15821caee9
Separate the plugin code from non-plugin code to break a potential cycle in crates. This will allow us to merge the new libproc_macro_tokens into libproc_macro.
108 lines
3.5 KiB
Rust
108 lines
3.5 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! # Proc_Macro
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//!
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//! A library for procedural macro writers.
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//!
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//! ## Usage
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//! This crate provides the `qquote!` macro for syntax creation.
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//!
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//! The `qquote!` macro imports `syntax::ext::proc_macro_shim::prelude::*`, so you
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//! will need to `extern crate syntax` for usage. (This is a temporary solution until more
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//! of the external API in libproc_macro_tokens is stabilized to support the token construction
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//! operations that the qausiquoter relies on.) The shim file also provides additional
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//! operations, such as `build_block_emitter` (as used in the `cond` example below).
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//!
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//! ## Quasiquotation
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//!
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//! The quasiquoter creates output that, when run, constructs the tokenstream specified as
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//! input. For example, `qquote!(5 + 5)` will produce a program, that, when run, will
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//! construct the TokenStream `5 | + | 5`.
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//!
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//! ### Unquoting
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//!
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//! Unquoting is currently done as `unquote`, and works by taking the single next
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//! TokenTree in the TokenStream as the unquoted term. Ergonomically, `unquote(foo)` works
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//! fine, but `unquote foo` is also supported.
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//!
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//! A simple example might be:
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//!
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//!```
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//!fn double(tmp: TokenStream) -> TokenStream {
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//! qquote!(unquote(tmp) * 2)
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//!}
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//!```
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//!
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//! ### Large Example: Implementing Scheme's `cond`
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//!
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//! Below is the full implementation of Scheme's `cond` operator.
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//!
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//! ```
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//! fn cond_rec(input: TokenStream) -> TokenStream {
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//! if input.is_empty() { return quote!(); }
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//!
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//! let next = input.slice(0..1);
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//! let rest = input.slice_from(1..);
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//!
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//! let clause : TokenStream = match next.maybe_delimited() {
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//! Some(ts) => ts,
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//! _ => panic!("Invalid input"),
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//! };
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//!
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//! // clause is ([test]) [rhs]
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//! if clause.len() < 2 { panic!("Invalid macro usage in cond: {:?}", clause) }
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//!
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//! let test: TokenStream = clause.slice(0..1);
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//! let rhs: TokenStream = clause.slice_from(1..);
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//!
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//! if ident_eq(&test[0], str_to_ident("else")) || rest.is_empty() {
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//! quote!({unquote(rhs)})
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//! } else {
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//! quote!({if unquote(test) { unquote(rhs) } else { cond!(unquote(rest)) } })
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//! }
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//! }
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//! ```
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//!
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#![crate_name = "proc_macro_plugin"]
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#![unstable(feature = "rustc_private", issue = "27812")]
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#![feature(plugin_registrar)]
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#![crate_type = "dylib"]
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#![crate_type = "rlib"]
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#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
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html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
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html_root_url = "https://doc.rust-lang.org/nightly/")]
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#![cfg_attr(not(stage0), deny(warnings))]
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#![feature(staged_api)]
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#![feature(rustc_diagnostic_macros)]
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#![feature(rustc_private)]
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extern crate rustc_plugin;
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extern crate syntax;
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extern crate syntax_pos;
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extern crate proc_macro_tokens;
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#[macro_use] extern crate log;
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mod qquote;
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use qquote::qquote;
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use rustc_plugin::Registry;
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// ____________________________________________________________________________________________
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// Main macro definition
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#[plugin_registrar]
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pub fn plugin_registrar(reg: &mut Registry) {
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reg.register_macro("qquote", qquote);
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}
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