Rollup merge of #91172 - Ethiraric:ethiraric/fix90979, r=petrochenkov

Warn when a `#[test]`-like built-in attribute macro is present multiple times.

Fixes #90979.

src/test/ui/attributes/duplicated-attributes.rs

@@ -0,0 +1,41 @@
+// Test that, if an item is annotated with a builtin attribute more than once, a warning is
+// emitted.
+// Tests https://github.com/rust-lang/rust/issues/90979
+
+// check-pass
+// compile-flags: --test
+
+#![feature(test)]
+#![feature(cfg_eval)]
+
+#[test]
+#[test]
+//~^ WARNING duplicated attribute
+fn f() {}
+
+// The following shouldn't trigger an error. The attribute is not duplicated.
+#[test]
+fn f2() {}
+
+// The following shouldn't trigger an error either. The second attribute is not #[test].
+#[test]
+#[inline]
+fn f3() {}
+
+extern crate test;
+use test::Bencher;
+
+#[bench]
+#[bench]
+//~^ WARNING duplicated attribute
+fn f4(_: &mut Bencher) {}
+
+#[cfg_eval]
+#[cfg_eval]
+//~^ WARNING duplicated attribute
+struct S;
+
+#[cfg_eval]
+struct S2;
+
+fn main() {}

src/test/ui/attributes/duplicated-attributes.stderr

@@ -0,0 +1,22 @@
+warning: duplicated attribute
+  --> $DIR/duplicated-attributes.rs:12:1
+   |
+LL | #[test]
+   | ^^^^^^^
+   |
+   = note: `#[warn(duplicate_macro_attributes)]` on by default
+
+warning: duplicated attribute
+  --> $DIR/duplicated-attributes.rs:29:1
+   |
+LL | #[bench]
+   | ^^^^^^^^
+
+warning: duplicated attribute
+  --> $DIR/duplicated-attributes.rs:34:1
+   |
+LL | #[cfg_eval]
+   | ^^^^^^^^^^^
+
+warning: 3 warnings emitted
+