src/tools/clippy/clippy_lints/src/inline_fn_without_body.rs

   1 //! checks for `#[inline]` on trait methods without bodies
   2
   3 use clippy_utils::diagnostics::span_lint_and_then;
   4 use clippy_utils::sugg::DiagnosticExt;
   5 use rustc_ast::ast::Attribute;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::{TraitFn, TraitItem, TraitItemKind};
   8 use rustc_lint::{LateContext, LateLintPass};
   9 use rustc_session::{declare_lint_pass, declare_tool_lint};
  10 use rustc_span::{sym, Symbol};
  11
  12 declare_clippy_lint! {
  13     /// ### What it does
  14     /// Checks for `#[inline]` on trait methods without bodies
  15     ///
  16     /// ### Why is this bad?
  17     /// Only implementations of trait methods may be inlined.
  18     /// The inline attribute is ignored for trait methods without bodies.
  19     ///
  20     /// ### Example
  21     /// ```rust
  22     /// trait Animal {
  23     ///     #[inline]
  24     ///     fn name(&self) -> &'static str;
  25     /// }
  26     /// ```
  27     #[clippy::version = "pre 1.29.0"]
  28     pub INLINE_FN_WITHOUT_BODY,
  29     correctness,
  30     "use of `#[inline]` on trait methods without bodies"
  31 }
  32
  33 declare_lint_pass!(InlineFnWithoutBody => [INLINE_FN_WITHOUT_BODY]);
  34
  35 impl<'tcx> LateLintPass<'tcx> for InlineFnWithoutBody {
  36     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
  37         if let TraitItemKind::Fn(_, TraitFn::Required(_)) = item.kind {
  38             let attrs = cx.tcx.hir().attrs(item.hir_id());
  39             check_attrs(cx, item.ident.name, attrs);
  40         }
  41     }
  42 }
  43
  44 fn check_attrs(cx: &LateContext<'_>, name: Symbol, attrs: &[Attribute]) {
  45     for attr in attrs {
  46         if !attr.has_name(sym::inline) {
  47             continue;
  48         }
  49
  50         span_lint_and_then(
  51             cx,
  52             INLINE_FN_WITHOUT_BODY,
  53             attr.span,
  54             &format!("use of `#[inline]` on trait method `{}` which has no body", name),
  55             |diag| {
  56                 diag.suggest_remove_item(cx, attr.span, "remove", Applicability::MachineApplicable);
  57             },
  58         );
  59     }
  60 }