Fill match arms assist ignores existing variants prefixed with Self::

[yaahc]

Right now if you have an enum that has some match arms and a match like this:

match x {
    Self::V1 => todo!(),
    Self::V2 => todo!(),
}

and you add a new variant and then run the fill match arms assist it will insert additional copies of V1 and V2 in the match arms that are prefixed with the types own name rather than Self.

[bnjjj]

Will check to fix it :)

[Havvy]

This is a special case of the fill match arms assist not understanding use and type aliases. For example, given the following enum and various matches on its variants...

pub(crate) enum Foo {A, B, C, D, E, F}
type Bar = Foo;
mod Mod {
    pub(crate) use super::Foo as ModFoo;
}

impl Foo {
    fn match_assist(self) {
        use Foo::*;

        match self {
            Foo::A => {},
            Self::B => {},
            Bar::C => {},
            Mod::ModFoo::D => {}
            E => {},
        }
    }
}

...Rust Analyzer detects that the match is non-exhaustive and suggests to fill in the missing match arms. When using it, it changes the example to...

pub(crate) enum Foo {A, B, C, D, E, F}
type Bar = Foo;
mod Mod {
    pub(crate) use super::Foo as ModFoo;
}

impl Foo {
    fn match_assist(self) {
        use Foo::*;

        match self {
            Foo::A => {},
            Self::B => {},
            Bar::C => {},
            Mod::ModFoo::D => {}
            E => {},
            Foo::B => {}
            Foo::C => {}
            Foo::D => {}
            Foo::E => {}
            Foo::F => {}
        }
    }
}

...add arms for B through F. It should only add an arm for F, as that's the only one missing.

This behavior remains the same in a fn outside of an impl (ignoring the Self case that obviously doesn't compile).

[pksunkara]

It duplicates E because of #1165 for sure.