custom_punctuation macro
diff --git a/src/custom_token.rs b/src/custom_token.rs
new file mode 100644
index 0000000..22008e8
--- /dev/null
+++ b/src/custom_token.rs
@@ -0,0 +1,536 @@
+// Not public API.
+#[doc(hidden)]
+#[macro_export(local_inner_macros)]
+macro_rules! punct_len {
+ (+) => ( 1usize );
+ (+=) => ( 2usize );
+ (&) => ( 1usize );
+ (&&) => ( 2usize );
+ (&=) => ( 2usize );
+ (@) => ( 1usize );
+ (!) => ( 1usize );
+ (^) => ( 1usize );
+ (^=) => ( 2usize );
+ (:) => ( 1usize );
+ (::) => ( 2usize );
+ (,) => ( 1usize );
+ (/) => ( 1usize );
+ (/=) => ( 2usize );
+ (.) => ( 1usize );
+ (..) => ( 2usize );
+ (...) => ( 3usize );
+ (..=) => ( 3usize );
+ (=) => ( 1usize );
+ (==) => ( 2usize );
+ (>=) => ( 2usize );
+ (>) => ( 1usize );
+ (<=) => ( 2usize );
+ (<) => ( 1usize );
+ (*=) => ( 2usize );
+ (!=) => ( 2usize );
+ (|) => ( 1usize );
+ (|=) => ( 2usize );
+ (||) => ( 2usize );
+ (#) => ( 1usize );
+ (?) => ( 1usize );
+ (->) => ( 2usize );
+ (<-) => ( 2usize );
+ (%) => ( 1usize );
+ (%=) => ( 2usize );
+ (=>) => ( 2usize );
+ (;) => ( 1usize );
+ (<<) => ( 2usize );
+ (<<=) => ( 3usize );
+ (>>) => ( 2usize );
+ (>>=) => ( 3usize );
+ (*) => ( 1usize );
+ (-) => ( 1usize );
+ (-=) => ( 2usize );
+ (~) => ( 1usize );
+ ($tt:tt) => ( compile_error!("Punctuation `{}` is not supported", stringify!($tt)) );
+ ($head:tt $($tail:tt)+) => ( punct_len!($head) $(+ punct_len!($tail))+ );
+}
+
+// Not public API.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! stringify_punct {
+ ($($tt:tt)*) => ( concat!($(stringify!($tt)),*) );
+}
+
+// Not public API.
+// Without this, local_inner_macros breaks when looking for concat!
+#[doc(hidden)]
+#[macro_export]
+macro_rules! my_concat {
+ ($($tt:tt)*) => ( concat!($($tt)*) );
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+/// Define a type that supports parsing and printing a given identifier as if it
+/// were a keyword.
+///
+/// # Usage
+///
+/// As a convention, it is recommended that this macro be invoked within a
+/// module called `kw` or `keyword` and that the resulting parser be invoked
+/// with a `kw::` or `keyword::` prefix.
+///
+/// ```edition2018
+/// mod kw {
+/// syn::custom_keyword!(whatever);
+/// }
+/// ```
+///
+/// The generated syntax tree node supports the following operations just like
+/// any built-in keyword token.
+///
+/// - [Peeking] — `input.peek(kw::whatever)`
+///
+/// - [Parsing] — `input.parse::<kw::whatever>()?`
+///
+/// - [Printing] — `quote!( ... #whatever_token ... )`
+///
+/// - Construction from a [`Span`] — `let whatever_token = kw::whatever(sp)`
+///
+/// - Field access to its span — `let sp = whatever_token.span`
+///
+/// [Peeking]: parse/struct.ParseBuffer.html#method.peek
+/// [Parsing]: parse/struct.ParseBuffer.html#method.parse
+/// [Printing]: https://docs.rs/quote/0.6/quote/trait.ToTokens.html
+/// [`Span`]: https://docs.rs/proc-macro2/0.4/proc_macro2/struct.Span.html
+///
+/// # Example
+///
+/// This example parses input that looks like `bool = true` or `str = "value"`.
