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proc_macro_registrar.rs
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// 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.
use std::mem;
use errors;
use syntax::ast::{self, Ident, NodeId};
use syntax::codemap::{ExpnInfo, NameAndSpan, MacroAttribute};
use syntax::ext::base::ExtCtxt;
use syntax::ext::build::AstBuilder;
use syntax::ext::expand::ExpansionConfig;
use syntax::parse::ParseSess;
use syntax::parse::token::{self, InternedString};
use syntax::feature_gate::Features;
use syntax::fold::Folder;
use syntax::ptr::P;
use syntax_pos::{Span, DUMMY_SP};
use syntax::visit::{self, Visitor};
use deriving;
struct CustomDerive {
trait_name: InternedString,
function_name: Ident,
span: Span,
attrs: Vec<InternedString>,
}
struct CollectCustomDerives<'a> {
derives: Vec<CustomDerive>,
in_root: bool,
handler: &'a errors::Handler,
is_proc_macro_crate: bool,
is_test_crate: bool,
}
pub fn modify(sess: &ParseSess,
resolver: &mut ::syntax::ext::base::Resolver,
mut krate: ast::Crate,
is_proc_macro_crate: bool,
is_test_crate: bool,
num_crate_types: usize,
handler: &errors::Handler,
features: &Features) -> ast::Crate {
let ecfg = ExpansionConfig::default("proc_macro".to_string());
let mut cx = ExtCtxt::new(sess, ecfg, resolver);
let mut collect = CollectCustomDerives {
derives: Vec::new(),
in_root: true,
handler: handler,
is_proc_macro_crate: is_proc_macro_crate,
is_test_crate: is_test_crate,
};
visit::walk_crate(&mut collect, &krate);
if !is_proc_macro_crate {
return krate
} else if !features.proc_macro {
let mut err = handler.struct_err("the `proc-macro` crate type is \
experimental");
err.help("add #![feature(proc_macro)] to the crate attributes to \
enable");
err.emit();
}
if num_crate_types > 1 {
handler.err("cannot mix `proc-macro` crate type with others");
}
krate.module.items.push(mk_registrar(&mut cx, &collect.derives));
if krate.exported_macros.len() > 0 {
handler.err("cannot export macro_rules! macros from a `proc-macro` \
crate type currently");
}
return krate
}
impl<'a> CollectCustomDerives<'a> {
fn check_not_pub_in_root(&self, vis: &ast::Visibility, sp: Span) {
if self.is_proc_macro_crate &&
self.in_root &&
*vis == ast::Visibility::Public {
self.handler.span_err(sp,
"`proc-macro` crate types cannot \
export any items other than functions \
tagged with `#[proc_macro_derive]` \
currently");
}
}
}
impl<'a> Visitor for CollectCustomDerives<'a> {
fn visit_item(&mut self, item: &ast::Item) {
// First up, make sure we're checking a bare function. If we're not then
// we're just not interested in this item.
//
// If we find one, try to locate a `#[proc_macro_derive]` attribute on
// it.
match item.node {
ast::ItemKind::Fn(..) => {}
_ => {
// Check for invalid use of proc_macro_derive
let attr = item.attrs.iter()
.filter(|a| a.check_name("proc_macro_derive"))
.next();
if let Some(attr) = attr {
self.handler.span_err(attr.span(),
"the `#[proc_macro_derive]` \
attribute may only be used \
on bare functions");
return;
}
self.check_not_pub_in_root(&item.vis, item.span);
return visit::walk_item(self, item)
}
}
let mut attrs = item.attrs.iter()
.filter(|a| a.check_name("proc_macro_derive"));
let attr = match attrs.next() {
Some(attr) => attr,
None => {
self.check_not_pub_in_root(&item.vis, item.span);
return visit::walk_item(self, item)
}
};
if let Some(a) = attrs.next() {
self.handler.span_err(a.span(), "multiple `#[proc_macro_derive]` \
attributes found");
}
if self.is_test_crate {
self.handler.span_err(attr.span(),
"`--test` cannot be used with proc-macro crates");
return;
}
if !self.is_proc_macro_crate {
self.handler.span_err(attr.span(),
"the `#[proc_macro_derive]` attribute is \
only usable with crates of the `proc-macro` \
crate type");
}
// Once we've located the `#[proc_macro_derive]` attribute, verify
// that it's of the form `#[proc_macro_derive(Foo)]` or
// `#[proc_macro_derive(Foo, attributes(A, ..))]`
let list = match attr.meta_item_list() {
Some(list) => list,
None => {
self.handler.span_err(attr.span(),
"attribute must be of form: \
#[proc_macro_derive(TraitName)]");
return
}
};
if list.len() != 1 && list.len() != 2 {
self.handler.span_err(attr.span(),
"attribute must have either one or two arguments");
return
}
let trait_attr = &list[0];
let attributes_attr = list.get(1);
let trait_name = match trait_attr.name() {
