cgp-macro-lib 0.7.0

Context-generic programming core component macros implemented as a library.
Documentation 
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use proc_macro2::TokenStream;
use quote::quote;
use syn::{ItemEnum, ItemImpl, parse2};

use crate::derive_has_fields::from_fields_enum::derive_from_fields_for_enum;
use crate::derive_has_fields::sum::variants_to_sum_type;
use crate::derive_has_fields::to_fields_enum::derive_to_fields_for_enum;
use crate::derive_has_fields::to_fields_ref_enum::derive_to_fields_ref_for_enum;

pub fn derive_has_fields_impls_from_enum(item_enum: &ItemEnum) -> syn::Result<Vec<ItemImpl>> {
    let struct_name = &item_enum.ident;
    let (impl_generics, type_generics, where_clause) = item_enum.generics.split_for_impl();

    let sum_type = variants_to_sum_type(&item_enum.variants, &TokenStream::new())?;

    let life = quote! { '__a };
    let sum_type_ref = variants_to_sum_type(&item_enum.variants, &quote! { & #life })?;

    let has_fields_impl: ItemImpl = parse2(quote! {
        impl #impl_generics
            HasFields for #struct_name #type_generics
        #where_clause
        {
            type Fields = #sum_type ;
        }
    })?;

    let has_fields_ref_impl: ItemImpl = parse2(quote! {
        impl #impl_generics
            HasFieldsRef for #struct_name #type_generics
        #where_clause
        {
            type FieldsRef< #life > = #sum_type_ref
            where
                Self: #life
            ;
        }
    })?;

    let from_fields_impl = derive_from_fields_for_enum(item_enum)?;

    let to_fields_impl = derive_to_fields_for_enum(item_enum)?;

    let to_fields_ref_impl = derive_to_fields_ref_for_enum(item_enum)?;

    Ok(vec![
        has_fields_impl,
        has_fields_ref_impl,
        from_fields_impl,
        to_fields_impl,
        to_fields_ref_impl,
    ])
}