src/lib.rs - platform/external/rust/crates/proc-macro-hack - Git at Google

 //! As of Rust 1.30, the language supports user-defined function-like procedural
 //! macros. However these can only be invoked in item position, not in
 //! statements or expressions.
 //!
 //! This crate implements an alternative type of procedural macro that can be
 //! invoked in statement or expression position.
 //!
 //! # Defining procedural macros
 //!
 //! Two crates are required to define a procedural macro.
 //!
 //! ## The implementation crate
 //!
 //! This crate must contain nothing but procedural macros. Private helper
 //! functions and private modules are fine but nothing can be public.
 //!
 //! [> example of an implementation crate][demo-hack-impl]
 //!
 //! Just like you would use a #\[proc_macro\] attribute to define a natively
 //! supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
 //! attribute to define a procedural macro that works in expression position.
 //! The function signature is the same as for ordinary function-like procedural
 //! macros.
 //!
 //! ```
 //! extern crate proc_macro;
 //!
 //! use proc_macro::TokenStream;
 //! use proc_macro_hack::proc_macro_hack;
 //! use quote::quote;
 //! use syn::{parse_macro_input, Expr};
 //!
 //! # const IGNORE: &str = stringify! {
 //! #[proc_macro_hack]
 //! # };
 //! pub fn add_one(input: TokenStream) -> TokenStream {
 //!     let expr = parse_macro_input!(input as Expr);
 //!     TokenStream::from(quote! {
 //!         1 + (#expr)
 //!     })
 //! }
 //! #
 //! # fn main() {}
 //! ```
 //!
 //! ## The declaration crate
 //!
 //! This crate is allowed to contain other public things if you need, for
 //! example traits or functions or ordinary macros.
 //!
 //! [> example of a declaration crate][demo-hack]
 //!
 //! Within the declaration crate there needs to be a re-export of your
 //! procedural macro from the implementation crate. The re-export also carries a
 //! \#\[proc_macro_hack\] attribute.
 //!
 //! ```
 //! use proc_macro_hack::proc_macro_hack;
 //!
 //! /// Add one to an expression.
 //! ///
 //! /// (Documentation goes here on the re-export, not in the other crate.)
 //! #[proc_macro_hack]
 //! pub use demo_hack_impl::add_one;
 //! #
 //! # fn main() {}
 //! ```
 //!
 //! Both crates depend on `proc-macro-hack`:
 //!
 //! ```toml
 //! [dependencies]
 //! proc-macro-hack = "0.5"
 //! ```
 //!
 //! Additionally, your implementation crate (but not your declaration crate) is
 //! a proc macro crate:
 //!
 //! ```toml
 //! [lib]
 //! proc-macro = true
 //! ```
 //!
 //! # Using procedural macros
 //!
 //! Users of your crate depend on your declaration crate (not your
 //! implementation crate), then use your procedural macros as usual.
 //!
 //! [> example of a downstream crate][example]
 //!
 //! ```
 //! use demo_hack::add_one;
 //!
 //! fn main() {
 //!     let two = 2;
 //!     let nine = add_one!(two) + add_one!(2 + 3);
 //!     println!("nine = {}", nine);
 //! }
 //! ```
 //!
 //! [demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
 //! [demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
 //! [example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
 //!
 //! # Limitations
 //!
 //! - Only proc macros in expression position are supported. Proc macros in
 //!   pattern position ([#20]) are not supported.
 //!
 //! - By default, nested invocations are not supported i.e. the code emitted by
 //!   a proc-macro-hack macro invocation cannot contain recursive calls to the
 //!   same proc-macro-hack macro nor calls to any other proc-macro-hack macros.
 //!   Use [`proc-macro-nested`] if you require support for nested invocations.
 //!
 //! - By default, hygiene is structured such that the expanded code can't refer
 //!   to local variables other than those passed by name somewhere in the macro
 //!   input. If your macro must refer to *local* variables that don't get named
 //!   in the macro input, use `#[proc_macro_hack(fake_call_site)]` on the
 //!   re-export in your declaration crate. *Most macros won't need this.*
 //!
 //! [#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
 //! [#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
 //! [`proc-macro-nested`]: https://docs.rs/proc-macro-nested

 #![recursion_limit = "512"]
 #![allow(clippy::needless_doctest_main, clippy::toplevel_ref_arg)]

 extern crate proc_macro;

