Reconsider struct initialization syntax

[lolbinarycat]

In Rust (which vine takes significant syntax inspiration from), the token : is used for two things:

• Giving types to things
• Initialization of structs

With 10+ years of hindsight, I think we can pretty definitively conclude this is a mistake.
The biggest problem is how this interferes with the type ascription,
so much so that type ascription as a feature was scrapped.

Another point of reference is Carbon, a language that also takes a lot of syntax inspiration from Rust, does not use : in struct literals.

This allows it to have more natural type ascription, which is especially noticeable for things like tuples.

Rust: let (x, y): (u8, u32) = (1, 2)

Carbon: let (x: u8, y: u32) = (1, 2)

[tjjfvi]

I recognize the reasons against using it for objects, and I have considered alternatives, but ultimately I decided this was the best option.

I will note that Vine does have type ascription within patterns:

let (x: N32, y: String) = (1, "abc");
let { a:: Bool, b:: Char } = { a: true, b: '!' };

(The a:: Bool is shorthand for a: a: Bool, which is the type-ascripted analogue to the a shorthand for a: a. The :: is somewhat unfortunate, but the alternatives are all worse IMO.)