Warning

This post was published 154 days ago. The information described in this article may have changed.

Info

This post is auto-generated from RSS feed The Rust Programming Language Forum - Latest topics. Source: Why cant `TypeId` equality be made `const`?

Why cant this function:

fn is_string<T: ?Sized + Any>() -> bool {
    TypeId::of::<String>() == TypeId::of::<T>()
}

be made const? The comparison is implemented in PartialEq::Eq. The types are known at compile time and consting will open up possibilities to write compile time constraints on templates.

I ultimately found a work around (but requires use of nightly intrinsics feature.)

const fn is_string<T: ?Sized + Any>() -> bool {
    core::intrinsics::type_id::<T>() == core::intrinsics::type_id::<String>()
}

The TypeId::t is a u128 value (comes from core::intrinsics::type_id::<T>()), so why not make the TypeId::as_u128 public? or better still allow conversion of TypeId::of::<T> as u128

(p.s. this is my 1st week with rust and just getting hang of things so sorry for if it's a noob question)

1 post - 1 participant

Read full topic

🏷️ rust_feed