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use crate::utils::{
add_extra_generic_param, numbered_vars, AttrParams, DeriveType, MultiFieldData,
State,
};
use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::{DeriveInput, Result};
use crate::utils::HashMap;
/// Provides the hook to expand `#[derive(TryInto)]` into an implementation of `TryInto`
#[allow(clippy::cognitive_complexity)]
pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> {
let state = State::with_attr_params(
input,
trait_name,
"try_into".into(),
AttrParams {
enum_: vec!["ignore", "owned", "ref", "ref_mut"],
variant: vec!["ignore", "owned", "ref", "ref_mut"],
struct_: vec!["ignore", "owned", "ref", "ref_mut"],
field: vec!["ignore"],
},
)?;
assert!(
state.derive_type == DeriveType::Enum,
"Only enums can derive TryInto"
);
let mut variants_per_types = HashMap::default();
for variant_state in state.enabled_variant_data().variant_states {
let multi_field_data = variant_state.enabled_fields_data();
let MultiFieldData {
variant_info,
field_types,
..
} = multi_field_data.clone();
for ref_type in variant_info.ref_types() {
variants_per_types
.entry((ref_type, field_types.clone()))
.or_insert_with(Vec::new)
.push(multi_field_data.clone());
}
}
let mut tokens = TokenStream::new();
for ((ref_type, ref original_types), ref multi_field_datas) in variants_per_types {
let input_type = &input.ident;
let pattern_ref = ref_type.pattern_ref();
let lifetime = ref_type.lifetime();
let reference_with_lifetime = ref_type.reference_with_lifetime();
let mut matchers = vec![];
let vars = &numbered_vars(original_types.len(), "");
for multi_field_data in multi_field_datas {
let patterns: Vec<_> = vars
.iter()
.map(|var| quote! { #pattern_ref #var })
.collect();
matchers.push(
multi_field_data.matcher(&multi_field_data.field_indexes, &patterns),
);
}
let vars = if vars.len() == 1 {
quote! { #(#vars)* }
} else {
quote! { (#(#vars),*) }
};
let output_type = if original_types.len() == 1 {
quote! { #(#original_types)* }.to_string()
} else {
let types = original_types
.iter()
.map(|t| quote! { #t }.to_string())
.collect::<Vec<_>>();
format!("({})", types.join(", "))
};
let variant_names = multi_field_datas
.iter()
.map(|d| {
d.variant_name
.expect("Somehow there was no variant name")
.to_string()
})
.collect::<Vec<_>>()
.join(", ");
let generics_impl;
let (_, ty_generics, where_clause) = input.generics.split_for_impl();
let (impl_generics, _, _) = if ref_type.is_ref() {
generics_impl = add_extra_generic_param(&input.generics, lifetime.clone());
generics_impl.split_for_impl()
} else {
input.generics.split_for_impl()
};
let try_from = quote! {
#[automatically_derived]
impl #impl_generics
::core::convert::TryFrom<#reference_with_lifetime #input_type #ty_generics> for
(#(#reference_with_lifetime #original_types),*)
#where_clause
{
type Error = ::derive_more::TryIntoError<#reference_with_lifetime #input_type>;
#[inline]
fn try_from(value: #reference_with_lifetime #input_type #ty_generics) -> ::core::result::Result<Self, Self::Error> {
match value {
#(#matchers)|* => ::core::result::Result::Ok(#vars),
_ => ::core::result::Result::Err(::derive_more::TryIntoError::new(value, #variant_names, #output_type)),
}
}
}
};
try_from.to_tokens(&mut tokens)
}
Ok(tokens)
}