src/tools/clippy/clippy_lints/src/blacklisted_name.rs

   1 use clippy_utils::{diagnostics::span_lint, is_test_module_or_function};
   2 use rustc_data_structures::fx::FxHashSet;
   3 use rustc_hir::{Item, Pat, PatKind};
   4 use rustc_lint::{LateContext, LateLintPass};
   5 use rustc_session::{declare_tool_lint, impl_lint_pass};
   6
   7 declare_clippy_lint! {
   8     /// **What it does:** Checks for usage of blacklisted names for variables, such
   9     /// as `foo`.
  10     ///
  11     /// **Why is this bad?** These names are usually placeholder names and should be
  12     /// avoided.
  13     ///
  14     /// **Known problems:** None.
  15     ///
  16     /// **Example:**
  17     /// ```rust
  18     /// let foo = 3.14;
  19     /// ```
  20     pub BLACKLISTED_NAME,
  21     style,
  22     "usage of a blacklisted/placeholder name"
  23 }
  24
  25 #[derive(Clone, Debug)]
  26 pub struct BlacklistedName {
  27     blacklist: FxHashSet<String>,
  28     test_modules_deep: u32,
  29 }
  30
  31 impl BlacklistedName {
  32     pub fn new(blacklist: FxHashSet<String>) -> Self {
  33         Self {
  34             blacklist,
  35             test_modules_deep: 0,
  36         }
  37     }
  38
  39     fn in_test_module(&self) -> bool {
  40         self.test_modules_deep != 0
  41     }
  42 }
  43
  44 impl_lint_pass!(BlacklistedName => [BLACKLISTED_NAME]);
  45
  46 impl<'tcx> LateLintPass<'tcx> for BlacklistedName {
  47     fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
  48         if is_test_module_or_function(cx.tcx, item) {
  49             self.test_modules_deep = self.test_modules_deep.saturating_add(1);
  50         }
  51     }
  52
  53     fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
  54         // Check whether we are under the `test` attribute.
  55         if self.in_test_module() {
  56             return;
  57         }
  58
  59         if let PatKind::Binding(.., ident, _) = pat.kind {
  60             if self.blacklist.contains(&ident.name.to_string()) {
  61                 span_lint(
  62                     cx,
  63                     BLACKLISTED_NAME,
  64                     ident.span,
  65                     &format!("use of a blacklisted/placeholder name `{}`", ident.name),
  66                 );
  67             }
  68         }
  69     }
  70
  71     fn check_item_post(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
  72         if is_test_module_or_function(cx.tcx, item) {
  73             self.test_modules_deep = self.test_modules_deep.saturating_sub(1);
  74         }
  75     }
  76 }