Peek for panic message in test output

crates/hir-ty/src/mir/eval.rs

@@ -428,6 +428,17 @@ impl MirEvalError {
         }
         Ok(())
     }
+
+    pub fn is_panic(&self) -> Option<&str> {
+        let mut err = self;
+        while let MirEvalError::InFunction(e, _) = err {
+            err = e;
+        }
+        match err {
+            MirEvalError::Panic(msg) => Some(msg),
+            _ => None,
+        }
+    }
 }
 
 impl std::fmt::Debug for MirEvalError {

crates/hir-ty/src/mir/eval/shim.rs

@@ -360,7 +360,7 @@ impl Evaluator<'_> {
                             ))
                         };
                     }
-                    let size = self.size_of_sized(&ty, locals, "begin panic arg")?;
+                    let size = self.size_of_sized(ty, locals, "begin panic arg")?;
                     let pointee = arg.interval.get(self)?;
                     arg = IntervalAndTy {
                         interval: Interval::new(Address::from_bytes(pointee)?, size),

crates/hir-ty/src/mir/eval/tests.rs

@@ -73,6 +73,13 @@ fn check_pass_and_stdio(ra_fixture: &str, expected_stdout: &str, expected_stderr
     }
 }
 
+fn check_panic(ra_fixture: &str, expected_panic: &str) {
+    let (db, file_ids) = TestDB::with_many_files(ra_fixture);
+    let file_id = *file_ids.last().unwrap();
+    let e = eval_main(&db, file_id).unwrap_err();
+    assert_eq!(e.is_panic().unwrap_or_else(|| panic!("unexpected error: {:?}", e)), expected_panic);
+}
+
 #[test]
 fn function_with_extern_c_abi() {
     check_pass(
@@ -96,13 +103,14 @@ fn panic_fmt() {
     //   -> core::panicking::const_panic_fmt
     //     -> #[rustc_const_panic_str] core::panicking::panic_display (hooked by CTFE for builtin panic)
     //       -> Err(ConstEvalError::Panic)
-    check_pass(
+    check_panic(
         r#"
 //- minicore: fmt, panic
 fn main() {
     panic!("hello, world!");
 }
     "#,
+        "hello, world!",
     );
 }
 
@@ -112,7 +120,7 @@ fn panic_display() {
     // -> panic_2021 (builtin macro redirection)
     //   -> #[rustc_const_panic_str] core::panicking::panic_display (hooked by CTFE for builtin panic)
     //     -> Err(ConstEvalError::Panic)
-    check_pass(
+    check_panic(
         r#"
 //- minicore: fmt, panic
 
@@ -120,6 +128,7 @@ fn main() {
     panic!("{}", "hello, world!");
 }
     "#,
+        "hello, world!",
     );
 }