 #[macro_use]
 mod quote;

 mod error;
 mod parse;

 use crate::error::{compile_error, Error};
 use crate::parse::*;
 use proc_macro::{token_stream, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
 use std::fmt::Write;
 use std::iter::Peekable;

 type Iter<'a> = &'a mut Peekable<token_stream::IntoIter>;
 type Visibility = Option<Span>;

 enum Input {
     Export(Export),
     Define(Define),
 }

 // pub use demo_hack_impl::{m1, m2 as qrst};
 struct Export {
     attrs: TokenStream,
     vis: Visibility,
     from: Ident,
     macros: Vec<Macro>,
 }

 // pub fn m1(input: TokenStream) -> TokenStream { ... }
 struct Define {
     attrs: TokenStream,
     name: Ident,
     body: TokenStream,
 }

 struct Macro {
     name: Ident,
     export_as: Ident,
 }

 #[proc_macro_attribute]
 pub fn proc_macro_hack(args: TokenStream, input: TokenStream) -> TokenStream {
     let ref mut args = args.into_iter().peekable();
     let ref mut input = input.into_iter().peekable();
     expand_proc_macro_hack(args, input).unwrap_or_else(compile_error)
 }

 fn expand_proc_macro_hack(args: Iter, input: Iter) -> Result<TokenStream, Error> {
     match parse_input(input)? {
         Input::Export(export) => {
             let args = parse_export_args(args)?;
             Ok(expand_export(export, args))
         }
         Input::Define(define) => {
             parse_define_args(args)?;
             Ok(expand_define(define))
         }
     }
 }

 #[doc(hidden)]
 #[proc_macro_derive(ProcMacroHack)]
 pub fn enum_hack(input: TokenStream) -> TokenStream {
     let ref mut input = input.into_iter().peekable();
     parse_enum_hack(input).unwrap_or_else(compile_error)
 }

 struct FakeCallSite {
     derive: Ident,
     rest: TokenStream,
 }

 #[doc(hidden)]
 #[proc_macro_attribute]
 pub fn fake_call_site(args: TokenStream, input: TokenStream) -> TokenStream {
     let ref mut args = args.into_iter().peekable();
     let ref mut input = input.into_iter().peekable();
     expand_fake_call_site(args, input).unwrap_or_else(compile_error)
 }

 fn expand_fake_call_site(args: Iter, input: Iter) -> Result<TokenStream, Error> {
     let span = match args.next() {
         Some(token) => token.span(),
         None => return Ok(input.collect()),
     };

     let input = parse_fake_call_site(input)?;
     let mut derive = input.derive;
     derive.set_span(span);
     let rest = input.rest;

     Ok(quote! {
         #[derive(#derive)]
         #rest
     })
 }

 struct ExportArgs {
     support_nested: bool,
     internal_macro_calls: u16,
     fake_call_site: bool,
 }

 fn expand_export(export: Export, args: ExportArgs) -> TokenStream {
     let dummy = dummy_name_for_export(&export);

     let attrs = export.attrs;
     let ref vis = export.vis.map(|span| Ident::new("pub", span));
     let macro_export = match vis {
         Some(_) => quote!(#[macro_export]),
         None => quote!(),
     };
     let crate_prefix = vis.as_ref().map(|_| quote!($crate::));
     let enum_variant = if args.support_nested {
         if args.internal_macro_calls == 0 {
             Ident::new("Nested", Span::call_site())
         } else {
             let name = format!("Nested{}", args.internal_macro_calls);
             Ident::new(&name, Span::call_site())
         }
     } else {
         Ident::new("Value", Span::call_site())
     };

     let from = export.from;
     let rules = export
         .macros
         .into_iter()
         .map(|Macro { name, export_as }| {
             let actual_name = actual_proc_macro_name(&name);
             let dispatch = dispatch_macro_name(&name);
             let call_site = call_site_macro_name(&name);

             let export_dispatch = if args.support_nested {
                 quote! {
                     #[doc(hidden)]
                     #vis use proc_macro_nested::dispatch as #dispatch;
                 }
             } else {
                 quote!()
             };

             let proc_macro_call = if args.support_nested {
                 let extra_bangs = (0..args.internal_macro_calls)
                     .map(|_| TokenTree::Punct(Punct::new('!', Spacing::Alone)))
                     .collect::<TokenStream>();
                 quote! {
                     #crate_prefix #dispatch! { ($($proc_macro)*) #extra_bangs }
                 }
             } else {
                 quote! {
                     proc_macro_call!()
                 }
             };

