303 lines
8.9 KiB
Rust
303 lines
8.9 KiB
Rust
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/// Define a type that supports parsing and printing a multi-character symbol
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/// as if it were a punctuation token.
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///
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/// # Usage
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///
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/// ```
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/// syn::custom_punctuation!(LeftRightArrow, <=>);
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/// ```
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///
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/// The generated syntax tree node supports the following operations just like
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/// any built-in punctuation token.
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///
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/// - [Peeking] — `input.peek(LeftRightArrow)`
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///
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/// - [Parsing] — `input.parse::<LeftRightArrow>()?`
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///
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/// - [Printing] — `quote!( ... #lrarrow ... )`
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///
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/// - Construction from a [`Span`] — `let lrarrow = LeftRightArrow(sp)`
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///
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/// - Construction from multiple [`Span`] — `let lrarrow = LeftRightArrow([sp, sp, sp])`
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///
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/// - Field access to its spans — `let spans = lrarrow.spans`
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///
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/// [Peeking]: crate::parse::ParseBuffer::peek
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/// [Parsing]: crate::parse::ParseBuffer::parse
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/// [Printing]: quote::ToTokens
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/// [`Span`]: proc_macro2::Span
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///
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/// # Example
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///
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/// ```
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/// use proc_macro2::{TokenStream, TokenTree};
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/// use syn::parse::{Parse, ParseStream, Peek, Result};
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/// use syn::punctuated::Punctuated;
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/// use syn::Expr;
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///
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/// syn::custom_punctuation!(PathSeparator, </>);
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///
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/// // expr </> expr </> expr ...
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/// struct PathSegments {
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/// segments: Punctuated<Expr, PathSeparator>,
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/// }
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///
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/// impl Parse for PathSegments {
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/// fn parse(input: ParseStream) -> Result<Self> {
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/// let mut segments = Punctuated::new();
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///
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/// let first = parse_until(input, PathSeparator)?;
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/// segments.push_value(syn::parse2(first)?);
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///
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/// while input.peek(PathSeparator) {
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/// segments.push_punct(input.parse()?);
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///
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/// let next = parse_until(input, PathSeparator)?;
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/// segments.push_value(syn::parse2(next)?);
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/// }
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///
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/// Ok(PathSegments { segments })
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/// }
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/// }
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///
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/// fn parse_until<E: Peek>(input: ParseStream, end: E) -> Result<TokenStream> {
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/// let mut tokens = TokenStream::new();
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/// while !input.is_empty() && !input.peek(end) {
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/// let next: TokenTree = input.parse()?;
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/// tokens.extend(Some(next));
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/// }
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/// Ok(tokens)
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/// }
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///
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/// fn main() {
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/// let input = r#" a::b </> c::d::e "#;
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/// let _: PathSegments = syn::parse_str(input).unwrap();
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/// }
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/// ```
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#[macro_export]
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macro_rules! custom_punctuation {
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($ident:ident, $($tt:tt)+) => {
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pub struct $ident {
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pub spans: $crate::custom_punctuation_repr!($($tt)+),
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}
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#[doc(hidden)]
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#[allow(dead_code, non_snake_case)]
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pub fn $ident<__S: $crate::__private::IntoSpans<$crate::custom_punctuation_repr!($($tt)+)>>(
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spans: __S,
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) -> $ident {
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let _validate_len = 0 $(+ $crate::custom_punctuation_len!(strict, $tt))*;
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$ident {
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spans: $crate::__private::IntoSpans::into_spans(spans)
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}
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}
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const _: () = {
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impl $crate::__private::Default for $ident {
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fn default() -> Self {
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$ident($crate::__private::Span::call_site())
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}
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}
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$crate::impl_parse_for_custom_punctuation!($ident, $($tt)+);
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$crate::impl_to_tokens_for_custom_punctuation!($ident, $($tt)+);
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$crate::impl_clone_for_custom_punctuation!($ident, $($tt)+);
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$crate::impl_extra_traits_for_custom_punctuation!($ident, $($tt)+);
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};
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};
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}
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// Not public API.
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#[cfg(feature = "parsing")]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_parse_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {
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impl $crate::__private::CustomToken for $ident {
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fn peek(cursor: $crate::buffer::Cursor) -> $crate::__private::bool {
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$crate::__private::peek_punct(cursor, $crate::stringify_punct!($($tt)+))
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}
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fn display() -> &'static $crate::__private::str {
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$crate::__private::concat!("`", $crate::stringify_punct!($($tt)+), "`")
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}
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}
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impl $crate::parse::Parse for $ident {
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fn parse(input: $crate::parse::ParseStream) -> $crate::parse::Result<$ident> {
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let spans: $crate::custom_punctuation_repr!($($tt)+) =
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$crate::__private::parse_punct(input, $crate::stringify_punct!($($tt)+))?;
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Ok($ident(spans))
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}
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}
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};
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}
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// Not public API.
