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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::panic;
use errors::FatalError;
use rustc_macro::{TokenStream, __internal};
use syntax::ast::{self, ItemKind};
use syntax::codemap::{ExpnInfo, MacroAttribute, NameAndSpan, Span};
use syntax::ext::base::*;
use syntax::fold::Folder;
use syntax::parse::token::intern;
use syntax::print::pprust;
pub struct CustomDerive {
inner: fn(TokenStream) -> TokenStream,
}
impl CustomDerive {
pub fn new(inner: fn(TokenStream) -> TokenStream) -> CustomDerive {
CustomDerive { inner: inner }
}
}
impl MultiItemModifier for CustomDerive {
fn expand(&self,
ecx: &mut ExtCtxt,
span: Span,
meta_item: &ast::MetaItem,
item: Annotatable)
-> Vec<Annotatable> {
let item = match item {
Annotatable::Item(item) => item,
Annotatable::ImplItem(_) |
Annotatable::TraitItem(_) => {
ecx.span_err(span, "custom derive attributes may only be \
applied to struct/enum items");
return Vec::new()
}
};
match item.node {
ItemKind::Struct(..) |
ItemKind::Enum(..) => {}
_ => {
ecx.span_err(span, "custom derive attributes may only be \
applied to struct/enum items");
return Vec::new()
}
}
let input_span = Span {
expn_id: ecx.codemap().record_expansion(ExpnInfo {
call_site: span,
callee: NameAndSpan {
format: MacroAttribute(intern(&pprust::meta_item_to_string(meta_item))),
span: Some(span),
allow_internal_unstable: true,
},
}),
..item.span
};
let input = __internal::new_token_stream(item);
let res = __internal::set_parse_sess(&ecx.parse_sess, || {
let inner = self.inner;
panic::catch_unwind(panic::AssertUnwindSafe(|| inner(input)))
});
let item = match res {
Ok(stream) => __internal::token_stream_items(stream),
Err(e) => {
let msg = "custom derive attribute panicked";
let mut err = ecx.struct_span_fatal(span, msg);
if let Some(s) = e.downcast_ref::<String>() {
err.help(&format!("message: {}", s));
}
if let Some(s) = e.downcast_ref::<&'static str>() {
err.help(&format!("message: {}", s));
}
err.emit();
panic!(FatalError);
}
};
// Right now we have no knowledge of spans at all in custom derive
// macros, everything is just parsed as a string. Reassign all spans to
// the input `item` for better errors here.
item.into_iter().flat_map(|item| {
ChangeSpan { span: input_span }.fold_item(item)
}).map(Annotatable::Item).collect()
}
}
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