Respect MSRV (MAYBE_BOUND_IN_WHERE)

book/src/lint_configuration.md

@@ -634,6 +634,7 @@ The minimum rust version that the project supports. Defaults to the `rust-versio
 * [`match_like_matches_macro`](https://rust-lang.github.io/rust-clippy/master/index.html#match_like_matches_macro)
 * [`mem_replace_with_default`](https://rust-lang.github.io/rust-clippy/master/index.html#mem_replace_with_default)
 * [`missing_const_for_fn`](https://rust-lang.github.io/rust-clippy/master/index.html#missing_const_for_fn)
+* [`multiple_bound_locations`](https://rust-lang.github.io/rust-clippy/master/index.html#multiple_bound_locations)
 * [`needless_borrow`](https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow)
 * [`option_as_ref_deref`](https://rust-lang.github.io/rust-clippy/master/index.html#option_as_ref_deref)
 * [`option_map_unwrap_or`](https://rust-lang.github.io/rust-clippy/master/index.html#option_map_unwrap_or)

clippy_lints/src/declared_lints.rs

@@ -502,7 +502,6 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::module_style::MOD_MODULE_FILES_INFO,
     crate::module_style::SELF_NAMED_MODULE_FILES_INFO,
     crate::multi_assignments::MULTI_ASSIGNMENTS_INFO,
-    crate::multiple_bound_locations::MULTIPLE_BOUND_LOCATIONS_INFO,
     crate::multiple_unsafe_ops_per_block::MULTIPLE_UNSAFE_OPS_PER_BLOCK_INFO,
     crate::mut_key::MUTABLE_KEY_TYPE_INFO,
     crate::mut_mut::MUT_MUT_INFO,
@@ -669,6 +668,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::to_digit_is_some::TO_DIGIT_IS_SOME_INFO,
     crate::to_string_trait_impl::TO_STRING_TRAIT_IMPL_INFO,
     crate::trailing_empty_array::TRAILING_EMPTY_ARRAY_INFO,
+    crate::trait_bounds::MULTIPLE_BOUND_LOCATIONS_INFO,
     crate::trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS_INFO,
     crate::trait_bounds::TYPE_REPETITION_IN_BOUNDS_INFO,
     crate::transmute::CROSSPOINTER_TRANSMUTE_INFO,

clippy_lints/src/lib.rs

@@ -231,7 +231,6 @@ mod missing_trait_methods;
 mod mixed_read_write_in_expression;
 mod module_style;
 mod multi_assignments;
-mod multiple_bound_locations;
 mod multiple_unsafe_ops_per_block;
 mod mut_key;
 mod mut_mut;
@@ -1117,7 +1116,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     });
     store.register_late_pass(move |_| Box::new(incompatible_msrv::IncompatibleMsrv::new(msrv())));
     store.register_late_pass(|_| Box::new(to_string_trait_impl::ToStringTraitImpl));
-    store.register_early_pass(|| Box::new(multiple_bound_locations::MultipleBoundLocations));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_lints/src/trait_bounds.rs

@@ -1,5 +1,5 @@
 use clippy_config::msrvs::{self, Msrv};
-use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg};
+use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sugg};
 use clippy_utils::source::{snippet, snippet_opt, snippet_with_applicability};
 use clippy_utils::{is_from_proc_macro, SpanlessEq, SpanlessHash};
 use core::hash::{Hash, Hasher};
@@ -86,6 +86,33 @@ declare_clippy_lint! {
     "check if the same trait bounds are specified more than once during a generic declaration"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Check if a generic is defined both in the bound predicate and in the `where` clause.
+    ///
+    /// ### Why is this bad?
+    /// It can be confusing for developers when seeing bounds for a generic in multiple places.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// fn ty<F: std::fmt::Debug>(a: F)
+    /// where
+    ///     F: Sized,
+    /// {}
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// fn ty<F>(a: F)
+    /// where
+    ///     F: Sized + std::fmt::Debug,
+    /// {}
+    /// ```
+    #[clippy::version = "1.77.0"]
+    pub MULTIPLE_BOUND_LOCATIONS,
+    suspicious,
+    "defining generic bounds in multiple locations"
+}
+
 #[derive(Clone)]
 pub struct TraitBounds {
     max_trait_bounds: u64,
@@ -99,10 +126,11 @@ impl TraitBounds {
     }
 }
 