+/// The key must be either the identifier `bool` or the identifier `str`. If
+/// `bool`, the value may be either `true` or `false`. If `str`, the value may
+/// be any string literal.
+///
+/// The symbols `bool` and `str` are not reserved keywords in Rust so these are
+/// not considered keywords in the `syn::token` module. Like any other
+/// identifier that is not a keyword, these can be declared as custom keywords
+/// by crates that need to use them as such.
+///
+/// ```edition2018
+/// use syn::{LitBool, LitStr, Result, Token};
+/// use syn::parse::{Parse, ParseStream};
+///
+/// mod kw {
+/// syn::custom_keyword!(bool);
+/// syn::custom_keyword!(str);
+/// }
+///
+/// enum Argument {
+/// Bool {
+/// bool_token: kw::bool,
+/// eq_token: Token![=],
+/// value: LitBool,
+/// },
+/// Str {
+/// str_token: kw::str,
+/// eq_token: Token![=],
+/// value: LitStr,
+/// },
+/// }
+///
+/// impl Parse for Argument {
+/// fn parse(input: ParseStream) -> Result<Self> {
+/// let lookahead = input.lookahead1();
+/// if lookahead.peek(kw::bool) {
+/// Ok(Argument::Bool {
+/// bool_token: input.parse::<kw::bool>()?,
+/// eq_token: input.parse()?,
+/// value: input.parse()?,
+/// })
+/// } else if lookahead.peek(kw::str) {
+/// Ok(Argument::Str {
+/// str_token: input.parse::<kw::str>()?,
+/// eq_token: input.parse()?,
+/// value: input.parse()?,
+/// })
+/// } else {
+/// Err(lookahead.error())
+/// }
+/// }
+/// }
+/// ```
+#[macro_export(local_inner_macros)]
+macro_rules! custom_keyword {
+ ($ident:ident) => {
+ #[allow(non_camel_case_types)]
+ pub struct $ident {
+ pub span: $crate::export::Span,
+ }
+
+ #[doc(hidden)]
+ #[allow(non_snake_case)]
+ pub fn $ident<__S: $crate::export::IntoSpans<[$crate::export::Span; 1]>>(
+ span: __S,
+ ) -> $ident {
+ $ident {
+ span: $crate::export::IntoSpans::into_spans(span)[0],
+ }
+ }
+
+ impl $crate::export::Default for $ident {
+ fn default() -> Self {
+ $ident {
+ span: $crate::export::Span::call_site(),
+ }
+ }
+ }
+
+ impl_parse_for_custom_keyword!($ident);
+ impl_to_tokens_for_custom_keyword!($ident);
+ impl_clone_for_custom_keyword!($ident);
+ impl_extra_traits_for_custom_keyword!($ident);
+ };
+}
+
+// Not public API.
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_parse_for_custom_keyword {
+ ($ident:ident) => {
+ // For peek.
+ impl $crate::token::CustomKeyword for $ident {
+ fn ident() -> &'static $crate::export::str {
+ stringify!($ident)
+ }
+
+ fn display() -> &'static $crate::export::str {
+ concat!("`", stringify!($ident), "`")
+ }
+ }
+
+ impl $crate::parse::Parse for $ident {
+ fn parse(input: $crate::parse::ParseStream) -> $crate::parse::Result<$ident> {
+ input.step(|cursor| {
+ if let $crate::export::Some((ident, rest)) = cursor.ident() {
+ if ident == stringify!($ident) {
+ return $crate::export::Ok(($ident { span: ident.span() }, rest));
+ }
+ }
+ $crate::export::Err(cursor.error(concat!(
+ "expected `",
+ stringify!($ident),
+ "`"
+ )))
+ })
+ }
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "parsing"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_parse_for_custom_keyword {
+ ($ident:ident) => {};
+}
+
+// Not public API.
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_to_tokens_for_custom_keyword {
+ ($ident:ident) => {
+ impl $crate::export::ToTokens for $ident {
+ fn to_tokens(&self, tokens: &mut $crate::export::TokenStream2) {
+ let ident = $crate::Ident::new(stringify!($ident), self.span);
+ $crate::export::TokenStreamExt::append(tokens, ident);
+ }
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "printing"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_to_tokens_for_custom_keyword {
+ ($ident:ident) => {};
+}
+
+// Not public API.
