rust_writer_proc 1.0.2

// SPDX-License-Identifier: GPL-3.0

#[cfg(test)]
mod tests;

use proc_macro2::Span;
use syn::{
	parse_quote, punctuated::Punctuated, GenericArgument, GenericParam, Ident, ItemStruct, Path,
	PathArguments, Token,
};

pub(crate) fn remove_impl_from_attr(struct_: &mut ItemStruct) {
	struct_.attrs = struct_
		.attrs
		.clone()
		.into_iter()
		.filter(|attr| !attr.path().is_ident("impl_from"))
		.collect()
}

pub(crate) struct ResolvedImplementors {
	pub(crate) implementors_idents: Vec<Ident>,
	pub(crate) implementors_types_paths: Vec<Path>,
	pub(crate) implementors_introduced_generics: Vec<GenericParam>,
}

const UNREACHABLE_MESSAGE: &str =
	"syn::PathArguments cannot be parsed with `const ident:type` in the arguments; qed;";

pub(crate) fn resolve_implementors_for_struct<'a, T>(
	iter: T,
	struct_: &ItemStruct,
) -> ResolvedImplementors
where
	T: Iterator<Item = &'a Path>,
{
	let mut implementors_idents: Vec<Ident> = Vec::new();
	let mut implementors_types_paths = Vec::new();
	let mut implementors_introduced_generics = Vec::new();

	for implementor in iter {
		let mut implementor = implementor.clone();

		let last_implementor_segment = implementor
			.segments
			.last_mut()
			.expect("At this point, implementors are valid paths; qed;");

		let implementor_ident_value = last_implementor_segment.ident.to_string().to_lowercase();

		let ident_count = implementors_idents
			.iter()
			.filter(|&ident| *ident == implementor_ident_value)
			.count();

		let ident = if ident_count > 0 {
			Ident::new(
				&(implementor_ident_value + "_" + &ident_count.to_string()),
				Span::call_site(),
			)
		} else {
			Ident::new(&implementor_ident_value, Span::call_site())
		};

		if let PathArguments::AngleBracketed(ref mut generics) = last_implementor_segment.arguments
		{
			let mut last_implementor_generics_idents: Punctuated<GenericArgument, Token![,]> =
				Punctuated::new();

			generics.args.iter().for_each(|argument| {
				let generic_param: GenericParam = parse_quote!(#argument);
				match generic_param {
					GenericParam::Lifetime(_) => {
						last_implementor_generics_idents.insert(0, parse_quote!(#generic_param));
						if !(struct_
							.generics
							.params
							.iter()
							.any(|generic| generic == &generic_param) ||
							implementors_introduced_generics.contains(&generic_param))
						{
							implementors_introduced_generics.push(generic_param);
						}
					},
					GenericParam::Type(ref generic) => {
						let generic_ident = &generic.ident;
						last_implementor_generics_idents.push(parse_quote!(#generic_ident));
						if !(struct_.generics.params.iter().any(|generic| {
							matches!(generic, GenericParam::Type(inner) if &inner.ident == generic_ident) ||
                // Support for generics const combines including their ident as a generic and the
                // actual const declaration inside the struct def.
								matches!(generic, GenericParam::Const(inner) if &inner.ident == generic_ident)
						}) || implementors_introduced_generics.contains(&generic_param))
						{
							implementors_introduced_generics.push(generic_param);
						}
					},
					GenericParam::Const(_) => unreachable!("{}", UNREACHABLE_MESSAGE),
				}
			});

			generics.args = last_implementor_generics_idents;
		}

		implementors_idents.push(ident);
		implementors_types_paths.push(implementor);
	}

	ResolvedImplementors {
		implementors_idents,
		implementors_types_paths,
		implementors_introduced_generics,
	}
}

pub(crate) fn add_new_implementors_generics(struct_: &mut ItemStruct, generics: Vec<GenericParam>) {
	for generic in generics {
		match generic {
			GenericParam::Lifetime(_) => struct_.generics.params.insert(0, generic),
			_ => struct_.generics.params.push(generic),
		}
	}
}