//! lint on inherent implementations use crate::utils::{in_macro, span_lint_and_then}; use rustc_data_structures::fx::FxHashMap; use rustc_hir::{def_id, Crate, Item, ItemKind}; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::{declare_tool_lint, impl_lint_pass}; use rustc_span::Span; declare_clippy_lint! { /// **What it does:** Checks for multiple inherent implementations of a struct /// /// **Why is this bad?** Splitting the implementation of a type makes the code harder to navigate. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// struct X; /// impl X { /// fn one() {} /// } /// impl X { /// fn other() {} /// } /// ``` /// /// Could be written: /// /// ```rust /// struct X; /// impl X { /// fn one() {} /// fn other() {} /// } /// ``` pub MULTIPLE_INHERENT_IMPL, restriction, "Multiple inherent impl that could be grouped" } #[allow(clippy::module_name_repetitions)] #[derive(Default)] pub struct MultipleInherentImpl { impls: FxHashMap, } impl_lint_pass!(MultipleInherentImpl => [MULTIPLE_INHERENT_IMPL]); impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MultipleInherentImpl { fn check_item(&mut self, _: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) { if let ItemKind::Impl { ref generics, of_trait: None, .. } = item.kind { // Remember for each inherent implementation encoutered its span and generics // but filter out implementations that have generic params (type or lifetime) // or are derived from a macro if !in_macro(item.span) && generics.params.is_empty() { self.impls.insert(item.hir_id.owner.to_def_id(), item.span); } } } fn check_crate_post(&mut self, cx: &LateContext<'a, 'tcx>, krate: &'tcx Crate<'_>) { if let Some(item) = krate.items.values().next() { // Retrieve all inherent implementations from the crate, grouped by type for impls in cx .tcx .crate_inherent_impls(item.hir_id.owner.to_def_id().krate) .inherent_impls .values() { // Filter out implementations that have generic params (type or lifetime) let mut impl_spans = impls.iter().filter_map(|impl_def| self.impls.get(impl_def)); if let Some(initial_span) = impl_spans.next() { impl_spans.for_each(|additional_span| { span_lint_and_then( cx, MULTIPLE_INHERENT_IMPL, *additional_span, "Multiple implementations of this structure", |db| { db.span_note(*initial_span, "First implementation here"); }, ) }) } } } } }