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use crate::key_value::KeyValueSeq;
use crate::value::{Value, ValueExpr, ValueIterExpr, Verbatim};
use crate::ParseRaw;
use proc_macro2::{Ident, Span, TokenStream};
use quote::{quote, ToTokens};
use syn::parse;
pub struct MapIterInput<V = Verbatim>(KeyValueSeq<V>);
impl<V> ParseRaw for MapIterInput<V>
where
ValueExpr<V>: ToTokens,
ValueIterExpr<V>: ToTokens,
{
fn parse_raw(input: TokenStream) -> parse::Result<Self> {
Ok(MapIterInput(KeyValueSeq::parse_raw(input)?))
}
}
impl<V> MapIterInput<V>
where
ValueExpr<V>: ToTokens,
ValueIterExpr<V>: ToTokens,
{
pub fn into_output(self) -> TokenStream {
let target = Ident::new("it", Span::call_site());
let updates = self.0.key_values().map(|kv| {
let key = kv.key();
let value = kv.value();
match key {
Value::One(expr) => quote! {
let #target = #target.chain(::std::iter::once((#expr, #value)));
},
Value::Many(expr) => quote! {
let #target = #target.chain(
::std::iter::IntoIterator::into_iter(#expr)
.zip(::std::iter::repeat(#value))
);
},
}
});
quote! {{
let #target = ::std::iter::empty();
#(#updates)*
#target
}}
}
}