+#[cfg(feature = "clone-impls")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_clone_for_custom_keyword {
+ ($ident:ident) => {
+ impl $crate::export::Copy for $ident {}
+
+ impl $crate::export::Clone for $ident {
+ fn clone(&self) -> Self {
+ *self
+ }
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "clone-impls"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_clone_for_custom_keyword {
+ ($ident:ident) => {};
+}
+
+// Not public API.
+#[cfg(feature = "extra-traits")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_extra_traits_for_custom_keyword {
+ ($ident:ident) => {
+ impl $crate::export::Debug for $ident {
+ fn fmt(&self, f: &mut $crate::export::Formatter) -> $crate::export::fmt::Result {
+ $crate::export::Formatter::write_str(f, stringify!($ident))
+ }
+ }
+
+ impl $crate::export::Eq for $ident {}
+
+ impl $crate::export::PartialEq for $ident {
+ fn eq(&self, _other: &Self) -> $crate::export::bool {
+ true
+ }
+ }
+
+ impl $crate::export::Hash for $ident {
+ fn hash<__H: $crate::export::Hasher>(&self, _state: &mut __H) {}
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "extra-traits"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_extra_traits_for_custom_keyword {
+ ($ident:ident) => {};
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+/// Define a type that supports parsing and printing a multi-character symbol
+/// as if it were a token.
+///
+/// # Usage
+///
+/// As a convention, it is recommended that this macro be invoked within a
+/// module called `punct` or `punctuation` and that the resulting parser be invoked
+/// with a `punct::` or `punctuation::` prefix.
+///
+/// ```edition2018
+/// mod punct {
+/// syn::custom_punctuation!(LeftRightArrow, <=>);
+/// }
+/// ```
+///
+/// The generated syntax tree node supports the following operations just like
+/// any built-in punctuation token.
+///
+/// - [Peeking] — `input.peek(punct::LeftRightArrow)`
+///
+/// - [Parsing] — `input.parse::<punct::LeftRightArrow>()?`
+///
+/// - [Printing] — `quote!( ... #left_right_arrow ... )`
+///
+/// - Construction from a [`Span`] — `let left_right_arrow = punct::LeftRightArrow(sp)`
+///
+/// - Construction from multiple [`Span`] — `let left_right_arrow = punct::LeftRightArrow([sp, sp, sp])`
+///
+/// - Field access to its spans — `let spans = left_right_arrow.spans`
+///
+/// [Peeking]: parse/struct.ParseBuffer.html#method.peek
+/// [Parsing]: parse/struct.ParseBuffer.html#method.parse
+/// [Printing]: https://docs.rs/quote/0.6/quote/trait.ToTokens.html
+/// [`Span`]: struct.Span.html
+///
+/// # Example
+///
+/// ```edition2018
+/// use syn::Expr;
+/// use syn::punctuated::Punctuated;
+/// use syn::parse::{Parse, ParseStream, Result};
+/// use syn::token::Paren;
+///
+/// mod punct {
+/// syn::custom_punctuation!(PathSeparator, </>);
+/// }
+///
+/// // (expr) </> (expr) </> (expr) ...
