lyonsyonii / akin Goto Github PK

Hi @LyonSyonII,

First of all, thanks for creating akin. I like the approach quit a lot.

I'm wondering if global substitutions, and generating items only once can be added to akin.

An example describes the use case best:

Imagine we would like to create an extension trait for serde_json::Value that adds methods like into_xy methods that return owned values.

I'd create and implement a trait like this:

trait ValueExt {
    fn into_null(self) -> Result<(), Self>;
    fn into_bool(self) -> Result<bool, Self>;
    fn into_array(self) -> Result<Vec<Value>, Self>;

    // etc...
}

impl ValueExt for Value {
    fn into_null(self) -> Result<(), Self> { todo!()}
    fn into_bool(self) -> Result<bool, Self> { todo!()}
    fn into_array(self) -> Result<Vec<Value>, Self>  { todo!()}
    
    // etc...
}

Instead of writing all of this by hand, I'd like to use akin to generate the trait and the trait implementation:

akin::akin! {
    let &ident = [ null, bool, array, /* ... */ ];
    let &Type = [
        { () },
        { bool },
        { Vec<Value> },
        // ...
    ];

    trait JsonValueExt {
        fn into_~*ident(self) -> Result<*Type, Self>;
    }

    impl ValueExt for serde_json::Value {
        fn into_~*ident(self) -> Result<*Type, Self> { todo!() }
    }
}

But of course this doesn't work (JsonValueExt is defined several times).

I'm wondering if this use case somehow can be supported.

For example via something like this:

akin::akin! {
    // ...
    
    #[akin(context)]
    trait JsonValueExt {
        // A new `akin` context
        fn into_~*ident(self) -> Result<*Type, Self>;
    }

    // ...
}

#[akin(context)] would tell akin to generate the decorated item only once, and substitute within the item (similar to how $($ident)+ works for macro_rules macros). Something like akin_context! { /* new context */ } probably also would be useful, for cases where attributes can't be used.

My first idea for a name of the new attribute was inner, but I think that wouldn't be ideal, because it should be possible to substitute things within the trait definition itself (e.g. for generic traits). Maybe there is a better name than context, however.

Similarly, the duplicate crate has a nice feature to define global substitutions, which often come in handy.

I'm wondering if this can be supported via something like:

akin::akin! {
    // ...
    
    const &foo = { println!("Hello, world!") };

    *foo
    // ...
}

...which would expand to just one println!("Hello, world!").

Using const here would be perfect semantically, I believe.

These features would make akin useful in even more cases.

Currently, I have created an additional macro_rules macro to generate the trait definition (duplicating the &Type and &ident definitions), which works but is not really ideal.

Would it be possible to add these features?

Currently, I haven't learned how to use procedural macros, so I currently can't add these features myself. But if you don't want to add this yourself, but would accept a PR, I could do this when I learn procedural macros at some point (however, that would most likely be at least several months into the future, if not more).

Thanks again for creating akin!

Hi @LyonSyonII

As of now I don't think there is a good way to express some repetitions:

impl<T> Foo for T where T: Baz<A> + Baz<B> + ... {}

//We could do
akin! {
    let &Type = [B, ...];
  
    let &bound = { + Baz<*Type> };
  
    impl<T> Foo for T where T: Baz<A> *bound {}
}

//Or
akin! {
    let &Type = [A, B, ...];
  
    let &separator = [NONE, +, ...]

    let &bound = { *separator Baz<*Type> };
  
    impl<T> Foo for T where T: *bound {}
}

It would be nice to be able to specify a separator. Maybe something along those lines:

akin! {
    let &Type = [A, B, ...];
  
    let &bound = { Baz<*Type> };
  
    impl<T> Foo for T where T: *{+}bound {}
}

Hi @LyonSyonII,

I just discovered a bug:

akin! {
  let &foo = [abc];
  let &foobar = [def];
  
  *foo
  *foobar
}

The foo of *foobar gets replaced with abc.

for example, I need to use akin to make the following code simpler, but some how can't get it to work. If akin can accept a parameter, it will be great!

impltableinfo!(2, T1, Q1, T2, Q2);
impltableinfo!(3, T1, Q1, T2, Q2, T3, Q3);
impltableinfo!(4, T1, Q1, T2, Q2, T3, Q3, T4, Q4);
impltableinfo!(5, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5);
impltableinfo!(6, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6);
impltableinfo!(7, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7);
impltableinfo!(8, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8);
impltableinfo!(9, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9);
impltableinfo!(10, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA);
impltableinfo!(11, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB);
impltableinfo!(12, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC);
impltableinfo!(13, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD);
impltableinfo!(14, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE);
impltableinfo!(15, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF);
impltableinfo!(16, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG);
impltableinfo!(17, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH);
impltableinfo!(18, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI);
impltableinfo!(19, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ);
impltableinfo!(20, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL);
impltableinfo!(21, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM);
impltableinfo!(22, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN);
impltableinfo!(23, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO);
impltableinfo!(24, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP);
impltableinfo!(25, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ);
impltableinfo!(26, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ, TR, QR);
impltableinfo!(27, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ, TR, QR, TS, QS);
impltableinfo!(28, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ, TR, QR, TS, QS, TT, QT);
impltableinfo!(29, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ, TR, QR, TS, QS, TT, QT, TU, QU);
impltableinfo!(30, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ, TR, QR, TS, QS, TT, QT, TU, QU, TV, QV);
impltableinfo!(31, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ, TR, QR, TS, QS, TT, QT, TU, QU, TV, QV, TW, QW);
impltableinfo!(32, T1, Q1, T2, Q2, T3, Q3, T4, Q4, T5, Q5, T6, Q6, T7, Q7, T8, Q8, T9, Q9, TA, QA, TB, QB, TC, QC, TD, QD, TE, QE, TF, QF, TG, QG, TH, QH, TI, QI, TJ, QJ, TL, QL, TM, QM, TN, QN, TO, QO, TP, QP, TQ, QQ, TR, QR, TS, QS, TT, QT, TU, QU, TV, QV, TW, QW, TX, QX);