Special case error message for a build-fail test that failed check build

src/tools/compiletest/src/runtest.rs

@@ -318,10 +318,29 @@ impl<'test> TestCx<'test> {
         }
     }
 
-    fn check_if_test_should_compile(&self, proc_res: &ProcRes, pm: Option<PassMode>) {
-        if self.should_compile_successfully(pm) {
+    fn check_if_test_should_compile(
+        &self,
+        fail_mode: Option<FailMode>,
+        pass_mode: Option<PassMode>,
+        proc_res: &ProcRes,
+    ) {
+        if self.should_compile_successfully(pass_mode) {
             if !proc_res.status.success() {
-                self.fatal_proc_rec("test compilation failed although it shouldn't!", proc_res);
+                match (fail_mode, pass_mode) {
+                    (Some(FailMode::Build), Some(PassMode::Check)) => {
+                        // A `build-fail` test needs to `check-pass`.
+                        self.fatal_proc_rec(
+                            "`build-fail` test is required to pass check build, but check build failed",
+                            proc_res,
+                        );
+                    }
+                    _ => {
+                        self.fatal_proc_rec(
+                            "test compilation failed although it shouldn't!",
+                            proc_res,
+                        );
+                    }
+                }
             }
         } else {
             if proc_res.status.success() {

src/tools/compiletest/src/runtest/incremental.rs

@@ -1,4 +1,4 @@
-use super::{TestCx, WillExecute};
+use super::{FailMode, TestCx, WillExecute};
 use crate::errors;
 
 impl TestCx<'_> {
@@ -96,7 +96,7 @@ impl TestCx<'_> {
     fn run_cfail_test(&self) {
         let pm = self.pass_mode();
         let proc_res = self.compile_test(WillExecute::No, self.should_emit_metadata(pm));
-        self.check_if_test_should_compile(&proc_res, pm);
+        self.check_if_test_should_compile(Some(FailMode::Build), pm, &proc_res);
         self.check_no_compiler_crash(&proc_res, self.props.should_ice);
 
         let output_to_check = self.get_output(&proc_res);

src/tools/compiletest/src/runtest/ui.rs

@@ -18,14 +18,14 @@ impl TestCx<'_> {
             let pm = Some(PassMode::Check);
             let proc_res =
                 self.compile_test_general(WillExecute::No, Emit::Metadata, pm, Vec::new());
-            self.check_if_test_should_compile(&proc_res, pm);
+            self.check_if_test_should_compile(self.props.fail_mode, pm, &proc_res);
         }
 
         let pm = self.pass_mode();
         let should_run = self.should_run(pm);
         let emit_metadata = self.should_emit_metadata(pm);
         let proc_res = self.compile_test(should_run, emit_metadata);
-        self.check_if_test_should_compile(&proc_res, pm);
+        self.check_if_test_should_compile(self.props.fail_mode, pm, &proc_res);
         if matches!(proc_res.truncated, Truncated::Yes)
             && !self.props.dont_check_compiler_stdout
             && !self.props.dont_check_compiler_stderr