Add a test for an LLVM crash "Vector elements must have same size"

tests/ui/derives/clone-vector-element-size.rs

@@ -0,0 +1,17 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/104037.
+//! LLVM used to hit an assertion "Vector elements must have same size"
+//! when compiling derived Clone with MIR optimisation level of 3.
+
+//@ build-pass
+//@ compile-flags: -Zmir-opt-level=3 -Copt-level=3
+
+#[derive(Clone)]
+pub struct Foo(Bar, u32);
+
+#[derive(Clone, Copy)]
+pub struct Bar(u8, u8, u8);
+
+fn main() {
+    let foo: Vec<Foo> = Vec::new();
+    let _ = foo.clone();
+}