             let export_call_site = if args.fake_call_site {
                 quote! {
                     #[doc(hidden)]
                     #vis use proc_macro_hack::fake_call_site as #call_site;
                 }
             } else {
                 quote!()
             };

             let do_derive = if !args.fake_call_site {
                 quote! {
                     #[derive(#crate_prefix #actual_name)]
                 }
             } else if crate_prefix.is_some() {
                 quote! {
                     use #crate_prefix #actual_name;
                     #[#crate_prefix #call_site ($($proc_macro)*)]
                     #[derive(#actual_name)]
                 }
             } else {
                 quote! {
                     #[#call_site ($($proc_macro)*)]
                     #[derive(#actual_name)]
                 }
             };

             quote! {
                 #[doc(hidden)]
                 #vis use #from::#actual_name;

                 #export_dispatch
                 #export_call_site

                 #attrs
                 #macro_export
                 macro_rules! #export_as {
                     ($($proc_macro:tt)*) => {{
                         #do_derive
                         #[allow(dead_code)]
                         enum ProcMacroHack {
                             #enum_variant = (stringify! { $($proc_macro)* }, 0).1,
                         }
                         #proc_macro_call
                     }};
                 }
             }
         })
         .collect();

     wrap_in_enum_hack(dummy, rules)
 }

 fn expand_define(define: Define) -> TokenStream {
     let attrs = define.attrs;
     let name = define.name;
     let dummy = actual_proc_macro_name(&name);
     let body = define.body;

     quote! {
         mod #dummy {
             extern crate proc_macro;
             pub use self::proc_macro::*;
         }

         #attrs
         #[proc_macro_derive(#dummy)]
         pub fn #dummy(input: #dummy::TokenStream) -> #dummy::TokenStream {
             use std::iter::FromIterator;

             let mut iter = input.into_iter();
             iter.next().unwrap(); // `enum`
             iter.next().unwrap(); // `ProcMacroHack`
             iter.next().unwrap(); // `#`
             iter.next().unwrap(); // `[allow(dead_code)]`

             let mut braces = match iter.next().unwrap() {
                 #dummy::TokenTree::Group(group) => group.stream().into_iter(),
                 _ => unimplemented!(),
             };
             let variant = braces.next().unwrap(); // `Value` or `Nested`
             let varname = variant.to_string();
             let support_nested = varname.starts_with("Nested");
             braces.next().unwrap(); // `=`

             let mut parens = match braces.next().unwrap() {
                 #dummy::TokenTree::Group(group) => group.stream().into_iter(),
                 _ => unimplemented!(),
             };
             parens.next().unwrap(); // `stringify`
             parens.next().unwrap(); // `!`

             let inner = match parens.next().unwrap() {
                 #dummy::TokenTree::Group(group) => group.stream(),
                 _ => unimplemented!(),
             };

             let output: #dummy::TokenStream = #name(inner.clone());

             fn count_bangs(input: #dummy::TokenStream) -> usize {
                 let mut count = 0;
                 for token in input {
                     match token {
                         #dummy::TokenTree::Punct(punct) => {
                             if punct.as_char() == '!' {
                                 count += 1;
                             }
                         }
                         #dummy::TokenTree::Group(group) => {
                             count += count_bangs(group.stream());
                         }
                         _ => {}
                     }
                 }
                 count
             }

             // macro_rules! proc_macro_call {
             //     () => { #output }
             // }
             #dummy::TokenStream::from_iter(vec![
                 #dummy::TokenTree::Ident(
                     #dummy::Ident::new("macro_rules", #dummy::Span::call_site()),
                 ),
                 #dummy::TokenTree::Punct(
                     #dummy::Punct::new('!', #dummy::Spacing::Alone),
                 ),
                 #dummy::TokenTree::Ident(
                     #dummy::Ident::new(
                         &if support_nested {
                             let extra_bangs = if varname == "Nested" {
                                 0
                             } else {
                                 varname["Nested".len()..].parse().unwrap()
                             };
                             format!("proc_macro_call_{}", extra_bangs + count_bangs(inner))
                         } else {
                             String::from("proc_macro_call")
                         },
                         #dummy::Span::call_site(),
                     ),
                 ),
                 #dummy::TokenTree::Group(
                     #dummy::Group::new(#dummy::Delimiter::Brace, #dummy::TokenStream::from_iter(vec![
                         #dummy::TokenTree::Group(
                             #dummy::Group::new(#dummy::Delimiter::Parenthesis, #dummy::TokenStream::new()),
                         ),
                         #dummy::TokenTree::Punct(
                             #dummy::Punct::new('=', #dummy::Spacing::Joint),
                         ),
                         #dummy::TokenTree::Punct(
                             #dummy::Punct::new('>', #dummy::Spacing::Alone),
                         ),
                         #dummy::TokenTree::Group(
                             #dummy::Group::new(#dummy::Delimiter::Brace, output),
                         ),
                     ])),
                 ),
             ])
         }

