1 files changed, 107 insertions, 0 deletions
diff --git a/src/libproc_macro_plugin/lib.rs b/src/libproc_macro_plugin/lib.rs
new file mode 100644
index 00000000000..c45762bfb6e
--- /dev/null
+++ b/src/libproc_macro_plugin/lib.rs
@@ -0,0 +1,107 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! # Proc_Macro
+//!
+//! A library for procedural macro writers.
+//!
+//! ## Usage
+//! This crate provides the `qquote!` macro for syntax creation.
+//!
+//! The `qquote!` macro imports `syntax::ext::proc_macro_shim::prelude::*`, so you
+//! will need to `extern crate syntax` for usage. (This is a temporary solution until more
+//! of the external API in libproc_macro_tokens is stabilized to support the token construction
+//! operations that the qausiquoter relies on.) The shim file also provides additional
+//! operations, such as `build_block_emitter` (as used in the `cond` example below).
+//!
+//! ## Quasiquotation
+//!
+//! The quasiquoter creates output that, when run, constructs the tokenstream specified as
+//! input. For example, `qquote!(5 + 5)` will produce a program, that, when run, will
+//! construct the TokenStream `5 | + | 5`.
+//!
+//! ### Unquoting
+//!
+//! Unquoting is currently done as `unquote`, and works by taking the single next
+//! TokenTree in the TokenStream as the unquoted term. Ergonomically, `unquote(foo)` works
+//! fine, but `unquote foo` is also supported.
+//!
+//! A simple example might be:
+//!
+//!```
+//!fn double(tmp: TokenStream) -> TokenStream {
+//!    qquote!(unquote(tmp) * 2)
+//!}
+//!```
+//!
+//! ### Large Example: Implementing Scheme's `cond`
+//!
+//! Below is the full implementation of Scheme's `cond` operator.
+//!
+//! ```
+//! fn cond_rec(input: TokenStream) -> TokenStream {
+//!   if input.is_empty() { return quote!(); }
+//!
+//!   let next = input.slice(0..1);
+//!   let rest = input.slice_from(1..);
+//!
+//!   let clause : TokenStream = match next.maybe_delimited() {
+//!     Some(ts) => ts,
+//!     _ => panic!("Invalid input"),
+//!   };
+//!
+//!   // clause is ([test]) [rhs]
+//!   if clause.len() < 2 { panic!("Invalid macro usage in cond: {:?}", clause) }
+//!
+//!   let test: TokenStream = clause.slice(0..1);
+//!   let rhs: TokenStream = clause.slice_from(1..);
+//!
+//!   if ident_eq(&test[0], str_to_ident("else")) || rest.is_empty() {
+//!     quote!({unquote(rhs)})
+//!   } else {
+//!     quote!({if unquote(test) { unquote(rhs) } else { cond!(unquote(rest)) } })
+//!   }
+//! }
+//! ```
+//!
+
+#![crate_name = "proc_macro_plugin"]
+#![unstable(feature = "rustc_private", issue = "27812")]
+#![feature(plugin_registrar)]
+#![crate_type = "dylib"]
+#![crate_type = "rlib"]
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
+       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
+       html_root_url = "https://doc.rust-lang.org/nightly/")]
+#![cfg_attr(not(stage0), deny(warnings))]
+
+#![feature(staged_api)]
+#![feature(rustc_diagnostic_macros)]
+#![feature(rustc_private)]
+
+extern crate rustc_plugin;
+extern crate syntax;
+extern crate syntax_pos;
+extern crate proc_macro_tokens;
+#[macro_use] extern crate log;
+
+mod qquote;
+
+use qquote::qquote;
+
+use rustc_plugin::Registry;
+
+// ____________________________________________________________________________________________
+// Main macro definition
+
+#[plugin_registrar]
+pub fn plugin_registrar(reg: &mut Registry) {
+    reg.register_macro("qquote", qquote);
+}