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+Rust Quasi-Quoting
+==================
+
+[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/quote-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/quote)
+[<img alt="crates.io" src="https://img.shields.io/crates/v/quote.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/quote)
+[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-quote-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/quote)
+[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/quote/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/quote/actions?query=branch%3Amaster)
+
+This crate provides the [`quote!`] macro for turning Rust syntax tree data
+structures into tokens of source code.
+
+[`quote!`]: https://docs.rs/quote/1.0/quote/macro.quote.html
+
+Procedural macros in Rust receive a stream of tokens as input, execute arbitrary
+Rust code to determine how to manipulate those tokens, and produce a stream of
+tokens to hand back to the compiler to compile into the caller's crate.
+Quasi-quoting is a solution to one piece of that &mdash; producing tokens to
+return to the compiler.
+
+The idea of quasi-quoting is that we write *code* that we treat as *data*.
+Within the `quote!` macro, we can write what looks like code to our text editor
+or IDE. We get all the benefits of the editor's brace matching, syntax
+highlighting, indentation, and maybe autocompletion. But rather than compiling
+that as code into the current crate, we can treat it as data, pass it around,
+mutate it, and eventually hand it back to the compiler as tokens to compile into
+the macro caller's crate.
+
+This crate is motivated by the procedural macro use case, but is a
+general-purpose Rust quasi-quoting library and is not specific to procedural
+macros.
+
+```toml
+[dependencies]
+quote = "1.0"
+```
+
+*Version requirement: Quote supports rustc 1.56 and up.*<br>
+[*Release notes*](https://github.com/dtolnay/quote/releases)
+
+<br>
+
+## Syntax
+
+The quote crate provides a [`quote!`] macro within which you can write Rust code
+that gets packaged into a [`TokenStream`] and can be treated as data. You should
+think of `TokenStream` as representing a fragment of Rust source code.
+
+[`TokenStream`]: https://docs.rs/proc-macro2/1.0/proc_macro2/struct.TokenStream.html
+
+Within the `quote!` macro, interpolation is done with `#var`. Any type
+implementing the [`quote::ToTokens`] trait can be interpolated. This includes
+most Rust primitive types as well as most of the syntax tree types from [`syn`].
+
+[`quote::ToTokens`]: https://docs.rs/quote/1.0/quote/trait.ToTokens.html
+[`syn`]: https://github.com/dtolnay/syn
+
+```rust
+let tokens = quote! {
+    struct SerializeWith #generics #where_clause {
+        value: &'a #field_ty,
+        phantom: core::marker::PhantomData<#item_ty>,
+    }
+
+    impl #generics serde::Serialize for SerializeWith #generics #where_clause {
+        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where
+            S: serde::Serializer,
+        {
+            #path(self.value, serializer)
+        }
+    }
+
+    SerializeWith {
+        value: #value,
+        phantom: core::marker::PhantomData::<#item_ty>,
+    }
+};
+```
+
+<br>
+
+## Repetition
+
+Repetition is done using `#(...)*` or `#(...),*` similar to `macro_rules!`. This
+iterates through the elements of any variable interpolated within the repetition
+and inserts a copy of the repetition body for each one. The variables in an
+interpolation may be anything that implements `IntoIterator`, including `Vec` or
+a pre-existing iterator.
+
+- `#(#var)*` — no separators
+- `#(#var),*` — the character before the asterisk is used as a separator
+- `#( struct #var; )*` — the repetition can contain other things
+- `#( #k => println!("{}", #v), )*` — even multiple interpolations
+
+Note that there is a difference between `#(#var ,)*` and `#(#var),*`—the latter
+does not produce a trailing comma. This matches the behavior of delimiters in
+`macro_rules!`.
+
+<br>
+
+## Returning tokens to the compiler
+
+The `quote!` macro evaluates to an expression of type
+`proc_macro2::TokenStream`. Meanwhile Rust procedural macros are expected to
+return the type `proc_macro::TokenStream`.
+
+The difference between the two types is that `proc_macro` types are entirely
+specific to procedural macros and cannot ever exist in code outside of a
+procedural macro, while `proc_macro2` types may exist anywhere including tests
+and non-macro code like main.rs and build.rs. This is why even the procedural
+macro ecosystem is largely built around `proc_macro2`, because that ensures the
+libraries are unit testable and accessible in non-macro contexts.
