592 lines
19 KiB
Rust
592 lines
19 KiB
Rust
//! [![github]](https://github.com/dtolnay/proc-macro-hack) [![crates-io]](https://crates.io/crates/proc-macro-hack) [![docs-rs]](https://docs.rs/proc-macro-hack)
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//!
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//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
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//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
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//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,PHN2ZyByb2xlPSJpbWciIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgdmlld0JveD0iMCAwIDUxMiA1MTIiPjxwYXRoIGZpbGw9IiNmNWY1ZjUiIGQ9Ik00ODguNiAyNTAuMkwzOTIgMjE0VjEwNS41YzAtMTUtOS4zLTI4LjQtMjMuNC0zMy43bC0xMDAtMzcuNWMtOC4xLTMuMS0xNy4xLTMuMS0yNS4zIDBsLTEwMCAzNy41Yy0xNC4xIDUuMy0yMy40IDE4LjctMjMuNCAzMy43VjIxNGwtOTYuNiAzNi4yQzkuMyAyNTUuNSAwIDI2OC45IDAgMjgzLjlWMzk0YzAgMTMuNiA3LjcgMjYuMSAxOS45IDMyLjJsMTAwIDUwYzEwLjEgNS4xIDIyLjEgNS4xIDMyLjIgMGwxMDMuOS01MiAxMDMuOSA1MmMxMC4xIDUuMSAyMi4xIDUuMSAzMi4yIDBsMTAwLTUwYzEyLjItNi4xIDE5LjktMTguNiAxOS45LTMyLjJWMjgzLjljMC0xNS05LjMtMjguNC0yMy40LTMzLjd6TTM1OCAyMTQuOGwtODUgMzEuOXYtNjguMmw4NS0zN3Y3My4zek0xNTQgMTA0LjFsMTAyLTM4LjIgMTAyIDM4LjJ2LjZsLTEwMiA0MS40LTEwMi00MS40di0uNnptODQgMjkxLjFsLTg1IDQyLjV2LTc5LjFsODUtMzguOHY3NS40em0wLTExMmwtMTAyIDQxLjQtMTAyLTQxLjR2LS42bDEwMi0zOC4yIDEwMiAzOC4ydi42em0yNDAgMTEybC04NSA0Mi41di03OS4xbDg1LTM4Ljh2NzUuNHptMC0xMTJsLTEwMiA0MS40LTEwMi00MS40di0uNmwxMDItMzguMiAxMDIgMzguMnYuNnoiPjwvcGF0aD48L3N2Zz4K
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//!
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//! <br>
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//!
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//! <table><tr><td><hr>
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//! <b>Note:</b> <i>As of Rust 1.45 this crate is superseded by native support
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//! for #[proc_macro] in expression position. Only consider using this crate if
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//! you care about supporting compilers between 1.31 and 1.45.</i>
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//! <hr></td></tr></table>
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//!
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//! Since Rust 1.30, the language supports user-defined function-like procedural
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//! macros. However these can only be invoked in item position, not in
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//! statements or expressions.
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//!
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//! This crate implements an alternative type of procedural macro that can be
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//! invoked in statement or expression position.
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//!
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//! # Defining procedural macros
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//!
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//! Two crates are required to define a procedural macro.
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//!
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//! ## The implementation crate
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//!
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//! This crate must contain nothing but procedural macros. Private helper
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//! functions and private modules are fine but nothing can be public.
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//!
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//! [» example of an implementation crate][demo-hack-impl]
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//!
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//! Just like you would use a #\[proc_macro\] attribute to define a natively
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//! supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
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//! attribute to define a procedural macro that works in expression position.
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//! The function signature is the same as for ordinary function-like procedural
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//! macros.
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//!
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//! ```
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//! # extern crate proc_macro;
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//! #
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//! use proc_macro::TokenStream;
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//! use proc_macro_hack::proc_macro_hack;
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//! use quote::quote;
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//! use syn::{parse_macro_input, Expr};
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//!
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//! # const IGNORE: &str = stringify! {
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//! #[proc_macro_hack]
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//! # };
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//! pub fn add_one(input: TokenStream) -> TokenStream {
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//! let expr = parse_macro_input!(input as Expr);
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//! TokenStream::from(quote! {
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//! 1 + (#expr)
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//! })
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//! }
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//! #
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//! # fn main() {}
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//! ```
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//!
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//! ## The declaration crate
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//!
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//! This crate is allowed to contain other public things if you need, for
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//! example traits or functions or ordinary macros.
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//!
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//! [» example of a declaration crate][demo-hack]
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//!
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//! Within the declaration crate there needs to be a re-export of your
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//! procedural macro from the implementation crate. The re-export also carries a
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//! \#\[proc_macro_hack\] attribute.
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//!
