0f5338cd90
The `restriction` group contains many lints which are not about necessarily “bad” things, but style choices — perhaps even style choices which contradict conventional Rust style — or are otherwise very situational. This results in silly wording like “Why is this bad? It isn't, but ...”, which I’ve seen confuse a newcomer at least once. To improve this situation, this commit replaces the “Why is this bad?” section heading with “Why restrict this?”, for most, but not all, restriction lints. I left alone the ones whose placement in the restriction group is more incidental. In order to make this make sense, I had to remove the “It isn't, but” texts from the contents of the sections. Sometimes further changes were needed, or there were obvious fixes to make, and I went ahead and made those changes without attempting to split them into another commit, even though many of them are not strictly necessary for the “Why restrict this?” project.
90 lines
3.4 KiB
Rust
90 lines
3.4 KiB
Rust
use clippy_utils::diagnostics::{span_lint, span_lint_hir_and_then};
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use clippy_utils::path_res;
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use clippy_utils::ty::implements_trait;
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use rustc_hir::def_id::{DefId, LocalDefId};
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use rustc_hir::{Item, ItemKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::Visibility;
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use rustc_session::declare_lint_pass;
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use rustc_span::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for types named `Error` that implement `Error`.
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///
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/// ### Why restrict this?
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/// It can become confusing when a codebase has 20 types all named `Error`, requiring either
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/// aliasing them in the `use` statement or qualifying them like `my_module::Error`. This
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/// hinders comprehension, as it requires you to memorize every variation of importing `Error`
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/// used across a codebase.
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///
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/// ### Example
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/// ```rust,ignore
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/// #[derive(Debug)]
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/// pub enum Error { ... }
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///
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/// impl std::fmt::Display for Error { ... }
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///
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/// impl std::error::Error for Error { ... }
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/// ```
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#[clippy::version = "1.73.0"]
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pub ERROR_IMPL_ERROR,
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restriction,
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"exported types named `Error` that implement `Error`"
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}
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declare_lint_pass!(ErrorImplError => [ERROR_IMPL_ERROR]);
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impl<'tcx> LateLintPass<'tcx> for ErrorImplError {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
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let Some(error_def_id) = cx.tcx.get_diagnostic_item(sym::Error) else {
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return;
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};
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match item.kind {
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ItemKind::TyAlias(..)
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if item.ident.name == sym::Error
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&& is_visible_outside_module(cx, item.owner_id.def_id)
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&& let ty = cx.tcx.type_of(item.owner_id).instantiate_identity()
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&& implements_trait(cx, ty, error_def_id, &[]) =>
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{
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span_lint(
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cx,
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ERROR_IMPL_ERROR,
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item.ident.span,
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"exported type alias named `Error` that implements `Error`",
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);
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},
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ItemKind::Impl(imp)
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if let Some(trait_def_id) = imp.of_trait.and_then(|t| t.trait_def_id())
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&& error_def_id == trait_def_id
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&& let Some(def_id) = path_res(cx, imp.self_ty).opt_def_id().and_then(DefId::as_local)
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&& let hir_id = cx.tcx.local_def_id_to_hir_id(def_id)
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&& let Some(ident) = cx.tcx.opt_item_ident(def_id.to_def_id())
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&& ident.name == sym::Error
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&& is_visible_outside_module(cx, def_id) =>
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{
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span_lint_hir_and_then(
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cx,
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ERROR_IMPL_ERROR,
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hir_id,
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ident.span,
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"exported type named `Error` that implements `Error`",
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|diag| {
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diag.span_note(item.span, "`Error` was implemented here");
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},
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);
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},
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_ => {},
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}
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}
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}
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/// Do not lint private `Error`s, i.e., ones without any `pub` (minus `pub(self)` of course) and
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/// which aren't reexported
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fn is_visible_outside_module(cx: &LateContext<'_>, def_id: LocalDefId) -> bool {
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!matches!(
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cx.tcx.visibility(def_id),
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Visibility::Restricted(mod_def_id) if cx.tcx.parent_module_from_def_id(def_id).to_def_id() == mod_def_id
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)
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}
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