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