rendered (draft)

Is this the opportunity to discuss possibly allowing numeric types to implicitly coerce when there's no loss of precision, e.g. u8 -> u32? I'm not necessarily advocating for it myself, but it has been requested in the past.

@bstrie I think that is a big enough change that it deserves its own RFC

Does this make coercion an special case of casts? Eg, is is true that with the changes every implicit coercion can also be written as an explicit cast?

Will generic integer literals be covered by this RFC? (Perhaps they aren't technically coercion...) I have a little frustration about generic literals with minus sign:

fn main() {
    for x in std::iter::range_step(3u32, 0, -1) {
        println!("{}", x);
    }
}

I don't like -1 silently evaluates to some 4 billion of type u32.

@nodakai fwiw that's unrelated to generics, a plain let x: u32 = -1; already silently evaluates to upwards of 4 billion. I don't think it's a coercion, it's just a legal value of unsigned integer literals.

@ben0x539 When you say "generics," you mean the <T> things, right? I'm talking about those literals which rustc call "generic integer":

fn main() {
    0.f();
}

<anon>:2:7: 2:10 error: type `<generic integer #0>` does not implement any method in scope named `f`

• http://is.gd/8yIej1

@nodakai Yeah, I thought you were talking about the <T> in fn range_step<T: ...>. Disregard that, I must have been confused. :)

I would like &T to coerce to T where T is a primitive. It would eliminate so many unnecessary explicit derefs.

Merged. Discussion. Tracking.