src/librustc_lint/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_data_structures::fx::FxHashMap;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::{GenericArg, HirId, MutTy, Mutability, Path, PathSegment, QPath, Ty, TyKind};
   8 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
   9 use rustc_span::hygiene::{ExpnKind, MacroKind};
  10 use rustc_span::symbol::{sym, Symbol};
  11 use syntax::ast::{Ident, Item, ItemKind};
  12
  13 declare_tool_lint! {
  14     pub rustc::DEFAULT_HASH_TYPES,
  15     Allow,
  16     "forbid HashMap and HashSet and suggest the FxHash* variants",
  17     report_in_external_macro: true
  18 }
  19
  20 pub struct DefaultHashTypes {
  21     map: FxHashMap<Symbol, Symbol>,
  22 }
  23
  24 impl DefaultHashTypes {
  25     // we are allowed to use `HashMap` and `HashSet` as identifiers for implementing the lint itself
  26     #[allow(rustc::default_hash_types)]
  27     pub fn new() -> Self {
  28         let mut map = FxHashMap::default();
  29         map.insert(sym::HashMap, sym::FxHashMap);
  30         map.insert(sym::HashSet, sym::FxHashSet);
  31         Self { map }
  32     }
  33 }
  34
  35 impl_lint_pass!(DefaultHashTypes => [DEFAULT_HASH_TYPES]);
  36
  37 impl EarlyLintPass for DefaultHashTypes {
  38     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
  39         if let Some(replace) = self.map.get(&ident.name) {
  40             let msg = format!("Prefer {} over {}, it has better performance", replace, ident);
  41             let mut db = cx.struct_span_lint(DEFAULT_HASH_TYPES, ident.span, &msg);
  42             db.span_suggestion(
  43                 ident.span,
  44                 "use",
  45                 replace.to_string(),
  46                 Applicability::MaybeIncorrect, // FxHashMap, ... needs another import
  47             );
  48             db.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<'a, 'tcx> LateLintPass<'a, '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, "usage of `ty::TyKind::<kind>`")
  89                     .span_suggestion(
  90                         span,
  91                         "try using ty::<kind> directly",
  92                         "ty".to_string(),
  93                         Applicability::MaybeIncorrect, // ty maybe needs an import
  94                     )
  95                     .emit();
  96             }
  97         }
  98     }
  99
 100     fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty<'tcx>) {
 101         match &ty.kind {
 102             TyKind::Path(qpath) => {
 103                 if let QPath::Resolved(_, path) = qpath {
 104                     if let Some(last) = path.segments.iter().last() {
 105                         if lint_ty_kind_usage(cx, last) {
 106                             cx.struct_span_lint(
 107                                 USAGE_OF_TY_TYKIND,
 108                                 path.span,
 109                                 "usage of `ty::TyKind`",
 110                             )
 111                             .help("try using `Ty` instead")
 112                             .emit();
 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(
 120                                         USAGE_OF_QUALIFIED_TY,
 121                                         path.span,
 122                                         &format!("usage of qualified `ty::{}`", t),
 123                                     )
 124                                     .span_suggestion(
 125                                         path.span,
 126                                         "try using it unqualified",
 127                                         t,
 128                                         // The import probably needs to be changed
 129                                         Applicability::MaybeIncorrect,
 130                                     )
 131                                     .emit();
 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_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(
 146                         TY_PASS_BY_REFERENCE,
 147                         ty.span,
 148                         &format!("passing `{}` by reference", t),
 149                     )
 150                     .span_suggestion(
 151                         ty.span,
 152                         "try passing by value",
 153                         t,
 154                         // Changing type of function argument
 155                         Applicability::MaybeIncorrect,
 156                     )
 157                     .emit();
 158                 }
 159             }
 160             _ => {}
 161         }
 162     }
 163 }
 164
 165 fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment<'_>) -> bool {
 166     if let Some(res) = segment.res {
 167         if let Some(did) = res.opt_def_id() {
 168             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 169         }
 170     }
 171
 172     false
 173 }
 174
 175 fn is_ty_or_ty_ctxt(cx: &LateContext<'_, '_>, ty: &Ty<'_>) -> Option<String> {
 176     match &ty.kind {
 177         TyKind::Path(qpath) => {
 178             if let QPath::Resolved(_, path) = qpath {
 179                 let did = path.res.opt_def_id()?;
 180                 if cx.tcx.is_diagnostic_item(sym::Ty, did) {
 181                     return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
 182                 } else if cx.tcx.is_diagnostic_item(sym::TyCtxt, did) {
 183                     return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
 184                 }
 185             }
 186         }
 187         _ => {}
 188     }
 189
 190     None
 191 }
 192
 193 fn gen_args(segment: &PathSegment<'_>) -> String {
 194     if let Some(args) = &segment.args {
 195         let lifetimes = args
 196             .args
 197             .iter()
 198             .filter_map(|arg| {
 199                 if let GenericArg::Lifetime(lt) = arg {
 200                     Some(lt.name.ident().to_string())
 201                 } else {
 202                     None
 203                 }
 204             })
 205             .collect::<Vec<_>>();
 206
 207         if !lifetimes.is_empty() {
 208             return format!("<{}>", lifetimes.join(", "));
 209         }
 210     }
 211
 212     String::new()
 213 }
 214
 215 declare_tool_lint! {
 216     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 217     Allow,
 218     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 219 }
 220
 221 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 222
 223 impl EarlyLintPass for LintPassImpl {
 224     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
 225         if let ItemKind::Impl { of_trait: Some(lint_pass), .. } = &item.kind {
 226             if let Some(last) = lint_pass.path.segments.last() {
 227                 if last.ident.name == sym::LintPass {
 228                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 229                     let call_site = expn_data.call_site;
 230                     if expn_data.kind != ExpnKind::Macro(MacroKind::Bang, sym::impl_lint_pass)
 231                         && call_site.ctxt().outer_expn_data().kind
 232                             != ExpnKind::Macro(MacroKind::Bang, sym::declare_lint_pass)
 233                     {
 234                         cx.struct_span_lint(
 235                             LINT_PASS_IMPL_WITHOUT_MACRO,
 236                             lint_pass.path.span,
 237                             "implementing `LintPass` by hand",
 238                         )
 239                         .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 240                         .emit();
 241                     }
 242                 }
 243             }
 244         }
 245     }
 246 }