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use super::TokenStreamExt;
use alloc::borrow::Cow;
use alloc::rc::Rc;
use core::iter;
use proc_macro2::{Group, Ident, Literal, Punct, Span, TokenStream, TokenTree};
/// Types that can be interpolated inside a `quote!` invocation.
///
/// [`quote!`]: macro.quote.html
pub trait ToTokens {
/// Write `self` to the given `TokenStream`.
///
/// The token append methods provided by the [`TokenStreamExt`] extension
/// trait may be useful for implementing `ToTokens`.
///
/// [`TokenStreamExt`]: trait.TokenStreamExt.html
///
/// # Example
///
/// Example implementation for a struct representing Rust paths like
/// `std::cmp::PartialEq`:
///
/// ```
/// use proc_macro2::{TokenTree, Spacing, Span, Punct, TokenStream};
/// use quote::{TokenStreamExt, ToTokens};
///
/// pub struct Path {
/// pub global: bool,
/// pub segments: Vec<PathSegment>,
/// }
///
/// impl ToTokens for Path {
/// fn to_tokens(&self, tokens: &mut TokenStream) {
/// for (i, segment) in self.segments.iter().enumerate() {
/// if i > 0 || self.global {
/// // Double colon `::`
/// tokens.append(Punct::new(':', Spacing::Joint));
/// tokens.append(Punct::new(':', Spacing::Alone));
/// }
/// segment.to_tokens(tokens);
/// }
/// }
/// }
/// #
/// # pub struct PathSegment;
/// #
/// # impl ToTokens for PathSegment {
/// # fn to_tokens(&self, tokens: &mut TokenStream) {
/// # unimplemented!()
/// # }
/// # }
/// ```
fn to_tokens(&self, tokens: &mut TokenStream);
/// Convert `self` directly into a `TokenStream` object.
///
/// This method is implicitly implemented using `to_tokens`, and acts as a
/// convenience method for consumers of the `ToTokens` trait.
fn to_token_stream(&self) -> TokenStream {
let mut tokens = TokenStream::new();
self.to_tokens(&mut tokens);
tokens
}
/// Convert `self` directly into a `TokenStream` object.
///
/// This method is implicitly implemented using `to_tokens`, and acts as a
/// convenience method for consumers of the `ToTokens` trait.
fn into_token_stream(self) -> TokenStream
where
Self: Sized,
{
self.to_token_stream()
}
}
impl<'a, T: ?Sized + ToTokens> ToTokens for &'a T {
fn to_tokens(&self, tokens: &mut TokenStream) {
(**self).to_tokens(tokens);
}
}
impl<'a, T: ?Sized + ToTokens> ToTokens for &'a mut T {
fn to_tokens(&self, tokens: &mut TokenStream) {
(**self).to_tokens(tokens);
}
}
impl<'a, T: ?Sized + ToOwned + ToTokens> ToTokens for Cow<'a, T> {
fn to_tokens(&self, tokens: &mut TokenStream) {
(**self).to_tokens(tokens);
}
}
impl<T: ?Sized + ToTokens> ToTokens for Box<T> {
fn to_tokens(&self, tokens: &mut TokenStream) {
(**self).to_tokens(tokens);
}
}
impl<T: ?Sized + ToTokens> ToTokens for Rc<T> {
fn to_tokens(&self, tokens: &mut TokenStream) {
(**self).to_tokens(tokens);
}
}
impl<T: ToTokens> ToTokens for Option<T> {
fn to_tokens(&self, tokens: &mut TokenStream) {
if let Some(ref t) = *self {
t.to_tokens(tokens);
}
}
}
impl ToTokens for str {
fn to_tokens(&self, tokens: &mut TokenStream) {
tokens.append(Literal::string(self));
}
}
impl ToTokens for String {
fn to_tokens(&self, tokens: &mut TokenStream) {
self.as_str().to_tokens(tokens);
}
}
macro_rules! primitive {
($($t:ident => $name:ident)*) => {
$(
impl ToTokens for $t {
fn to_tokens(&self, tokens: &mut TokenStream) {
tokens.append(Literal::$name(*self));
}
}
)*
};
}
primitive! {
i8 => i8_suffixed
i16 => i16_suffixed
i32 => i32_suffixed
i64 => i64_suffixed
i128 => i128_suffixed
isize => isize_suffixed
u8 => u8_suffixed
u16 => u16_suffixed
u32 => u32_suffixed
u64 => u64_suffixed
u128 => u128_suffixed
usize => usize_suffixed
f32 => f32_suffixed
f64 => f64_suffixed
}
impl ToTokens for char {
fn to_tokens(&self, tokens: &mut TokenStream) {
tokens.append(Literal::character(*self));
}
}
impl ToTokens for bool {
fn to_tokens(&self, tokens: &mut TokenStream) {
let word = if *self { "true" } else { "false" };
tokens.append(Ident::new(word, Span::call_site()));
}
}
impl ToTokens for Group {
fn to_tokens(&self, tokens: &mut TokenStream) {
tokens.append(self.clone());
}
}
impl ToTokens for Ident {
fn to_tokens(&self, tokens: &mut TokenStream) {
tokens.append(self.clone());
}
}
impl ToTokens for Punct {
fn to_tokens(&self, tokens: &mut TokenStream) {
tokens.append(self.clone());
}
}
impl ToTokens for Literal {
fn to_tokens(&self, tokens: &mut TokenStream) {
tokens.append(self.clone());
}
}
impl ToTokens for TokenTree {
fn to_tokens(&self, dst: &mut TokenStream) {
dst.append(self.clone());
}
}
impl ToTokens for TokenStream {
fn to_tokens(&self, dst: &mut TokenStream) {
dst.extend(iter::once(self.clone()));
}
fn into_token_stream(self) -> TokenStream {
self
}
}