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 }
  17
  18 pub struct DefaultHashTypes {
  19     map: FxHashMap<Symbol, Symbol>,
  20 }
  21
  22 impl DefaultHashTypes {
  23     // we are allowed to use `HashMap` and `HashSet` as identifiers for implementing the lint itself
  24     #[allow(rustc::default_hash_types)]
  25     pub fn new() -> Self {
  26         let mut map = FxHashMap::default();
  27         map.insert(sym::HashMap, sym::FxHashMap);
  28         map.insert(sym::HashSet, sym::FxHashSet);
  29         Self { map }
  30     }
  31 }
  32
  33 impl_lint_pass!(DefaultHashTypes => [DEFAULT_HASH_TYPES]);
  34
  35 impl EarlyLintPass for DefaultHashTypes {
  36     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
  37         if let Some(replace) = self.map.get(&ident.name) {
  38             let msg = format!("Prefer {} over {}, it has better performance", replace, ident);
  39             let mut db = cx.struct_span_lint(DEFAULT_HASH_TYPES, ident.span, &msg);
  40             db.span_suggestion(
  41                 ident.span,
  42                 "use",
  43                 replace.to_string(),
  44                 Applicability::MaybeIncorrect, // FxHashMap, ... needs another import
  45             );
  46             db.note(&format!("a `use rustc_data_structures::fx::{}` may be necessary", replace))
  47                 .emit();
  48         }
  49     }
  50 }
  51
  52 declare_tool_lint! {
  53     pub rustc::USAGE_OF_TY_TYKIND,
  54     Allow,
  55     "usage of `ty::TyKind` outside of the `ty::sty` module"
  56 }
  57
  58 declare_tool_lint! {
  59     pub rustc::TY_PASS_BY_REFERENCE,
  60     Allow,
  61     "passing `Ty` or `TyCtxt` by reference"
  62 }
  63
  64 declare_tool_lint! {
  65     pub rustc::USAGE_OF_QUALIFIED_TY,
  66     Allow,
  67     "using `ty::{Ty,TyCtxt}` instead of importing it"
  68 }
  69
  70 declare_lint_pass!(TyTyKind => [
  71     USAGE_OF_TY_TYKIND,
  72     TY_PASS_BY_REFERENCE,
  73     USAGE_OF_QUALIFIED_TY,
  74 ]);
  75
  76 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyTyKind {
  77     fn check_path(&mut self, cx: &LateContext<'_, '_>, path: &'tcx Path<'tcx>, _: HirId) {
  78         let segments = path.segments.iter().rev().skip(1).rev();
  79
  80         if let Some(last) = segments.last() {
  81             let span = path.span.with_hi(last.ident.span.hi());
  82             if lint_ty_kind_usage(cx, last) {
  83                 cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, "usage of `ty::TyKind::<kind>`")
  84                     .span_suggestion(
  85                         span,
  86                         "try using ty::<kind> directly",
  87                         "ty".to_string(),
  88                         Applicability::MaybeIncorrect, // ty maybe needs an import
  89                     )
  90                     .emit();
  91             }
  92         }
  93     }
  94
  95     fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty<'tcx>) {
  96         match &ty.kind {
  97             TyKind::Path(qpath) => {
  98                 if let QPath::Resolved(_, path) = qpath {
  99                     if let Some(last) = path.segments.iter().last() {
 100                         if lint_ty_kind_usage(cx, last) {
 101                             cx.struct_span_lint(
 102                                 USAGE_OF_TY_TYKIND,
 103                                 path.span,
 104                                 "usage of `ty::TyKind`",
 105                             )
 106                             .help("try using `Ty` instead")
 107                             .emit();
 108                         } else {
 109                             if ty.span.from_expansion() {
 110                                 return;
 111                             }
 112                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
 113                                 if path.segments.len() > 1 {
 114                                     cx.struct_span_lint(
 115                                         USAGE_OF_QUALIFIED_TY,
 116                                         path.span,
 117                                         &format!("usage of qualified `ty::{}`", t),
 118                                     )
 119                                     .span_suggestion(
 120                                         path.span,
 121                                         "try using it unqualified",
 122                                         t,
 123                                         // The import probably needs to be changed
 124                                         Applicability::MaybeIncorrect,
 125                                     )
 126                                     .emit();
 127                                 }
 128                             }
 129                         }
 130                     }
 131                 }
 132             }
 133             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
 134                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner_def_id()) {
 135                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 136                         return;
 137                     }
 138                 }
 139                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 140                     cx.struct_span_lint(
 141                         TY_PASS_BY_REFERENCE,
 142                         ty.span,
 143                         &format!("passing `{}` by reference", t),
 144                     )
 145                     .span_suggestion(
 146                         ty.span,
 147                         "try passing by value",
 148                         t,
 149                         // Changing type of function argument
 150                         Applicability::MaybeIncorrect,
 151                     )
 152                     .emit();
 153                 }
 154             }
 155             _ => {}
 156         }
 157     }
 158 }
 159
 160 fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment<'_>) -> bool {
 161     if let Some(res) = segment.res {
 162         if let Some(did) = res.opt_def_id() {
 163             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 164         }
 165     }
 166
 167     false
 168 }
 169
 170 fn is_ty_or_ty_ctxt(cx: &LateContext<'_, '_>, ty: &Ty<'_>) -> Option<String> {
 171     match &ty.kind {
 172         TyKind::Path(qpath) => {
 173             if let QPath::Resolved(_, path) = qpath {
 174                 let did = path.res.opt_def_id()?;
 175                 if cx.tcx.is_diagnostic_item(sym::Ty, did) {
 176                     return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
 177                 } else if cx.tcx.is_diagnostic_item(sym::TyCtxt, did) {
 178                     return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
 179                 }
 180             }
 181         }
 182         _ => {}
 183     }
 184
 185     None
 186 }
 187
 188 fn gen_args(segment: &PathSegment<'_>) -> String {
 189     if let Some(args) = &segment.args {
 190         let lifetimes = args
 191             .args
 192             .iter()
 193             .filter_map(|arg| {
 194                 if let GenericArg::Lifetime(lt) = arg {
 195                     Some(lt.name.ident().to_string())
 196                 } else {
 197                     None
 198                 }
 199             })
 200             .collect::<Vec<_>>();
 201
 202         if !lifetimes.is_empty() {
 203             return format!("<{}>", lifetimes.join(", "));
 204         }
 205     }
 206
 207     String::new()
 208 }
 209
 210 declare_tool_lint! {
 211     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 212     Allow,
 213     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 214 }
 215
 216 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 217
 218 impl EarlyLintPass for LintPassImpl {
 219     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
 220         if let ItemKind::Impl(_, _, _, _, Some(lint_pass), _, _) = &item.kind {
 221             if let Some(last) = lint_pass.path.segments.last() {
 222                 if last.ident.name == sym::LintPass {
 223                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 224                     let call_site = expn_data.call_site;
 225                     if expn_data.kind.descr() != sym::impl_lint_pass
 226                         && call_site.ctxt().outer_expn_data().kind.descr() != sym::declare_lint_pass
 227                     {
 228                         cx.struct_span_lint(
 229                             LINT_PASS_IMPL_WITHOUT_MACRO,
 230                             lint_pass.path.span,
 231                             "implementing `LintPass` by hand",
 232                         )
 233                         .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 234                         .emit();
 235                     }
 236                 }
 237             }
 238         }
 239     }
 240 }