Add more test cases.

Author: ywxt

tests/parallel/deadlock-issue-120759.rs

@@ -0,0 +1,24 @@
+// Test for #120759, which causes a deadlock bug
+//
+//@ compile-flags: -Z threads=50
+
+#![crate_type= "lib"]
+#![feature(transmutability)]
+
+mod assert {
+    use std::mem::{Assume, BikeshedIntrinsicFrom};
+    pub struct Context;
+
+    pub fn is_maybe_transmutable<Src, Dst>(&self, cpu: &mut CPU)
+    where
+        Dst: BikeshedIntrinsicFrom<Src, Context>,
+    {
+    }
+}
+
+fn should_pad_explicitly_packed_field() {
+    #[repr(C)]
+    struct ExplicitlyPadded(ExplicitlyPadded);
+
+    assert::is_maybe_transmutable::<ExplicitlyPadded, ()>();
+}