compiler/rustc_lint/src/internal.rs

   1 //! Some lints that are only useful in the compiler or crates that use compiler internals, such as
   2 //! Clippy.
   3
   4 use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
   5 use rustc_ast as ast;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::def::Res;
   8 use rustc_hir::{def_id::DefId, Expr, ExprKind, GenericArg, PatKind, Path, PathSegment, QPath};
   9 use rustc_hir::{HirId, Impl, Item, ItemKind, Node, Pat, Ty, TyKind};
  10 use rustc_middle::ty;
  11 use rustc_session::{declare_lint_pass, declare_tool_lint};
  12 use rustc_span::hygiene::{ExpnKind, MacroKind};
  13 use rustc_span::symbol::{kw, sym, Symbol};
  14 use rustc_span::Span;
  15 use tracing::debug;
  16
  17 declare_tool_lint! {
  18     pub rustc::DEFAULT_HASH_TYPES,
  19     Allow,
  20     "forbid HashMap and HashSet and suggest the FxHash* variants",
  21     report_in_external_macro: true
  22 }
  23
  24 declare_lint_pass!(DefaultHashTypes => [DEFAULT_HASH_TYPES]);
  25
  26 impl LateLintPass<'_> for DefaultHashTypes {
  27     fn check_path(&mut self, cx: &LateContext<'_>, path: &Path<'_>, hir_id: HirId) {
  28         let Res::Def(rustc_hir::def::DefKind::Struct, def_id) = path.res else { return };
  29         if matches!(cx.tcx.hir().get(hir_id), Node::Item(Item { kind: ItemKind::Use(..), .. })) {
  30             // don't lint imports, only actual usages
  31             return;
  32         }
  33         let replace = match cx.tcx.get_diagnostic_name(def_id) {
  34             Some(sym::HashMap) => "FxHashMap",
  35             Some(sym::HashSet) => "FxHashSet",
  36             _ => return,
  37         };
  38         cx.struct_span_lint(DEFAULT_HASH_TYPES, path.span, |lint| {
  39             let msg = format!(
  40                 "prefer `{}` over `{}`, it has better performance",
  41                 replace,
  42                 cx.tcx.item_name(def_id)
  43             );
  44             lint.build(&msg)
  45                 .note(&format!("a `use rustc_data_structures::fx::{}` may be necessary", replace))
  46                 .emit();
  47         });
  48     }
  49 }
  50
  51 /// Helper function for lints that check for expressions with calls and use typeck results to
  52 /// get the `DefId` and `SubstsRef` of the function.
  53 fn typeck_results_of_method_fn<'tcx>(
  54     cx: &LateContext<'tcx>,
  55     expr: &Expr<'_>,
  56 ) -> Option<(Span, DefId, ty::subst::SubstsRef<'tcx>)> {
  57     // FIXME(rustdoc): Lints which use this function use typecheck results which can cause
  58     // `rustdoc` to error if there are resolution failures.
  59     //
  60     // As internal lints are currently always run if there are `unstable_options`, they are added
  61     // to the lint store of rustdoc. Internal lints are also not used via the `lint_mod` query.
  62     // Crate lints run outside of a query so rustdoc currently doesn't disable them.
  63     //
  64     // Instead of relying on this, either change crate lints to a query disabled by rustdoc, only
  65     // run internal lints if the user is explicitly opting in or figure out a different way to
  66     // avoid running lints for rustdoc.
