1 files changed, 150 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/declare_interior_mutable_const/traits.rs b/src/tools/clippy/tests/ui/declare_interior_mutable_const/traits.rs
new file mode 100644
index 000000000..256a336db
--- /dev/null
+++ b/src/tools/clippy/tests/ui/declare_interior_mutable_const/traits.rs
@@ -0,0 +1,150 @@
+#![warn(clippy::declare_interior_mutable_const)]
+
+use std::borrow::Cow;
+use std::cell::Cell;
+use std::sync::atomic::AtomicUsize;
+
+macro_rules! declare_const {
+    ($name:ident: $ty:ty = $e:expr) => {
+        const $name: $ty = $e;
+    };
+}
+
+// a constant whose type is a concrete type should be linted at the definition site.
+trait ConcreteTypes {
+    const ATOMIC: AtomicUsize; //~ ERROR interior mutable
+    const INTEGER: u64;
+    const STRING: String;
+    declare_const!(ANOTHER_ATOMIC: AtomicUsize = Self::ATOMIC); //~ ERROR interior mutable
+}
+
+impl ConcreteTypes for u64 {
+    const ATOMIC: AtomicUsize = AtomicUsize::new(9);
+    const INTEGER: u64 = 10;
+    const STRING: String = String::new();
+}
+
+// a helper trait used below
+trait ConstDefault {
+    const DEFAULT: Self;
+}
+
+// a constant whose type is a generic type should be linted at the implementation site.
+trait GenericTypes<T, U> {
+    const TO_REMAIN_GENERIC: T;
+    const TO_BE_CONCRETE: U;
+
+    const HAVING_DEFAULT: T = Self::TO_REMAIN_GENERIC;
+    declare_const!(IN_MACRO: T = Self::TO_REMAIN_GENERIC);
+}
+
+impl<T: ConstDefault> GenericTypes<T, AtomicUsize> for u64 {
+    const TO_REMAIN_GENERIC: T = T::DEFAULT;
+    const TO_BE_CONCRETE: AtomicUsize = AtomicUsize::new(11); //~ ERROR interior mutable
+}
+
+// a helper type used below
+struct Wrapper<T>(T);
+
+// a constant whose type is an associated type should be linted at the implementation site, too.
+trait AssocTypes {
+    type ToBeFrozen;
+    type ToBeUnfrozen;
+    type ToBeGenericParam;
+
+    const TO_BE_FROZEN: Self::ToBeFrozen;
+    const TO_BE_UNFROZEN: Self::ToBeUnfrozen;
+    const WRAPPED_TO_BE_UNFROZEN: Wrapper<Self::ToBeUnfrozen>;
+    // to ensure it can handle things when a generic type remains after normalization.
+    const WRAPPED_TO_BE_GENERIC_PARAM: Wrapper<Self::ToBeGenericParam>;
+}
+
+impl<T: ConstDefault> AssocTypes for Vec<T> {
+    type ToBeFrozen = u16;
+    type ToBeUnfrozen = AtomicUsize;
+    type ToBeGenericParam = T;
+
+    const TO_BE_FROZEN: Self::ToBeFrozen = 12;
+    const TO_BE_UNFROZEN: Self::ToBeUnfrozen = AtomicUsize::new(13); //~ ERROR interior mutable
+    const WRAPPED_TO_BE_UNFROZEN: Wrapper<Self::ToBeUnfrozen> = Wrapper(AtomicUsize::new(14)); //~ ERROR interior mutable
+    const WRAPPED_TO_BE_GENERIC_PARAM: Wrapper<Self::ToBeGenericParam> = Wrapper(T::DEFAULT);
+}
+
+// a helper trait used below
+trait AssocTypesHelper {
+    type NotToBeBounded;
+    type ToBeBounded;
+
+    const NOT_TO_BE_BOUNDED: Self::NotToBeBounded;
+}
+
+// a constant whose type is an assoc type originated from a generic param bounded at the definition
+// site should be linted at there.
+trait AssocTypesFromGenericParam<T>
+where
+    T: AssocTypesHelper<ToBeBounded = AtomicUsize>,
+{
+    const NOT_BOUNDED: T::NotToBeBounded;
+    const BOUNDED: T::ToBeBounded; //~ ERROR interior mutable
+}
+
+impl<T> AssocTypesFromGenericParam<T> for u64
+where
+    T: AssocTypesHelper<ToBeBounded = AtomicUsize>,
+{
+    // an associated type could remain unknown in a trait impl.
+    const NOT_BOUNDED: T::NotToBeBounded = T::NOT_TO_BE_BOUNDED;
+    const BOUNDED: T::ToBeBounded = AtomicUsize::new(15);
+}
+
+// a constant whose type is `Self` should be linted at the implementation site as well.
+// (`Option` requires `Sized` bound.)
+trait SelfType: Sized {
+    const SELF: Self;
+    // this was the one in the original issue (#5050).
+    const WRAPPED_SELF: Option<Self>;
+}
+
+impl SelfType for u64 {
+    const SELF: Self = 16;
+    const WRAPPED_SELF: Option<Self> = Some(20);
+}
+
+impl SelfType for AtomicUsize {
+    // this (interior mutable `Self` const) exists in `parking_lot`.
+    // `const_trait_impl` will replace it in the future, hopefully.
+    const SELF: Self = AtomicUsize::new(17); //~ ERROR interior mutable
+    const WRAPPED_SELF: Option<Self> = Some(AtomicUsize::new(21)); //~ ERROR interior mutable
+}
+
+// Even though a constant contains a generic type, if it also have an interior mutable type,
+// it should be linted at the definition site.
+trait BothOfCellAndGeneric<T> {
+    // this is a false negative in the current implementation.
+    const DIRECT: Cell<T>;
+    const INDIRECT: Cell<*const T>; //~ ERROR interior mutable
+}
+
+impl<T: ConstDefault> BothOfCellAndGeneric<T> for u64 {
+    const DIRECT: Cell<T> = Cell::new(T::DEFAULT);
+    const INDIRECT: Cell<*const T> = Cell::new(std::ptr::null());
+}
+
+struct Local<T>(T);
+
+// a constant in an inherent impl are essentially the same as a normal const item
+// except there can be a generic or associated type.
+impl<T> Local<T>
+where
+    T: ConstDefault + AssocTypesHelper<ToBeBounded = AtomicUsize>,
+{
+    const ATOMIC: AtomicUsize = AtomicUsize::new(18); //~ ERROR interior mutable
+    const COW: Cow<'static, str> = Cow::Borrowed("tuvwxy");
+
+    const GENERIC_TYPE: T = T::DEFAULT;
+
+    const ASSOC_TYPE: T::NotToBeBounded = T::NOT_TO_BE_BOUNDED;
+    const BOUNDED_ASSOC_TYPE: T::ToBeBounded = AtomicUsize::new(19); //~ ERROR interior mutable
+}
+
+fn main() {}