Make builtin_deref just return a Ty

compiler/rustc_const_eval/src/util/check_validity_requirement.rs

@@ -115,7 +115,7 @@ fn might_permit_raw_init_lax<'tcx>(
 
     // Special magic check for references and boxes (i.e., special pointer types).
     if let Some(pointee) = this.ty.builtin_deref(false) {
-        let pointee = cx.layout_of(pointee.ty)?;
+        let pointee = cx.layout_of(pointee)?;
         // We need to ensure that the LLVM attributes `aligned` and `dereferenceable(size)` are satisfied.
         if pointee.align.abi.bytes() > 1 {
             // 0x01-filling is not aligned.