example for --explain E0018 claims to demo it, but does not

[pnkfelix]

example for --explain E0018 claims to demo it, but does not

I was reading over

http://doc.rust-lang.org/error-index.html#E0018

And I thought: "this should compile fine. If that yields an error, it's a bug."

So I checked. It does not yield the error.

Here is the text in question:

The value of static and const variables must be known at compile time. You can't cast a pointer as an integer because we can't know what value the address will take.

However, pointers to other constants' addresses are allowed in constants, example:

const X: u32 = 50;
const Y: *const u32 = &X;

Therefore, casting one of these non-constant pointers to an integer results in a non-constant integer which lead to this error. Example:

const X: u32 = 50;
const Y: *const u32 = &X;
println!("{:?}", Y);

[daboross]

For reference, here's some code which (I believe) does fail with this: https://github.com/rust-lang/rust/blob/master/src/test/compile-fail/issue-18294.rs

[pnkfelix]

Yes, it seems like the example in the explanation have lost the *const T as usize step that you can see in that compile-fail test.