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 syntax::ast::{Ident, Item, ItemKind};
  11 use syntax::symbol::{sym, Symbol};
  12
  13 declare_tool_lint! {
  14     pub rustc::DEFAULT_HASH_TYPES,
  15     Allow,
  16     "forbid HashMap and HashSet and suggest the FxHash* variants"
  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 }
  58
  59 declare_tool_lint! {
  60     pub rustc::TY_PASS_BY_REFERENCE,
  61     Allow,
  62     "passing `Ty` or `TyCtxt` by reference"
  63 }
  64
  65 declare_tool_lint! {
  66     pub rustc::USAGE_OF_QUALIFIED_TY,
  67     Allow,
  68     "using `ty::{Ty,TyCtxt}` instead of importing it"
  69 }
  70
  71 declare_lint_pass!(TyTyKind => [
  72     USAGE_OF_TY_TYKIND,
  73     TY_PASS_BY_REFERENCE,
  74     USAGE_OF_QUALIFIED_TY,
  75 ]);
  76
  77 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyTyKind {
  78     fn check_path(&mut self, cx: &LateContext<'_, '_>, path: &'tcx Path, _: HirId) {
  79         let segments = path.segments.iter().rev().skip(1).rev();
  80
  81         if let Some(last) = segments.last() {
  82             let span = path.span.with_hi(last.ident.span.hi());
  83             if lint_ty_kind_usage(cx, last) {
  84                 cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, "usage of `ty::TyKind::<kind>`")
  85                     .span_suggestion(
  86                         span,
  87                         "try using ty::<kind> directly",
  88                         "ty".to_string(),
  89                         Applicability::MaybeIncorrect, // ty maybe needs an import
  90                     )
  91                     .emit();
  92             }
  93         }
  94     }
  95
  96     fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty) {
  97         match &ty.node {
  98             TyKind::Path(qpath) => {
  99                 if let QPath::Resolved(_, path) = qpath {
 100                     if let Some(last) = path.segments.iter().last() {
 101                         if lint_ty_kind_usage(cx, last) {
 102                             cx.struct_span_lint(
 103                                 USAGE_OF_TY_TYKIND,
 104                                 path.span,
 105                                 "usage of `ty::TyKind`",
 106                             )
 107                             .help("try using `Ty` instead")
 108                             .emit();
 109                         } else {
 110                             if ty.span.from_expansion() {
 111                                 return;
 112                             }
 113                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
 114                                 if path.segments.len() > 1 {
 115                                     cx.struct_span_lint(
 116                                         USAGE_OF_QUALIFIED_TY,
 117                                         path.span,
 118                                         &format!("usage of qualified `ty::{}`", t),
 119                                     )
 120                                     .span_suggestion(
 121                                         path.span,
 122                                         "try using it unqualified",
 123                                         t,
 124                                         // The import probably needs to be changed
 125                                         Applicability::MaybeIncorrect,
 126                                     )
 127                                     .emit();
 128                                 }
 129                             }
 130                         }
 131                     }
 132                 }
 133             }
 134             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::MutImmutable }) => {
 135                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner_def_id()) {
 136                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 137                         return;
 138                     }
 139                 }
 140                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 141                     cx.struct_span_lint(
 142                         TY_PASS_BY_REFERENCE,
 143                         ty.span,
 144                         &format!("passing `{}` by reference", t),
 145                     )
 146                     .span_suggestion(
 147                         ty.span,
 148                         "try passing by value",
 149                         t,
 150                         // Changing type of function argument
 151                         Applicability::MaybeIncorrect,
 152                     )
 153                     .emit();
 154                 }
 155             }
 156             _ => {}
 157         }
 158     }
 159 }
 160
 161 fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment) -> bool {
 162     if segment.ident.name == sym::TyKind {
 163         if let Some(res) = segment.res {
 164             if let Some(did) = res.opt_def_id() {
 165                 return cx.match_def_path(did, TYKIND_PATH);
 166             }
 167         }
 168     }
 169
 170     false
 171 }
 172
 173 const TYKIND_PATH: &[Symbol] = &[sym::rustc, sym::ty, sym::sty, sym::TyKind];
 174 const TY_PATH: &[Symbol] = &[sym::rustc, sym::ty, sym::Ty];
 175 const TYCTXT_PATH: &[Symbol] = &[sym::rustc, sym::ty, sym::context, sym::TyCtxt];
 176
 177 fn is_ty_or_ty_ctxt(cx: &LateContext<'_, '_>, ty: &Ty) -> Option<String> {
 178     match &ty.node {
 179         TyKind::Path(qpath) => {
 180             if let QPath::Resolved(_, path) = qpath {
 181                 let did = path.res.opt_def_id()?;
 182                 if cx.match_def_path(did, TY_PATH) {
 183                     return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
 184                 } else if cx.match_def_path(did, TYCTXT_PATH) {
 185                     return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
 186                 }
 187             }
 188         }
 189         _ => {}
 190     }
 191
 192     None
 193 }
 194
 195 fn gen_args(segment: &PathSegment) -> String {
 196     if let Some(args) = &segment.args {
 197         let lifetimes = args
 198             .args
 199             .iter()
 200             .filter_map(|arg| {
 201                 if let GenericArg::Lifetime(lt) = arg {
 202                     Some(lt.name.ident().to_string())
 203                 } else {
 204                     None
 205                 }
 206             })
 207             .collect::<Vec<_>>();
 208
 209         if !lifetimes.is_empty() {
 210             return format!("<{}>", lifetimes.join(", "));
 211         }
 212     }
 213
 214     String::new()
 215 }
 216
 217 declare_tool_lint! {
 218     pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
 219     Allow,
 220     "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
 221 }
 222
 223 declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
 224
 225 impl EarlyLintPass for LintPassImpl {
 226     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
 227         if let ItemKind::Impl(_, _, _, _, Some(lint_pass), _, _) = &item.node {
 228             if let Some(last) = lint_pass.path.segments.last() {
 229                 if last.ident.name == sym::LintPass {
 230                     let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
 231                     let call_site = expn_data.call_site;
 232                     if expn_data.kind.descr() != sym::impl_lint_pass &&
 233                        call_site.ctxt().outer_expn_data().kind.descr() != sym::declare_lint_pass {
 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 }