Some(name) => name,
_ => {
self.handler.span_err(trait_attr.span(), "not a meta item");
return
}
};
if !trait_attr.is_word() {
self.handler.span_err(trait_attr.span(), "must only be one word");
}
if deriving::is_builtin_trait(&trait_name) {
self.handler.span_err(trait_attr.span(),
"cannot override a built-in #[derive] mode");
}
if self.derives.iter().any(|d| d.trait_name == trait_name) {
self.handler.span_err(trait_attr.span(),
"derive mode defined twice in this crate");
}
let proc_attrs: Vec<_> = if let Some(attr) = attributes_attr {
if !attr.check_name("attributes") {
self.handler.span_err(attr.span(), "second argument must be `attributes`")
}
attr.meta_item_list().unwrap_or_else(|| {
self.handler.span_err(attr.span(),
"attribute must be of form: \
`attributes(foo, bar)`");
&[]
}).into_iter().filter_map(|attr| {
let name = match attr.name() {
Some(name) => name,
_ => {
self.handler.span_err(attr.span(), "not a meta item");
return None;
},
};
if !attr.is_word() {
self.handler.span_err(attr.span(), "must only be one word");
return None;
}
Some(name)
}).collect()
} else {
Vec::new()
};
if self.in_root {
self.derives.push(CustomDerive {
span: item.span,
trait_name: trait_name,
function_name: item.ident,
attrs: proc_attrs,
});
} else {
let msg = "functions tagged with `#[proc_macro_derive]` must \
currently reside in the root of the crate";
self.handler.span_err(item.span, msg);
}
visit::walk_item(self, item);
}
fn visit_mod(&mut self, m: &ast::Mod, _s: Span, id: NodeId) {
let mut prev_in_root = self.in_root;
if id != ast::CRATE_NODE_ID {
prev_in_root = mem::replace(&mut self.in_root, false);
}
visit::walk_mod(self, m);
self.in_root = prev_in_root;
}
fn visit_mac(&mut self, mac: &ast::Mac) {
visit::walk_mac(self, mac)
}
}
// Creates a new module which looks like:
//
// mod $gensym {
// extern crate proc_macro;
//
// use proc_macro::__internal::Registry;
//
// #[plugin_registrar]
// fn registrar(registrar: &mut Registry) {
// registrar.register_custom_derive($name_trait1, ::$name1, &[]);
// registrar.register_custom_derive($name_trait2, ::$name2, &["attribute_name"]);
// // ...
// }
// }
fn mk_registrar(cx: &mut ExtCtxt,
custom_derives: &[CustomDerive]) -> P<ast::Item> {
let eid = cx.codemap().record_expansion(ExpnInfo {
call_site: DUMMY_SP,
callee: NameAndSpan {
format: MacroAttribute(token::intern("proc_macro")),
span: None,
allow_internal_unstable: true,
}
});
let span = Span { expn_id: eid, ..DUMMY_SP };
let proc_macro = token::str_to_ident("proc_macro");
let krate = cx.item(span,
proc_macro,
Vec::new(),
ast::ItemKind::ExternCrate(None));
let __internal = token::str_to_ident("__internal");
let registry = token::str_to_ident("Registry");
let registrar = token::str_to_ident("registrar");
let register_custom_derive = token::str_to_ident("register_custom_derive");
let stmts = custom_derives.iter().map(|cd| {
let path = cx.path_global(cd.span, vec![cd.function_name]);
let trait_name = cx.expr_str(cd.span, cd.trait_name.clone());
let attrs = cx.expr_vec_slice(
span,
cd.attrs.iter().map(|s| cx.expr_str(cd.span, s.clone())).collect::<Vec<_>>()
);
(path, trait_name, attrs)
}).map(|(path, trait_name, attrs)| {
let registrar = cx.expr_ident(span, registrar);
let ufcs_path = cx.path(span, vec![proc_macro, __internal, registry,
register_custom_derive]);
cx.expr_call(span,
cx.expr_path(ufcs_path),
vec![registrar, trait_name, cx.expr_path(path), attrs])
}).map(|expr| {
cx.stmt_expr(expr)
}).collect::<Vec<_>>();
let path = cx.path(span, vec![proc_macro, __internal, registry]);
let registrar_path = cx.ty_path(path);
let arg_ty = cx.ty_rptr(span, registrar_path, None, ast::Mutability::Mutable);
let func = cx.item_fn(span,
registrar,
vec![cx.arg(span, registrar, arg_ty)],
cx.ty(span, ast::TyKind::Tup(Vec::new())),
cx.block(span, stmts));
let derive_registrar = token::intern_and_get_ident("rustc_derive_registrar");
let derive_registrar = cx.meta_word(span, derive_registrar);
let derive_registrar = cx.attribute(span, derive_registrar);
let func = func.map(|mut i| {
i.attrs.push(derive_registrar);
i.vis = ast::Visibility::Public;
i
});
let ident = ast::Ident::with_empty_ctxt(token::gensym("registrar"));
let module = cx.item_mod(span, span, ident, Vec::new(), vec![krate, func]).map(|mut i| {
i.vis = ast::Visibility::Public;
i
});
cx.monotonic_expander().fold_item(module).pop().unwrap()
}