+/// struct PathSegments {
+/// segments: Punctuated<Expr, punct::PathSeparator>,
+/// }
+///
+/// impl Parse for PathSegments {
+/// fn parse(input: ParseStream) -> Result<Self> {
+/// let mut segments = Punctuated::new();
+///
+/// let la = input.lookahead1();
+/// if la.peek(Paren) {
+/// segments.push_value(input.parse()?);
+/// } else {
+/// return Err(la.error());
+/// }
+///
+/// while input.peek(punct::PathSeparator) {
+/// segments.push_punct(input.parse()?);
+/// segments.push_value(input.parse()?);
+/// }
+///
+/// Ok(PathSegments { segments })
+/// }
+/// }
+///
+/// let _: PathSegments = syn::parse_str(stringify!(("five") </> ("hundred"))).unwrap();
+/// ```
+///
+#[macro_export(local_inner_macros)]
+macro_rules! custom_punctuation {
+ ($ident:ident, $($tt:tt)*) => {
+ pub struct $ident {
+ pub spans: [$crate::export::Span; punct_len!($($tt)*)],
+ }
+
+ #[doc(hidden)]
+ #[allow(non_snake_case)]
+ pub fn $ident<__S: $crate::export::IntoSpans<[$crate::export::Span; punct_len!($($tt)*)]>>(
+ spans: __S,
+ ) -> $ident {
+ $ident {
+ spans: $crate::export::IntoSpans::into_spans(spans)
+ }
+ }
+
+ impl $crate::export::Default for $ident {
+ fn default() -> Self {
+ $ident($crate::export::Span::call_site())
+ }
+ }
+
+ impl_parsing_for_custom_punctuation!($ident, $($tt)*);
+ impl_printing_for_custom_punctuation!($ident, $($tt)*);
+ impl_clone_for_custom_punctuation!($ident, $($tt)*);
+ impl_extra_traits_for_custom_punctuation!($ident, $($tt)*);
+ };
+}
+
+// Not public API.
+#[cfg(feature = "parsing")]
+#[doc(hidden)]
+#[macro_export(local_inner_macros)]
+macro_rules! impl_parsing_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {
+ impl $crate::token::CustomToken for $ident {
+ fn peek(cursor: $crate::buffer::Cursor) -> bool {
+ $crate::token::parsing::peek_punct(cursor, stringify_punct!($($tt)*))
+ }
+
+ fn display() -> &'static $crate::export::str {
+ my_concat!("`", stringify_punct!($($tt)*), "`")
+ }
+ }
+
+ impl $crate::parse::Parse for $ident {
+ fn parse(input: $crate::parse::ParseStream) -> $crate::parse::Result<$ident> {
+ let spans: [$crate::export::Span; punct_len!($($tt)*)] =
+ $crate::token::parsing::punct(input, stringify_punct!($($tt)*))?;
+ Ok($ident(spans))
+ }
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "parsing"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_parsing_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {};
+}
+
+// Not public API.
+#[cfg(feature = "printing")]
+#[doc(hidden)]
+#[macro_export(local_inner_macros)]
+macro_rules! impl_printing_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {
+ impl $crate::export::ToTokens for $ident {
+ fn to_tokens(&self, tokens: &mut $crate::export::TokenStream2) {
+ $crate::token::printing::punct(stringify_punct!($($tt)*), &self.spans, tokens)
+ }
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "printing"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_printing_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {};
+}
+
+// Not public API.
+#[cfg(feature = "clone-impls")]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_clone_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {
+ impl $crate::export::Copy for $ident {}
+
+ impl $crate::export::Clone for $ident {
+ fn clone(&self) -> Self {
+ *self
+ }
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "clone-impls"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_clone_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {};
+}
+
+// Not public API.
+#[cfg(feature = "extra-traits")]
+#[doc(hidden)]
+#[macro_export(local_inner_macros)]
+macro_rules! impl_extra_traits_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {
+ impl $crate::export::Debug for $ident {
+ fn fmt(&self, f: &mut $crate::export::Formatter) -> $crate::export::fmt::Result {
+ $crate::export::Formatter::write_str(f, stringify_punct!($($tt)*))
+ }
+ }
+
+ impl $crate::export::Eq for $ident {}
+
+ impl $crate::export::PartialEq for $ident {
+ fn eq(&self, _other: &Self) -> $crate::export::bool {
+ true
+ }
+ }
+
+ impl $crate::export::Hash for $ident {
+ fn hash<__H: $crate::export::Hasher>(&self, _state: &mut __H) {}
+ }
+ };
+}
+
+// Not public API.
+#[cfg(not(feature = "extra-traits"))]
+#[doc(hidden)]
+#[macro_export]
+macro_rules! impl_extra_traits_for_custom_punctuation {
+ ($ident: ident, $($tt:tt)*) => {};
+}