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::{Item, ItemKind};
   6 use rustc_data_structures::fx::FxHashMap;
   7 use rustc_errors::Applicability;
   8 use rustc_hir::def::Res;
   9 use rustc_hir::{GenericArg, HirId, MutTy, Mutability, Path, PathSegment, QPath, Ty, TyKind};
  10 use rustc_middle::ty;
  11 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
  12 use rustc_span::hygiene::{ExpnKind, MacroKind};
  13 use rustc_span::symbol::{sym, Ident, Symbol};
  14
  15 declare_tool_lint! {
  16     pub rustc::DEFAULT_HASH_TYPES,
  17     Allow,
  18     "forbid HashMap and HashSet and suggest the FxHash* variants",
  19     report_in_external_macro: true
  20 }
  21
  22 pub struct DefaultHashTypes {
  23     map: FxHashMap<Symbol, Symbol>,
  24 }
  25
  26 impl DefaultHashTypes {
  27     // we are allowed to use `HashMap` and `HashSet` as identifiers for implementing the lint itself
  28     #[allow(rustc::default_hash_types)]
  29     pub fn new() -> Self {
  30         let mut map = FxHashMap::default();
  31         map.insert(sym::HashMap, sym::FxHashMap);
  32         map.insert(sym::HashSet, sym::FxHashSet);
  33         Self { map }
  34     }
  35 }
  36
  37 impl_lint_pass!(DefaultHashTypes => [DEFAULT_HASH_TYPES]);
  38
  39 impl EarlyLintPass for DefaultHashTypes {
  40     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
  41         if let Some(replace) = self.map.get(&ident.name) {
  42             cx.struct_span_lint(DEFAULT_HASH_TYPES, ident.span, |lint| {
  43                 // FIXME: We can avoid a copy here. Would require us to take String instead of &str.
  44                 let msg = format!("Prefer {} over {}, it has better performance", replace, ident);
  45                 lint.build(&msg)
  46                     .span_suggestion(
  47                         ident.span,
  48                         "use",
  49                         replace.to_string(),
  50                         Applicability::MaybeIncorrect, // FxHashMap, ... needs another import
  51                     )
  52                     .note(&format!(
  53                         "a `use rustc_data_structures::fx::{}` may be necessary",
  54                         replace
  55                     ))
  56                     .emit();
  57             });
  58         }
  59     }
  60 }
  61
  62 declare_tool_lint! {
  63     pub rustc::USAGE_OF_TY_TYKIND,
  64     Allow,
  65     "usage of `ty::TyKind` outside of the `ty::sty` module",
  66     report_in_external_macro: true
  67 }
  68
  69 declare_tool_lint! {
  70     pub rustc::TY_PASS_BY_REFERENCE,
  71     Allow,
  72     "passing `Ty` or `TyCtxt` by reference",
  73     report_in_external_macro: true
  74 }
  75
  76 declare_tool_lint! {
  77     pub rustc::USAGE_OF_QUALIFIED_TY,
  78     Allow,
  79     "using `ty::{Ty,TyCtxt}` instead of importing it",
  80     report_in_external_macro: true
  81 }
  82
  83 declare_lint_pass!(TyTyKind => [
  84     USAGE_OF_TY_TYKIND,
  85     TY_PASS_BY_REFERENCE,
  86     USAGE_OF_QUALIFIED_TY,
  87 ]);
  88
  89 impl<'tcx> LateLintPass<'tcx> for TyTyKind {
  90     fn check_path(&mut self, cx: &LateContext<'_>, path: &'tcx Path<'tcx>, _: HirId) {
  91         let segments = path.segments.iter().rev().skip(1).rev();
  92
  93         if let Some(last) = segments.last() {
  94             let span = path.span.with_hi(last.ident.span.hi());
  95             if lint_ty_kind_usage(cx, last) {
  96                 cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, |lint| {
  97                     lint.build("usage of `ty::TyKind::<kind>`")
  98                         .span_suggestion(
  99                             span,
 100                             "try using ty::<kind> directly",
 101                             "ty".to_string(),
 102                             Applicability::MaybeIncorrect, // ty maybe needs an import
 103                         )
 104                         .emit();
 105                 })
 106             }
 107         }
 108     }
 109
 110     fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx Ty<'tcx>) {
 111         match &ty.kind {
 112             TyKind::Path(qpath) => {
 113                 if let QPath::Resolved(_, path) = qpath {
 114                     if let Some(last) = path.segments.iter().last() {
 115                         if lint_ty_kind_usage(cx, last) {
 116                             cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
 117                                 lint.build("usage of `ty::TyKind`")
 118                                     .help("try using `Ty` instead")
 119                                     .emit();
 120                             })
 121                         } else {
 122                             if ty.span.from_expansion() {
 123                                 return;
 124                             }
 125                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
 126                                 if path.segments.len() > 1 {
 127                                     cx.struct_span_lint(USAGE_OF_QUALIFIED_TY, path.span, |lint| {
 128                                         lint.build(&format!("usage of qualified `ty::{}`", t))
 129                                             .span_suggestion(
 130                                                 path.span,
 131                                                 "try using it unqualified",
 132                                                 t,
 133                                                 // The import probably needs to be changed
 134                                                 Applicability::MaybeIncorrect,
 135                                             )
