except equal parameters from the uniqueness check

2 files changed, 74 insertions, 0 deletions

diff --git a/tests/ui/impl-trait/rpit/non-defining-use-lifetimes.rs b/tests/ui/impl-trait/rpit/non-defining-use-lifetimes.rs
new file mode 100644
index 00000000000..aa60ec27e00
--- /dev/null
+++ b/tests/ui/impl-trait/rpit/non-defining-use-lifetimes.rs
@@ -0,0 +1,38 @@
+// issue: #111935
+// FIXME(aliemjay): outdated due to "once modulo regions" restriction.
+// FIXME(aliemjay): mod `infer` should fail.
+
+#![allow(unconditional_recursion)]
+
+// Lt indirection is necessary to make the lifetime of the function late-bound,
+// in order to bypass some other bugs.
+type Lt<'lt> = Option<*mut &'lt ()>;
+
+mod statik {
+    use super::*;
+    // invalid defining use: Opaque<'static> := ()
+    fn foo<'a>(_: Lt<'a>) -> impl Sized + 'a {
+        let _: () = foo(Lt::<'static>::None);
+        //~^ ERROR opaque type used twice with different lifetimes
+    }
+}
+
+mod infer {
+    use super::*;
+    // invalid defining use: Opaque<'_> := ()
+    fn foo<'a>(_: Lt<'a>) -> impl Sized + 'a {
+        let _: () = foo(Lt::<'_>::None);
+    }
+}
+
+mod equal {
+    use super::*;
+    // invalid defining use: Opaque<'a, 'a> := ()
+    // because of the use of equal lifetimes in args
+    fn foo<'a, 'b>(_: Lt<'a>, _: Lt<'b>) -> impl Sized + 'a + 'b {
+        let _: () = foo(Lt::<'a>::None, Lt::<'a>::None);
+        //~^ ERROR opaque type used twice with different lifetimes
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/rpit/non-defining-use-lifetimes.stderr b/tests/ui/impl-trait/rpit/non-defining-use-lifetimes.stderr
new file mode 100644
index 00000000000..fe6bf71abdb
--- /dev/null
+++ b/tests/ui/impl-trait/rpit/non-defining-use-lifetimes.stderr
@@ -0,0 +1,36 @@
+error: opaque type used twice with different lifetimes
+  --> $DIR/non-defining-use-lifetimes.rs:15:16
+   |
+LL |       fn foo<'a>(_: Lt<'a>) -> impl Sized + 'a {
+   |  ______________________________________________-
+LL | |         let _: () = foo(Lt::<'static>::None);
+   | |                ^^ lifetime `'static` used here
+LL | |
+LL | |     }
+   | |_____- lifetime `'a` previously used here
+   |
+note: if all non-lifetime generic parameters are the same, but the lifetime parameters differ, it is not possible to differentiate the opaque types
+  --> $DIR/non-defining-use-lifetimes.rs:15:16
+   |
+LL |         let _: () = foo(Lt::<'static>::None);
+   |                ^^
+
+error: opaque type used twice with different lifetimes
+  --> $DIR/non-defining-use-lifetimes.rs:33:16
+   |
+LL |       fn foo<'a, 'b>(_: Lt<'a>, _: Lt<'b>) -> impl Sized + 'a + 'b {
+   |  __________________________________________________________________-
+LL | |         let _: () = foo(Lt::<'a>::None, Lt::<'a>::None);
+   | |                ^^ lifetime `'a` used here
+LL | |
+LL | |     }
+   | |_____- lifetime `'b` previously used here
+   |
+note: if all non-lifetime generic parameters are the same, but the lifetime parameters differ, it is not possible to differentiate the opaque types
+  --> $DIR/non-defining-use-lifetimes.rs:33:16
+   |
+LL |         let _: () = foo(Lt::<'a>::None, Lt::<'a>::None);
+   |                ^^
+
+error: aborting due to 2 previous errors
+