Undefined behavior in safe rust using `rustc_layout_scalar_valid_range_start`

[bart358]

Given the following struct:

#[rustc_layout_scalar_valid_range_start(2)]
struct NonZeroAndOneU8(u8);

trying to initialise it directly with NonZeroAndOneU8(1) (rightfully) results in the error:

error[[E0133]](https://doc.rust-lang.org/nightly/error_codes/E0133.html): initializing type with `rustc_layout_scalar_valid_range` attr is unsafe and requires unsafe function or block
 --> src/main.rs:9:5
  |
9 |     NonZeroAndOneU8(1);
  |     ^^^^^^^^^^^^^^^^^^ initializing type with `rustc_layout_scalar_valid_range` attr
  |
  = note: initializing a layout restricted type's field with a value outside the valid range is undefined behavior

For more information about this error, try `rustc --explain E0133`.
error: could not compile `playground` (bin "playground") due to previous error

But Some(1).map(NonZeroAndOneU8).unwrap() compiles just fine returning NonZeroAndOneU8(1) which is an invalid state (link to the playground).