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//! ```
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//! use proc_macro_hack::proc_macro_hack;
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//!
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//! /// Add one to an expression.
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//! ///
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//! /// (Documentation goes here on the re-export, not in the other crate.)
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//! #[proc_macro_hack]
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//! pub use demo_hack_impl::add_one;
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//! #
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//! # fn main() {}
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//! ```
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//!
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//! Both crates depend on `proc-macro-hack`:
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//!
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//! ```toml
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//! [dependencies]
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//! proc-macro-hack = "0.5"
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//! ```
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//!
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//! Additionally, your implementation crate (but not your declaration crate) is
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//! a proc macro crate:
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//!
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//! ```toml
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//! [lib]
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//! proc-macro = true
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//! ```
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//!
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//! # Using procedural macros
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//!
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//! Users of your crate depend on your declaration crate (not your
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//! implementation crate), then use your procedural macros as usual.
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//!
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//! [» example of a downstream crate][example]
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//!
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//! ```
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//! use demo_hack::add_one;
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//!
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//! fn main() {
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//! let two = 2;
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//! let nine = add_one!(two) + add_one!(2 + 3);
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//! println!("nine = {}", nine);
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//! }
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//! ```
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//!
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//! [demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
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//! [demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
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//! [example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
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//!
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//! # Limitations
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//!
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//! - Only proc macros in expression position are supported. Proc macros in
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//! pattern position ([#20]) are not supported.
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//!
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//! - By default, nested invocations are not supported i.e. the code emitted by
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//! a proc-macro-hack macro invocation cannot contain recursive calls to the
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//! same proc-macro-hack macro nor calls to any other proc-macro-hack macros.
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//! Use [`proc-macro-nested`] if you require support for nested invocations.
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//!
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//! - By default, hygiene is structured such that the expanded code can't refer
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//! to local variables other than those passed by name somewhere in the macro
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//! input. If your macro must refer to *local* variables that don't get named
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//! in the macro input, use `#[proc_macro_hack(fake_call_site)]` on the
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//! re-export in your declaration crate. *Most macros won't need this.*
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//!
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//! - On compilers that are new enough to natively support proc macros in
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//! expression position, proc-macro-hack does not automatically use that
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//! support, since the hygiene can be subtly different between the two
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//! implementations. To opt in to compiling your macro to native
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//! `#[proc_macro]` on sufficiently new compilers, use
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//! `#[proc_macro_hack(only_hack_old_rustc)]` on the re-export in your
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//! declaration crate.
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//!
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//! [#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
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//! [#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
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//! [`proc-macro-nested`]: https://docs.rs/proc-macro-nested
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#![recursion_limit = "512"]
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#![allow(clippy::needless_doctest_main, clippy::toplevel_ref_arg)]
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extern crate proc_macro;
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#[macro_use]
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mod quote;
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mod error;
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mod iter;
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mod parse;
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use crate::error::{compile_error, Error};
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use crate::iter::Iter;
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use crate::parse::{
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parse_define_args, parse_enum_hack, parse_export_args, parse_fake_call_site, parse_input,
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};
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use proc_macro::{Ident, Punct, Spacing, Span, TokenStream, TokenTree};
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use std::fmt::Write;
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type Visibility = Option<Ident>;
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enum Input {
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Export(Export),
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Define(Define),
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}
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// pub use demo_hack_impl::{m1, m2 as qrst};
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struct Export {
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attrs: TokenStream,
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vis: Visibility,
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from: Ident,
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macros: Vec<Macro>,
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}
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// pub fn m1(input: TokenStream) -> TokenStream { ... }
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struct Define {
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attrs: TokenStream,
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name: Ident,
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body: TokenStream,
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}
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struct Macro {
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name: Ident,
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export_as: Ident,
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}
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#[proc_macro_attribute]
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pub fn proc_macro_hack(args: TokenStream, input: TokenStream) -> TokenStream {
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let ref mut args = iter::new(args);
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let ref mut input = iter::new(input);
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expand_proc_macro_hack(args, input).unwrap_or_else(compile_error)
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}
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fn expand_proc_macro_hack(args: Iter, input: Iter) -> Result<TokenStream, Error> {
