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::{
   9     GenericArg, HirId, Item, ItemKind, MutTy, Mutability, Node, Path, PathSegment, QPath, Ty,
  10     TyKind,
  11 };
  12 use rustc_middle::ty;
  13 use rustc_session::{declare_lint_pass, declare_tool_lint};
  14 use rustc_span::hygiene::{ExpnKind, MacroKind};
  15 use rustc_span::symbol::{kw, sym, Symbol};
  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 def_id = match path.res {
  29             Res::Def(rustc_hir::def::DefKind::Struct, id) => id,
  30             _ => return,
  31         };
  32         if matches!(cx.tcx.hir().get(hir_id), Node::Item(Item { kind: ItemKind::Use(..), .. })) {
  33             // don't lint imports, only actual usages
  34             return;
  35         }
  36         let replace = match cx.tcx.get_diagnostic_name(def_id) {
  37             Some(sym::HashMap) => "FxHashMap",
  38             Some(sym::HashSet) => "FxHashSet",
  39             _ => return,
  40         };
  41         cx.struct_span_lint(DEFAULT_HASH_TYPES, path.span, |lint| {
  42             let msg = format!(
  43                 "prefer `{}` over `{}`, it has better performance",
  44                 replace,
  45                 cx.tcx.item_name(def_id)
  46             );
  47             lint.build(&msg)
  48                 .note(&format!("a `use rustc_data_structures::fx::{}` may be necessary", replace))
  49                 .emit();
  50         });
  51     }
  52 }
  53
  54 declare_tool_lint! {
  55     pub rustc::USAGE_OF_TY_TYKIND,
  56     Allow,
  57     "usage of `ty::TyKind` outside of the `ty::sty` module",
  58     report_in_external_macro: true
  59 }
  60
  61 declare_tool_lint! {
  62     pub rustc::TY_PASS_BY_REFERENCE,
  63     Allow,
  64     "passing `Ty` or `TyCtxt` by reference",
  65     report_in_external_macro: true
  66 }
  67
  68 declare_tool_lint! {
  69     pub rustc::USAGE_OF_QUALIFIED_TY,
  70     Allow,
  71     "using `ty::{Ty,TyCtxt}` instead of importing it",
  72     report_in_external_macro: true
  73 }
  74
  75 declare_lint_pass!(TyTyKind => [
  76     USAGE_OF_TY_TYKIND,
  77     TY_PASS_BY_REFERENCE,
  78     USAGE_OF_QUALIFIED_TY,
  79 ]);
  80
  81 impl<'tcx> LateLintPass<'tcx> for TyTyKind {
  82     fn check_path(&mut self, cx: &LateContext<'_>, path: &'tcx Path<'tcx>, _: HirId) {
  83         let segments = path.segments.iter().rev().skip(1).rev();
  84
  85         if let Some(last) = segments.last() {
  86             let span = path.span.with_hi(last.ident.span.hi());
  87             if lint_ty_kind_usage(cx, last) {
  88                 cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, |lint| {
  89                     lint.build("usage of `ty::TyKind::<kind>`")
  90                         .span_suggestion(
  91                             span,
  92                             "try using ty::<kind> directly",
  93                             "ty".to_string(),
  94                             Applicability::MaybeIncorrect, // ty maybe needs an import
  95                         )
  96                         .emit();
  97                 })
  98             }
  99         }
 100     }
 101
 102     fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx Ty<'tcx>) {
 103         match &ty.kind {
 104             TyKind::Path(qpath) => {
 105                 if let QPath::Resolved(_, path) = qpath {
 106                     if let Some(last) = path.segments.iter().last() {
 107                         if lint_ty_kind_usage(cx, last) {
 108                             cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
 109                                 lint.build("usage of `ty::TyKind`")
 110                                     .help("try using `Ty` instead")
 111                                     .emit();
 112                             })
 113                         } else {
 114                             if ty.span.from_expansion() {
 115                                 return;
 116                             }
 117                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
 118                                 if path.segments.len() > 1 {
 119                                     cx.struct_span_lint(USAGE_OF_QUALIFIED_TY, path.span, |lint| {
 120                                         lint.build(&format!("usage of qualified `ty::{}`", t))
 121                                             .span_suggestion(
 122                                                 path.span,
 123                                                 "try using it unqualified",
 124                                                 t,
 125                                                 // The import probably needs to be changed
 126                                                 Applicability::MaybeIncorrect,
 127                                             )
 128                                             .emit();
 129                                     })
 130                                 }
 131                             }
 132                         }
 133                     }
 134                 }
 135             }
 136             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
 137                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner.to_def_id()) {
 138                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 139                         return;
 140                     }
 141                 }
 142                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 143                     cx.struct_span_lint(TY_PASS_BY_REFERENCE, ty.span, |lint| {
 144                         lint.build(&format!("passing `{}` by reference", t))
 145                             .span_suggestion(
 146                                 ty.span,
 147                                 "try passing by value",
 148                                 t,
 149                                 // Changing type of function argument
 150                                 Applicability::MaybeIncorrect,
 151                             )
 152                             .emit();
 153                     })
 154                 }
 155             }
 156             _ => {}
 157         }
 158     }
 159 }
 160
 161 fn lint_ty_kind_usage(cx: &LateContext<'_>, segment: &PathSegment<'_>) -> bool {
 162     if let Some(res) = segment.res {
 163         if let Some(did) = res.opt_def_id() {
 164             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 165         }
 166     }
 167
 168     false
 169 }
 170
 171 fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, ty: &Ty<'_>) -> Option<String> {
 172     if let TyKind::Path(qpath) = &ty.kind {
 173         if let QPath::Resolved(_, path) = qpath {
 174             match path.res {
 175                 Res::Def(_, def_id) => {
 176                     if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(def_id)
 177                     {
 178                         return Some(format!(
 179                             "{}{}",
 180                             name,
 181                             gen_args(path.segments.last().unwrap())
 182                         ));
 183                     }
 184                 }
 185                 // Only lint on `&Ty` and `&TyCtxt` if it is used outside of a trait.
