attrimpl 0.1.1

The crate provides attributes to automatically implement common traits and reduce boilerplate code.
Documentation 
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use quote::quote;

use crate::{directive::Directive, syn_field::SynField};

pub struct SynItemStruct {
    item_struct: syn::ItemStruct,
    fields: Vec<SynField>,
}

impl SynItemStruct {
    pub fn parse(mut item_struct: syn::ItemStruct) -> syn::Result<Self> {
        Ok(SynItemStruct {
            fields: SynField::parse(&mut item_struct.fields)?,
            item_struct,
        })
    }
}

impl quote::ToTokens for SynItemStruct {
    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
        let item_struct = &self.item_struct;

        tokens.extend(quote! {
            #item_struct
        });

        for field in &self.fields {
            for directive in field.directives.iter() {
                directive_to_tokens(item_struct, &field.field, field.index, directive, tokens);
            }
        }
    }
}

fn directive_to_tokens(
    item_struct: &syn::ItemStruct,
    field: &syn::Field,
    field_index: usize,
    directive: &Directive,
    tokens: &mut proc_macro2::TokenStream,
) {
    if *directive == "from" {
        from_to_tokens(item_struct, field, field_index, tokens);
    } else if *directive == "into" {
        into_to_tokens(item_struct, field, field_index, tokens);
    } else if *directive == "convert" {
        from_to_tokens(item_struct, field, field_index, tokens);
        into_to_tokens(item_struct, field, field_index, tokens);
    } else {
        panic!(
            "unsupported directive for struct, directive = {}",
            directive
        );
    }
}

fn from_to_tokens(
    item_struct: &syn::ItemStruct,
    field: &syn::Field,
    _field_index: usize,
    tokens: &mut proc_macro2::TokenStream,
) {
    let ident = &item_struct.ident;
    let generic_params = &item_struct.generics.params;
    let where_clause = item_struct.generics.where_clause.as_ref();
    let field_type = &field.ty;

    tokens.extend(if let Some(field_ident) = &field.ident {
        // it is a struct with named fields
        quote! {
            impl<#generic_params> ::core::convert::From<#field_type> for #ident
            #where_clause {
                fn from(value: #field_type) -> Self {
                    Self {
                        #field_ident: value,
                    }
                }
            }
        }
    } else {
        // it is a tuple struct
        quote! {
            impl<#generic_params> ::core::convert::From<#field_type> for #ident
            #where_clause {
                fn from(value: #field_type) -> Self {
                    Self(value)
                }
            }
        }
    });

    tokens.extend(quote! {
        impl<#generic_params> ::core::convert::From<#field_type> for ::std::boxed::Box<#ident>
        #where_clause {
            fn from(value: #field_type) -> Self {
                ::std::boxed::Box::new(#ident::from(value))
            }
        }
    });
}

fn into_to_tokens(
    item_struct: &syn::ItemStruct,
    field: &syn::Field,
    field_index: usize,
    tokens: &mut proc_macro2::TokenStream,
) {
    let ident = &item_struct.ident;
    let generic_params = &item_struct.generics.params;
    let where_clause = item_struct.generics.where_clause.as_ref();
    let field_type = &field.ty;

    let field_reference_name = field
        .ident
        .as_ref()
        .map(|ident| quote! { #ident })
        .clone()
        .unwrap_or_else(|| {
            let field_index = syn::Index::from(field_index);
            quote! { #field_index }
        });

    tokens.extend(quote! {
        impl<#generic_params> ::core::convert::Into<#field_type> for #ident
        #where_clause {
            fn into(self) -> #field_type {
                self.#field_reference_name
            }
        }
    });
}