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Allen Hsu
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Add repeated where clause or trait bound lint.
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‎CHANGELOG.md‎

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@@ -3661,6 +3661,7 @@ Released 2018-09-13
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[`ref_option_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#ref_option_ref
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[`regex_macro`]: https://rust-lang.github.io/rust-clippy/master/index.html#regex_macro
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[`repeat_once`]: https://rust-lang.github.io/rust-clippy/master/index.html#repeat_once
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[`repeated_where_clause_or_trait_bound`]: https://rust-lang.github.io/rust-clippy/master/index.html#repeated_where_clause_or_trait_bound
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[`replace_consts`]: https://rust-lang.github.io/rust-clippy/master/index.html#replace_consts
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[`rest_pat_in_fully_bound_structs`]: https://rust-lang.github.io/rust-clippy/master/index.html#rest_pat_in_fully_bound_structs
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[`result_map_or_into_option`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_map_or_into_option

‎clippy_lints/src/lib.register_lints.rs‎

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@@ -493,6 +493,7 @@ store.register_lints(&[
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temporary_assignment::TEMPORARY_ASSIGNMENT,
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to_digit_is_some::TO_DIGIT_IS_SOME,
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trailing_empty_array::TRAILING_EMPTY_ARRAY,
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trait_bounds::REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND,
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trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS,
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trait_bounds::TYPE_REPETITION_IN_BOUNDS,
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transmute::CROSSPOINTER_TRANSMUTE,

‎clippy_lints/src/lib.register_nursery.rs‎

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@@ -28,6 +28,7 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
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LintId::of(strings::STRING_LIT_AS_BYTES),
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LintId::of(suspicious_operation_groupings::SUSPICIOUS_OPERATION_GROUPINGS),
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LintId::of(trailing_empty_array::TRAILING_EMPTY_ARRAY),
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LintId::of(trait_bounds::REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND),
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LintId::of(trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS),
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LintId::of(trait_bounds::TYPE_REPETITION_IN_BOUNDS),
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LintId::of(transmute::TRANSMUTE_UNDEFINED_REPR),

‎clippy_lints/src/trait_bounds.rs‎

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@@ -69,6 +69,35 @@ declare_clippy_lint! {
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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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declare_clippy_lint! {
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/// ### What it does
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/// Checks for multiple instances of the same where clause or trait bound
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///
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/// ### Why is this bad?
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/// Adds to code noise
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///
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/// ### Example
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/// ```rust
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/// fn foo<T: Default + Default>(bar: T) {}
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/// ```
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/// Use instead:
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/// ```rust
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/// fn foo<T: Default>(bar: T) {}
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/// ```
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///
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/// ```rust
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/// fn foo<T>(bar: T) where T: Default + Default {}
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/// ```
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/// Use instead:
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/// ```rust
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/// fn foo<T>(bar: T) where T: Default {}
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/// ```
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#[clippy::version = "1.62.0"]
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pub REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND,
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pedantic,
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"Traits are repeated within trait bounds or where clause"
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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,
@@ -81,12 +110,13 @@ impl TraitBounds {
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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_lint_pass!(TraitBounds => [TYPE_REPETITION_IN_BOUNDS, TRAIT_DUPLICATION_IN_BOUNDS, REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND]);
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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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check_bounds_or_where_duplication(cx, gen);
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}
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fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'tcx>) {
@@ -250,6 +280,53 @@ fn check_trait_bound_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
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}
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}
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fn check_bounds_or_where_duplication(cx: &LateContext<'_>, gen: &'_ Generics<'_>) {
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if gen.span.from_expansion() {
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return;
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}
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for param in gen.params {
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let mut map = FxHashMap::default();
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if let ParamName::Plain(name) = param.name {
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for (definition, _, span_direct) in param.bounds.iter().rev().filter_map(get_trait_info_from_bound) {
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if let Some(span_direct) = map.insert((name, definition), span_direct) {
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span_lint_and_help(
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cx,
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REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND,
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span_direct,
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"this trait bound has already been specified",
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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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for predicate in gen.where_clause.predicates {
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if let WherePredicate::BoundPredicate(ref bound_predicate) = predicate {
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let mut where_clauses = FxHashMap::default();
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for (definition, _, span_direct) in 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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.rev()
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{
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if let Some(span_direct) = where_clauses.insert(definition, span_direct) {
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span_lint_and_help(
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cx,
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REPEATED_WHERE_CLAUSE_OR_TRAIT_BOUND,
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span_direct,
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"this where clause has already been specified",
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None,
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"consider removing this where clause",
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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))

