1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113

use super::ToTokens;

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 {
    fn append<U>(&mut self, token: U)
    where
        U: Into<TokenTree>;

    fn append_all<T, I>(&mut self, iter: I)
    where
        T: ToTokens,
        I: IntoIterator<Item = T>;

    fn append_separated<T, I, U>(&mut self, iter: I, op: U)
    where
        T: ToTokens,
        I: IntoIterator<Item = T>,
        U: ToTokens;

    fn append_terminated<T, I, U>(&mut self, iter: I, term: U)
    where
        T: ToTokens,
        I: IntoIterator<Item = T>,
        U: ToTokens;
}

impl TokenStreamExt for TokenStream {
    /// 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>,
    {
        self.extend(Some(token.into()));
    }

    /// For use by `ToTokens` implementations.
    ///
    /// ```
    /// # #[macro_use] extern crate quote;
    /// # extern crate proc_macro2;
    /// # use quote::{TokenStreamExt, ToTokens};
    /// # use proc_macro2::TokenStream;
    /// # fn main() {
    /// 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<T, I>(&mut self, iter: I)
    where
        T: ToTokens,
        I: IntoIterator<Item = T>,
    {
        for token in iter {
            token.to_tokens(self);
        }
    }

    /// For use by `ToTokens` implementations.
    ///
    /// Appends all of the items in the iterator `I`, separated by the tokens
    /// `U`.
    fn append_separated<T, I, U>(&mut self, iter: I, op: U)
    where
        T: ToTokens,
        I: IntoIterator<Item = T>,
        U: ToTokens,
    {
        for (i, token) in iter.into_iter().enumerate() {
            if i > 0 {
                op.to_tokens(self);
            }
            token.to_tokens(self);
        }
    }

    /// 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<T, I, U>(&mut self, iter: I, term: U)
    where
        T: ToTokens,
        I: IntoIterator<Item = T>,
        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 {}
}