check the the right field

Author: beepster4096

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -455,7 +455,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             cg_base = match elem.clone() {
                 mir::ProjectionElem::Deref => {
                     // a box with a non-zst allocator should not be directly dereferenced
-                    if cg_base.layout.ty.is_box() && !cg_base.layout.field(cx, 0).is_zst() {
+                    if cg_base.layout.ty.is_box() && !cg_base.layout.field(cx, 1).is_zst() {
                         let ptr = cg_base.project_field(bx, 0).project_field(bx, 0);
 
                         bx.load_operand(ptr).deref(bx.cx())