clippy_lints/src/macro_use.rs

   1 use clippy_utils::diagnostics::span_lint_hir_and_then;
   2 use clippy_utils::source::snippet;
   3 use hir::def::{DefKind, Res};
   4 use if_chain::if_chain;
   5 use rustc_ast::ast;
   6 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   7 use rustc_errors::Applicability;
   8 use rustc_hir as hir;
   9 use rustc_lint::{LateContext, LateLintPass, LintContext};
  10 use rustc_session::{declare_tool_lint, impl_lint_pass};
  11 use rustc_span::{edition::Edition, sym, Span};
  12
  13 declare_clippy_lint! {
  14     /// ### What it does
  15     /// Checks for `#[macro_use] use...`.
  16     ///
  17     /// ### Why is this bad?
  18     /// Since the Rust 2018 edition you can import
  19     /// macro's directly, this is considered idiomatic.
  20     ///
  21     /// ### Example
  22     /// ```rust,ignore
  23     /// #[macro_use]
  24     /// use some_macro;
  25     /// ```
  26     #[clippy::version = "1.44.0"]
  27     pub MACRO_USE_IMPORTS,
  28     pedantic,
  29     "#[macro_use] is no longer needed"
  30 }
  31
  32 #[derive(Clone, Debug, PartialEq, Eq)]
  33 struct PathAndSpan {
  34     path: String,
  35     span: Span,
  36 }
  37
  38 /// `MacroRefData` includes the name of the macro
  39 /// and the path from `SourceMap::span_to_filename`.
  40 #[derive(Debug, Clone)]
  41 pub struct MacroRefData {
  42     name: String,
  43 }
  44
  45 impl MacroRefData {
  46     pub fn new(name: String) -> Self {
  47         Self { name }
  48     }
  49 }
  50
  51 #[derive(Default)]
  52 #[expect(clippy::module_name_repetitions)]
  53 pub struct MacroUseImports {
  54     /// the actual import path used and the span of the attribute above it. The value is
  55     /// the location, where the lint should be emitted.
  56     imports: Vec<(String, Span, hir::HirId)>,
  57     /// the span of the macro reference, kept to ensure only one reference is used per macro call.
  58     collected: FxHashSet<Span>,
  59     mac_refs: Vec<MacroRefData>,
  60 }
  61
  62 impl_lint_pass!(MacroUseImports => [MACRO_USE_IMPORTS]);
  63
  64 impl MacroUseImports {
  65     fn push_unique_macro(&mut self, cx: &LateContext<'_>, span: Span) {
  66         let call_site = span.source_callsite();
  67         let name = snippet(cx, cx.sess().source_map().span_until_char(call_site, '!'), "_");
  68         if span.source_callee().is_some() && !self.collected.contains(&call_site) {
  69             let name = if name.contains("::") {
  70                 name.split("::").last().unwrap().to_string()
  71             } else {
  72                 name.to_string()
  73             };
  74
  75             self.mac_refs.push(MacroRefData::new(name));
  76             self.collected.insert(call_site);
  77         }
  78     }
  79
  80     fn push_unique_macro_pat_ty(&mut self, cx: &LateContext<'_>, span: Span) {
  81         let call_site = span.source_callsite();
  82         let name = snippet(cx, cx.sess().source_map().span_until_char(call_site, '!'), "_");
  83         if span.source_callee().is_some() && !self.collected.contains(&call_site) {
  84             self.mac_refs.push(MacroRefData::new(name.to_string()));
  85             self.collected.insert(call_site);
  86         }
  87     }
  88 }
  89
  90 impl<'tcx> LateLintPass<'tcx> for MacroUseImports {
  91     fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
  92         if_chain! {
  93             if cx.sess().opts.edition >= Edition::Edition2018;
  94             if let hir::ItemKind::Use(path, _kind) = &item.kind;
  95             let hir_id = item.hir_id();
  96             let attrs = cx.tcx.hir().attrs(hir_id);
  97             if let Some(mac_attr) = attrs.iter().find(|attr| attr.has_name(sym::macro_use));
  98             if let Res::Def(DefKind::Mod, id) = path.res;
  99             if !id.is_local();
 100             then {
 101                 for kid in cx.tcx.module_children(id).iter() {
 102                     if let Res::Def(DefKind::Macro(_mac_type), mac_id) = kid.res {
 103                         let span = mac_attr.span;
 104                         let def_path = cx.tcx.def_path_str(mac_id);
 105                         self.imports.push((def_path, span, hir_id));
 106                     }
 107                 }
 108             } else {
 109                 if item.span.from_expansion() {
 110                     self.push_unique_macro_pat_ty(cx, item.span);
 111                 }
 112             }
 113         }
 114     }
 115     fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
 116         if attr.span.from_expansion() {
 117             self.push_unique_macro(cx, attr.span);
 118         }
 119     }
 120     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
 121         if expr.span.from_expansion() {
