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use proc_macro2::{Spacing, Span, TokenStream, TokenTree};
use quote::{quote, ToTokens};
use syn::Ident;
/// Analog to Option<TokenStream>, except when put into the quote!
/// macro, `MaybeVoid::Void` will produce `()`
#[derive(Clone, Default)]
pub enum MaybeVoid {
Some(TokenStream),
#[default]
Void,
}
impl MaybeVoid {
pub fn replace(&mut self, stream: TokenStream) -> MaybeVoid {
std::mem::replace(self, MaybeVoid::Some(stream))
}
pub fn take(&mut self) -> MaybeVoid {
std::mem::replace(self, MaybeVoid::Void)
}
}
impl ToTokens for MaybeVoid {
fn to_tokens(&self, out: &mut TokenStream) {
match self {
MaybeVoid::Some(stream) => out.extend(stream.clone()),
MaybeVoid::Void => out.extend(quote!(())),
}
}
fn to_token_stream(&self) -> TokenStream {
match self {
MaybeVoid::Some(stream) => stream.clone(),
MaybeVoid::Void => quote!(()),
}
}
fn into_token_stream(self) -> TokenStream {
match self {
MaybeVoid::Some(stream) => stream,
MaybeVoid::Void => quote!(()),
}
}
}
pub fn is_punct(tt: &TokenTree, expect: char) -> bool {
matches!(tt, TokenTree::Punct(punct) if punct.as_char() == expect && punct.spacing() == Spacing::Alone)
}
/// If supplied `tt` is a punct matching a char, returns `None`, else returns `tt`
pub fn expect_punct(tt: Option<TokenTree>, expect: char) -> Option<TokenTree> {
tt.filter(|tt| !is_punct(tt, expect))
}
pub trait ToIdent {
fn to_ident(&self) -> Ident;
}
impl ToIdent for str {
fn to_ident(&self) -> Ident {
Ident::new(self, Span::call_site())
}
}
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