1 files changed, 12 insertions, 0 deletions

diff --git a/src/test/ui/impl-trait/issues/issue-57979-nested-impl-trait-in-assoc-proj.rs b/src/test/ui/impl-trait/issues/issue-57979-nested-impl-trait-in-assoc-proj.rs
new file mode 100644
index 000000000..5a444d3df
--- /dev/null
+++ b/src/test/ui/impl-trait/issues/issue-57979-nested-impl-trait-in-assoc-proj.rs
@@ -0,0 +1,12 @@
+// rust-lang/rust#57979 : the initial support for `impl Trait` didn't
+// properly check syntax hidden behind an associated type projection.
+// Here we test behavior of occurrences of `impl Trait` within an
+// `impl Trait` in that context.
+
+pub trait Foo<T> { }
+pub trait Bar { }
+pub trait Quux { type Assoc; }
+pub fn demo(_: impl Quux<Assoc=impl Foo<impl Bar>>) { }
+//~^ ERROR nested `impl Trait` is not allowed
+
+fn main() { }