ItemId>,
  82     /// Used by `calculate_doc_coverage`.
  83     pub(crate) output_format: OutputFormat,
  84 }
  85
  86 impl<'tcx> DocContext<'tcx> {
  87     pub(crate) fn sess(&self) -> &'tcx Session {
  88         self.tcx.sess
  89     }
  90
  91     pub(crate) fn with_param_env<T, F: FnOnce(&mut Self) -> T>(
  92         &mut self,
  93         def_id: DefId,
  94         f: F,
  95     ) -> T {
  96         let old_param_env = mem::replace(&mut self.param_env, self.tcx.param_env(def_id));
  97         let ret = f(self);
  98         self.param_env = old_param_env;
  99         ret
 100     }
 101
 102     pub(crate) fn enter_resolver<F, R>(&self, f: F) -> R
 103     where
 104         F: FnOnce(&mut resolve::Resolver<'_>) -> R,
 105     {
 106         self.resolver.borrow_mut().access(f)
 107     }
 108
 109     /// Call the closure with the given parameters set as
 110     /// the substitutions for a type alias' RHS.
 111     pub(crate) fn enter_alias<F, R>(
 112         &mut self,
 113         substs: FxHashMap<DefId, clean::SubstParam>,
 114         f: F,
 115     ) -> R
 116     where
 117         F: FnOnce(&mut Self) -> R,
 118     {
 119         let old_substs = mem::replace(&mut self.substs, substs);
 120         let r = f(self);
 121         self.substs = old_substs;
 122         r
 123     }
 124
 125     /// Like `hir().local_def_id_to_hir_id()`, but skips calling it on fake DefIds.
 126     /// (This avoids a slice-index-out-of-bounds panic.)
 127     pub(crate) fn as_local_hir_id(tcx: TyCtxt<'_>, item_id: ItemId) -> Option<HirId> {
 128         match item_id {
 129             ItemId::DefId(real_id) => {
 130                 real_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
 131             }
 132             // FIXME: Can this be `Some` for `Auto` or `Blanket`?
 133             _ => None,
 134         }
 135     }
 136
 137     pub(crate) fn with_all_traits(&mut self, f: impl FnOnce(&mut Self, &[DefId])) {
 138         let all_traits = self.resolver_caches.all_traits.take();
 139         f(self, all_traits.as_ref().expect("`all_traits` are already borrowed"));
 140         self.resolver_caches.all_traits = all_traits;
 141     }
 142
 143     pub(crate) fn with_all_trait_impls(&mut self, f: impl FnOnce(&mut Self, &[DefId])) {
 144         let all_trait_impls = self.resolver_caches.all_trait_impls.take();
 145         f(self, all_trait_impls.as_ref().expect("`all_trait_impls` are already borrowed"));
 146         self.resolver_caches.all_trait_impls = all_trait_impls;
 147     }
 148 }
 149
 150 /// Creates a new diagnostic `Handler` that can be used to emit warnings and errors.
 151 ///
 152 /// If the given `error_format` is `ErrorOutputType::Json` and no `SourceMap` is given, a new one
 153 /// will be created for the handler.
 154 pub(crate) fn new_handler(
 155     error_format: ErrorOutputType,
 156     source_map: Option<Lrc<source_map::SourceMap>>,
 157     debugging_opts: &DebuggingOptions,
 158 ) -> rustc_errors::Handler {
 159     let fallback_bundle =
 160         rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
 161     let emitter: Box<dyn Emitter + sync::Send> = match error_format {
 162         ErrorOutputType::HumanReadable(kind) => {
 163             let (short, color_config) = kind.unzip();
 164             Box::new(
 165                 EmitterWriter::stderr(
 166                     color_config,
 167                     source_map.map(|sm| sm as _),
 168                     None,
 169                     fallback_bundle,
 170                     short,
 171                     debugging_opts.teach,
 172                     debugging_opts.terminal_width,
 173                     false,
 174                 )
 175                 .ui_testing(debugging_opts.ui_testing),
 176             )
 177         }
 178         ErrorOutputType::Json { pretty, json_rendered } => {
 179             let source_map = source_map.unwrap_or_else(|| {
 180                 Lrc::new(source_map::SourceMap::new(source_map::FilePathMapping::empty()))
 181             });
 182             Box::new(
 183                 JsonEmitter::stderr(
 184                     None,
 185                     source_map,
 186                     None,
 187                     fallback_bundle,
 188                     pretty,
 189                     json_rendered,
 190                     debugging_opts.terminal_width,
 191                     false,
 192                 )
 193                 .ui_testing(debugging_opts.ui_testing),
 194             )
 195         }
 196     };
 197
 198     rustc_errors::Handler::with_emitter_and_flags(
 199         emitter,
 200         debugging_opts.diagnostic_handler_flags(true),
 201     )
 202 }
 203
 204 /// Parse, resolve, and typecheck the given crate.
