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use proc_macro::TokenStream;
use quote::{format_ident, quote};
use syn::{
parse::{Parse, ParseStream},
parse_macro_input,
token::Comma,
Ident, LitInt, Result,
};
struct AllTuples {
macro_ident: Ident,
start: usize,
end: usize,
idents: Vec<Ident>,
}
impl Parse for AllTuples {
fn parse(input: ParseStream) -> Result<Self> {
let macro_ident = input.parse::<Ident>()?;
input.parse::<Comma>()?;
let start = input.parse::<LitInt>()?.base10_parse()?;
input.parse::<Comma>()?;
let end = input.parse::<LitInt>()?.base10_parse()?;
input.parse::<Comma>()?;
let mut idents = vec![input.parse::<Ident>()?];
while input.parse::<Comma>().is_ok() {
idents.push(input.parse::<Ident>()?);
}
Ok(AllTuples {
macro_ident,
start,
end,
idents,
})
}
}
#[proc_macro]
pub fn all_tuples(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as AllTuples);
let len = input.end - input.start;
let mut ident_tuples = Vec::with_capacity(len);
for i in input.start..=input.end {
let idents = input
.idents
.iter()
.map(|ident| format_ident!("{}{}", ident, i));
if input.idents.len() < 2 {
ident_tuples.push(quote! {
#(#idents)*
});
} else {
ident_tuples.push(quote! {
(#(#idents),*)
});
}
}
let macro_ident = &input.macro_ident;
let invocations = (input.start..=input.end).map(|i| {
let ident_tuples = &ident_tuples[..i];
quote! {
#macro_ident!(#(#ident_tuples),*);
}
});
TokenStream::from(quote! {
#(
#invocations
)*
})
}