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#[cfg(not(feature = "parsing"))]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_parse_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {};
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}
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// Not public API.
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#[cfg(feature = "printing")]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_to_tokens_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {
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impl $crate::__private::ToTokens for $ident {
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fn to_tokens(&self, tokens: &mut $crate::__private::TokenStream2) {
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$crate::__private::print_punct($crate::stringify_punct!($($tt)+), &self.spans, tokens)
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}
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}
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};
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}
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// Not public API.
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#[cfg(not(feature = "printing"))]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_to_tokens_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {};
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}
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// Not public API.
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#[cfg(feature = "clone-impls")]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_clone_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {
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impl $crate::__private::Copy for $ident {}
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#[allow(clippy::expl_impl_clone_on_copy)]
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impl $crate::__private::Clone for $ident {
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fn clone(&self) -> Self {
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*self
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}
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}
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};
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}
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// Not public API.
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#[cfg(not(feature = "clone-impls"))]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_clone_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {};
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}
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// Not public API.
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#[cfg(feature = "extra-traits")]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_extra_traits_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {
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impl $crate::__private::Debug for $ident {
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fn fmt(&self, f: &mut $crate::__private::Formatter) -> $crate::__private::FmtResult {
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$crate::__private::Formatter::write_str(f, $crate::__private::stringify!($ident))
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}
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}
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impl $crate::__private::Eq for $ident {}
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impl $crate::__private::PartialEq for $ident {
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fn eq(&self, _other: &Self) -> $crate::__private::bool {
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true
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}
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}
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impl $crate::__private::Hash for $ident {
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fn hash<__H: $crate::__private::Hasher>(&self, _state: &mut __H) {}
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}
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};
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}
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// Not public API.
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#[cfg(not(feature = "extra-traits"))]
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#[doc(hidden)]
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#[macro_export]
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macro_rules! impl_extra_traits_for_custom_punctuation {
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($ident:ident, $($tt:tt)+) => {};
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}
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// Not public API.
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#[doc(hidden)]
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#[macro_export]
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macro_rules! custom_punctuation_repr {
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($($tt:tt)+) => {
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[$crate::__private::Span; 0 $(+ $crate::custom_punctuation_len!(lenient, $tt))+]
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};
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}
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// Not public API.
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#[doc(hidden)]
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#[macro_export]
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#[rustfmt::skip]
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macro_rules! custom_punctuation_len {
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($mode:ident, +) => { 1 };
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($mode:ident, +=) => { 2 };
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($mode:ident, &) => { 1 };
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($mode:ident, &&) => { 2 };
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($mode:ident, &=) => { 2 };
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($mode:ident, @) => { 1 };
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($mode:ident, !) => { 1 };
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($mode:ident, ^) => { 1 };
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($mode:ident, ^=) => { 2 };
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($mode:ident, :) => { 1 };
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($mode:ident, ::) => { 2 };
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($mode:ident, ,) => { 1 };
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($mode:ident, /) => { 1 };
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($mode:ident, /=) => { 2 };
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($mode:ident, .) => { 1 };
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($mode:ident, ..) => { 2 };
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($mode:ident, ...) => { 3 };
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($mode:ident, ..=) => { 3 };
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($mode:ident, =) => { 1 };
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($mode:ident, ==) => { 2 };
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($mode:ident, >=) => { 2 };
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($mode:ident, >) => { 1 };
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($mode:ident, <=) => { 2 };
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($mode:ident, <) => { 1 };
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($mode:ident, *=) => { 2 };
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($mode:ident, !=) => { 2 };
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($mode:ident, |) => { 1 };
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($mode:ident, |=) => { 2 };
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($mode:ident, ||) => { 2 };
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($mode:ident, #) => { 1 };
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($mode:ident, ?) => { 1 };
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($mode:ident, ->) => { 2 };
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($mode:ident, <-) => { 2 };
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($mode:ident, %) => { 1 };
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($mode:ident, %=) => { 2 };
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($mode:ident, =>) => { 2 };
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($mode:ident, ;) => { 1 };
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($mode:ident, <<) => { 2 };
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($mode:ident, <<=) => { 3 };
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($mode:ident, >>) => { 2 };
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($mode:ident, >>=) => { 3 };
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($mode:ident, *) => { 1 };
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($mode:ident, -) => { 1 };
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($mode:ident, -=) => { 2 };
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($mode:ident, ~) => { 1 };
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(lenient, $tt:tt) => { 0 };
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(strict, $tt:tt) => {{ $crate::custom_punctuation_unexpected!($tt); 0 }};
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}
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// Not public API.
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#[doc(hidden)]
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#[macro_export]
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macro_rules! custom_punctuation_unexpected {
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() => {};
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}
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// Not public API.
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#[doc(hidden)]
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#[macro_export]
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macro_rules! stringify_punct {
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($($tt:tt)+) => {
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$crate::__private::concat!($($crate::__private::stringify!($tt)),+)
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};
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}
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