105 lines
3.5 KiB
Rust
105 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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use std::panic;
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use errors::FatalError;
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use proc_macro::{TokenStream, __internal};
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use syntax::ast::{self, ItemKind, Attribute, Mac};
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use syntax::attr::{mark_used, mark_known};
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use syntax::codemap::Span;
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use syntax::ext::base::*;
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use syntax::fold::Folder;
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use syntax::visit::Visitor;
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struct MarkAttrs<'a>(&'a [ast::Name]);
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impl<'a> Visitor<'a> for MarkAttrs<'a> {
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fn visit_attribute(&mut self, attr: &Attribute) {
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if self.0.contains(&attr.name()) {
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mark_used(attr);
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mark_known(attr);
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}
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}
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fn visit_mac(&mut self, _mac: &Mac) {}
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}
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pub struct CustomDerive {
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inner: fn(TokenStream) -> TokenStream,
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attrs: Vec<ast::Name>,
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}
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impl CustomDerive {
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pub fn new(inner: fn(TokenStream) -> TokenStream, attrs: Vec<ast::Name>) -> CustomDerive {
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CustomDerive { inner: inner, attrs: attrs }
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}
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}
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impl MultiItemModifier for CustomDerive {
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fn expand(&self,
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ecx: &mut ExtCtxt,
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span: Span,
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_meta_item: &ast::MetaItem,
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item: Annotatable)
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-> Vec<Annotatable> {
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let item = match item {
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Annotatable::Item(item) => item,
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Annotatable::ImplItem(_) |
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Annotatable::TraitItem(_) => {
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ecx.span_err(span, "custom derive attributes may only be \
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applied to struct/enum items");
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return Vec::new()
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}
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};
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match item.node {
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ItemKind::Struct(..) |
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ItemKind::Enum(..) => {},
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_ => {
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ecx.span_err(span, "custom derive attributes may only be \
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applied to struct/enum items");
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return Vec::new()
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}
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}
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// Mark attributes as known, and used.
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MarkAttrs(&self.attrs).visit_item(&item);
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let input = __internal::new_token_stream(ecx.resolver.eliminate_crate_var(item.clone()));
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let res = __internal::set_parse_sess(&ecx.parse_sess, || {
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let inner = self.inner;
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panic::catch_unwind(panic::AssertUnwindSafe(|| inner(input)))
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});
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let new_items = match res {
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Ok(stream) => __internal::token_stream_items(stream),
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Err(e) => {
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let msg = "custom derive attribute panicked";
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let mut err = ecx.struct_span_fatal(span, msg);
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if let Some(s) = e.downcast_ref::<String>() {
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err.help(&format!("message: {}", s));
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}
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if let Some(s) = e.downcast_ref::<&'static str>() {
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err.help(&format!("message: {}", s));
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}
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err.emit();
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panic!(FatalError);
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}
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};
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let mut res = vec![Annotatable::Item(item)];
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// Reassign spans of all expanded items to the input `item`
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// for better errors here.
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res.extend(new_items.into_iter().flat_map(|item| {
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ChangeSpan { span: span }.fold_item(item)
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}).map(Annotatable::Item));
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res
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}
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}
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