         fn #name #body
     }
 }

 fn actual_proc_macro_name(conceptual: &Ident) -> Ident {
     Ident::new(
         &format!("proc_macro_hack_{}", conceptual),
         conceptual.span(),
     )
 }

 fn dispatch_macro_name(conceptual: &Ident) -> Ident {
     Ident::new(
         &format!("proc_macro_call_{}", conceptual),
         conceptual.span(),
     )
 }

 fn call_site_macro_name(conceptual: &Ident) -> Ident {
     Ident::new(
         &format!("proc_macro_fake_call_site_{}", conceptual),
         conceptual.span(),
     )
 }

 fn dummy_name_for_export(export: &Export) -> String {
     let mut dummy = String::new();
     let from = unraw(&export.from).to_string();
     write!(dummy, "_{}{}", from.len(), from).unwrap();
     for m in &export.macros {
         let name = unraw(&m.name).to_string();
         write!(dummy, "_{}{}", name.len(), name).unwrap();
     }
     dummy
 }

 fn unraw(ident: &Ident) -> Ident {
     let string = ident.to_string();
     if string.starts_with("r#") {
         Ident::new(&string[2..], ident.span())
     } else {
         ident.clone()
     }
 }

 fn wrap_in_enum_hack(dummy: String, inner: TokenStream) -> TokenStream {
     let dummy = Ident::new(&dummy, Span::call_site());
     quote! {
         #[derive(proc_macro_hack::ProcMacroHack)]
         enum #dummy {
             Value = (stringify! { #inner }, 0).1,
         }
     }
 }
	//! As of Rust 1.30, the language supports user-defined function-like procedural
	//! macros. However these can only be invoked in item position, not in
	//! statements or expressions.
	//!
	//! This crate implements an alternative type of procedural macro that can be
	//! invoked in statement or expression position.
	//!
	//! # Defining procedural macros
	//!
	//! Two crates are required to define a procedural macro.
	//!
	//! ## The implementation crate
	//!
	//! This crate must contain nothing but procedural macros. Private helper
	//! functions and private modules are fine but nothing can be public.
	//!
	//! [> example of an implementation crate][demo-hack-impl]
	//!
	//! Just like you would use a #\[proc_macro\] attribute to define a natively
	//! supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
	//! attribute to define a procedural macro that works in expression position.
	//! The function signature is the same as for ordinary function-like procedural
	//! macros.
	//!
	//! ```
	//! extern crate proc_macro;
	//!
	//! use proc_macro::TokenStream;
	//! use proc_macro_hack::proc_macro_hack;
	//! use quote::quote;
	//! use syn::{parse_macro_input, Expr};
	//!
	//! # const IGNORE: &str = stringify! {
	//! #[proc_macro_hack]
	//! # };
	//! pub fn add_one(input: TokenStream) -> TokenStream {
	//! let expr = parse_macro_input!(input as Expr);
	//! TokenStream::from(quote! {
	//! 1 + (#expr)
	//! })
	//! }
	//! #
	//! # fn main() {}
	//! ```
	//!
	//! ## The declaration crate
	//!
	//! This crate is allowed to contain other public things if you need, for
	//! example traits or functions or ordinary macros.
	//!
	//! [> example of a declaration crate][demo-hack]
	//!
	//! Within the declaration crate there needs to be a re-export of your
	//! procedural macro from the implementation crate. The re-export also carries a
	//! \#\[proc_macro_hack\] attribute.
	//!
	//! ```
	//! use proc_macro_hack::proc_macro_hack;
	//!
	//! /// Add one to an expression.
	//! ///
	//! /// (Documentation goes here on the re-export, not in the other crate.)
	//! #[proc_macro_hack]
	//! pub use demo_hack_impl::add_one;
	//! #
	//! # fn main() {}
	//! ```
	//!
	//! Both crates depend on `proc-macro-hack`:
	//!
	//! ```toml
	//! [dependencies]
	//! proc-macro-hack = "0.5"
	//! ```
	//!
	//! Additionally, your implementation crate (but not your declaration crate) is
	//! a proc macro crate:
	//!
	//! ```toml
	//! [lib]
	//! proc-macro = true
	//! ```
	//!
	//! # Using procedural macros
	//!
	//! Users of your crate depend on your declaration crate (not your
	//! implementation crate), then use your procedural macros as usual.
	//!
	//! [> example of a downstream crate][example]
	//!
	//! ```
	//! use demo_hack::add_one;
	//!
	//! fn main() {
	//! let two = 2;
	//! let nine = add_one!(two) + add_one!(2 + 3);
	//! println!("nine = {}", nine);
	//! }
	//! ```
	//!
	//! [demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
	//! [demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
	//! [example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
	//!
	//! # Limitations
	//!
	//! - Only proc macros in expression position are supported. Proc macros in
	//! pattern position ([#20]) are not supported.
	//!
	//! - By default, nested invocations are not supported i.e. the code emitted by
	//! a proc-macro-hack macro invocation cannot contain recursive calls to the
	//! same proc-macro-hack macro nor calls to any other proc-macro-hack macros.
	//! Use [`proc-macro-nested`] if you require support for nested invocations.
	//!
	//! - By default, hygiene is structured such that the expanded code can't refer
	//! to local variables other than those passed by name somewhere in the macro
	//! input. If your macro must refer to local variables that don't get named
	//! in the macro input, use `#[proc_macro_hack(fake_call_site)]` on the
	//! re-export in your declaration crate. Most macros won't need this.
	//!
	//! [#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
	//! [#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
	//! [`proc-macro-nested`]: https://docs.rs/proc-macro-nested