  67     if cx.tcx.sess.opts.actually_rustdoc {
  68         return None;
  69     }
  70
  71     match expr.kind {
  72         ExprKind::MethodCall(segment, _, _)
  73             if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) =>
  74         {
  75             Some((segment.ident.span, def_id, cx.typeck_results().node_substs(expr.hir_id)))
  76         },
  77         _ => {
  78             match cx.typeck_results().node_type(expr.hir_id).kind() {
  79                 &ty::FnDef(def_id, substs) => Some((expr.span, def_id, substs)),
  80                 _ => None,
  81             }
  82         }
  83     }
  84 }
  85
  86 declare_tool_lint! {
  87     pub rustc::POTENTIAL_QUERY_INSTABILITY,
  88     Allow,
  89     "require explicit opt-in when using potentially unstable methods or functions",
  90     report_in_external_macro: true
  91 }
  92
  93 declare_lint_pass!(QueryStability => [POTENTIAL_QUERY_INSTABILITY]);
  94
  95 impl LateLintPass<'_> for QueryStability {
  96     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
  97         let Some((span, def_id, substs)) = typeck_results_of_method_fn(cx, expr) else { return };
  98         if let Ok(Some(instance)) = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs) {
  99             let def_id = instance.def_id();
 100             if cx.tcx.has_attr(def_id, sym::rustc_lint_query_instability) {
 101                 cx.struct_span_lint(POTENTIAL_QUERY_INSTABILITY, span, |lint| {
 102                     let msg = format!(
 103                         "using `{}` can result in unstable query results",
 104                         cx.tcx.item_name(def_id)
 105                     );
 106                     lint.build(&msg)
 107                         .note("if you believe this case to be fine, allow this lint and add a comment explaining your rationale")
 108                         .emit();
 109                 })
 110             }
 111         }
 112     }
 113 }
 114
 115 declare_tool_lint! {
 116     pub rustc::USAGE_OF_TY_TYKIND,
 117     Allow,
 118     "usage of `ty::TyKind` outside of the `ty::sty` module",
 119     report_in_external_macro: true
 120 }
 121
 122 declare_tool_lint! {
 123     pub rustc::USAGE_OF_QUALIFIED_TY,
 124     Allow,
 125     "using `ty::{Ty,TyCtxt}` instead of importing it",
 126     report_in_external_macro: true
 127 }
 128
 129 declare_lint_pass!(TyTyKind => [
 130     USAGE_OF_TY_TYKIND,
 131     USAGE_OF_QUALIFIED_TY,
 132 ]);
 133
 134 impl<'tcx> LateLintPass<'tcx> for TyTyKind {
 135     fn check_path(
 136         &mut self,
 137         cx: &LateContext<'tcx>,
 138         path: &'tcx rustc_hir::Path<'tcx>,
 139         _: rustc_hir::HirId,
 140     ) {
 141         if let Some(segment) = path.segments.iter().nth_back(1)
 142         && let Some(res) = &segment.res
 143         && lint_ty_kind_usage(cx, res)
 144         {
 145             let span = path.span.with_hi(
 146                 segment.args.map_or(segment.ident.span, |a| a.span_ext).hi()
 147             );
 148             cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
 149                 lint.build("usage of `ty::TyKind::<kind>`")
 150                     .span_suggestion(
 151                         span,
 152                         "try using `ty::<kind>` directly",
 153                         "ty".to_string(),
 154                         Applicability::MaybeIncorrect, // ty maybe needs an import
 155                     )
 156                     .emit();
 157             });
 158         }
 159     }
 160
 161     fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx Ty<'tcx>) {
 162         match &ty.kind {
 163             TyKind::Path(QPath::Resolved(_, path)) => {
 164                 if lint_ty_kind_usage(cx, &path.res) {
 165                     cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
 166                         let hir = cx.tcx.hir();
 167                         match hir.find(hir.get_parent_node(ty.hir_id)) {
 168                             Some(Node::Pat(Pat {
 169                                 kind:
 170                                     PatKind::Path(qpath)
 171                                     | PatKind::TupleStruct(qpath, ..)
 172                                     | PatKind::Struct(qpath, ..),
 173                                 ..
 174                             })) => {
 175                                 if let QPath::TypeRelative(qpath_ty, ..) = qpath
 176                                     && qpath_ty.hir_id == ty.hir_id
 177                                 {
 178                                     lint.build("usage of `ty::TyKind::<kind>`")
 179                                         .span_suggestion(
 180                                             path.span,
 181                                             "try using `ty::<kind>` directly",
 182                                             "ty".to_string(),
 183                                             Applicability::MaybeIncorrect, // ty maybe needs an import
 184                                         )
 185                                         .emit();
 186                                     return;
 187                                 }
 188                             }
 189                             Some(Node::Expr(Expr {
 190                                 kind: ExprKind::Path(qpath),
 191                                 ..
 192                             })) => {
 193                                 if let QPath::TypeRelative(qpath_ty, ..) = qpath
 194                                     && qpath_ty.hir_id == ty.hir_id
 195                                 {
 196                                     lint.build("usage of `ty::TyKind::<kind>`")
 197                                         .span_suggestion(
 198                                             path.span,
 199                                             "try using `ty::<kind>` directly",
 200                                             "ty".to_string(),
 201                                             Applicability::MaybeIncorrect, // ty maybe needs an import
 202                                         )
 203                                         .emit();
 204                                     return;
 205                                 }
 206                             }
 207                             // Can't unify these two branches because qpath below is `&&` and above is `&`
 208                             // and `A | B` paths don't play well together with adjustments, apparently.
 209                             Some(Node::Expr(Expr {
 210                                 kind: ExprKind::Struct(qpath, ..),
 211                                 ..
