limit special FileCheck revision checks

Author: DavisRayM

src/tools/compiletest/src/header.rs

@@ -951,10 +951,12 @@ impl Config {
                         raw,
                         testfile.display()
                     );
-                } else if FORBIDDEN_REVISION_NAMES.contains(&revision.as_str()) {
+                } else if matches!(self.mode, Mode::Assembly | Mode::Codegen | Mode::MirOpt)
+                    && FORBIDDEN_REVISION_NAMES.contains(&revision.as_str())
+                {
                     panic!(
-                        "invalid revision: `{}` in line `{}`: {}",
-                        revision,
+                        "revision name `{revision}` is not permitted in a test suite that uses `FileCheck` annotations\n\
+                         as it is confusing when used as custom `FileCheck` prefix: `{revision}` in line `{}`: {}",
                         raw,
                         testfile.display()
                     );

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

@@ -553,17 +553,47 @@ fn test_duplicate_revisions() {
     parse_rs(&config, "//@ revisions: rpass1 rpass1");
 }
 
+fn test_file_check_revisions() {
+    let revisions = ["CHECK", "COM", "NEXT", "SAME", "EMPTY", "NOT", "COUNT", "DAG", "LABEL"];
+}
+
 #[test]
 fn test_forbidden_revisions() {
-    let config: Config = cfg().build();
     let revisions = ["CHECK", "COM", "NEXT", "SAME", "EMPTY", "NOT", "COUNT", "DAG", "LABEL"];
+    let check_enforced_modes = ["assembly", "codegen", "mir-opt"];
+    let check_skipped_modes = [
+        "pretty",
+        "debuginfo",
+        "rustdoc",
+        "rustdoc-json",
+        "codegen-units",
+        "incremental",
+        "ui",
+        "js-doc-test",
+        "coverage-map",
+        "coverage-run",
+        "crashes",
+    ];
+
     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()))
+        let content = format!("//@ revisions: {rev}");
+        for mode in check_skipped_modes {
+            let config = cfg().mode(mode).build();
+            parse_rs(&config, &content);
+        }
+
+        for mode in check_enforced_modes {
+            let mut res = std::panic::catch_unwind(|| {
+                let config = cfg().mode(mode).build();
+                parse_rs(&config, &content);
+            });
+            assert!(res.is_err());
+            assert!(
+                res.unwrap_err()
+                    .downcast_ref::<String>()
+                    .unwrap()
+                    .contains(format!("revision name `{rev}` is not permitted in a test suite that uses `FileCheck` annotations").as_str())
+            );
         }
     }
 }