-impl_lint_pass!(TraitBounds => [TYPE_REPETITION_IN_BOUNDS, TRAIT_DUPLICATION_IN_BOUNDS]);
+impl_lint_pass!(TraitBounds => [TYPE_REPETITION_IN_BOUNDS, TRAIT_DUPLICATION_IN_BOUNDS, MULTIPLE_BOUND_LOCATIONS]);
 
 impl<'tcx> LateLintPass<'tcx> for TraitBounds {
     fn check_generics(&mut self, cx: &LateContext<'tcx>, gen: &'tcx Generics<'_>) {
+        self.check_multiple_bound_location(cx, gen);
         self.check_type_repetition(cx, gen);
         check_trait_bound_duplication(cx, gen);
     }
@@ -237,6 +265,55 @@ impl TraitBounds {
         }
     }
 
+    fn check_multiple_bound_location<'tcx>(&self, cx: &LateContext<'tcx>, gen: &'tcx Generics<'_>) {
+        let mut generic_params_with_bounds = FxHashMap::default();
+
+        for bound in gen.predicates {
+            if let WherePredicate::BoundPredicate(p) = bound
+                && p.origin == PredicateOrigin::GenericParam
+                && p.bounds
+                    .iter()
+                    .any(|b| !self.cannot_combine_maybe_bound(cx, b))
+                && let Some((_, ident)) = p.bounded_ty.as_generic_param()
+            {
+                generic_params_with_bounds.insert(ident.name, ident.span);
+            } else if let WherePredicate::RegionPredicate(p) = bound
+                && !p.in_where_clause
+                && !p.bounds.is_empty()
+            {
+                let ident = p.lifetime.ident;
+                generic_params_with_bounds.insert(ident.name, ident.span);
+            }
+        }
+
+        fn emit_lint(cx: &LateContext<'_>, bound_span: Span, where_span: Span) {
+            span_lint(
+                cx,
+                MULTIPLE_BOUND_LOCATIONS,
+                vec![bound_span, where_span],
+                "bound is defined in more than one place",
+            );
+        }
+
+        for bound in gen.predicates {
+            if let WherePredicate::BoundPredicate(p) = bound
+                && p.origin == PredicateOrigin::WhereClause
+                && !p.bounds.is_empty()
+                && let Some((_, ident)) = p.bounded_ty.as_generic_param()
+                && let Some(bound_span) = generic_params_with_bounds.get(&ident.name)
+            {
+                emit_lint(cx, *bound_span, ident.span);
+            } else if let WherePredicate::RegionPredicate(p) = bound
+                && p.in_where_clause
+                && !p.bounds.is_empty()
+                && let ident = p.lifetime.ident
+                && let Some(bound_span) = generic_params_with_bounds.get(&ident.name)
+            {
+                emit_lint(cx, *bound_span, ident.span);
+            }
+        }
+    }
+
     fn check_type_repetition<'tcx>(&self, cx: &LateContext<'tcx>, gen: &'tcx Generics<'_>) {
         struct SpanlessTy<'cx, 'tcx> {
             ty: &'tcx Ty<'tcx>,

tests/ui/multiple_bound_locations.rs

@@ -57,4 +57,26 @@ impl<F> C<F> {
     }
 }
 
+#[clippy::msrv = "1.14.0"]
+mod issue12370_fail {
+    trait Trait {}
+
+    fn f<T: ?Sized>()
+    where
+        T: Trait,
+    {
+    }
+}
+
+#[clippy::msrv = "1.15.0"]
+mod issue12370_pass {
+    trait Trait {}
+
+    fn f<T: ?Sized>()
+    where
+        T: Trait,
+    {
+    }
+}
+
 fn main() {}

tests/ui/multiple_bound_locations.stderr

@@ -55,5 +55,14 @@ LL |     fn ty_pred<F: Sized>()
 LL |         for<'a> F: Send + 'a,
    |                 ^
 
-error: aborting due to 6 previous errors
+error: bound is defined in more than one place
+  --> tests/ui/multiple_bound_locations.rs:75:10
+   |
+LL |     fn f<T: ?Sized>()
+   |          ^
+LL |     where
+LL |         T: Trait,
+   |         ^
+
+error: aborting due to 7 previous errors