1 files changed, 273 insertions, 0 deletions
diff --git a/rust/quote/to_tokens.rs b/rust/quote/to_tokens.rs
new file mode 100644
index 000000000000..1af1089e1423
--- /dev/null
+++ b/rust/quote/to_tokens.rs
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use super::TokenStreamExt;
+use alloc::borrow::Cow;
+use alloc::rc::Rc;
+use core::iter;
+use proc_macro2::{Group, Ident, Literal, Punct, Span, TokenStream, TokenTree};
+use std::ffi::{CStr, CString};
+
+/// Types that can be interpolated inside a `quote!` invocation.
+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`.
+    ///
+    /// # 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<T: ?Sized + ToTokens> ToTokens for &T {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        (**self).to_tokens(tokens);
+    }
+}
+
+impl<T: ?Sized + ToTokens> ToTokens for &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(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);
+    }
+}
+
+impl ToTokens for i8 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::i8_suffixed(*self));
+    }
+}
+
+impl ToTokens for i16 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::i16_suffixed(*self));
+    }
+}
+
+impl ToTokens for i32 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::i32_suffixed(*self));
+    }
+}
+
+impl ToTokens for i64 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::i64_suffixed(*self));
+    }
+}
+
+impl ToTokens for i128 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::i128_suffixed(*self));
+    }
+}
+
+impl ToTokens for isize {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::isize_suffixed(*self));
+    }
+}
+
+impl ToTokens for u8 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::u8_suffixed(*self));
+    }
+}
+
+impl ToTokens for u16 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::u16_suffixed(*self));
+    }
+}
+
+impl ToTokens for u32 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::u32_suffixed(*self));
+    }
+}
+
+impl ToTokens for u64 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::u64_suffixed(*self));
+    }
+}
+
+impl ToTokens for u128 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::u128_suffixed(*self));
+    }
+}
+
+impl ToTokens for usize {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::usize_suffixed(*self));
+    }
+}
+
+impl ToTokens for f32 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::f32_suffixed(*self));
+    }
+}
+
+impl ToTokens for f64 {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::f64_suffixed(*self));
+    }
+}
+
+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 CStr {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::c_string(self));
+    }
+}
+
+impl ToTokens for CString {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.append(Literal::c_string(self));
+    }
+}
+
+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, tokens: &mut TokenStream) {
+        tokens.append(self.clone());
+    }
+}
+
+impl ToTokens for TokenStream {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        tokens.extend(iter::once(self.clone()));
+    }
+
+    fn into_token_stream(self) -> TokenStream {
+        self
+    }
+}