1 files changed, 66 insertions, 0 deletions
diff --git a/tests/coverage/bad_counter_ids.rs b/tests/coverage/bad_counter_ids.rs
new file mode 100644
index 000000000..ef5460102
--- /dev/null
+++ b/tests/coverage/bad_counter_ids.rs
@@ -0,0 +1,66 @@
+#![feature(coverage_attribute)]
+// compile-flags: --edition=2021 -Copt-level=0 -Zmir-opt-level=3
+
+// Regression test for <https://github.com/rust-lang/rust/issues/117012>.
+//
+// If some coverage counters were removed by MIR optimizations, we need to take
+// care not to refer to those counter IDs in coverage mappings, and instead
+// replace them with a constant zero value. If we don't, `llvm-cov` might see
+// a too-large counter ID and silently discard the entire function from its
+// coverage reports.
+
+#[derive(Debug, PartialEq, Eq)]
+struct Foo(u32);
+
+fn eq_good() {
+    println!("a");
+    assert_eq!(Foo(1), Foo(1));
+}
+
+fn eq_good_message() {
+    println!("b");
+    assert_eq!(Foo(1), Foo(1), "message b");
+}
+
+fn ne_good() {
+    println!("c");
+    assert_ne!(Foo(1), Foo(3));
+}
+
+fn ne_good_message() {
+    println!("d");
+    assert_ne!(Foo(1), Foo(3), "message d");
+}
+
+fn eq_bad() {
+    println!("e");
+    assert_eq!(Foo(1), Foo(3));
+}
+
+fn eq_bad_message() {
+    println!("f");
+    assert_eq!(Foo(1), Foo(3), "message f");
+}
+
+fn ne_bad() {
+    println!("g");
+    assert_ne!(Foo(1), Foo(1));
+}
+
+fn ne_bad_message() {
+    println!("h");
+    assert_ne!(Foo(1), Foo(1), "message h");
+}
+
+#[coverage(off)]
+fn main() {
+    eq_good();
+    eq_good_message();
+    ne_good();
+    ne_good_message();
+
+    assert!(std::panic::catch_unwind(eq_bad).is_err());
+    assert!(std::panic::catch_unwind(eq_bad_message).is_err());
+    assert!(std::panic::catch_unwind(ne_bad).is_err());
+    assert!(std::panic::catch_unwind(ne_bad_message).is_err());
+}