	#![recursion_limit = "512"]
	#![allow(clippy::needless_doctest_main, clippy::toplevel_ref_arg)]

	extern crate proc_macro;

	#[macro_use]
	mod quote;

	mod error;
	mod parse;

	use crate::error::{compile_error, Error};
	use crate::parse::*;
	use proc_macro::{token_stream, Ident, Punct, Spacing, Span, TokenStream, TokenTree};
	use std::fmt::Write;
	use std::iter::Peekable;

	type Iter<'a> = &'a mut Peekable<token_stream::IntoIter>;
	type Visibility = Option<Span>;

	enum Input {
	Export(Export),
	Define(Define),
	}

	// pub use demo_hack_impl::{m1, m2 as qrst};
	struct Export {
	attrs: TokenStream,
	vis: Visibility,
	from: Ident,
	macros: Vec<Macro>,
	}

	// pub fn m1(input: TokenStream) -> TokenStream { ... }
	struct Define {
	attrs: TokenStream,
	name: Ident,
	body: TokenStream,
	}

	struct Macro {
	name: Ident,
	export_as: Ident,
	}

	#[proc_macro_attribute]
	pub fn proc_macro_hack(args: TokenStream, input: TokenStream) -> TokenStream {
	let ref mut args = args.into_iter().peekable();
	let ref mut input = input.into_iter().peekable();
	expand_proc_macro_hack(args, input).unwrap_or_else(compile_error)
	}

	fn expand_proc_macro_hack(args: Iter, input: Iter) -> Result<TokenStream, Error> {
	match parse_input(input)? {
	Input::Export(export) => {
	let args = parse_export_args(args)?;
	Ok(expand_export(export, args))
	}
	Input::Define(define) => {
	parse_define_args(args)?;
	Ok(expand_define(define))
	}
	}
	}