 205 pub(crate) fn create_config(
 206     RustdocOptions {
 207         input,
 208         crate_name,
 209         proc_macro_crate,
 210         error_format,
 211         libs,
 212         externs,
 213         mut cfgs,
 214         check_cfgs,
 215         codegen_options,
 216         debugging_opts,
 217         target,
 218         edition,
 219         maybe_sysroot,
 220         lint_opts,
 221         describe_lints,
 222         lint_cap,
 223         scrape_examples_options,
 224         ..
 225     }: RustdocOptions,
 226 ) -> rustc_interface::Config {
 227     // Add the doc cfg into the doc build.
 228     cfgs.push("doc".to_string());
 229
 230     let cpath = Some(input.clone());
 231     let input = Input::File(input);
 232
 233     // By default, rustdoc ignores all lints.
 234     // Specifically unblock lints relevant to documentation or the lint machinery itself.
 235     let mut lints_to_show = vec![
 236         // it's unclear whether these should be part of rustdoc directly (#77364)
 237         rustc_lint::builtin::MISSING_DOCS.name.to_string(),
 238         rustc_lint::builtin::INVALID_DOC_ATTRIBUTES.name.to_string(),
 239         // these are definitely not part of rustdoc, but we want to warn on them anyway.
 240         rustc_lint::builtin::RENAMED_AND_REMOVED_LINTS.name.to_string(),
 241         rustc_lint::builtin::UNKNOWN_LINTS.name.to_string(),
 242         rustc_lint::builtin::UNEXPECTED_CFGS.name.to_string(),
 243         // this lint is needed to support `#[expect]` attributes
 244         rustc_lint::builtin::UNFULFILLED_LINT_EXPECTATIONS.name.to_string(),
 245     ];
 246     lints_to_show.extend(crate::lint::RUSTDOC_LINTS.iter().map(|lint| lint.name.to_string()));
 247
 248     let (lint_opts, lint_caps) = crate::lint::init_lints(lints_to_show, lint_opts, |lint| {
 249         Some((lint.name_lower(), lint::Allow))
 250     });
 251
 252     let crate_types =
 253         if proc_macro_crate { vec![CrateType::ProcMacro] } else { vec![CrateType::Rlib] };
 254     let test = scrape_examples_options.map(|opts| opts.scrape_tests).unwrap_or(false);
 255     // plays with error output here!
 256     let sessopts = config::Options {
 257         maybe_sysroot,
 258         search_paths: libs,
 259         crate_types,
 260         lint_opts,
 261         lint_cap,
 262         cg: codegen_options,
 263         externs,
 264         target_triple: target,
 265         unstable_features: UnstableFeatures::from_environment(crate_name.as_deref()),
 266         actually_rustdoc: true,
 267         debugging_opts,
 268         error_format,
 269         edition,
 270         describe_lints,
 271         crate_name,
 272         test,
 273         ..Options::default()
 274     };
 275
 276     interface::Config {
 277         opts: sessopts,
 278         crate_cfg: interface::parse_cfgspecs(cfgs),
 279         crate_check_cfg: interface::parse_check_cfg(check_cfgs),
 280         input,
 281         input_path: cpath,
 282         output_file: None,
 283         output_dir: None,
 284         file_loader: None,
 285         diagnostic_output: DiagnosticOutput::Default,
 286         lint_caps,
 287         parse_sess_created: None,
 288         register_lints: Some(box crate::lint::register_lints),
 289         override_queries: Some(|_sess, providers, _external_providers| {
 290             // Most lints will require typechecking, so just don't run them.