‎tests/ui/repeated_where_clause_or_trait_bound.rs‎

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@@ -0,0 +1,92 @@
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#![deny(clippy::repeated_where_clause_or_trait_bound)]
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fn bad_foo<T: Clone + Clone + Clone + Copy, U: Clone + Copy>(arg0: T, argo1: U) {
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unimplemented!();
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}
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fn bad_bar<T, U>(arg0: T, arg1: U)
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where
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T: Clone + Clone + Clone + Copy,
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U: Clone + Copy,
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{
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unimplemented!();
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}
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fn good_bar<T: Clone + Copy, U: Clone + Copy>(arg0: T, arg1: U) {
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unimplemented!();
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}
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fn good_foo<T, U>(arg0: T, arg1: U)
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where
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T: Clone + Copy,
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U: Clone + Copy,
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{
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unimplemented!();
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}
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trait GoodSelfTraitBound: Clone + Copy {
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fn f();
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}
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trait GoodSelfWhereClause {
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fn f()
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where
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Self: Clone + Copy;
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}
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trait BadSelfTraitBound: Clone + Clone + Clone {
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fn f();
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}
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trait BadSelfWhereClause {
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fn f()
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where
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Self: Clone + Clone + Clone;
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}
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trait GoodTraitBound<T: Clone + Copy, U: Clone + Copy> {
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fn f();
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}
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trait GoodWhereClause<T, U> {
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fn f()
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where
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T: Clone + Copy,
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U: Clone + Copy;
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}
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trait BadTraitBound<T: Clone + Clone + Clone + Copy, U: Clone + Copy> {
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fn f();
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}
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trait BadWhereClause<T, U> {
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fn f()
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where
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T: Clone + Clone + Clone + Copy,
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U: Clone + Copy;
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}
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struct GoodStructBound<T: Clone + Copy, U: Clone + Copy> {
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t: T,
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u: U,
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}
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impl<T: Clone + Copy, U: Clone + Copy> GoodTraitBound<T, U> for GoodStructBound<T, U> {
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// this should not warn
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fn f() {}
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}
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struct GoodStructWhereClause;
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impl<T, U> GoodTraitBound<T, U> for GoodStructWhereClause
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where
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T: Clone + Copy,
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U: Clone + Copy,
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{
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// this should not warn
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fn f() {}
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}
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fn no_error_separate_arg_bounds(program: impl AsRef<()>, dir: impl AsRef<()>, args: &[impl AsRef<()>]) {}
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fn main() {}

‎tests/ui/repeated_where_clause_or_trait_bound.stderr‎

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@@ -0,0 +1,87 @@
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error: this trait bound has already been specified
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--> $DIR/repeated_where_clause_or_trait_bound.rs:3:31
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|
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LL | fn bad_foo<T: Clone + Clone + Clone + Copy, U: Clone + Copy>(arg0: T, argo1: U) {
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| ^^^^^
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|
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note: the lint level is defined here
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--> $DIR/repeated_where_clause_or_trait_bound.rs:1:9
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|
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LL | #![deny(clippy::repeated_where_clause_or_trait_bound)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: consider removing this trait bound
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error: this trait bound has already been specified
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--> $DIR/repeated_where_clause_or_trait_bound.rs:3:23
16+
|
17+
LL | fn bad_foo<T: Clone + Clone + Clone + Copy, U: Clone + Copy>(arg0: T, argo1: U) {
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| ^^^^^
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|
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= help: consider removing this trait bound
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error: this where clause has already been specified
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--> $DIR/repeated_where_clause_or_trait_bound.rs:9:24
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|
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LL | T: Clone + Clone + Clone + Copy,
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| ^^^^^
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|
28+
= help: consider removing this where clause
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error: this where clause has already been specified
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--> $DIR/repeated_where_clause_or_trait_bound.rs:9:16
32+
|
33+
LL | T: Clone + Clone + Clone + Copy,
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| ^^^^^
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|
36+
= help: consider removing this where clause
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error: this where clause has already been specified
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--> $DIR/repeated_where_clause_or_trait_bound.rs:44:31
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|
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LL | Self: Clone + Clone + Clone;
42+
| ^^^^^
43+
|
44+
= help: consider removing this where clause
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46+
error: this where clause has already been specified
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--> $DIR/repeated_where_clause_or_trait_bound.rs:44:23
48+
|
49+
LL | Self: Clone + Clone + Clone;
50+
| ^^^^^
51+
|
52+
= help: consider removing this where clause
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54+
error: this trait bound has already been specified
55+
--> $DIR/repeated_where_clause_or_trait_bound.rs:58:40
56+
|
57+
LL | trait BadTraitBound<T: Clone + Clone + Clone + Copy, U: Clone + Copy> {
58+
| ^^^^^
59+
|
60+
= help: consider removing this trait bound
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62+
error: this trait bound has already been specified
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--> $DIR/repeated_where_clause_or_trait_bound.rs:58:32
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|
65+
LL | trait BadTraitBound<T: Clone + Clone + Clone + Copy, U: Clone + Copy> {
66+
| ^^^^^
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|
68+
= help: consider removing this trait bound
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70+
error: this where clause has already been specified
71+
--> $DIR/repeated_where_clause_or_trait_bound.rs:65:28
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|
73+
LL | T: Clone + Clone + Clone + Copy,
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| ^^^^^
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|
76+
= help: consider removing this where clause
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78+
error: this where clause has already been specified
79+
--> $DIR/repeated_where_clause_or_trait_bound.rs:65:20
80+
|
81+
LL | T: Clone + Clone + Clone + Copy,
82+
| ^^^^^
83+
|
84+
= help: consider removing this where clause
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86+
error: aborting due to 10 previous errors
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