rustdoc prints the names of private consts when used as const generic parameter defaults

const VALUE: usize = 1;
type Ty = ();
pub trait Foo<const N: usize = VALUE, T = Ty> {}

Rustdoc generates the following pseudocode for this trait’s documentation page:

pub trait Foo<const N: usize = VALUE, T = ()> { }

This seems inconsistent to me: non-public constants should be replaced with their value just like non-public type aliases are, because crates should be free to have aliases for their own things privately without affecting the public view.

Another case is when a public constant uses a private constant; in that case, the private constant is named and the final value is. I’m not sure whether that’s good, but it at least answers the question of what the value is.

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rustc --version --verbose:

rustc 1.82.0-nightly (41dd149fd 2024-08-11)
binary: rustc
commit-hash: 41dd149fd6a6a06795fc6b9f54cb49af2f61775f
commit-date: 2024-08-11
host: x86_64-apple-darwin
release: 1.82.0-nightly
LLVM version: 19.1.0

@rustbot label +T-rustdoc

Start with the minimal Rust snippet in the issue and run rustdoc to reproduce the generated trait documentation. Trace the rustdoc entry point that renders const generic defaults; done means private constants are represented by their values rather than private names, with the public-constant case covered as well.