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// FIXME(3492): remove once docs are ready
#![allow(missing_docs)]
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
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,
})
}
}
/// Helper macro to generate tuple pyramids. Useful to generate scaffolding to work around Rust
/// lacking variadics. Invoking `all_tuples!(impl_foo, start, end, P, Q, ..)`
/// invokes `impl_foo` providing ident tuples through arity `start..=end`.
/// # Examples
/// A single parameter.
/// ```
/// use std::marker::PhantomData;
/// use bevy_utils_proc_macros::all_tuples;
///
/// struct Foo<T> {
/// // ..
/// _phantom: PhantomData<T>
/// }
///
/// trait WrappedInFoo {
/// type Tup;
/// }
///
/// macro_rules! impl_wrapped_in_foo {
/// ($($T:ident),*) => {
/// impl<$($T),*> WrappedInFoo for ($($T,)*) {
/// type Tup = ($(Foo<$T>,)*);
/// }
/// };
/// }
///
/// all_tuples!(impl_wrapped_in_foo, 0, 15, T);
/// // impl_wrapped_in_foo!();
/// // impl_wrapped_in_foo!(P0);
/// // impl_wrapped_in_foo!(P0, P1);
/// // ..
/// // impl_wrapped_in_foo!(P0 .. P14);
/// ```
/// Multiple parameters.
/// ```
/// use bevy_utils_proc_macros::all_tuples;
///
/// trait Append {
/// type Out<Item>;
/// fn append<Item>(tup: Self, item: Item) -> Self::Out<Item>;
/// }
///
/// impl Append for () {
/// type Out<Item> = (Item,);
/// fn append<Item>(_: Self, item: Item) -> Self::Out<Item> {
/// (item,)
/// }
/// }
///
/// macro_rules! impl_append {
/// ($(($P:ident, $p:ident)),*) => {
/// impl<$($P),*> Append for ($($P,)*) {
/// type Out<Item> = ($($P),*, Item);
/// fn append<Item>(($($p,)*): Self, item: Item) -> Self::Out<Item> {
/// ($($p),*, item)
/// }
/// }
/// }
/// }
///
/// all_tuples!(impl_append, 1, 15, P, p);
/// // impl_append!((P0, p0));
/// // impl_append!((P0, p0), (P1, p1));
/// // impl_append!((P0, p0), (P1, p1), (P2, p2));
/// // ..
/// // impl_append!((P0, p0) .. (P14, p14));
/// ````
#[proc_macro]
pub fn all_tuples(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as AllTuples);
let len = 1 + input.end - input.start;
let mut ident_tuples = Vec::with_capacity(len);
for i in 0..=len {
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
)*
})
}
#[proc_macro]
pub fn all_tuples_with_size(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as AllTuples);
let len = 1 + input.end - input.start;
let mut ident_tuples = Vec::with_capacity(len);
for i in 0..=len {
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!(#i, #(#ident_tuples),*);
}
});
TokenStream::from(quote! {
#(
#invocations
)*
})
}