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use syn::parse::{Parse, ParseStream};
use syn::{GenericArgument, ItemType, Path, Type, TypeParamBound, TypeTuple};
pub struct FactoryTypeAlias
{
pub type_alias: ItemType,
pub factory_interface: Path,
pub arg_types: TypeTuple,
pub return_type: Type,
}
impl Parse for FactoryTypeAlias
{
#[allow(clippy::match_wildcard_for_single_variants)]
fn parse(input: ParseStream) -> syn::Result<Self>
{
let type_alias = match input.parse::<ItemType>() {
Ok(type_alias) => Ok(type_alias),
Err(_) => Err(input.error("Expected a type alias")),
}?;
let aliased_trait = match &type_alias.ty.as_ref() {
Type::TraitObject(alias_type) => Ok(alias_type),
&_ => Err(input.error("Expected the aliased type to be a trait")),
}?;
if aliased_trait.bounds.len() != 1 {
return Err(input.error("Expected the aliased trait to have a single bound."));
}
let bound_path = &match aliased_trait.bounds.first().unwrap() {
TypeParamBound::Trait(trait_bound) => Ok(trait_bound),
&_ => {
Err(input.error("Expected the bound of the aliased trait to be a trait"))
}
}?
.path;
if bound_path.segments.is_empty()
|| bound_path.segments.last().unwrap().ident != "IFactory"
{
return Err(input
.error("Expected the bound of the aliased trait to be 'dyn IFactory'"));
}
let angle_bracketed_args = match &bound_path.segments.last().unwrap().arguments {
syn::PathArguments::AngleBracketed(angle_bracketed_args) => {
Ok(angle_bracketed_args)
}
&_ => {
Err(input.error("Expected angle bracketed arguments for 'dyn IFactory'"))
}
}?;
let arg_types = match &angle_bracketed_args.args[0] {
GenericArgument::Type(arg_types_type) => match arg_types_type {
Type::Tuple(arg_types) => Ok(arg_types),
&_ => Err(input.error(concat!(
"Expected the first angle bracketed argument ",
"of 'dyn IFactory' to be a type tuple"
))),
},
&_ => Err(input.error(concat!(
"Expected the first angle bracketed argument ",
"of 'dyn IFactory' to be a type"
))),
}?;
let return_type = match &angle_bracketed_args.args[1] {
GenericArgument::Type(arg_type) => Ok(arg_type),
&_ => Err(input.error(concat!(
"Expected the second angle bracketed argument ",
"of 'dyn IFactory' to be a type"
))),
}?;
Ok(Self {
type_alias: type_alias.clone(),
factory_interface: bound_path.clone(),
arg_types: arg_types.clone(),
return_type: return_type.clone(),
})
}
}
|
