GitHub - viktorlott/totally-safe: Welcome to TotallySafe, the Rust library that lets you boldly go where no safe code has gone before-—all without a single unsafe block!

[dependencies]
totally_safe = "0.1.1"

use totally_safe::TotallySafe;

fn main() {
    let mut value = Box::new(100);
    let copied = value.copy();
	// malloc: Double free of object
}

pub trait TotallySafe {
    /// Returns a reference to `self` with an arbitrary lifetime.
    ///
    /// This method allows you to obtain a reference to `self` that is bound
    /// to any given lifetime. It can be useful when you need to coerce
    /// a reference to have a different lifetime in certain contexts.
    ///
    /// # Example
    ///
    /// ```rust
    /// let instance = MyType::new();
    /// let any_lifetime_ref: &MyType = instance.as_ref_alias();
    /// // `any_lifetime_ref` now has an arbitrary lifetime.
    /// ```
    fn as_ref_alias<'x, 'any>(&'x self) -> &'any Self {
        (((|inc, _| inc) as for<'a, 'b> fn(&'b Self, &'a &'b ()) -> &'a Self)
            as for<'a, 'b> fn(&'x Self, &'a &'b ()) -> &'a Self)(self, &&())
    }

    /// Returns a mutable reference to `self` with an arbitrary lifetime.
    ///
    /// This method allows you to obtain a mutable reference to `self` that is bound
    /// to any given lifetime. It's useful when you need to coerce
    /// a mutable reference to have a different lifetime in certain situations.
    ///
    /// # Example
    ///
    /// ```rust
    /// let mut instance = MyType::new();
    /// let any_lifetime_mut_ref: &mut MyType = instance.as_mut_alias();
    /// // `any_lifetime_mut_ref` now has an arbitrary lifetime.
    /// ```
    fn as_mut_alias<'x, 'any>(&'x mut self) -> &'any mut Self {
        (((|inc, _| inc) as for<'a, 'b> fn(&'b mut Self, &'a &'b ()) -> &'a mut Self)
            as for<'a, 'b> fn(&'x mut Self, &'a &'b ()) -> &'a mut Self)(self, &&())
    }

    /// Returns an array of mutable references to `self`.
    ///
    /// This method allows you to obtain an array of `N` mutable references to `self`.
    /// It's perfect for those times when one mutable reference just isn't enough!
    /// Now you can be in multiple places at once (well, sort of).
    ///
    /// # Example
    ///
    /// ```rust
    /// fn mutate(q: &mut MyType, w: &mut MyType) { *q = w.copy() }
    ///
    /// let mut instance = MyType::new();
    /// let [a, b] = instance.as_mut_alias_array();
    ///
    /// mutate(a, b);
    ///
    /// ```
    fn as_mut_alias_array<'x, 'any, const N: usize>(&'x mut self) -> [&'any mut Self; N]
    where
        Self: Sized,
    {
        core::array::from_fn(|_| self.as_mut_alias())
    }

    /// Converts `self` into an instance of type `B`.
    ///
    /// This method consumes `self` and transforms it into a value of type `B`.
    /// It's particularly useful when you need to change the type of an object
    /// while retaining the underlying data in a compatible form.
    ///
    /// # Example
    ///
    /// ```rust
    /// let instance = MyType::new();
    /// let other_instance: OtherType = instance.transmute_into();
    /// // `other_instance` is now of type `OtherType`.
    /// ```
    fn transmute_into<B>(self) -> B
    where
        Self: Sized,
    {
        let mut data = Err::<Option<Box<Self>>, Option<Box<B>>>(None);
        let option_b = data.as_mut_alias().as_mut().err().unwrap();
        *data.as_mut_alias() = Ok(Some(Box::new(self)));
        *option_b.take().unwrap()
    }

    /// Creates a copy of `self` by duplicating its raw bytes.
    ///
    /// This method generates a new instance of `Self` by performing a byte-wise copy
    /// of the original object. It's particularly useful when you need to create a
    /// duplicate of an object without relying on the `Clone` trait, or when dealing
    /// with types that do not implement `Clone`.
    ///
    /// # Example
    ///
    /// ```rust
    /// let mut instance = MyType::new();
    /// let copy = instance.copy();
    /// // `copy` is now a duplicate of `instance`.
    /// ```
    fn copy(&mut self) -> Self
    where
        Self: Sized,
    {
        *core::ptr::slice_from_raw_parts(
            core::ptr::from_ref(self).cast::<u8>(),
            core::mem::size_of_val(self),
        )
        .transmute_into::<&[u8]>()
        .to_vec()
        .into_boxed_slice()
        .transmute_into::<Box<Self>>()
    }

    /// Copies exactly `SIZE` bytes from `self` and reinterprets them
    /// as a new `Self`.
    ///
    /// Works like `copy()`, but lets you explicitly choose how many
    /// bytes are copied. Misusing the `SIZE` parameter (e.g., wrong
    /// size or invalid bit pattern) is **Undefined Behavior**.
    ///
    /// # Example
    ///
    /// ```rust
    /// // SAFETY: SIZE must equal the full size of MyType, and MyType must allow byte-wise copying.
    /// let sim = value.copy_with_size::<{ core::mem::size_of::<MyType>() }>();
    /// ```
    fn copy_with_size<const SIZE: usize>(&mut self) -> Self
    where
        Self: Sized,
    {
        core::ptr::slice_from_raw_parts(core::ptr::from_ref(self).cast::<u8>(), SIZE)
            .transmute_into::<&[u8]>()
            .try_into()
            .map(core::convert::identity::<[u8; SIZE]>)
            .unwrap()
            .transmute_into()
    }
}

impl<T: ?Sized> TotallySafe for T {}