263 lines
10 KiB
Rust
263 lines
10 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::source::{snippet, snippet_with_applicability};
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use clippy_utils::{SpanlessEq, SpanlessHash};
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use core::hash::{Hash, Hasher};
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use if_chain::if_chain;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_data_structures::unhash::UnhashMap;
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use rustc_errors::Applicability;
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use rustc_hir::def::Res;
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use rustc_hir::{
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GenericBound, Generics, Item, ItemKind, Node, Path, PathSegment, PredicateOrigin, QPath, TraitItem, Ty, TyKind,
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WherePredicate,
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};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::Span;
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use std::fmt::Write as _;
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declare_clippy_lint! {
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/// ### What it does
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/// This lint warns about unnecessary type repetitions in trait bounds
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///
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/// ### Why is this bad?
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/// Repeating the type for every bound makes the code
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/// less readable than combining the bounds
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///
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/// ### Example
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/// ```rust
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/// pub fn foo<T>(t: T) where T: Copy, T: Clone {}
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// pub fn foo<T>(t: T) where T: Copy + Clone {}
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/// ```
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#[clippy::version = "1.38.0"]
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pub TYPE_REPETITION_IN_BOUNDS,
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nursery,
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"Types are repeated unnecessary in trait bounds use `+` instead of using `T: _, T: _`"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for cases where generics are being used and multiple
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/// syntax specifications for trait bounds are used simultaneously.
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///
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/// ### Why is this bad?
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/// Duplicate bounds makes the code
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/// less readable than specifying them only once.
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///
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/// ### Example
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/// ```rust
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/// fn func<T: Clone + Default>(arg: T) where T: Clone + Default {}
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// # mod hidden {
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/// fn func<T: Clone + Default>(arg: T) {}
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/// # }
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///
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/// // or
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///
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/// fn func<T>(arg: T) where T: Clone + Default {}
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/// ```
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#[clippy::version = "1.47.0"]
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pub TRAIT_DUPLICATION_IN_BOUNDS,
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nursery,
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"Check if the same trait bounds are specified twice during a function declaration"
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}
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#[derive(Copy, Clone)]
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pub struct TraitBounds {
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max_trait_bounds: u64,
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}
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impl TraitBounds {
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#[must_use]
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pub fn new(max_trait_bounds: u64) -> Self {
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Self { max_trait_bounds }
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}
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}
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impl_lint_pass!(TraitBounds => [TYPE_REPETITION_IN_BOUNDS, TRAIT_DUPLICATION_IN_BOUNDS]);
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impl<'tcx> LateLintPass<'tcx> for TraitBounds {
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fn check_generics(&mut self, cx: &LateContext<'tcx>, gen: &'tcx Generics<'_>) {
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self.check_type_repetition(cx, gen);
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check_trait_bound_duplication(cx, gen);
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}
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fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'tcx>) {
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let mut self_bounds_map = FxHashMap::default();
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for predicate in item.generics.predicates {
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if_chain! {
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if let WherePredicate::BoundPredicate(ref bound_predicate) = predicate;
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if bound_predicate.origin != PredicateOrigin::ImplTrait;
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if !bound_predicate.span.from_expansion();
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if let TyKind::Path(QPath::Resolved(_, Path { segments, .. })) = bound_predicate.bounded_ty.kind;
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if let Some(PathSegment {
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res: Some(Res::SelfTy{ trait_: Some(def_id), alias_to: _ }), ..