 291             providers.lint_mod = |_, _| {};
 292             // Prevent `rustc_typeck::check_crate` from calling `typeck` on all bodies.
 293             providers.typeck_item_bodies = |_, _| {};
 294             // hack so that `used_trait_imports` won't try to call typeck
 295             providers.used_trait_imports = |_, _| {
 296                 static EMPTY_SET: LazyLock<FxHashSet<LocalDefId>> =
 297                     LazyLock::new(FxHashSet::default);
 298                 &EMPTY_SET
 299             };
 300             // In case typeck does end up being called, don't ICE in case there were name resolution errors
 301             providers.typeck = move |tcx, def_id| {
 302                 // Closures' tables come from their outermost function,
 303                 // as they are part of the same "inference environment".
 304                 // This avoids emitting errors for the parent twice (see similar code in `typeck_with_fallback`)
 305                 let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id()).expect_local();
 306                 if typeck_root_def_id != def_id {
 307                     return tcx.typeck(typeck_root_def_id);
 308                 }
 309
 310                 let hir = tcx.hir();
 311                 let body = hir.body(hir.body_owned_by(hir.local_def_id_to_hir_id(def_id)));
 312                 debug!("visiting body for {:?}", def_id);
 313                 EmitIgnoredResolutionErrors::new(tcx).visit_body(body);
 314                 (rustc_interface::DEFAULT_QUERY_PROVIDERS.typeck)(tcx, def_id)
 315             };
 316         }),
 317         make_codegen_backend: None,
 318         registry: rustc_driver::diagnostics_registry(),
 319     }
 320 }
 321
 322 pub(crate) fn run_global_ctxt(
 323     tcx: TyCtxt<'_>,
 324     resolver: Rc<RefCell<interface::BoxedResolver>>,
 325     resolver_caches: ResolverCaches,
 326     show_coverage: bool,
 327     render_options: RenderOptions,
 328     output_format: OutputFormat,
 329 ) -> (clean::Crate, RenderOptions, Cache) {
 330     // Certain queries assume that some checks were run elsewhere
 331     // (see https://github.com/rust-lang/rust/pull/73566#issuecomment-656954425),
 332     // so type-check everything other than function bodies in this crate before running lints.
 333
 334     // NOTE: this does not call `tcx.analysis()` so that we won't
 335     // typeck function bodies or run the default rustc lints.
 336     // (see `override_queries` in the `config`)
 337
 338     // HACK(jynelson) this calls an _extremely_ limited subset of `typeck`
 339     // and might break if queries change their assumptions in the future.
 340
 341     // NOTE: This is copy/pasted from typeck/lib.rs and should be kept in sync with those changes.
 342     tcx.sess.time("item_types_checking", || {
 343         tcx.hir().for_each_module(|module| tcx.ensure().check_mod_item_types(module))
 344     });
 345     tcx.sess.abort_if_errors();
 346     tcx.sess.time("missing_docs", || {
 347         rustc_lint::check_crate(tcx, rustc_lint::builtin::MissingDoc::new);
 348     });
 349     tcx.sess.time("check_mod_attrs", || {
 350         tcx.hir().for_each_module(|module| tcx.ensure().check_mod_attrs(module))
 351     });
 352     rustc_passes::stability::check_unused_or_stable_features(tcx);
 353
 354     let auto_traits = resolver_caches
 355         .all_traits
 356         .as_ref()
 357         .expect("`all_traits` are already borrowed")
 358         .iter()
 359         .copied()
 360         .filter(|&trait_def_id| tcx.trait_is_auto(trait_def_id))
 361         .collect();
 362     let access_levels = AccessLevels {
 363         map: tcx.privacy_access_levels(()).map.iter().map(|(k, v)| (k.to_def_id(), *v)).collect(),
 364     };
 365
 366     let mut ctxt = DocContext {
 367         tcx,
 368         resolver,
 369         resolver_caches,
 370         param_env: ParamEnv::empty(),
 371         external_traits: Default::default(),
 372         active_extern_traits: Default::default(),
 373         substs: Default::default(),
 374         impl_trait_bounds: Default::default(),
 375         generated_synthetics: Default::default(),
 376         auto_traits,
 377         cache: Cache::new(access_levels, render_options.document_private),
 378         inlined: FxHashSet::default(),
 379         output_format,
 380         render_options,
 381     };
 382
 383     // Small hack to force the Sized trait to be present.
