update README and add COMPILETEST_VERBOSE_CRASHES env var which when set print stdout, stderr and exit code of "crashes" tests, useful for debugging or adding new tests

Author: matthiaskrgr

src/tools/compiletest/src/runtest.rs

@@ -364,16 +364,21 @@ impl<'test> TestCx<'test> {
     fn run_crash_test(&self) {
         let pm = self.pass_mode();
         let proc_res = self.compile_test(WillExecute::No, self.should_emit_metadata(pm));
-        /*
-        eprintln!("{}", proc_res.status);
-        eprintln!("{}", proc_res.stdout);
-        eprintln!("{}", proc_res.stderr);
-        eprintln!("{}", proc_res.cmdline);
-        */
+
+        if std::env::var("COMPILETEST_VERBOSE_CRASHES").is_ok() {
+            eprintln!("{}", proc_res.status);
+            eprintln!("{}", proc_res.stdout);
+            eprintln!("{}", proc_res.stderr);
+            eprintln!("{}", proc_res.cmdline);
+        }
 
         // if a test does not crash, consider it an error
         if proc_res.status.success() || matches!(proc_res.status.code(), Some(1 | 0)) {
-            self.fatal(&format!("test no longer crashes/triggers ICE! Please annotate it and add it as test to tests/ui or wherever you see fit"));
+            self.fatal(&format!(
+                "test no longer crashes/triggers ICE! Please give it a mearningful name, \
+            add a doc-comment to the start of the test explaining why it exists and \
+            move it to tests/ui or wherever you see fit."
+            ));
         }
     }
 

tests/crashes/README.md

@@ -10,4 +10,7 @@ When adding crashes from https://github.com/rust-lang/rust/issues, the
 issue number should be noted in the file name (12345.rs should suffice)
 and perhaps also inside the file via `//@ known-bug #4321`
 
-If you happen to fix one of the crashes, please move it to `tests/ui`! :)
+If you happen to fix one of the crashes, please move it to a fitting
+subdirectory in `tests/ui` and give it a meaningful name.
+Also please add a doc comment at the top of the file explaining why
+this test exists. :)