	#[doc(hidden)]
	#[proc_macro_derive(ProcMacroHack)]
	pub fn enum_hack(input: TokenStream) -> TokenStream {
	let ref mut input = input.into_iter().peekable();
	parse_enum_hack(input).unwrap_or_else(compile_error)
	}

	struct FakeCallSite {
	derive: Ident,
	rest: TokenStream,
	}

	#[doc(hidden)]
	#[proc_macro_attribute]
	pub fn fake_call_site(args: TokenStream, input: TokenStream) -> TokenStream {
	let ref mut args = args.into_iter().peekable();
	let ref mut input = input.into_iter().peekable();
	expand_fake_call_site(args, input).unwrap_or_else(compile_error)
	}

	fn expand_fake_call_site(args: Iter, input: Iter) -> Result<TokenStream, Error> {
	let span = match args.next() {
	Some(token) => token.span(),
	None => return Ok(input.collect()),
	};

	let input = parse_fake_call_site(input)?;
	let mut derive = input.derive;
	derive.set_span(span);
	let rest = input.rest;

	Ok(quote! {
	#[derive(#derive)]
	#rest
	})
	}

	struct ExportArgs {
	support_nested: bool,
	internal_macro_calls: u16,
	fake_call_site: bool,
	}

	fn expand_export(export: Export, args: ExportArgs) -> TokenStream {
	let dummy = dummy_name_for_export(&export);

	let attrs = export.attrs;
	let ref vis = export.vis.map(\|span\| Ident::new("pub", span));
	let macro_export = match vis {
	Some(_) => quote!(#[macro_export]),
	None => quote!(),
	};
	let crate_prefix = vis.as_ref().map(\|_\| quote!($crate::));
	let enum_variant = if args.support_nested {
	if args.internal_macro_calls == 0 {
	Ident::new("Nested", Span::call_site())
	} else {
	let name = format!("Nested{}", args.internal_macro_calls);
	Ident::new(&name, Span::call_site())
	}
	} else {
	Ident::new("Value", Span::call_site())
	};

	let from = export.from;
	let rules = export
	.macros
	.into_iter()
	.map(\|Macro { name, export_as }\| {
	let actual_name = actual_proc_macro_name(&name);
	let dispatch = dispatch_macro_name(&name);
	let call_site = call_site_macro_name(&name);

	let export_dispatch = if args.support_nested {
	quote! {
	#[doc(hidden)]
	#vis use proc_macro_nested::dispatch as #dispatch;
	}
	} else {
	quote!()
	};

	let proc_macro_call = if args.support_nested {
	let extra_bangs = (0..args.internal_macro_calls)
	.map(\|_\| TokenTree::Punct(Punct::new('!', Spacing::Alone)))
	.collect::<TokenStream>();
	quote! {
	#crate_prefix #dispatch! { ($($proc_macro)*) #extra_bangs }
	}
	} else {
	quote! {
	proc_macro_call!()
	}
	};

	let export_call_site = if args.fake_call_site {
	quote! {
	#[doc(hidden)]
	#vis use proc_macro_hack::fake_call_site as #call_site;
	}
	} else {
	quote!()
	};

	let do_derive = if !args.fake_call_site {
	quote! {
	#[derive(#crate_prefix #actual_name)]
	}
	} else if crate_prefix.is_some() {
	quote! {
	use #crate_prefix #actual_name;
	#[#crate_prefix #call_site ($($proc_macro)*)]
	#[derive(#actual_name)]
	}
	} else {
	quote! {
	#[#call_site ($($proc_macro)*)]
	#[derive(#actual_name)]
	}
	};

	quote! {
	#[doc(hidden)]
	#vis use #from::#actual_name;

	#export_dispatch
	#export_call_site

	#attrs
	#macro_export
	macro_rules! #export_as {
	($($proc_macro:tt)*) => {{
	#do_derive
	#[allow(dead_code)]
	enum ProcMacroHack {
	#enum_variant = (stringify! { $($proc_macro)* }, 0).1,
	}
	#proc_macro_call
	}};
	}
	}
	})
	.collect();

	wrap_in_enum_hack(dummy, rules)
	}

	fn expand_define(define: Define) -> TokenStream {
	let attrs = define.attrs;
	let name = define.name;
	let dummy = actual_proc_macro_name(&name);
	let body = define.body;

	quote! {
	mod #dummy {
	extern crate proc_macro;
	pub use self::proc_macro::*;
	}

