Rustdoc unexpectedly de-aliases type aliases in some situations

[ilyvion]

Here's a relatively minimal example that demonstrates the problem:

pub type Color1 = (u8, u8, u8, u8);

pub struct Color2 {
    r: u8,
    g: u8,
    b: u8,
    a: u8,
}

impl Color2 {
    pub fn new_with_alpha(r: u8, g: u8, b: u8, a: u8) -> Self {
        Self { r, g, b, a }
    }
}

impl From<Color2> for Color1 {
    fn from(c: Color2) -> Self {
        (c.r, c.g, c.b, c.a)
    }
}

impl From<Color1> for Color2 {
    fn from((r, g, b, a): Color1) -> Self {
        Self::new_with_alpha(r, g, b, a)
    }
}

If you run cargo doc on this, you'll get this:

As you can see, it says From<(u8, u8, u8, u8)> for Color2, despite saying Color1 everywhere else, including on the fn from(...) in the From implementation. I expected to get Color1 in the From<...> too.

[ragnese]

Question: Does rustdoc (generally) de-alias when the type is private? Or will it sometimes show a private type alias?

[mortendahl]

Is any work being done on this? I'm running into the same issue.