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| 1 | +use rustc_ast::visit::FnKind; |
| 2 | +use rustc_ast::{NodeId, WherePredicate}; |
| 3 | +use rustc_data_structures::fx::FxHashMap; |
| 4 | +use rustc_lint::{EarlyContext, EarlyLintPass}; |
| 5 | +use rustc_session::declare_lint_pass; |
| 6 | +use rustc_span::Span; |
| 7 | + |
| 8 | +use clippy_utils::diagnostics::span_lint; |
| 9 | +use clippy_utils::source::snippet_opt; |
| 10 | + |
| 11 | +declare_clippy_lint! { |
| 12 | + /// ### What it does |
| 13 | + /// Check if a generic is defined both in the bound predicate and in the `where` clause. |
| 14 | + /// |
| 15 | + /// ### Why is this bad? |
| 16 | + /// It can be confusing for developers when seeing bounds for a generic in multiple places. |
| 17 | + /// |
| 18 | + /// ### Example |
| 19 | + /// ```no_run |
| 20 | + /// fn ty<F: std::fmt::Debug>(a: F) |
| 21 | + /// where |
| 22 | + /// F: Sized, |
| 23 | + /// {} |
| 24 | + /// ``` |
| 25 | + /// Use instead: |
| 26 | + /// ```no_run |
| 27 | + /// fn ty<F>(a: F) |
| 28 | + /// where |
| 29 | + /// F: Sized + std::fmt::Debug, |
| 30 | + /// {} |
| 31 | + /// ``` |
| 32 | + #[clippy::version = "1.77.0"] |
| 33 | + pub MULTIPLE_BOUND_LOCATIONS, |
| 34 | + suspicious, |
| 35 | + "defining generic bounds in multiple locations" |
| 36 | +} |
| 37 | + |
| 38 | +declare_lint_pass!(MultipleBoundLocations => [MULTIPLE_BOUND_LOCATIONS]); |
| 39 | + |
| 40 | +impl EarlyLintPass for MultipleBoundLocations { |
| 41 | + fn check_fn(&mut self, cx: &EarlyContext<'_>, kind: FnKind<'_>, _: Span, _: NodeId) { |
| 42 | + if let FnKind::Fn(_, _, _, _, generics, _) = kind |
| 43 | + && !generics.params.is_empty() |
| 44 | + && !generics.where_clause.predicates.is_empty() |
| 45 | + { |
| 46 | + let mut generic_params_with_bounds = FxHashMap::default(); |
| 47 | + |
| 48 | + for param in &generics.params { |
| 49 | + if !param.bounds.is_empty() { |
| 50 | + generic_params_with_bounds.insert(param.ident.name.as_str(), param.ident.span); |
| 51 | + } |
| 52 | + } |
| 53 | + for clause in &generics.where_clause.predicates { |
| 54 | + match clause { |
| 55 | + WherePredicate::BoundPredicate(pred) => { |
| 56 | + if (!pred.bound_generic_params.is_empty() || !pred.bounds.is_empty()) |
| 57 | + && let Some(name) = snippet_opt(cx, pred.bounded_ty.span) |
| 58 | + && let Some(bound_span) = generic_params_with_bounds.get(name.as_str()) |
| 59 | + { |
| 60 | + emit_lint(cx, *bound_span, pred.bounded_ty.span); |
| 61 | + } |
| 62 | + }, |
| 63 | + WherePredicate::RegionPredicate(pred) => { |
| 64 | + if !pred.bounds.is_empty() |
| 65 | + && let Some(bound_span) = generic_params_with_bounds.get(&pred.lifetime.ident.name.as_str()) |
| 66 | + { |
| 67 | + emit_lint(cx, *bound_span, pred.lifetime.ident.span); |
| 68 | + } |
| 69 | + }, |
| 70 | + WherePredicate::EqPredicate(_) => {}, |
| 71 | + } |
| 72 | + } |
| 73 | + } |
| 74 | + } |
| 75 | +} |
| 76 | + |
| 77 | +fn emit_lint(cx: &EarlyContext<'_>, bound_span: Span, where_span: Span) { |
| 78 | + span_lint( |
| 79 | + cx, |
| 80 | + MULTIPLE_BOUND_LOCATIONS, |
| 81 | + vec![bound_span, where_span], |
| 82 | + "bound is defined in more than one place", |
| 83 | + ); |
| 84 | +} |
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