Add test to check unused_lifetimes don't duplicate "parameter is never used" error

2 files changed, 20 insertions, 0 deletions

diff --git a/tests/ui/single-use-lifetime/dedup.rs b/tests/ui/single-use-lifetime/dedup.rs
new file mode 100644
index 00000000000..16b39609a6d
--- /dev/null
+++ b/tests/ui/single-use-lifetime/dedup.rs
@@ -0,0 +1,9 @@
+// Check that `unused_lifetimes` lint doesn't duplicate a "parameter is never used" error.
+// Fixed in <https://github.com/rust-lang/rust/pull/96833>.
+// Issue: <https://github.com/rust-lang/rust/issues/72587>.
+
+#![warn(unused_lifetimes)]
+struct Foo<'a>;
+//~^ ERROR parameter `'a` is never used
+
+fn main() {}
diff --git a/tests/ui/single-use-lifetime/dedup.stderr b/tests/ui/single-use-lifetime/dedup.stderr
new file mode 100644
index 00000000000..6d02cb3c714
--- /dev/null
+++ b/tests/ui/single-use-lifetime/dedup.stderr
@@ -0,0 +1,11 @@
+error[E0392]: lifetime parameter `'a` is never used
+  --> $DIR/dedup.rs:6:12
+   |
+LL | struct Foo<'a>;
+   |            ^^ unused lifetime parameter
+   |
+   = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0392`.