impl From<Infallible> for MyType does not solve coercion problems

[AaronKutch]

playground link with all the impls and functions in example usage
The gist is that I have an impl impl TryFrom<usize> for InvariantType and function signatures with TryInto<InvariantType, Error = MyErrorType>. This enables many ergonomics, but trying to input a plain InvariantType into the function conflicts with the blanket impl TryFrom<T> for T which has a return type ! instead of Error = MyErrorType.

Since ! can and will coerce into anything through a future impl<T> From<!> for T , and there is a current workaround:

impl From<Infallible> for MyError {
    fn from(_: Infallible) -> Self {
        unreachable!()
    }
}

it should work, but adding this to the playground link does not change the error message at all.

Also in the playground link, there is a nearly identical error related to a From<NonZeroUsize> for BitWidth and its blanket impls. In that case, I can't even apply the attempted workaround because of orphan rules.

[jonas-schievink]

Adding the From impl does not create a TryFrom impl for an unrelated type. Change typical_function to take a generic error E instead and add where MyError: From<E> to its bounds.

[AaronKutch]

Thank you, the fix is

pub fn typical_function<W, E>(target_width: W) -> Result<(), MyError>
where
    W: TryInto<BitWidth, Error = E>,
    MyError: From<E>,
{

and add the From<Infallible> impl. playground link.