diff --git a/src/parse.rs b/src/parse.rs index 50fe110b58..13f488d143 100644 --- a/src/parse.rs +++ b/src/parse.rs @@ -1096,6 +1096,58 @@ impl<'a> ParseBuffer<'a> { /// /// Cursors are immutable so no operations you perform against the cursor /// will affect the state of this parse stream. + /// + /// # Example + /// + /// ``` + /// use proc_macro2::TokenStream; + /// use syn::buffer::Cursor; + /// use syn::parse::{ParseStream, Result}; + /// + /// // Run a parser that returns T, but get its output as TokenStream instead of T. + /// // This works without T needing to implement ToTokens. + /// fn recognize_token_stream( + /// recognizer: fn(ParseStream) -> Result, + /// ) -> impl Fn(ParseStream) -> Result { + /// move |input| { + /// let begin = input.cursor(); + /// recognizer(input)?; + /// let end = input.cursor(); + /// Ok(tokens_between(begin, end)) + /// } + /// } + /// + /// // Collect tokens between two cursors as a TokenStream. + /// fn tokens_between(begin: Cursor, end: Cursor) -> TokenStream { + /// assert!(begin <= end); + /// + /// let mut cursor = begin; + /// let mut tokens = TokenStream::new(); + /// while cursor < end { + /// let (token, next) = cursor.token_tree().unwrap(); + /// tokens.extend(std::iter::once(token)); + /// cursor = next; + /// } + /// tokens + /// } + /// + /// fn main() { + /// use quote::quote; + /// use syn::parse::{Parse, Parser}; + /// use syn::Token; + /// + /// // Parse syn::Type as a TokenStream, surrounded by angle brackets. + /// fn example(input: ParseStream) -> Result { + /// let _langle: Token![<] = input.parse()?; + /// let ty = recognize_token_stream(syn::Type::parse)(input)?; + /// let _rangle: Token![>] = input.parse()?; + /// Ok(ty) + /// } + /// + /// let tokens = quote! { u8> }; + /// println!("{}", example.parse2(tokens).unwrap()); + /// } + /// ``` pub fn cursor(&self) -> Cursor<'a> { self.cell.get() }