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::hir::{GenericArg, HirId, MutTy, Mutability, Path, PathSegment, QPath, Ty, TyKind};
   5 use crate::lint::{
   6     EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintArray, LintContext, LintPass,
   7 };
   8 use errors::Applicability;
   9 use rustc_data_structures::fx::FxHashMap;
  10 use rustc_session::declare_tool_lint;
  11 use syntax::ast::{Ident, Item, ItemKind};
  12 use syntax::symbol::{sym, Symbol};
  13
  14 declare_tool_lint! {
  15     pub rustc::DEFAULT_HASH_TYPES,
  16     Allow,
  17     "forbid HashMap and HashSet and suggest the FxHash* variants"
  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 }
  59
  60 declare_tool_lint! {
  61     pub rustc::TY_PASS_BY_REFERENCE,
  62     Allow,
  63     "passing `Ty` or `TyCtxt` by reference"
  64 }
  65
  66 declare_tool_lint! {
  67     pub rustc::USAGE_OF_QUALIFIED_TY,
  68     Allow,
  69     "using `ty::{Ty,TyCtxt}` instead of importing it"
  70 }
  71
  72 declare_lint_pass!(TyTyKind => [
  73     USAGE_OF_TY_TYKIND,
  74     TY_PASS_BY_REFERENCE,
  75     USAGE_OF_QUALIFIED_TY,
  76 ]);
  77
  78 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyTyKind {
  79     fn check_path(&mut self, cx: &LateContext<'_, '_>, path: &'tcx Path, _: HirId) {
  80         let segments = path.segments.iter().rev().skip(1).rev();
  81
  82         if let Some(last) = segments.last() {
  83             let span = path.span.with_hi(last.ident.span.hi());
  84             if lint_ty_kind_usage(cx, last) {
  85                 cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, "usage of `ty::TyKind::<kind>`")
  86                     .span_suggestion(
  87                         span,
  88                         "try using ty::<kind> directly",
  89                         "ty".to_string(),
  90                         Applicability::MaybeIncorrect, // ty maybe needs an import
  91                     )
  92                     .emit();
  93             }
  94         }
  95     }
  96
  97     fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty) {
  98         match &ty.kind {
  99             TyKind::Path(qpath) => {
 100                 if let QPath::Resolved(_, path) = qpath {
 101                     if let Some(last) = path.segments.iter().last() {
 102                         if lint_ty_kind_usage(cx, last) {
 103                             cx.struct_span_lint(
 104                                 USAGE_OF_TY_TYKIND,
 105                                 path.span,
 106                                 "usage of `ty::TyKind`",
 107                             )
 108                             .help("try using `Ty` instead")
 109                             .emit();
 110                         } else {
 111                             if ty.span.from_expansion() {
 112                                 return;
 113                             }
 114                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
 115                                 if path.segments.len() > 1 {
 116                                     cx.struct_span_lint(
 117                                         USAGE_OF_QUALIFIED_TY,
 118                                         path.span,
 119                                         &format!("usage of qualified `ty::{}`", t),
 120                                     )
 121                                     .span_suggestion(
 122                                         path.span,
 123                                         "try using it unqualified",
 124                                         t,
 125                                         // The import probably needs to be changed
 126                                         Applicability::MaybeIncorrect,
 127                                     )
 128                                     .emit();
 129                                 }
 130                             }
 131                         }
 132                     }
 133                 }
 134             }
 135             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
 136                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner_def_id()) {
 137                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 138                         return;
 139                     }
 140                 }
 141                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 142                     cx.struct_span_lint(
 143                         TY_PASS_BY_REFERENCE,
 144                         ty.span,
 145                         &format!("passing `{}` by reference", t),
 146                     )
 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 fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment) -> bool {
 163     if let Some(res) = segment.res {
 164         if let Some(did) = res.opt_def_id() {
 165             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 166         }
 167     }
 168
 169     false
 170 }
 171
 172 fn is_ty_or_ty_ctxt(cx: &LateContext<'_, '_>, ty: &Ty) -> Option<String> {
 173     match &ty.kind {
 174         TyKind::Path(qpath) => {
 175             if let QPath::Resolved(_, path) = qpath {
 176                 let did = path.res.opt_def_id()?;
 177                 if cx.tcx.is_diagnostic_item(sym::Ty, did) {
 178                     return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
 179                 } else if cx.tcx.is_diagnostic_item(sym::TyCtxt, did) {
 180                     return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
 181                 }
 182             }
 183         }
 184         _ => {}
 185     }
 186
 187     None
 188 }
 189
 190 fn gen_args(segment: &PathSegment) -> String {
 191     if let Some(args) = &segment.args {
 192         let lifetimes = args
 193             .args
 194             .iter()
 195             .filter_map(|arg| {
 196                 if let GenericArg::Lifetime(lt) = arg {
 197                     Some(lt.name.ident().to_string())
 198                 } else {
 199                     None
 200                 }
 201             })
 202             .collect::<Vec<_>>();
 203
 204         if !lifetimes.is_empty() {
 205             return format!("<{}>", lifetimes.join(", "));
 206         }
 207     }
 208
 209     String::new()
 210 }
 211
 212 declare_tool_lint! {
 213     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 214     Allow,
 215     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 216 }
 217
 218 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 219
 220 impl EarlyLintPass for LintPassImpl {
 221     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
 222         if let ItemKind::Impl(_, _, _, _, Some(lint_pass), _, _) = &item.kind {
 223             if let Some(last) = lint_pass.path.segments.last() {
 224                 if last.ident.name == sym::LintPass {
 225                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 226                     let call_site = expn_data.call_site;
 227                     if expn_data.kind.descr() != sym::impl_lint_pass
 228                         && call_site.ctxt().outer_expn_data().kind.descr() != sym::declare_lint_pass
 229                     {
 230                         cx.struct_span_lint(
 231                             LINT_PASS_IMPL_WITHOUT_MACRO,
 232                             lint_pass.path.span,
 233                             "implementing `LintPass` by hand",
 234                         )
 235                         .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 236                         .emit();
 237                     }
 238                 }
 239             }
 240         }
 241     }
 242 }