Tracking issue for RFC 2302, Tuple struct construction with `Self(v1, v2, ..)`

[Centril]

This is a tracking issue for the RFC "Tuple struct construction with Self(v1, v2, ..)" (rust-lang/rfcs#2302).

Steps:

• Implement the RFC (Implement RFC 2302: tuple_struct_self_ctor #53751)
• Adjust documentation (see instructions on forge)
• Stabilization PR (see instructions on forge)

Unresolved questions:

None

[shepmaster]

Code that implements this has been merged.

#![feature(self_struct_ctor)]

struct Example(i32, bool);

impl Example {
    fn new() -> Self {
        Self(42, true)
    }
}

playground

[Centril]

@rfcbot merge

Stabilization report & proposal

Feature name: #![feature(self_struct_ctor)]
Version target: 1.32 (2019-01-18)

Originally accepted in rust-lang/rfcs#2302, I propose that we stabilize self_struct_ctor.
This has been in nightly since 2018-09-15 which is ~8 weeks ago.

The proposed change is not a blocker for anyone but it is a nice quality of life feature in some cases and more importantly, it makes the language less surprising and easier to learn. Furthermore, we do already permit Self { foo: ... }.

What is being stabilized

Relevant artefacts:

• Implementation
• Unstable book
• Feature gate
• Main tests

The changes are:

1. Self becomes a legal pattern and expression for unit structs in impls (both inherent and trait impls...).

match Self {
    Self => ...
}

2. Self(x1, x2, ...) becomes a legal pattern and expression for tuple structs in impls (both inherent and trait impls...).

match Self(0, 1) {
    Self(x, y) => ...
}

3. Self becomes a legal function pointer in impls (...).

opt.map(Self)

4. Points 1-3 work through type aliases just like Self { field: <thing> } does.

What is not being stabilized

Mentions of enum variants through Self is not being stabilized. For example:

enum Foo { Variant(u8), }

impl Foo {
    fn bar() {
        let x = Self::Variant(1);
    }
}

Divergences from RFC

None

[rfcbot]

Team member @Centril has proposed to merge this. The next step is review by the rest of the tagged teams:

• @Centril
• @aturon
• @cramertj
• @eddyb
• @joshtriplett
• @nikomatsakis
• @nrc
• @pnkfelix
• @scottmcm
• @withoutboats

No concerns currently listed.

Once a majority of reviewers approve (and none object), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.