From 20a16bb3c54ea7523ebd0c933fe5674aea50942e Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 9 Aug 2024 21:14:07 -0400
Subject: [PATCH] Add test

Co-authored-by: Georg Semmler <github@weiznich.de>
---
 ...ot_apply_attribute_without_feature_flag.rs | 21 +++++++++++++++++++
 ...pply_attribute_without_feature_flag.stderr | 21 +++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.rs
 create mode 100644 tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.stderr

diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.rs b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.rs
new file mode 100644
index 0000000000000..5548fa2f52e17
--- /dev/null
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.rs
@@ -0,0 +1,21 @@
+#![allow(unknown_or_malformed_diagnostic_attributes)]
+
+trait Foo {}
+
+#[diagnostic::do_not_recommend]
+impl<A> Foo for (A,) {}
+
+#[diagnostic::do_not_recommend]
+impl<A, B> Foo for (A, B) {}
+
+#[diagnostic::do_not_recommend]
+impl<A, B, C> Foo for (A, B, C) {}
+
+impl Foo for i32 {}
+
+fn check(a: impl Foo) {}
+
+fn main() {
+    check(());
+    //~^ ERROR the trait bound `(): Foo` is not satisfied
+}
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.stderr
new file mode 100644
index 0000000000000..e56af28f3fb5d
--- /dev/null
+++ b/tests/ui/diagnostic_namespace/do_not_recommend/do_not_apply_attribute_without_feature_flag.stderr
@@ -0,0 +1,21 @@
+error[E0277]: the trait bound `(): Foo` is not satisfied
+  --> $DIR/do_not_apply_attribute_without_feature_flag.rs:19:11
+   |
+LL |     check(());
+   |     ----- ^^ the trait `Foo` is not implemented for `()`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = help: the following other types implement trait `Foo`:
+             (A, B)
+             (A, B, C)
+             (A,)
+note: required by a bound in `check`
+  --> $DIR/do_not_apply_attribute_without_feature_flag.rs:16:18
+   |
+LL | fn check(a: impl Foo) {}
+   |                  ^^^ required by this bound in `check`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.