refactor: use macros to derive merge_right

[tusharmath]

Currently MergeRight implementation is implemented by hand and is quite verbose. Let's use macro to reduce verbosity.

Technical Requirements

• Create a new project tailcall-macros to implement this procedural macro.
• Move trait MergeRight into tailcall-macros.
• Drop existing hand written implementation of merge_right.

Additional Information
You could start with something like:

[lib]
proc-macro = true

[dependencies]
syn = { version = "1.0", features = ["derive", "full"] }
quote = "1.0"
proc-macro2 = "1.0"

Then, in lib.rs, you can start implementing your macro:

extern crate proc_macro;

use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, Data, DeriveInput, Fields};

#[proc_macro_derive(MergeRight)]
pub fn merge_right_derive(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);

    let name = input.ident;
    let gen = match input.data {
        // Implement for structs
        Data::Struct(data) => {
            let fields = if let Fields::Named(fields) = data.fields {
                fields.named
            } else {
                // Adjust this match arm to handle other kinds of struct fields (unnamed/tuple structs, unit structs)
                unimplemented!()
            };

            let merge_logic = fields.iter().map(|f| {
                let name = &f.ident;
                quote! {
                    #name: self.#name.merge_right(other.#name),
                }
            });

            quote! {
                impl MergeRight for #name {
                    fn merge_right(self, other: Self) -> Self {
                        Self {
                            #(#merge_logic)*
                        }
                    }
                }
            }
        },
        // Implement for enums
        Data::Enum(_) => quote! {
            impl MergeRight for #name {
                fn merge_right(self, other: Self) -> Self {
                    other
                }
            }
        },
        // Optionally handle or disallow unions
        Data::Union(_) => unimplemented!(),
    };

    gen.into()
}

[tusharmath]

/bounty 100$

[algora-pbc]

💎 $100 bounty created by tailcallhq
🙋 If you start working on this, comment /attempt #1700 along with your implementation plan
👉 To claim this bounty, submit a pull request that includes the text /claim #1700 somewhere in its body

🙏 Thank you for contributing to tailcallhq/tailcall!.
🧐 Checkout our guidelines before you get started.

Attempt	Started (GMT+0)	Solution
🔴 @ssddOnTop	Apr 11, 2024, 8:47:13 AM	WIP
🟢 @Shylock-Hg	Apr 13, 2024, 12:43:45 PM	#1723

[ssddOnTop]

/attempt

Algora profile	Completed bounties	Tech	Active attempts	Options
@ssddOnTop	36 tailcallhq bounties	Rust, Java, C & more		Cancel attempt

[algora-pbc]

@ssddOnTop: Reminder that in 1 days the bounty will become up for grabs, so please submit a pull request before then 🙏

[ologbonowiwi]

• Drop existing hand written implementation of merge_right.

From my findings, we'll need to keep the manual implementations for external types (HashSet<T>, Vec<T>, Option<T>, etc) and use the macro on our internal types. Makes sense @tusharmath?

[tusharmath]

Yes.

[algora-pbc]

The bounty is up for grabs! Everyone is welcome to /attempt #1700 🙌

[Shylock-Hg]

/attempt

Algora profile	Completed bounties	Tech	Active attempts	Options
@Shylock-Hg	3 tailcallhq bounties + 3 bounties from 3 projects	C++, C, Shell & more		Cancel attempt

[algora-pbc]

💡 @Shylock-Hg submitted a pull request that claims the bounty. You can visit your bounty board to reward.

[ologbonowiwi]

I have a draft locally but forgot to declare my attempt.

In the queue 🤚🏽

[algora-pbc]

@Shylock-Hg: You've been awarded a $100 bounty by tailcallhq! We'll notify you once it is processed.

[algora-pbc]

🎉🎈 @Shylock-Hg has been awarded $100! 🎈🎊

• Share on socials
• Give feedback