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match parse_input(input)? {
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Input::Export(export) => {
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let args = parse_export_args(args)?;
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Ok(expand_export(export, args))
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}
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Input::Define(define) => {
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parse_define_args(args)?;
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Ok(expand_define(define))
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}
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}
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}
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#[doc(hidden)]
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#[proc_macro_derive(ProcMacroHack)]
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pub fn enum_hack(input: TokenStream) -> TokenStream {
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let ref mut input = iter::new(input);
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parse_enum_hack(input).unwrap_or_else(compile_error)
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}
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struct FakeCallSite {
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derive: Ident,
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rest: TokenStream,
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}
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#[doc(hidden)]
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#[proc_macro_attribute]
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pub fn fake_call_site(args: TokenStream, input: TokenStream) -> TokenStream {
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let ref mut args = iter::new(args);
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let ref mut input = iter::new(input);
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expand_fake_call_site(args, input).unwrap_or_else(compile_error)
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}
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fn expand_fake_call_site(args: Iter, input: Iter) -> Result<TokenStream, Error> {
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let span = match args.next() {
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Some(token) => token.span(),
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None => return Ok(input.collect()),
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};
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let input = parse_fake_call_site(input)?;
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let mut derive = input.derive;
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derive.set_span(span);
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let rest = input.rest;
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Ok(quote! {
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#[derive(#derive)]
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#rest
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})
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}
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struct ExportArgs {
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support_nested: bool,
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internal_macro_calls: u16,
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fake_call_site: bool,
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only_hack_old_rustc: bool,
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}
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fn expand_export(export: Export, args: ExportArgs) -> TokenStream {
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if args.only_hack_old_rustc && cfg!(not(need_proc_macro_hack)) {
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return expand_export_nohack(export);
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}
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let dummy = dummy_name_for_export(&export);
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let attrs = export.attrs;
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let vis = export.vis;
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let macro_export = match vis {
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Some(_) => quote!(#[macro_export]),
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None => quote!(),
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};
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let crate_prefix = vis.as_ref().map(|_| quote!($crate::));
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let enum_variant = if args.support_nested {
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if args.internal_macro_calls == 0 {
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Ident::new("Nested", Span::call_site())
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} else {
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let name = format!("Nested{}", args.internal_macro_calls);
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Ident::new(&name, Span::call_site())
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}
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} else {
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Ident::new("Value", Span::call_site())
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};
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let from = export.from;
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let mut actual_names = TokenStream::new();
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let mut export_dispatch = TokenStream::new();
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let mut export_call_site = TokenStream::new();
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let mut macro_rules = TokenStream::new();
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for Macro { name, export_as } in &export.macros {
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let hacked = hacked_proc_macro_name(&name);
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let dispatch = dispatch_macro_name(&name);
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let call_site = call_site_macro_name(&name);
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if !actual_names.is_empty() {
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actual_names.extend(quote!(,));
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}
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actual_names.extend(quote!(#hacked));
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if !export_dispatch.is_empty() {
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export_dispatch.extend(quote!(,));
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}
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export_dispatch.extend(quote!(dispatch as #dispatch));
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if !export_call_site.is_empty() {
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export_call_site.extend(quote!(,));
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}
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export_call_site.extend(quote!(fake_call_site as #call_site));
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let do_derive = if !args.fake_call_site {
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quote! {
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#[derive(#crate_prefix #hacked)]
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}
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} else if crate_prefix.is_some() {
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quote! {
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use #crate_prefix #hacked;
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#[#crate_prefix #call_site ($($proc_macro)*)]
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#[derive(#hacked)]
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}
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} else {
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quote! {
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#[#call_site ($($proc_macro)*)]
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#[derive(#hacked)]
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}
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};
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let proc_macro_call = if args.support_nested {
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let extra_bangs = (0..args.internal_macro_calls)
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.map(|_| TokenTree::Punct(Punct::new('!', Spacing::Alone)))
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.collect::<TokenStream>();
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quote! {
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#crate_prefix #dispatch! { ($($proc_macro)*) #extra_bangs }
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}
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} else {
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quote! {
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proc_macro_call!()
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}
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};
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macro_rules.extend(quote! {
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#attrs
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#macro_export
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macro_rules! #export_as {
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($($proc_macro:tt)*) => {{
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#do_derive
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#[allow(dead_code)]
