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::symbol::{sym, Symbol};
  10 use syntax::ast::{Ident, Item, ItemKind};
  11
  12 declare_tool_lint! {
  13     pub rustc::DEFAULT_HASH_TYPES,
  14     Allow,
  15     "forbid HashMap and HashSet and suggest the FxHash* variants",
  16     report_in_external_macro: true
  17 }
  18
  19 pub struct DefaultHashTypes {
  20     map: FxHashMap<Symbol, Symbol>,
  21 }
  22
  23 impl DefaultHashTypes {
  24     // we are allowed to use `HashMap` and `HashSet` as identifiers for implementing the lint itself
  25     #[allow(rustc::default_hash_types)]
  26     pub fn new() -> Self {
  27         let mut map = FxHashMap::default();
  28         map.insert(sym::HashMap, sym::FxHashMap);
  29         map.insert(sym::HashSet, sym::FxHashSet);
  30         Self { map }
  31     }
  32 }
  33
  34 impl_lint_pass!(DefaultHashTypes => [DEFAULT_HASH_TYPES]);
  35
  36 impl EarlyLintPass for DefaultHashTypes {
  37     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
  38         if let Some(replace) = self.map.get(&ident.name) {
  39             let msg = format!("Prefer {} over {}, it has better performance", replace, ident);
  40             let mut db = cx.struct_span_lint(DEFAULT_HASH_TYPES, ident.span, &msg);
  41             db.span_suggestion(
  42                 ident.span,
  43                 "use",
  44                 replace.to_string(),
  45                 Applicability::MaybeIncorrect, // FxHashMap, ... needs another import
  46             );
  47             db.note(&format!("a `use rustc_data_structures::fx::{}` may be necessary", replace))
  48                 .emit();
  49         }
  50     }
  51 }
  52
  53 declare_tool_lint! {
  54     pub rustc::USAGE_OF_TY_TYKIND,
  55     Allow,
  56     "usage of `ty::TyKind` outside of the `ty::sty` module",
  57     report_in_external_macro: true
  58 }
  59
  60 declare_tool_lint! {
  61     pub rustc::TY_PASS_BY_REFERENCE,
  62     Allow,
  63     "passing `Ty` or `TyCtxt` by reference",
  64     report_in_external_macro: true
  65 }
  66
  67 declare_tool_lint! {
  68     pub rustc::USAGE_OF_QUALIFIED_TY,
  69     Allow,
  70     "using `ty::{Ty,TyCtxt}` instead of importing it",
  71     report_in_external_macro: true
  72 }
  73
  74 declare_lint_pass!(TyTyKind => [
  75     USAGE_OF_TY_TYKIND,
  76     TY_PASS_BY_REFERENCE,
  77     USAGE_OF_QUALIFIED_TY,
  78 ]);
  79
  80 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyTyKind {
  81     fn check_path(&mut self, cx: &LateContext<'_, '_>, path: &'tcx Path<'tcx>, _: HirId) {
  82         let segments = path.segments.iter().rev().skip(1).rev();
  83
  84         if let Some(last) = segments.last() {
  85             let span = path.span.with_hi(last.ident.span.hi());
  86             if lint_ty_kind_usage(cx, last) {
  87                 cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, "usage of `ty::TyKind::<kind>`")
  88                     .span_suggestion(
  89                         span,
  90                         "try using ty::<kind> directly",
  91                         "ty".to_string(),
  92                         Applicability::MaybeIncorrect, // ty maybe needs an import
  93                     )
  94                     .emit();
  95             }
  96         }
  97     }
  98
  99     fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty<'tcx>) {
 100         match &ty.kind {
 101             TyKind::Path(qpath) => {
 102                 if let QPath::Resolved(_, path) = qpath {
 103                     if let Some(last) = path.segments.iter().last() {
 104                         if lint_ty_kind_usage(cx, last) {
 105                             cx.struct_span_lint(
 106                                 USAGE_OF_TY_TYKIND,
 107                                 path.span,
 108                                 "usage of `ty::TyKind`",
 109                             )
 110                             .help("try using `Ty` instead")
 111                             .emit();
 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(
 119                                         USAGE_OF_QUALIFIED_TY,
 120                                         path.span,
 121                                         &format!("usage of qualified `ty::{}`", t),
 122                                     )
 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             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
 138                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner_def_id()) {
 139                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 140                         return;
 141                     }
 142                 }
 143                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 144                     cx.struct_span_lint(
 145                         TY_PASS_BY_REFERENCE,
 146                         ty.span,
 147                         &format!("passing `{}` by reference", t),
 148                     )
 149                     .span_suggestion(
 150                         ty.span,
 151                         "try passing by value",
 152                         t,
 153                         // Changing type of function argument
 154                         Applicability::MaybeIncorrect,
 155                     )
 156                     .emit();
 157                 }
 158             }
 159             _ => {}
 160         }
 161     }
 162 }
 163
 164 fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment<'_>) -> bool {
 165     if let Some(res) = segment.res {
 166         if let Some(did) = res.opt_def_id() {
 167             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 168         }
 169     }
 170
 171     false
 172 }
 173
 174 fn is_ty_or_ty_ctxt(cx: &LateContext<'_, '_>, ty: &Ty<'_>) -> Option<String> {
 175     match &ty.kind {
 176         TyKind::Path(qpath) => {
 177             if let QPath::Resolved(_, path) = qpath {
 178                 let did = path.res.opt_def_id()?;
 179                 if cx.tcx.is_diagnostic_item(sym::Ty, did) {
 180                     return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
 181                 } else if cx.tcx.is_diagnostic_item(sym::TyCtxt, did) {
 182                     return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
 183                 }
 184             }
 185         }
 186         _ => {}
 187     }
 188
 189     None
 190 }
 191
 192 fn gen_args(segment: &PathSegment<'_>) -> String {
 193     if let Some(args) = &segment.args {
 194         let lifetimes = args
 195             .args
 196             .iter()
 197             .filter_map(|arg| {
 198                 if let GenericArg::Lifetime(lt) = arg {
 199                     Some(lt.name.ident().to_string())
 200                 } else {
 201                     None
 202                 }
 203             })
 204             .collect::<Vec<_>>();
 205
 206         if !lifetimes.is_empty() {
 207             return format!("<{}>", lifetimes.join(", "));
 208         }
 209     }
 210
 211     String::new()
 212 }
 213
 214 declare_tool_lint! {
 215     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 216     Allow,
 217     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 218 }
 219
 220 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 221
 222 impl EarlyLintPass for LintPassImpl {
 223     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
 224         if let ItemKind::Impl(_, _, _, _, Some(lint_pass), _, _) = &item.kind {
 225             if let Some(last) = lint_pass.path.segments.last() {
 226                 if last.ident.name == sym::LintPass {
 227                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 228                     let call_site = expn_data.call_site;
 229                     if expn_data.kind.descr() != sym::impl_lint_pass
 230                         && call_site.ctxt().outer_expn_data().kind.descr() != sym::declare_lint_pass
 231                     {
 232                         cx.struct_span_lint(
 233                             LINT_PASS_IMPL_WITHOUT_MACRO,
 234                             lint_pass.path.span,
 235                             "implementing `LintPass` by hand",
 236                         )
 237                         .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 238                         .emit();
 239                     }
 240                 }
 241             }
 242         }
 243     }
 244 }