 212                             })) => {
 213                                 if let QPath::TypeRelative(qpath_ty, ..) = qpath
 214                                     && qpath_ty.hir_id == ty.hir_id
 215                                 {
 216                                     lint.build("usage of `ty::TyKind::<kind>`")
 217                                         .span_suggestion(
 218                                             path.span,
 219                                             "try using `ty::<kind>` directly",
 220                                             "ty".to_string(),
 221                                             Applicability::MaybeIncorrect, // ty maybe needs an import
 222                                         )
 223                                         .emit();
 224                                     return;
 225                                 }
 226                             }
 227                             _ => {}
 228                         }
 229                         lint.build("usage of `ty::TyKind`").help("try using `Ty` instead").emit();
 230                     })
 231                 } else if !ty.span.from_expansion() && let Some(t) = is_ty_or_ty_ctxt(cx, &path) {
 232                     if path.segments.len() > 1 {
 233                         cx.struct_span_lint(USAGE_OF_QUALIFIED_TY, path.span, |lint| {
 234                             lint.build(&format!("usage of qualified `ty::{}`", t))
 235                                 .span_suggestion(
 236                                     path.span,
 237                                     "try importing it and using it unqualified",
 238                                     t,
 239                                     // The import probably needs to be changed
 240                                     Applicability::MaybeIncorrect,
 241                                 )
 242                                 .emit();
 243                         })
 244                     }
 245                 }
 246             }
 247             _ => {}
 248         }
 249     }
 250 }
 251
 252 fn lint_ty_kind_usage(cx: &LateContext<'_>, res: &Res) -> bool {
 253     if let Some(did) = res.opt_def_id() {
 254         cx.tcx.is_diagnostic_item(sym::TyKind, did) || cx.tcx.is_diagnostic_item(sym::IrTyKind, did)
 255     } else {
 256         false
 257     }
 258 }
 259
 260 fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &Path<'_>) -> Option<String> {
 261     match &path.res {
 262         Res::Def(_, def_id) => {
 263             if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(*def_id) {
 264                 return Some(format!("{}{}", name, gen_args(path.segments.last().unwrap())));
 265             }
 266         }
 267         // Only lint on `&Ty` and `&TyCtxt` if it is used outside of a trait.
 268         Res::SelfTy { trait_: None, alias_to: Some((did, _)) } => {
 269             if let ty::Adt(adt, substs) = cx.tcx.type_of(did).kind() {
 270                 if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(adt.did())
 271                 {
 272                     // NOTE: This path is currently unreachable as `Ty<'tcx>` is
 273                     // defined as a type alias meaning that `impl<'tcx> Ty<'tcx>`
 274                     // is not actually allowed.
 275                     //
 276                     // I(@lcnr) still kept this branch in so we don't miss this
 277                     // if we ever change it in the future.
 278                     return Some(format!("{}<{}>", name, substs[0]));
 279                 }
 280             }
 281         }
 282         _ => (),
 283     }
 284
 285     None
 286 }
 287
 288 fn gen_args(segment: &PathSegment<'_>) -> String {
 289     if let Some(args) = &segment.args {
 290         let lifetimes = args
 291             .args
 292             .iter()
 293             .filter_map(|arg| {
 294                 if let GenericArg::Lifetime(lt) = arg {
 295                     Some(lt.name.ident().to_string())
 296                 } else {
 297                     None
 298                 }
 299             })
 300             .collect::<Vec<_>>();
 301
 302         if !lifetimes.is_empty() {
 303             return format!("<{}>", lifetimes.join(", "));
 304         }
 305     }
 306
 307     String::new()
 308 }
 309
 310 declare_tool_lint! {
 311     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 312     Allow,
 313     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 314 }
 315
 316 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 317
 318 impl EarlyLintPass for LintPassImpl {
 319     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
 320         if let ast::ItemKind::Impl(box ast::Impl { of_trait: Some(lint_pass), .. }) = &item.kind {
 321             if let Some(last) = lint_pass.path.segments.last() {
 322                 if last.ident.name == sym::LintPass {
 323                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 324                     let call_site = expn_data.call_site;
 325                     if expn_data.kind != ExpnKind::Macro(MacroKind::Bang, sym::impl_lint_pass)
 326                         && call_site.ctxt().outer_expn_data().kind
 327                             != ExpnKind::Macro(MacroKind::Bang, sym::declare_lint_pass)