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enum ProcMacroHack {
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#enum_variant = (stringify! { $($proc_macro)* }, 0).1,
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}
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#proc_macro_call
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}};
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}
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});
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}
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if export.macros.len() != 1 {
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export_dispatch = quote!({#export_dispatch});
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export_call_site = quote!({#export_call_site});
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actual_names = quote!({#actual_names});
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}
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let export_dispatch = if args.support_nested {
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quote! {
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#[doc(hidden)]
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#vis use proc_macro_nested::#export_dispatch;
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}
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} else {
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quote!()
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};
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let export_call_site = if args.fake_call_site {
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quote! {
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#[doc(hidden)]
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#vis use proc_macro_hack::#export_call_site;
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}
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} else {
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quote!()
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};
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let expanded = quote! {
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#[doc(hidden)]
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#vis use #from::#actual_names;
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#export_dispatch
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#export_call_site
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#macro_rules
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};
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wrap_in_enum_hack(dummy, expanded)
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}
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fn expand_export_nohack(export: Export) -> TokenStream {
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let attrs = export.attrs;
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let vis = export.vis;
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let from = export.from;
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let mut names = TokenStream::new();
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for Macro { name, export_as } in &export.macros {
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let pub_name = pub_proc_macro_name(&name);
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if !names.is_empty() {
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names.extend(quote!(,));
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}
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names.extend(quote!(#pub_name as #export_as));
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}
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if export.macros.len() != 1 {
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names = quote!({#names});
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}
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quote! {
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#attrs
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#vis use #from::#names;
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}
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}
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fn expand_define(define: Define) -> TokenStream {
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let attrs = define.attrs;
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let name = define.name;
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let pub_name = pub_proc_macro_name(&name);
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let hacked = hacked_proc_macro_name(&name);
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let body = define.body;
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quote! {
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mod #pub_name {
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extern crate proc_macro;
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pub use self::proc_macro::*;
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}
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#attrs
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#[doc(hidden)]
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#[proc_macro_derive(#hacked)]
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pub fn #hacked(input: #pub_name::TokenStream) -> #pub_name::TokenStream {
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use std::iter::FromIterator;
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let mut iter = input.into_iter();
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iter.next().unwrap(); // `enum`
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iter.next().unwrap(); // `ProcMacroHack`
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iter.next().unwrap(); // `#`
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iter.next().unwrap(); // `[allow(dead_code)]`
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let mut braces = match iter.next().unwrap() {
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#pub_name::TokenTree::Group(group) => group.stream().into_iter(),
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_ => unimplemented!(),
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};
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let variant = braces.next().unwrap(); // `Value` or `Nested`
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let varname = variant.to_string();
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let support_nested = varname.starts_with("Nested");
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braces.next().unwrap(); // `=`
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let mut parens = match braces.next().unwrap() {
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#pub_name::TokenTree::Group(group) => group.stream().into_iter(),
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_ => unimplemented!(),
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};
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parens.next().unwrap(); // `stringify`
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parens.next().unwrap(); // `!`
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let inner = match parens.next().unwrap() {
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#pub_name::TokenTree::Group(group) => group.stream(),
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_ => unimplemented!(),
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};
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let output: #pub_name::TokenStream = #name(inner.clone());
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fn count_bangs(input: #pub_name::TokenStream) -> usize {
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let mut count = 0;
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for token in input {
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match token {
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#pub_name::TokenTree::Punct(punct) => {
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if punct.as_char() == '!' {
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count += 1;
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}
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}
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#pub_name::TokenTree::Group(group) => {
|
|
count += count_bangs(group.stream());
|
|
}
|
|
_ => {}
|
|
}
|
|
}
|
|
count
|
|
}
|
|
|
|
// macro_rules! proc_macro_call {
|
|
// () => { #output }
|
|
// }
|
|
#pub_name::TokenStream::from_iter(vec![
|
|
#pub_name::TokenTree::Ident(
|
|
#pub_name::Ident::new("macro_rules", #pub_name::Span::call_site()),
|
|
),
|
|
#pub_name::TokenTree::Punct(
|
|
#pub_name::Punct::new('!', #pub_name::Spacing::Alone),
|
|
),
|
|
#pub_name::TokenTree::Ident(
|
|
#pub_name::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")
|
|
},
|
|
#pub_name::Span::call_site(),
|
|
),
|
|
),
|
|
#pub_name::TokenTree::Group(
|
|
#pub_name::Group::new(#pub_name::Delimiter::Brace, #pub_name::TokenStream::from_iter(vec![
|
|
#pub_name::TokenTree::Group(
|
|
#pub_name::Group::new(#pub_name::Delimiter::Parenthesis, #pub_name::TokenStream::new()),
|
|
),
|
|
#pub_name::TokenTree::Punct(
|
|
#pub_name::Punct::new('=', #pub_name::Spacing::Joint),
|
|
),
|
|
#pub_name::TokenTree::Punct(
|
|
#pub_name::Punct::new('>', #pub_name::Spacing::Alone),
|
|
),
|
|
#pub_name::TokenTree::Group(
|
|
#pub_name::Group::new(#pub_name::Delimiter::Brace, output),
|
|
),
|
|
])),
|
|
),
|
|
])
|
|
}
|
|
|
|
#attrs
|
|
#[proc_macro]
|
|
pub fn #pub_name(input: #pub_name::TokenStream) -> #pub_name::TokenStream {
|
|
#name(input)
|
|
}
|
|
|
|
fn #name #body
|
|
}
|
|
}
|
|
|
|
fn pub_proc_macro_name(conceptual: &Ident) -> Ident {
|
|
Ident::new(
|
|
&format!("proc_macro_hack_{}", conceptual),
|
|
conceptual.span(),
|
|
)
|
|
}
|
|
|
|
fn hacked_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,
|
|
}
|
|
}
|
|
}
|