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make TrivialClone a #[marker]-trait to keep it from appearing in error messages

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This commit is contained in:
joboet
2025-02-11 11:42:22 +01:00
parent 47342cf971
commit 7b72cc6156
3 changed files with 5 additions and 12 deletions
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library/core/src/clone.rs
+4
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@@ -275,6 +275,10 @@ fn clone_from(&mut self, source: &Self)
// its invariant holds whenever `Clone` is implemented, even if the actual
// `TrivialClone` bound would not be satisfied because of lifetime bounds.
#[rustc_unsafe_specialization_marker]
// If `#[derive(Clone, Clone, Copy)]` is written, there will be multiple
// implementations of `TrivialClone`. To keep it from appearing in error
// messages, make it a `#[marker]` trait.
#[marker]
pub const unsafe trait TrivialClone: [const] Clone {}
/// Derive macro generating an impl of the trait `Clone`.
tests/ui/derives/duplicate-derive-copy-clone-diagnostics.rs
-1
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@@ -6,7 +6,6 @@
#[derive(Copy, Clone)]
//~^ ERROR conflicting implementations of trait `Clone` for type `E`
//~| ERROR conflicting implementations of trait `Copy` for type `E`
//~| ERROR conflicting implementations of trait `TrivialClone` for type `E`
enum E {}
fn main() {}
tests/ui/derives/duplicate-derive-copy-clone-diagnostics.stderr
+1 -11
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@@ -6,16 +6,6 @@ LL | #[derive(Copy, Clone)]
LL | #[derive(Copy, Clone)]
| ^^^^ conflicting implementation for `E`
error[E0119]: conflicting implementations of trait `TrivialClone` for type `E`
--> $DIR/duplicate-derive-copy-clone-diagnostics.rs:6:16
|
LL | #[derive(Copy, Clone)]
| ----- first implementation here
LL | #[derive(Copy, Clone)]
| ^^^^^ conflicting implementation for `E`
|
= note: this error originates in the derive macro `Clone` (in Nightly builds, run with -Z macro-backtrace for more info)
error[E0119]: conflicting implementations of trait `Clone` for type `E`
--> $DIR/duplicate-derive-copy-clone-diagnostics.rs:6:16
|
@@ -24,6 +14,6 @@ LL | #[derive(Copy, Clone)]
LL | #[derive(Copy, Clone)]
| ^^^^^ conflicting implementation for `E`
error: aborting due to 3 previous errors
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0119`.