 328                     {
 329                         cx.struct_span_lint(
 330                             LINT_PASS_IMPL_WITHOUT_MACRO,
 331                             lint_pass.path.span,
 332                             |lint| {
 333                                 lint.build("implementing `LintPass` by hand")
 334                                     .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 335                                     .emit();
 336                             },
 337                         )
 338                     }
 339                 }
 340             }
 341         }
 342     }
 343 }
 344
 345 declare_tool_lint! {
 346     pub rustc::EXISTING_DOC_KEYWORD,
 347     Allow,
 348     "Check that documented keywords in std and core actually exist",
 349     report_in_external_macro: true
 350 }
 351
 352 declare_lint_pass!(ExistingDocKeyword => [EXISTING_DOC_KEYWORD]);
 353
 354 fn is_doc_keyword(s: Symbol) -> bool {
 355     s <= kw::Union
 356 }
 357
 358 impl<'tcx> LateLintPass<'tcx> for ExistingDocKeyword {
 359     fn check_item(&mut self, cx: &LateContext<'_>, item: &rustc_hir::Item<'_>) {
 360         for attr in cx.tcx.hir().attrs(item.hir_id()) {
 361             if !attr.has_name(sym::doc) {
 362                 continue;
 363             }
 364             if let Some(list) = attr.meta_item_list() {
 365                 for nested in list {
 366                     if nested.has_name(sym::keyword) {
 367                         let v = nested
 368                             .value_str()
 369                             .expect("#[doc(keyword = \"...\")] expected a value!");
 370                         if is_doc_keyword(v) {
 371                             return;
 372                         }
 373                         cx.struct_span_lint(EXISTING_DOC_KEYWORD, attr.span, |lint| {
 374                             lint.build(&format!(
 375                                 "Found non-existing keyword `{}` used in \
 376                                      `#[doc(keyword = \"...\")]`",
 377                                 v,
 378                             ))
 379                             .help("only existing keywords are allowed in core/std")
 380                             .emit();
 381                         });
 382                     }
 383                 }
 384             }
 385         }
 386     }
 387 }
 388
 389 declare_tool_lint! {
 390     pub rustc::UNTRANSLATABLE_DIAGNOSTIC,
 391     Allow,
 392     "prevent creation of diagnostics which cannot be translated",
 393     report_in_external_macro: true
 394 }
 395
 396 declare_tool_lint! {
 397     pub rustc::DIAGNOSTIC_OUTSIDE_OF_IMPL,
 398     Allow,
 399     "prevent creation of diagnostics outside of `SessionDiagnostic`/`AddSubdiagnostic` impls",
 400     report_in_external_macro: true
 401 }
 402
 403 declare_lint_pass!(Diagnostics => [ UNTRANSLATABLE_DIAGNOSTIC, DIAGNOSTIC_OUTSIDE_OF_IMPL ]);
 404
 405 impl LateLintPass<'_> for Diagnostics {
 406     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
 407         let Some((span, def_id, substs)) = typeck_results_of_method_fn(cx, expr) else { return };
 408         debug!(?span, ?def_id, ?substs);
 409         if let Ok(Some(instance)) = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs) &&
 410             !cx.tcx.has_attr(instance.def_id(), sym::rustc_lint_diagnostics)
 411         {
 412             return;
 413         }
 414
 415         let mut found_impl = false;
 416         for (_, parent) in cx.tcx.hir().parent_iter(expr.hir_id) {
 417             debug!(?parent);
 418             if let Node::Item(Item { kind: ItemKind::Impl(impl_), .. }) = parent &&
 419                 let Impl { of_trait: Some(of_trait), .. } = impl_ &&
 420                 let Some(def_id) = of_trait.trait_def_id() &&
 421                 let Some(name) = cx.tcx.get_diagnostic_name(def_id) &&
 422                 matches!(name, sym::SessionDiagnostic | sym::AddSubdiagnostic)
 423             {
 424                 found_impl = true;
 425                 break;
 426             }
 427         }
 428         debug!(?found_impl);
 429         if !found_impl {
 430             cx.struct_span_lint(DIAGNOSTIC_OUTSIDE_OF_IMPL, span, |lint| {
 431                 lint.build("diagnostics should only be created in `SessionDiagnostic`/`AddSubdiagnostic` impls")
 432                     .emit();
 433             })
 434         }
 435
 436         let mut found_diagnostic_message = false;
 437         for ty in substs.types() {
 438             debug!(?ty);
 439             if let Some(adt_def) = ty.ty_adt_def() &&
 440                 let Some(name) =  cx.tcx.get_diagnostic_name(adt_def.did()) &&
 441                 matches!(name, sym::DiagnosticMessage | sym::SubdiagnosticMessage)
 442             {
 443                 found_diagnostic_message = true;
 444                 break;
 445             }
 446         }
 447         debug!(?found_diagnostic_message);
 448         if !found_diagnostic_message {
 449             cx.struct_span_lint(UNTRANSLATABLE_DIAGNOSTIC, span, |lint| {
 450                 lint.build("diagnostics should be created using translatable messages").emit();
 451             })
 452         }
 453     }
 454 }