+
+There is a [`From`]-conversion in both directions so returning the output of
+`quote!` from a procedural macro usually looks like `tokens.into()` or
+`proc_macro::TokenStream::from(tokens)`.
+
+[`From`]: https://doc.rust-lang.org/std/convert/trait.From.html
+
+<br>
+
+## Examples
+
+### Combining quoted fragments
+
+Usually you don't end up constructing an entire final `TokenStream` in one
+piece. Different parts may come from different helper functions. The tokens
+produced by `quote!` themselves implement `ToTokens` and so can be interpolated
+into later `quote!` invocations to build up a final result.
+
+```rust
+let type_definition = quote! {...};
+let methods = quote! {...};
+
+let tokens = quote! {
+    #type_definition
+    #methods
+};
+```
+
+### Constructing identifiers
+
+Suppose we have an identifier `ident` which came from somewhere in a macro
+input and we need to modify it in some way for the macro output. Let's consider
+prepending the identifier with an underscore.
+
+Simply interpolating the identifier next to an underscore will not have the
+behavior of concatenating them. The underscore and the identifier will continue
+to be two separate tokens as if you had written `_ x`.
+
+```rust
+// incorrect
+quote! {
+    let mut _#ident = 0;
+}
+```
+
+The solution is to build a new identifier token with the correct value. As this
+is such a common case, the `format_ident!` macro provides a convenient utility
+for doing so correctly.
+
+```rust
+let varname = format_ident!("_{}", ident);
+quote! {
+    let mut #varname = 0;
+}
+```
+
+Alternatively, the APIs provided by Syn and proc-macro2 can be used to directly
+build the identifier. This is roughly equivalent to the above, but will not
+handle `ident` being a raw identifier.
+
+```rust
+let concatenated = format!("_{}", ident);
+let varname = syn::Ident::new(&concatenated, ident.span());
+quote! {
+    let mut #varname = 0;
+}
+```
+
+### Making method calls
+
+Let's say our macro requires some type specified in the macro input to have a
+constructor called `new`. We have the type in a variable called `field_type` of
+type `syn::Type` and want to invoke the constructor.
+
+```rust
+// incorrect
+quote! {
+    let value = #field_type::new();
+}
+```
+
+This works only sometimes. If `field_type` is `String`, the expanded code
+contains `String::new()` which is fine. But if `field_type` is something like
+`Vec<i32>` then the expanded code is `Vec<i32>::new()` which is invalid syntax.
+Ordinarily in handwritten Rust we would write `Vec::<i32>::new()` but for macros
+often the following is more convenient.
+
+```rust
+quote! {
+    let value = <#field_type>::new();
+}
+```
+
+This expands to `<Vec<i32>>::new()` which behaves correctly.
+
+A similar pattern is appropriate for trait methods.
+
+```rust
+quote! {
+    let value = <#field_type as core::default::Default>::default();
+}
+```
+
+<br>
+
+## Hygiene
+
+Any interpolated tokens preserve the `Span` information provided by their
+`ToTokens` implementation. Tokens that originate within a `quote!` invocation
+are spanned with [`Span::call_site()`].
+
+[`Span::call_site()`]: https://docs.rs/proc-macro2/1.0/proc_macro2/struct.Span.html#method.call_site
+
+A different span can be provided explicitly through the [`quote_spanned!`]
+macro.
+
+[`quote_spanned!`]: https://docs.rs/quote/1.0/quote/macro.quote_spanned.html
+
+<br>
+
+## Non-macro code generators
+
+When using `quote` in a build.rs or main.rs and writing the output out to a
+file, consider having the code generator pass the tokens through [prettyplease]
+before writing. This way if an error occurs in the generated code it is
+convenient for a human to read and debug.
+
+Be aware that no kind of hygiene or span information is retained when tokens are
+written to a file; the conversion from tokens to source code is lossy.
+
+Example usage in build.rs:
+
+```rust
+let output = quote! { ... };
+let syntax_tree = syn::parse2(output).unwrap();
+let formatted = prettyplease::unparse(&syntax_tree);
+
+let out_dir = env::var_os("OUT_DIR").unwrap();
+let dest_path = Path::new(&out_dir).join("out.rs");
+fs::write(dest_path, formatted).unwrap();
+```
+
+[prettyplease]: https://github.com/dtolnay/prettyplease
+
+<br>
+
+#### License
+
+<sup>
+Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
+2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
+</sup>
+
+<br>
+
+<sub>
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
+be dual licensed as above, without any additional terms or conditions.
+</sub>