[feature request] #![no_std] support

[rowan-sl]

Although this would be less future-proof than the current implementation, a #![no_std] compatable backend for this crate could be provided by a transmute implementation like this one (using fake_static)

#![forbid(unsafe_code)]
#![no_std]

use core::cell::{Cell,UnsafeCell};

// may want to just depend on fake_static? instead of re-defining

fn helper<'a, 'b, T>(_: &'a &'b (), v: &'b T) -> &'a T { v }

/// Use black magic fuckery to turn any `&T` into a `&'static T`.
/// May introduce undefined behavior.
pub fn make_static<'a, T>(input: &'a T) -> &'static T {
    let f: fn(_, &'a T) -> &'static T = helper;
    f(&&(), input)
}

pub fn transmute<T, U: 'static>(e: T) -> U {
    // Store a None `U` value and get a reference to it:
    let mut value: Result<Cell<Option<UnsafeCell<U>>>, Cell<Option<UnsafeCell<T>>>> = Ok(Cell::new(None));
    let u_ref: &Cell<Option<UnsafeCell<U>>> = if let Ok(v) = &value { make_static(v) } else { unreachable!() };
    // Store a Some `T` value:
    value = Err(Cell::new(Some(UnsafeCell::new(e))));
    // Use our previous `U` reference to access the stored `T` value:
    u_ref.take().unwrap().into_inner()
}

concerns

• too powerfull to be left alive
• may require the addition of a MSRV (maximum supported rust version)
• code readability