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_ast::ast::{Ident, Item, ItemKind};
   6 use rustc_data_structures::fx::FxHashMap;
   7 use rustc_errors::Applicability;
   8 use rustc_hir::{GenericArg, HirId, MutTy, Mutability, Path, PathSegment, QPath, Ty, TyKind};
   9 use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
  10 use rustc_span::hygiene::{ExpnKind, MacroKind};
  11 use rustc_span::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     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             cx.struct_span_lint(DEFAULT_HASH_TYPES, ident.span, |lint| {
  41                 // FIXME: We can avoid a copy here. Would require us to take String instead of &str.
  42                 let msg = format!("Prefer {} over {}, it has better performance", replace, ident);
  43                 lint.build(&msg)
  44                     .span_suggestion(
  45                         ident.span,
  46                         "use",
  47                         replace.to_string(),
  48                         Applicability::MaybeIncorrect, // FxHashMap, ... needs another import
  49                     )
  50                     .note(&format!(
  51                         "a `use rustc_data_structures::fx::{}` may be necessary",
  52                         replace
  53                     ))
  54                     .emit();
  55             });
  56         }
  57     }
  58 }
  59
  60 declare_tool_lint! {
  61     pub rustc::USAGE_OF_TY_TYKIND,
  62     Allow,
  63     "usage of `ty::TyKind` outside of the `ty::sty` module",
  64     report_in_external_macro: true
  65 }
  66
  67 declare_tool_lint! {
  68     pub rustc::TY_PASS_BY_REFERENCE,
  69     Allow,
  70     "passing `Ty` or `TyCtxt` by reference",
  71     report_in_external_macro: true
  72 }
  73
  74 declare_tool_lint! {
  75     pub rustc::USAGE_OF_QUALIFIED_TY,
  76     Allow,
  77     "using `ty::{Ty,TyCtxt}` instead of importing it",
  78     report_in_external_macro: true
  79 }
  80
  81 declare_lint_pass!(TyTyKind => [
  82     USAGE_OF_TY_TYKIND,
  83     TY_PASS_BY_REFERENCE,
  84     USAGE_OF_QUALIFIED_TY,
  85 ]);
  86
  87 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyTyKind {
  88     fn check_path(&mut self, cx: &LateContext<'_, '_>, path: &'tcx Path<'tcx>, _: HirId) {
  89         let segments = path.segments.iter().rev().skip(1).rev();
  90
  91         if let Some(last) = segments.last() {
  92             let span = path.span.with_hi(last.ident.span.hi());
  93             if lint_ty_kind_usage(cx, last) {
  94                 cx.struct_span_lint(USAGE_OF_TY_TYKIND, span, |lint| {
  95                     lint.build("usage of `ty::TyKind::<kind>`")
  96                         .span_suggestion(
  97                             span,
  98                             "try using ty::<kind> directly",
  99                             "ty".to_string(),
 100                             Applicability::MaybeIncorrect, // ty maybe needs an import
 101                         )
 102                         .emit();
 103                 })
 104             }
 105         }
 106     }
 107
 108     fn check_ty(&mut self, cx: &LateContext<'_, '_>, ty: &'tcx Ty<'tcx>) {
 109         match &ty.kind {
 110             TyKind::Path(qpath) => {
 111                 if let QPath::Resolved(_, path) = qpath {
 112                     if let Some(last) = path.segments.iter().last() {
 113                         if lint_ty_kind_usage(cx, last) {
 114                             cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
 115                                 lint.build("usage of `ty::TyKind`")
 116                                     .help("try using `Ty` instead")
 117                                     .emit();
 118                             })
 119                         } else {
 120                             if ty.span.from_expansion() {
 121                                 return;
 122                             }
 123                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
 124                                 if path.segments.len() > 1 {
 125                                     cx.struct_span_lint(USAGE_OF_QUALIFIED_TY, path.span, |lint| {
 126                                         lint.build(&format!("usage of qualified `ty::{}`", t))
 127                                             .span_suggestion(
 128                                                 path.span,
 129                                                 "try using it unqualified",
 130                                                 t,
 131                                                 // The import probably needs to be changed
 132                                                 Applicability::MaybeIncorrect,
 133                                             )
 134                                             .emit();
 135                                     })
 136                                 }
 137                             }
 138                         }
 139                     }
 140                 }
 141             }
 142             TyKind::Rptr(_, MutTy { ty: inner_ty, mutbl: Mutability::Not }) => {
 143                 if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner.to_def_id()) {
 144                     if cx.tcx.impl_trait_ref(impl_did).is_some() {
 145                         return;
 146                     }
 147                 }
 148                 if let Some(t) = is_ty_or_ty_ctxt(cx, &inner_ty) {
 149                     cx.struct_span_lint(TY_PASS_BY_REFERENCE, ty.span, |lint| {
 150                         lint.build(&format!("passing `{}` by reference", t))
 151                             .span_suggestion(
 152                                 ty.span,
 153                                 "try passing by value",
 154                                 t,
 155                                 // Changing type of function argument
 156                                 Applicability::MaybeIncorrect,
 157                             )
 158                             .emit();
 159                     })
 160                 }
 161             }
 162             _ => {}
 163         }
 164     }
 165 }
 166
 167 fn lint_ty_kind_usage(cx: &LateContext<'_, '_>, segment: &PathSegment<'_>) -> bool {
 168     if let Some(res) = segment.res {
 169         if let Some(did) = res.opt_def_id() {
 170             return cx.tcx.is_diagnostic_item(sym::TyKind, did);
 171         }
 172     }
 173
 174     false
 175 }
 176
 177 fn is_ty_or_ty_ctxt(cx: &LateContext<'_, '_>, ty: &Ty<'_>) -> Option<String> {
 178     if let TyKind::Path(qpath) = &ty.kind {
 179         if let QPath::Resolved(_, path) = qpath {
 180             let did = path.res.opt_def_id()?;
 181             if cx.tcx.is_diagnostic_item(sym::Ty, did) {
 182                 return Some(format!("Ty{}", gen_args(path.segments.last().unwrap())));
 183             } else if cx.tcx.is_diagnostic_item(sym::TyCtxt, did) {
 184                 return Some(format!("TyCtxt{}", gen_args(path.segments.last().unwrap())));
 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 { of_trait: 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 != ExpnKind::Macro(MacroKind::Bang, sym::impl_lint_pass)
 230                         && call_site.ctxt().outer_expn_data().kind
 231                             != ExpnKind::Macro(MacroKind::Bang, sym::declare_lint_pass)
 232                     {
 233                         cx.struct_span_lint(
 234                             LINT_PASS_IMPL_WITHOUT_MACRO,
 235                             lint_pass.path.span,
 236                             |lint| {
 237                                 lint.build("implementing `LintPass` by hand")
 238                                     .help("try using `declare_lint_pass!` or `impl_lint_pass!` instead")
 239                                     .emit();
 240                             },
 241                         )
 242                     }
 243                 }
 244             }
 245         }
 246     }
 247 }