	#attrs
	#[proc_macro_derive(#dummy)]
	pub fn #dummy(input: #dummy::TokenStream) -> #dummy::TokenStream {
	use std::iter::FromIterator;

	let mut iter = input.into_iter();
	iter.next().unwrap(); // `enum`
	iter.next().unwrap(); // `ProcMacroHack`
	iter.next().unwrap(); // `#`
	iter.next().unwrap(); // `[allow(dead_code)]`

	let mut braces = match iter.next().unwrap() {
	#dummy::TokenTree::Group(group) => group.stream().into_iter(),
	_ => unimplemented!(),
	};
	let variant = braces.next().unwrap(); // `Value` or `Nested`
	let varname = variant.to_string();
	let support_nested = varname.starts_with("Nested");
	braces.next().unwrap(); // `=`

	let mut parens = match braces.next().unwrap() {
	#dummy::TokenTree::Group(group) => group.stream().into_iter(),
	_ => unimplemented!(),
	};
	parens.next().unwrap(); // `stringify`
	parens.next().unwrap(); // `!`

	let inner = match parens.next().unwrap() {
	#dummy::TokenTree::Group(group) => group.stream(),
	_ => unimplemented!(),
	};

	let output: #dummy::TokenStream = #name(inner.clone());

	fn count_bangs(input: #dummy::TokenStream) -> usize {
	let mut count = 0;
	for token in input {
	match token {
	#dummy::TokenTree::Punct(punct) => {
	if punct.as_char() == '!' {
	count += 1;
	}
	}
	#dummy::TokenTree::Group(group) => {
	count += count_bangs(group.stream());
	}
	_ => {}
	}
	}
	count
	}

	// macro_rules! proc_macro_call {
	// () => { #output }
	// }
	#dummy::TokenStream::from_iter(vec![
	#dummy::TokenTree::Ident(
	#dummy::Ident::new("macro_rules", #dummy::Span::call_site()),
	),
	#dummy::TokenTree::Punct(
	#dummy::Punct::new('!', #dummy::Spacing::Alone),
	),
	#dummy::TokenTree::Ident(
	#dummy::Ident::new(
	&if support_nested {
	let extra_bangs = if varname == "Nested" {
	0
	} else {
	varname["Nested".len()..].parse().unwrap()
	};
	format!("proc_macro_call_{}", extra_bangs + count_bangs(inner))
	} else {
	String::from("proc_macro_call")
	},
	#dummy::Span::call_site(),
	),
	),
	#dummy::TokenTree::Group(
	#dummy::Group::new(#dummy::Delimiter::Brace, #dummy::TokenStream::from_iter(vec![
	#dummy::TokenTree::Group(
	#dummy::Group::new(#dummy::Delimiter::Parenthesis, #dummy::TokenStream::new()),
	),
	#dummy::TokenTree::Punct(
	#dummy::Punct::new('=', #dummy::Spacing::Joint),
	),
	#dummy::TokenTree::Punct(
	#dummy::Punct::new('>', #dummy::Spacing::Alone),
	),
	#dummy::TokenTree::Group(
	#dummy::Group::new(#dummy::Delimiter::Brace, output),
	),
	])),
	),
	])
	}

	fn #name #body
	}
	}

	fn actual_proc_macro_name(conceptual: &Ident) -> Ident {
	Ident::new(
	&format!("proc_macro_hack_{}", conceptual),
	conceptual.span(),
	)
	}

	fn dispatch_macro_name(conceptual: &Ident) -> Ident {
	Ident::new(
	&format!("proc_macro_call_{}", conceptual),
	conceptual.span(),
	)
	}

	fn call_site_macro_name(conceptual: &Ident) -> Ident {
	Ident::new(
	&format!("proc_macro_fake_call_site_{}", conceptual),
	conceptual.span(),
	)
	}

	fn dummy_name_for_export(export: &Export) -> String {
	let mut dummy = String::new();
	let from = unraw(&export.from).to_string();
	write!(dummy, "_{}{}", from.len(), from).unwrap();
	for m in &export.macros {
	let name = unraw(&m.name).to_string();
	write!(dummy, "_{}{}", name.len(), name).unwrap();
	}
	dummy
	}

	fn unraw(ident: &Ident) -> Ident {
	let string = ident.to_string();
	if string.starts_with("r#") {
	Ident::new(&string[2..], ident.span())
	} else {
	ident.clone()
	}
	}

	fn wrap_in_enum_hack(dummy: String, inner: TokenStream) -> TokenStream {
	let dummy = Ident::new(&dummy, Span::call_site());
	quote! {
	#[derive(proc_macro_hack::ProcMacroHack)]
	enum #dummy {
	Value = (stringify! { #inner }, 0).1,
	}
	}
	}