 186                 Res::SelfTy(None, Some((did, _))) => {
 187                     if let ty::Adt(adt, substs) = cx.tcx.type_of(did).kind() {
 188                         if let Some(name @ (sym::Ty | sym::TyCtxt)) =
 189                             cx.tcx.get_diagnostic_name(adt.did)
 190                         {
 191                             // NOTE: This path is currently unreachable as `Ty<'tcx>` is
 192                             // defined as a type alias meaning that `impl<'tcx> Ty<'tcx>`
 193                             // is not actually allowed.
 194                             //
 195                             // I(@lcnr) still kept this branch in so we don't miss this
 196                             // if we ever change it in the future.
 197                             return Some(format!("{}<{}>", name, substs[0]));
 198                         }
 199                     }
 200                 }
 201                 _ => (),
 202             }
 203         }
 204     }
 205
 206     None
 207 }
 208
 209 fn gen_args(segment: &PathSegment<'_>) -> String {
 210     if let Some(args) = &segment.args {
 211         let lifetimes = args
 212             .args
 213             .iter()
 214             .filter_map(|arg| {
 215                 if let GenericArg::Lifetime(lt) = arg {
 216                     Some(lt.name.ident().to_string())
 217                 } else {
 218                     None
 219                 }
 220             })
 221             .collect::<Vec<_>>();
 222
 223         if !lifetimes.is_empty() {
 224             return format!("<{}>", lifetimes.join(", "));
 225         }
 226     }
 227
 228     String::new()
 229 }
 230
 231 declare_tool_lint! {
 232     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 233     Allow,
 234     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 235 }
 236
 237 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 238
 239 impl EarlyLintPass for LintPassImpl {
 240     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
 241         if let ast::ItemKind::Impl(box ast::ImplKind { of_trait: Some(lint_pass), .. }) = &item.kind
 242         {
 243             if let Some(last) = lint_pass.path.segments.last() {
 244                 if last.ident.name == sym::LintPass {
 245                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 246                     let call_site = expn_data.call_site;
 247                     if expn_data.kind != ExpnKind::Macro(MacroKind::Bang, sym::impl_lint_pass)
 248                         && call_site.ctxt().outer_expn_data().kind
 249                             != ExpnKind::Macro(MacroKind::Bang, sym::declare_lint_pass)
 250                     {
 251                         cx.struct_span_lint(
 252                             LINT_PASS_IMPL_WITHOUT_MACRO,
 253                             lint_pass.path.span,
 254                             |lint| {
 255                                 lint.build("implementing `LintPass` by hand")
 256                                     .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 257                                     .emit();
 258                             },
 259                         )
 260                     }
 261                 }
 262             }
 263         }
 264     }
 265 }
 266
 267 declare_tool_lint! {
 268     pub rustc::EXISTING_DOC_KEYWORD,
 269     Allow,
 270     "Check that documented keywords in std and core actually exist",
 271     report_in_external_macro: true
 272 }
 273
 274 declare_lint_pass!(ExistingDocKeyword => [EXISTING_DOC_KEYWORD]);
 275
 276 fn is_doc_keyword(s: Symbol) -> bool {
 277     s <= kw::Union
 278 }
 279
 280 impl<'tcx> LateLintPass<'tcx> for ExistingDocKeyword {
 281     fn check_item(&mut self, cx: &LateContext<'_>, item: &rustc_hir::Item<'_>) {
 282         for attr in cx.tcx.hir().attrs(item.hir_id()) {
 283             if !attr.has_name(sym::doc) {
 284                 continue;
 285             }
 286             if let Some(list) = attr.meta_item_list() {
 287                 for nested in list {
 288                     if nested.has_name(sym::keyword) {
 289                         let v = nested
 290                             .value_str()
 291                             .expect("#[doc(keyword = \"...\")] expected a value!");
 292                         if is_doc_keyword(v) {
 293                             return;
 294                         }
 295                         cx.struct_span_lint(EXISTING_DOC_KEYWORD, attr.span, |lint| {
 296                             lint.build(&format!(
 297                                 "Found non-existing keyword `{}` used in \
 298                                      `#[doc(keyword = \"...\")]`",
 299                                 v,
 300                             ))
 301                             .help("only existing keywords are allowed in core/std")
 302                             .emit();
 303                         });
 304                     }
 305                 }
 306             }
 307         }
 308     }
 309 }