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::Resolved(_, path)) => {
 105                 if let Some(last) = path.segments.iter().last() {
 106                     if lint_ty_kind_usage(cx, last) {
 107                         cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
 108                             lint.build("usage of `ty::TyKind`")
 109                                 .help("try using `Ty` instead")
 110                                 .emit();
 111                         })
 112                     } else {
 113                         if ty.span.from_expansion() {
 114                             return;
 115                         }
 116                         if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
 117                             if path.segments.len() > 1 {
 118                                 cx.struct_span_lint(USAGE_OF_QUALIFIED_TY, path.span, |lint| {
 119                                     lint.build(&format!("usage of qualified `ty::{}`", t))
 120                                         .span_suggestion(
 121                                             path.span,
 122                                             "try using it unqualified",
 123                                             t,
 124                                             // The import probably needs to be changed
 125                                             Applicability::MaybeIncorrect,
 126                                         )
 127                                         .emit();
 128                                 })
 129                             }
 130                         }
 131                     }
 132                 }
 133             }
 134             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
 135                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner.to_def_id()) {
 136                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 137                         return;
 138                     }
 139                 }
 140                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 141                     cx.struct_span_lint(TY_PASS_BY_REFERENCE, ty.span, |lint| {
 142                         lint.build(&format!("passing `{}` by reference", t))
 143                             .span_suggestion(
 144                                 ty.span,
 145                                 "try passing by value",
 146                                 t,
 147                                 // Changing type of function argument
 148                                 Applicability::MaybeIncorrect,
 149                             )
 150                             .emit();
 151                     })
 152                 }
 153             }
 154             _ => {}
 155         }
 156     }
 157 }
 158
 159 fn lint_ty_kind_usage(cx: &LateContext<'_>, segment: &PathSegment<'_>) -> bool {
 160     if let Some(res) = segment.res {
 161         if let Some(did) = res.opt_def_id() {
 162             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 163         }
 164     }
 165
 166     false
 167 }
 168
 169 fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, ty: &Ty<'_>) -> Option<String> {
 170     if let TyKind::Path(QPath::Resolved(_, path)) = &ty.kind {
 171         match path.res {
 172             Res::Def(_, def_id) => {
 173                 if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(def_id) {
 174                     return Some(format!("{}{}", name, gen_args(path.segments.last().unwrap())));
 175                 }
 176             }
 177             // Only lint on `&Ty` and `&TyCtxt` if it is used outside of a trait.
 178             Res::SelfTy(None, Some((did, _))) => {
 179                 if let ty::Adt(adt, substs) = cx.tcx.type_of(did).kind() {
 180                     if let Some(name @ (sym::Ty | sym::TyCtxt)) =
 181                         cx.tcx.get_diagnostic_name(adt.did)
 182                     {
 183                         // NOTE: This path is currently unreachable as `Ty<'tcx>` is
 184                         // defined as a type alias meaning that `impl<'tcx> Ty<'tcx>`
 185                         // is not actually allowed.
 186                         //
 187                         // I(@lcnr) still kept this branch in so we don't miss this
 188                         // if we ever change it in the future.
 189                         return Some(format!("{}<{}>", name, substs[0]));
 190                     }
 191                 }
 192             }
 193             _ => (),
 194         }
 195     }
 196
 197     None
 198 }
 199
 200 fn gen_args(segment: &PathSegment<'_>) -> String {
 201     if let Some(args) = &segment.args {
 202         let lifetimes = args
 203             .args
 204             .iter()
 205             .filter_map(|arg| {
 206                 if let GenericArg::Lifetime(lt) = arg {
 207                     Some(lt.name.ident().to_string())
 208                 } else {
 209                     None
 210                 }
 211             })
 212             .collect::<Vec<_>>();
 213
 214         if !lifetimes.is_empty() {
 215             return format!("<{}>", lifetimes.join(", "));
 216         }
 217     }
 218
 219     String::new()
 220 }
 221
 222 declare_tool_lint! {
 223     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 224     Allow,
 225     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 226 }
 227
 228 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 229
 230 impl EarlyLintPass for LintPassImpl {
 231     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
 232         if let ast::ItemKind::Impl(box ast::ImplKind { of_trait: Some(lint_pass), .. }) = &item.kind
 233         {
 234             if let Some(last) = lint_pass.path.segments.last() {
 235                 if last.ident.name == sym::LintPass {
 236                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 237                     let call_site = expn_data.call_site;
 238                     if expn_data.kind != ExpnKind::Macro(MacroKind::Bang, sym::impl_lint_pass)
 239                         && call_site.ctxt().outer_expn_data().kind
 240                             != ExpnKind::Macro(MacroKind::Bang, sym::declare_lint_pass)
 241                     {
 242                         cx.struct_span_lint(
 243                             LINT_PASS_IMPL_WITHOUT_MACRO,
 244                             lint_pass.path.span,
 245                             |lint| {
 246                                 lint.build("implementing `LintPass` by hand")
 247                                     .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 248                                     .emit();
 249                             },
 250                         )
 251                     }
 252                 }
 253             }
 254         }
 255     }
 256 }
 257
 258 declare_tool_lint! {
 259     pub rustc::EXISTING_DOC_KEYWORD,
 260     Allow,
 261     "Check that documented keywords in std and core actually exist",
 262     report_in_external_macro: true
 263 }
 264
 265 declare_lint_pass!(ExistingDocKeyword => [EXISTING_DOC_KEYWORD]);
 266
 267 fn is_doc_keyword(s: Symbol) -> bool {
 268     s <= kw::Union
 269 }
 270
 271 impl<'tcx> LateLintPass<'tcx> for ExistingDocKeyword {
 272     fn check_item(&mut self, cx: &LateContext<'_>, item: &rustc_hir::Item<'_>) {
 273         for attr in cx.tcx.hir().attrs(item.hir_id()) {
 274             if !attr.has_name(sym::doc) {
 275                 continue;
 276             }
 277             if let Some(list) = attr.meta_item_list() {
 278                 for nested in list {
 279                     if nested.has_name(sym::keyword) {
 280                         let v = nested
 281                             .value_str()
 282                             .expect("#[doc(keyword = \"...\")] expected a value!");
 283                         if is_doc_keyword(v) {
 284                             return;
 285                         }
 286                         cx.struct_span_lint(EXISTING_DOC_KEYWORD, attr.span, |lint| {
 287                             lint.build(&format!(
 288                                 "Found non-existing keyword `{}` used in \
 289                                      `#[doc(keyword = \"...\")]`",
 290                                 v,
 291                             ))
 292                             .help("only existing keywords are allowed in core/std")
 293                             .emit();
 294                         });
 295                     }
 296                 }
 297             }
 298         }
 299     }
 300 }