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}) = segments.first();
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if let Some(
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Node::Item(
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Item {
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kind: ItemKind::Trait(_, _, _, self_bounds, _),
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.. }
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)
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) = cx.tcx.hir().get_if_local(*def_id);
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then {
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if self_bounds_map.is_empty() {
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for bound in self_bounds.iter() {
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let Some((self_res, self_segments, _)) = get_trait_info_from_bound(bound) else { continue };
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self_bounds_map.insert(self_res, self_segments);
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}
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}
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bound_predicate
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.bounds
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.iter()
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.filter_map(get_trait_info_from_bound)
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.for_each(|(trait_item_res, trait_item_segments, span)| {
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if let Some(self_segments) = self_bounds_map.get(&trait_item_res) {
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if SpanlessEq::new(cx).eq_path_segments(self_segments, trait_item_segments) {
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span_lint_and_help(
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cx,
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TRAIT_DUPLICATION_IN_BOUNDS,
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span,
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"this trait bound is already specified in trait declaration",
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None,
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"consider removing this trait bound",
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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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}
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}
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impl TraitBounds {
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fn check_type_repetition<'tcx>(self, cx: &LateContext<'tcx>, gen: &'tcx Generics<'_>) {
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struct SpanlessTy<'cx, 'tcx> {
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ty: &'tcx Ty<'tcx>,
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cx: &'cx LateContext<'tcx>,
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}
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impl PartialEq for SpanlessTy<'_, '_> {
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fn eq(&self, other: &Self) -> bool {
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let mut eq = SpanlessEq::new(self.cx);
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eq.inter_expr().eq_ty(self.ty, other.ty)
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}
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}
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impl Hash for SpanlessTy<'_, '_> {
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fn hash<H: Hasher>(&self, h: &mut H) {
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let mut t = SpanlessHash::new(self.cx);
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t.hash_ty(self.ty);
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h.write_u64(t.finish());
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}
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}
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impl Eq for SpanlessTy<'_, '_> {}
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if gen.span.from_expansion() {
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return;
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}
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let mut map: UnhashMap<SpanlessTy<'_, '_>, Vec<&GenericBound<'_>>> = UnhashMap::default();
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let mut applicability = Applicability::MaybeIncorrect;
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for bound in gen.predicates {
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if_chain! {
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if let WherePredicate::BoundPredicate(ref p) = bound;
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if p.origin != PredicateOrigin::ImplTrait;
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if p.bounds.len() as u64 <= self.max_trait_bounds;
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if !p.span.from_expansion();
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if let Some(ref v) = map.insert(
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SpanlessTy { ty: p.bounded_ty, cx },
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p.bounds.iter().collect::<Vec<_>>()
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);
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then {
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let mut hint_string = format!(
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"consider combining the bounds: `{}:",
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snippet(cx, p.bounded_ty.span, "_")
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);
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for b in v.iter() {
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if let GenericBound::Trait(ref poly_trait_ref, _) = b {
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let path = &poly_trait_ref.trait_ref.path;
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let _ = write!(hint_string,
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" {} +",
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snippet_with_applicability(cx, path.span, "..", &mut applicability)
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);
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}
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}
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for b in p.bounds.iter() {
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if let GenericBound::Trait(ref poly_trait_ref, _) = b {
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let path = &poly_trait_ref.trait_ref.path;
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let _ = write!(hint_string,
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" {} +",
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snippet_with_applicability(cx, path.span, "..", &mut applicability)
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);
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}
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}
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hint_string.truncate(hint_string.len() - 2);
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hint_string.push('`');
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span_lint_and_help(
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cx,
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TYPE_REPETITION_IN_BOUNDS,
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p.span,
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"this type has already been used as a bound predicate",
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None,
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&hint_string,
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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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fn check_trait_bound_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
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if gen.span.from_expansion() || gen.params.is_empty() || gen.predicates.is_empty() {
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return;
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}
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let mut map = FxHashMap::<_, Vec<_>>::default();
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for predicate in gen.predicates {
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if_chain! {
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if let WherePredicate::BoundPredicate(ref bound_predicate) = predicate;
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if bound_predicate.origin != PredicateOrigin::ImplTrait;
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if !bound_predicate.span.from_expansion();
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if let TyKind::Path(QPath::Resolved(_, Path { segments, .. })) = bound_predicate.bounded_ty.kind;
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if let Some(segment) = segments.first();
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then {
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for (res_where, _, span_where) in bound_predicate.bounds.iter().filter_map(get_trait_info_from_bound) {
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let trait_resolutions_direct = map.entry(segment.ident).or_default();
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if let Some((_, span_direct)) = trait_resolutions_direct
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.iter()
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.find(|(res_direct, _)| *res_direct == res_where) {
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span_lint_and_help(
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cx,
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TRAIT_DUPLICATION_IN_BOUNDS,
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*span_direct,
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"this trait bound is already specified in the where clause",
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None,
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"consider removing this trait bound",
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);
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}
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else {
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trait_resolutions_direct.push((res_where, span_where));
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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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fn get_trait_info_from_bound<'a>(bound: &'a GenericBound<'_>) -> Option<(Res, &'a [PathSegment<'a>], Span)> {
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if let GenericBound::Trait(t, _) = bound {
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Some((t.trait_ref.path.res, t.trait_ref.path.segments, t.span))
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} else {
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None
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}
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}
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