 136                                             .emit();
 137                                     })
 138                                 }
 139                             }
 140                         }
 141                     }
 142                 }
 143             }
 144             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
 145                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner.to_def_id()) {
 146                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 147                         return;
 148                     }
 149                 }
 150                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 151                     cx.struct_span_lint(TY_PASS_BY_REFERENCE, ty.span, |lint| {
 152                         lint.build(&format!("passing `{}` by reference", t))
 153                             .span_suggestion(
 154                                 ty.span,
 155                                 "try passing by value",
 156                                 t,
 157                                 // Changing type of function argument
 158                                 Applicability::MaybeIncorrect,
 159                             )
 160                             .emit();
 161                     })
 162                 }
 163             }
 164             _ => {}
 165         }
 166     }
 167 }
 168
 169 fn lint_ty_kind_usage(cx: &LateContext<'_>, segment: &PathSegment<'_>) -> bool {
 170     if let Some(res) = segment.res {
 171         if let Some(did) = res.opt_def_id() {
 172             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 173         }
 174     }
 175
 176     false
 177 }
 178
 179 fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, ty: &Ty<'_>) -> Option<String> {
 180     if let TyKind::Path(qpath) = &ty.kind {
 181         if let QPath::Resolved(_, path) = qpath {
 182             match path.res {
 183                 Res::Def(_, did) => {
 184                     if cx.tcx.is_diagnostic_item(sym::Ty, did) {
 185                         return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
 186                     } else if cx.tcx.is_diagnostic_item(sym::TyCtxt, did) {
 187                         return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
 188                     }
 189                 }
 190                 // Only lint on `&Ty` and `&TyCtxt` if it is used outside of a trait.
 191                 Res::SelfTy(None, Some((did, _))) => {
 192                     if let ty::Adt(adt, substs) = cx.tcx.type_of(did).kind() {
 193                         if cx.tcx.is_diagnostic_item(sym::Ty, adt.did) {
 194                             // NOTE: This path is currently unreachable as `Ty<'tcx>` is
 195                             // defined as a type alias meaning that `impl<'tcx> Ty<'tcx>`
 196                             // is not actually allowed.
 197                             //
 198                             // I(@lcnr) still kept this branch in so we don't miss this
 199                             // if we ever change it in the future.
 200                             return Some(format!("Ty<{}>", substs[0]));
 201                         } else if cx.tcx.is_diagnostic_item(sym::TyCtxt, adt.did) {
 202                             return Some(format!("TyCtxt<{}>", substs[0]));
 203                         }
 204                     }
 205                 }
 206                 _ => (),
 207             }
 208         }
 209     }
 210
 211     None
 212 }
 213
 214 fn gen_args(segment: &PathSegment<'_>) -> String {
 215     if let Some(args) = &segment.args {
 216         let lifetimes = args
 217             .args
 218             .iter()
 219             .filter_map(|arg| {
 220                 if let GenericArg::Lifetime(lt) = arg {
 221                     Some(lt.name.ident().to_string())
 222                 } else {
 223                     None
 224                 }
 225             })
 226             .collect::<Vec<_>>();
 227
 228         if !lifetimes.is_empty() {
 229             return format!("<{}>", lifetimes.join(", "));
 230         }
 231     }
 232
 233     String::new()
 234 }
 235
 236 declare_tool_lint! {
 237     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 238     Allow,
 239     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 240 }
 241
 242 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 243
 244 impl EarlyLintPass for LintPassImpl {
 245     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
 246         if let ItemKind::Impl { of_trait: Some(lint_pass), .. } = &item.kind {
 247             if let Some(last) = lint_pass.path.segments.last() {
 248                 if last.ident.name == sym::LintPass {
 249                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 250                     let call_site = expn_data.call_site;
 251                     if expn_data.kind != ExpnKind::Macro(MacroKind::Bang, sym::impl_lint_pass)
 252                         && call_site.ctxt().outer_expn_data().kind
 253                             != ExpnKind::Macro(MacroKind::Bang, sym::declare_lint_pass)
 254                     {
 255                         cx.struct_span_lint(
 256                             LINT_PASS_IMPL_WITHOUT_MACRO,
 257                             lint_pass.path.span,
 258                             |lint| {
 259                                 lint.build("implementing `LintPass` by hand")
 260                                     .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 261                                     .emit();
 262                             },
 263                         )
 264                     }
 265                 }
 266             }
 267         }
 268     }
 269 }