 122             self.push_unique_macro(cx, expr.span);
 123         }
 124     }
 125     fn check_stmt(&mut self, cx: &LateContext<'_>, stmt: &hir::Stmt<'_>) {
 126         if stmt.span.from_expansion() {
 127             self.push_unique_macro(cx, stmt.span);
 128         }
 129     }
 130     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
 131         if pat.span.from_expansion() {
 132             self.push_unique_macro_pat_ty(cx, pat.span);
 133         }
 134     }
 135     fn check_ty(&mut self, cx: &LateContext<'_>, ty: &hir::Ty<'_>) {
 136         if ty.span.from_expansion() {
 137             self.push_unique_macro_pat_ty(cx, ty.span);
 138         }
 139     }
 140     fn check_crate_post(&mut self, cx: &LateContext<'_>) {
 141         let mut used = FxHashMap::default();
 142         let mut check_dup = vec![];
 143         for (import, span, hir_id) in &self.imports {
 144             let found_idx = self.mac_refs.iter().position(|mac| import.ends_with(&mac.name));
 145
 146             if let Some(idx) = found_idx {
 147                 self.mac_refs.remove(idx);
 148                 let seg = import.split("::").collect::<Vec<_>>();
 149
 150                 match seg.as_slice() {
 151                     // an empty path is impossible
 152                     // a path should always consist of 2 or more segments
 153                     [] | [_] => return,
 154                     [root, item] => {
 155                         if !check_dup.contains(&(*item).to_string()) {
 156                             used.entry(((*root).to_string(), span, hir_id))
 157                                 .or_insert_with(Vec::new)
 158                                 .push((*item).to_string());
 159                             check_dup.push((*item).to_string());
 160                         }
 161                     },
 162                     [root, rest @ ..] => {
 163                         if rest.iter().all(|item| !check_dup.contains(&(*item).to_string())) {
 164                             let filtered = rest
 165                                 .iter()
 166                                 .filter_map(|item| {
 167                                     if check_dup.contains(&(*item).to_string()) {
 168                                         None
 169                                     } else {
 170                                         Some((*item).to_string())
 171                                     }
 172                                 })
 173                                 .collect::<Vec<_>>();
 174                             used.entry(((*root).to_string(), span, hir_id))
 175                                 .or_insert_with(Vec::new)
 176                                 .push(filtered.join("::"));
 177                             check_dup.extend(filtered);
 178                         } else {
 179                             let rest = rest.to_vec();
 180                             used.entry(((*root).to_string(), span, hir_id))
 181                                 .or_insert_with(Vec::new)
 182                                 .push(rest.join("::"));
 183                             check_dup.extend(rest.iter().map(ToString::to_string));
 184                         }
 185                     },
 186                 }
 187             }
 188         }
 189
 190         let mut suggestions = vec![];
 191         for ((root, span, hir_id), path) in used {
 192             if path.len() == 1 {
 193                 suggestions.push((span, format!("{root}::{}", path[0]), hir_id));
 194             } else {
 195                 suggestions.push((span, format!("{root}::{{{}}}", path.join(", ")), hir_id));
 196             }
 197         }
 198
 199         // If mac_refs is not empty we have encountered an import we could not handle
 200         // such as `std::prelude::v1::foo` or some other macro that expands to an import.
 201         if self.mac_refs.is_empty() {
 202             for (span, import, hir_id) in suggestions {
 203                 let help = format!("use {import};");
 204                 span_lint_hir_and_then(
 205                     cx,
 206                     MACRO_USE_IMPORTS,
 207                     *hir_id,
 208                     *span,
 209                     "`macro_use` attributes are no longer needed in the Rust 2018 edition",
 210                     |diag| {
 211                         diag.span_suggestion(
 212                             *span,
 213                             "remove the attribute and import the macro directly, try",
 214                             help,
 215                             Applicability::MaybeIncorrect,
 216                         );
 217                     },
 218                 );
 219             }
 220         }
 221     }
 222 }