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use super::ToTokens;
use core::iter;
use proc_macro2::{TokenStream, TokenTree};
/// TokenStream extension trait with methods for appending tokens.
///
/// This trait is sealed and cannot be implemented outside of the `quote` crate.
pub trait TokenStreamExt: private::Sealed {
/// For use by `ToTokens` implementations.
///
/// Appends the token specified to this list of tokens.
fn append<U>(&mut self, token: U)
where
U: Into<TokenTree>;
/// For use by `ToTokens` implementations.
///
/// ```
/// # use quote::{quote, TokenStreamExt, ToTokens};
/// # use proc_macro2::TokenStream;
/// #
/// struct X;
///
/// impl ToTokens for X {
/// fn to_tokens(&self, tokens: &mut TokenStream) {
/// tokens.append_all(&[true, false]);
/// }
/// }
///
/// let tokens = quote!(#X);
/// assert_eq!(tokens.to_string(), "true false");
/// ```
fn append_all<I>(&mut self, iter: I)
where
I: IntoIterator,
I::Item: ToTokens;
/// For use by `ToTokens` implementations.
///
/// Appends all of the items in the iterator `I`, separated by the tokens
/// `U`.
fn append_separated<I, U>(&mut self, iter: I, op: U)
where
I: IntoIterator,
I::Item: ToTokens,
U: ToTokens;
/// For use by `ToTokens` implementations.
///
/// Appends all tokens in the iterator `I`, appending `U` after each
/// element, including after the last element of the iterator.
fn append_terminated<I, U>(&mut self, iter: I, term: U)
where
I: IntoIterator,
I::Item: ToTokens,
U: ToTokens;
}
impl TokenStreamExt for TokenStream {
fn append<U>(&mut self, token: U)
where
U: Into<TokenTree>,
{
self.extend(iter::once(token.into()));
}
fn append_all<I>(&mut self, iter: I)
where
I: IntoIterator,
I::Item: ToTokens,
{
for token in iter {
token.to_tokens(self);
}
}
fn append_separated<I, U>(&mut self, iter: I, op: U)
where
I: IntoIterator,
I::Item: ToTokens,
U: ToTokens,
{
for (i, token) in iter.into_iter().enumerate() {
if i > 0 {
op.to_tokens(self);
}
token.to_tokens(self);
}
}
fn append_terminated<I, U>(&mut self, iter: I, term: U)
where
I: IntoIterator,
I::Item: ToTokens,
U: ToTokens,
{
for token in iter {
token.to_tokens(self);
term.to_tokens(self);
}
}
}
mod private {
use proc_macro2::TokenStream;
pub trait Sealed {}
impl Sealed for TokenStream {}
}