deny usage of FileCheck prefixes as revision names

src/tools/compiletest/src/header.rs

@@ -934,6 +934,9 @@ fn iter_header(
 
 impl Config {
     fn parse_and_update_revisions(&self, testfile: &Path, line: &str, existing: &mut Vec<String>) {
+        const FORBIDDEN_REVISION_NAMES: [&str; 9] =
+            ["CHECK", "COM", "NEXT", "SAME", "EMPTY", "NOT", "COUNT", "DAG", "LABEL"];
+
         if let Some(raw) = self.parse_name_value_directive(line, "revisions") {
             if self.mode == Mode::RunMake {
                 panic!("`run-make` tests do not support revisions: {}", testfile.display());
@@ -948,6 +951,13 @@ impl Config {
                         raw,
                         testfile.display()
                     );
+                } else if FORBIDDEN_REVISION_NAMES.contains(&revision.as_str()) {
+                    panic!(
+                        "invalid revision: `{}` in line `{}`: {}",
+                        revision,
+                        raw,
+                        testfile.display()
+                    );
                 }
                 existing.push(revision);
             }

src/tools/compiletest/src/header/tests.rs

@@ -553,6 +553,21 @@ fn test_duplicate_revisions() {
     parse_rs(&config, "//@ revisions: rpass1 rpass1");
 }
 
+#[test]
+fn test_forbidden_revisions() {
+    let config: Config = cfg().build();
+    let revisions = ["CHECK", "COM", "NEXT", "SAME", "EMPTY", "NOT", "COUNT", "DAG", "LABEL"];
+    for rev in revisions {
+        let res = std::panic::catch_unwind(|| {
+            parse_rs(&config, format!("//@ revisions: {rev}").as_str());
+        });
+        assert!(res.is_err());
+        if let Some(msg) = res.unwrap_err().downcast_ref::<String>() {
+            assert!(msg.contains(format!("invalid revision: `{rev}` in line ` {rev}`").as_str()))
+        }
+    }
+}
+
 #[test]
 fn ignore_arch() {
     let archs = [