move has_repr to layout, handle repr(transparent) properly

compiler/rustc_middle/src/ty/layout.rs

@@ -755,6 +755,7 @@ where
                     largest_niche: None,
                     align: tcx.data_layout.i8_align,
                     size: Size::ZERO,
+                    has_repr_align: false,
                 })
             }
 
@@ -1104,15 +1105,6 @@ where
     fn is_unit(this: TyAndLayout<'tcx>) -> bool {
         matches!(this.ty.kind(), ty::Tuple(list) if list.len() == 0)
     }
-
-    fn repr_options(this: TyAndLayout<'tcx>) -> ReprOptions {
-        match *this.ty.kind() {
-            ty::Adt(def, ..) => def.repr(),
-            _ => {
-                bug!("TyAndLayout::repr_options({:?}): not applicable", this)
-            }
-        }
-    }
 }
 
 /// Calculates whether a function's ABI can unwind or not.