2 files changed, 60 insertions, 0 deletions
diff --git a/tests/ui/transmute/issue-115402-overflow-size.rs b/tests/ui/transmute/issue-115402-overflow-size.rs
new file mode 100644
index 00000000000..91168041ed6
--- /dev/null
+++ b/tests/ui/transmute/issue-115402-overflow-size.rs
@@ -0,0 +1,27 @@
+#![crate_type = "lib"]
+#![feature(transmutability)]
+mod assert {
+    use std::mem::BikeshedIntrinsicFrom;
+    struct Context;
+
+    pub fn is_maybe_transmutable<Src, Dst>()
+    where
+        Dst: BikeshedIntrinsicFrom<Src, Context>,
+    {
+    }
+}
+
+fn main() {
+    pub union Uninit {
+        a: [u8; usize::MAX],
+    }
+
+    #[repr(C)]
+    struct ExplicitlyPadded(Uninit);
+
+    assert::is_maybe_transmutable::<(), ExplicitlyPadded>();
+    //~^ ERROR `()` cannot be safely transmuted into `ExplicitlyPadded`
+
+    assert::is_maybe_transmutable::<ExplicitlyPadded, ()>();
+    //~^ ERROR `ExplicitlyPadded` cannot be safely transmuted into `()`
+}
diff --git a/tests/ui/transmute/issue-115402-overflow-size.stderr b/tests/ui/transmute/issue-115402-overflow-size.stderr
new file mode 100644
index 00000000000..08d180f6427
--- /dev/null
+++ b/tests/ui/transmute/issue-115402-overflow-size.stderr
@@ -0,0 +1,33 @@
+error[E0277]: `()` cannot be safely transmuted into `ExplicitlyPadded` in the defining scope of `assert::Context`
+  --> $DIR/issue-115402-overflow-size.rs:22:41
+   |
+LL |     assert::is_maybe_transmutable::<(), ExplicitlyPadded>();
+   |                                         ^^^^^^^^^^^^^^^^ values of the type `ExplicitlyPadded` are too big for the current architecture
+   |
+note: required by a bound in `is_maybe_transmutable`
+  --> $DIR/issue-115402-overflow-size.rs:9:14
+   |
+LL |     pub fn is_maybe_transmutable<Src, Dst>()
+   |            --------------------- required by a bound in this function
+LL |     where
+LL |         Dst: BikeshedIntrinsicFrom<Src, Context>,
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_maybe_transmutable`
+
+error[E0277]: `ExplicitlyPadded` cannot be safely transmuted into `()` in the defining scope of `assert::Context`
+  --> $DIR/issue-115402-overflow-size.rs:25:55
+   |
+LL |     assert::is_maybe_transmutable::<ExplicitlyPadded, ()>();
+   |                                                       ^^ values of the type `ExplicitlyPadded` are too big for the current architecture
+   |
+note: required by a bound in `is_maybe_transmutable`
+  --> $DIR/issue-115402-overflow-size.rs:9:14
+   |
+LL |     pub fn is_maybe_transmutable<Src, Dst>()
+   |            --------------------- required by a bound in this function
+LL |     where
+LL |         Dst: BikeshedIntrinsicFrom<Src, Context>,
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_maybe_transmutable`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.