Add test for soundness issue on new solver

Author: lsunsi

tests/ui/const-generics/dyn-trait-ill-typed.rs

@@ -0,0 +1,14 @@
+//! Regression test for <https://github.com/rust-lang/trait-system-refactor-initiative/issues/296>.
+//@ compile-flags: -Znext-solver=globally
+//@ check-pass
+
+// CHECK PASS TO SHOW IT PASSES, BUT IT SHOULD NOT
+// THIS CODE SEGFAULTS, WITH REASON
+
+fn foo<const M: u32>() -> Box<dyn Tr<M>> {
+    loop {}
+}
+
+trait Tr<const N: usize> {}
+
+fn main() {}