 384     //
 385     // Note that in case of `#![no_core]`, the trait is not available.
 386     if let Some(sized_trait_did) = ctxt.tcx.lang_items().sized_trait() {
 387         let mut sized_trait = build_external_trait(&mut ctxt, sized_trait_did);
 388         sized_trait.is_auto = true;
 389         ctxt.external_traits
 390             .borrow_mut()
 391             .insert(sized_trait_did, TraitWithExtraInfo { trait_: sized_trait, is_notable: false });
 392     }
 393
 394     debug!("crate: {:?}", tcx.hir().krate());
 395
 396     let mut krate = tcx.sess.time("clean_crate", || clean::krate(&mut ctxt));
 397
 398     if krate.module.doc_value().map(|d| d.is_empty()).unwrap_or(true) {
 399         let help = format!(
 400             "The following guide may be of use:\n\
 401             {}/rustdoc/how-to-write-documentation.html",
 402             crate::DOC_RUST_LANG_ORG_CHANNEL
 403         );
 404         tcx.struct_lint_node(
 405             crate::lint::MISSING_CRATE_LEVEL_DOCS,
 406             DocContext::as_local_hir_id(tcx, krate.module.item_id).unwrap(),
 407             |lint| {
 408                 let mut diag =
 409                     lint.build("no documentation found for this crate's top-level module");
 410                 diag.help(&help);
 411                 diag.emit();
 412             },
 413         );
 414     }
 415
 416     fn report_deprecated_attr(name: &str, diag: &rustc_errors::Handler, sp: Span) {
 417         let mut msg =
 418             diag.struct_span_warn(sp, &format!("the `#![doc({})]` attribute is deprecated", name));
 419         msg.note(
 420             "see issue #44136 <https://github.com/rust-lang/rust/issues/44136> \
 421             for more information",
 422         );
 423
 424         if name == "no_default_passes" {
 425             msg.help("`#![doc(no_default_passes)]` no longer functions; you may want to use `#![doc(document_private_items)]`");
 426         } else if name.starts_with("passes") {
 427             msg.help("`#![doc(passes = \"...\")]` no longer functions; you may want to use `#![doc(document_private_items)]`");
 428         } else if name.starts_with("plugins") {
 429             msg.warn("`#![doc(plugins = \"...\")]` no longer functions; see CVE-2018-1000622 <https://nvd.nist.gov/vuln/detail/CVE-2018-1000622>");
 430         }
 431
 432         msg.emit();
 433     }
 434
 435     // Process all of the crate attributes, extracting plugin metadata along
 436     // with the passes which we are supposed to run.
