use super::TokenStreamExt; use core::iter; use proc_macro2::{Group, Ident, Literal, Punct, Span, TokenStream, TokenTree}; use std::borrow::Cow; use std::rc::Rc; /// 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, /// } /// /// 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 ToTokens for Box { fn to_tokens(&self, tokens: &mut TokenStream) { (**self).to_tokens(tokens); } } impl ToTokens for Rc { fn to_tokens(&self, tokens: &mut TokenStream) { (**self).to_tokens(tokens); } } impl ToTokens for Option { 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 } }