|  | #![feature(rustc_attrs)] | 
|  |  | 
|  | use std::cell::Cell; | 
|  |  | 
|  | #[rustc_layout_scalar_valid_range_start(1)] | 
|  | #[repr(transparent)] | 
|  | pub(crate) struct NonZero<T>(pub(crate) T); | 
|  | fn main() {} | 
|  |  | 
|  | const fn foo() -> NonZero<Cell<u32>> { | 
|  | let mut x = unsafe { NonZero(Cell::new(1)) }; | 
|  | let y = &x.0; | 
|  | //~^ ERROR borrow of layout constrained field with interior mutability | 
|  | unsafe { NonZero(Cell::new(1)) } | 
|  | } | 
|  |  | 
|  | const fn bar() -> NonZero<Cell<u32>> { | 
|  | let mut x = unsafe { NonZero(Cell::new(1)) }; | 
|  | let y = unsafe { &x.0 }; | 
|  | unsafe { NonZero(Cell::new(1)) } | 
|  | } |