 437     for attr in krate.module.attrs.lists(sym::doc) {
 438         let diag = ctxt.sess().diagnostic();
 439
 440         let name = attr.name_or_empty();
 441         // `plugins = "..."`, `no_default_passes`, and `passes = "..."` have no effect
 442         if attr.is_word() && name == sym::no_default_passes {
 443             report_deprecated_attr("no_default_passes", diag, attr.span());
 444         } else if attr.value_str().is_some() {
 445             match name {
 446                 sym::passes => {
 447                     report_deprecated_attr("passes = \"...\"", diag, attr.span());
 448                 }
 449                 sym::plugins => {
 450                     report_deprecated_attr("plugins = \"...\"", diag, attr.span());
 451                 }
 452                 _ => (),
 453             }
 454         }
 455
 456         if attr.is_word() && name == sym::document_private_items {
 457             ctxt.render_options.document_private = true;
 458         }
 459     }
 460
 461     info!("Executing passes");
 462
 463     for p in passes::defaults(show_coverage) {
 464         let run = match p.condition {
 465             Always => true,
 466             WhenDocumentPrivate => ctxt.render_options.document_private,
 467             WhenNotDocumentPrivate => !ctxt.render_options.document_private,
 468             WhenNotDocumentHidden => !ctxt.render_options.document_hidden,
 469         };
 470         if run {
 471             debug!("running pass {}", p.pass.name);
 472             krate = tcx.sess.time(p.pass.name, || (p.pass.run)(krate, &mut ctxt));
 473         }
 474     }
 475
 476     tcx.sess.time("check_lint_expectations", || tcx.check_expectations(Some(sym::rustdoc)));
 477
 478     if tcx.sess.diagnostic().has_errors_or_lint_errors().is_some() {
 479         rustc_errors::FatalError.raise();
 480     }
 481
 482     krate = tcx.sess.time("create_format_cache", || Cache::populate(&mut ctxt, krate));
 483
 484     (krate, ctxt.render_options, ctxt.cache)
 485 }
 486
 487 /// Due to <https://github.com/rust-lang/rust/pull/73566>,
 488 /// the name resolution pass may find errors that are never emitted.
 489 /// If typeck is called after this happens, then we'll get an ICE:
 490 /// 'Res::Error found but not reported'. To avoid this, emit the errors now.
 491 struct EmitIgnoredResolutionErrors<'tcx> {
 492     tcx: TyCtxt<'tcx>,
 493 }
 494
 495 impl<'tcx> EmitIgnoredResolutionErrors<'tcx> {
 496     fn new(tcx: TyCtxt<'tcx>) -> Self {
 497         Self { tcx }
 498     }
 499 }
 500
 501 impl<'tcx> Visitor<'tcx> for EmitIgnoredResolutionErrors<'tcx> {
 502     type NestedFilter = nested_filter::OnlyBodies;
 503
 504     fn nested_visit_map(&mut self) -> Self::Map {
 505         // We need to recurse into nested closures,
 506         // since those will fallback to the parent for type checking.
 507         self.tcx.hir()
 508     }
 509
 510     fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
 511         debug!("visiting path {:?}", path);
 512         if path.res == Res::Err {
 513             // We have less context here than in rustc_resolve,
 514             // so we can only emit the name and span.
 515             // However we can give a hint that rustc_resolve will have more info.
 516             let label = format!(
 517                 "could not resolve path `{}`",
 518                 path.segments
 519                     .iter()
 520                     .map(|segment| segment.ident.as_str())
 521                     .intersperse("::")
 522                     .collect::<String>()
 523             );
 524             let mut err = rustc_errors::struct_span_err!(
 525                 self.tcx.sess,
 526                 path.span,
 527                 E0433,
 528                 "failed to resolve: {}",
 529                 label
 530             );
 531             err.span_label(path.span, label);
 532             err.note("this error was originally ignored because you are running `rustdoc`");
 533             err.note("try running again with `rustc` or `cargo check` and you may get a more detailed error");
 534             err.emit();
 535         }
 536         // We could have an outer resolution that succeeded,
 537         // but with generic parameters that failed.
 538         // Recurse into the segments so we catch those too.
 539         intravisit::walk_path(self, path);
 540     }
 541 }
 542
 543 /// `DefId` or parameter index (`ty::ParamTy.index`) of a synthetic type parameter
 544 /// for `impl Trait` in argument position.
 545 #[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
 546 pub(crate) enum ImplTraitParam {
 547     DefId(DefId),
 548     ParamIndex(u32),
 549 }
 550
 551 impl From<DefId> for ImplTraitParam {
 552     fn from(did: DefId) -> Self {
 553         ImplTraitParam::DefId(did)
 554     }
 555 }
 556
 557 impl From<u32> for ImplTraitParam {
 558     fn from(idx: u32) -> Self {
 559         ImplTraitParam::ParamIndex(idx)
 560     }
 561 }