Rfcs: Language feature: turboball as postfix operator

[swfsql]

Have the ::() ( turboball / rotating-arm / sonic spin ) to be a general postfix operator.

This is a suggestion to the discussion at

• https://internals.rust-lang.org/t/idea-universal-pipelining-a-k-a-making-await-generic/9973
• https://github.com/rust-lang/rfcs/pull/2442

and the proposed syntax is similar to turbofish but it doesn't collide with field access nor namespaces nor turbofish and it does not include new symbols.

for example, have..

a::(match) {
    // ..
}

..be equivalent to..

match a {
    // ..
}

---

and then possibly deal with macros as well:

have..

("{}", 1)::(println!);

..be equivalent to..

println!("{}", 1);

---

So applying this to the async and postfix situations,
If await is a "await prefix" (let x = await thing;), it's turboball would be let x = thing::(await);
If it's macro-like (let x = await!(thing);), it's turboball would be let x = (thing)::(await!).

note: as macro tokens would still require surroundings ((), [], {}), then macro cascading, if possible, would still require russian-dolling..

(
    (
        (res_res_res)::(try!)
    )::(try!)
)::(try!)

..unless you would always insert surrounding parenthesis - but this could interfere with other stuff, idk - or if you would treat unit-tuple (or "empty" as a sugar to the unit-tuple) as parenthesis surrounding insertion, something like..

res_res_res
    ::(())::(try!)
    ::(())::(try!)
    ::(())::(try!)

..and/or..

res_res_res
    ::()::(try!)
    ::()::(try!)
    ::()::(try!)

..then I guess cascading macros would work.

---

I don't know if every expression "modifier"/variant should be included (or if this makes sense).

For example..

object
    .a()
    .b()
    .c()
    ::(&)

..may be equivalent to..

&object
    .a()
    .b()
    .c()

or even, if..

result::()::(try!)

..were equivalent to..

try!(result)

..then the ExprTry (result?) wouldn't be necessary.

Except that as a ExprTry structure, it still holds the "expression information" (see <ExprTry>::expr field) and not only "token stream information" (as normal macros do - see <ExprMacro>::mac.tts field). So ::(try!) couldn't really replace ExprTry structure (and it's inner information).

---

About calling functions that require multiple parameters, the linked discussion suggests using clojures for that. If not by this, I'd personally prefer inserting the parameters into a tuple and then calling a loosened wrapper of the desired function - or use some mapping (like a loosening map) to destructure the input and forward to the normal desired function.

So the example foo(24, bar(baz(data), 42)) would be..

baz(data)
    .pipe(|bar_0| bar(bar_0, 42))
    .pipe(|foo_1|, foo(24, foo_1))

..and would not require turboball (like what was suggested by CAD97).

[swfsql]

I've published a crate for anyone interested in exploring this syntax: https://crates.io/crates/sonic_spin

[scottmcm]

Hmm, if we had postfix match then

.pipe(|bar_0| bar(bar_0, 42))

would be

.match { bar_0 => bar(bar_0, 42) }