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// Copyright 2012-2015 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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//! Builder types for generating the "item data" section of the
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//! metadata. This section winds up looking like this:
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//!
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//! ```
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//! <common::data> // big list of item-like things...
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//! <common::data_item> // ...for most def-ids, there is an entry.
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//! </common::data_item>
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//! </common::data>
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//! ```
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//!
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//! As we generate this listing, we collect the offset of each
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//! `data_item` entry and store it in an index. Then, when we load the
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//! metadata, we can skip right to the metadata for a particular item.
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//!
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//! In addition to the offset, we need to track the data that was used
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//! to generate the contents of each `data_item`. This is so that we
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//! can figure out which HIR nodes contributed to that data for
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//! incremental compilation purposes.
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//!
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//! The `IndexBuilder` facilitates both of these. It is created
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//! with an RBML encoder isntance (`rbml_w`) along with an
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//! `EncodingContext` (`ecx`), which it encapsulates. It has one main
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//! method, `record()`. You invoke `record` like so to create a new
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//! `data_item` element in the list:
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//!
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//! ```
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//! index.record(some_def_id, callback_fn, data)
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//! ```
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//!
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//! What record will do is to (a) record the current offset, (b) emit
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//! the `common::data_item` tag, and then call `callback_fn` with the
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//! given data as well as an `ItemContentBuilder`. Once `callback_fn`
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//! returns, the `common::data_item` tag will be closed.
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//!
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//! The `ItemContentBuilder` is another type that just offers access
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//! to the `ecx` and `rbml_w` that were given in, as well as
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//! maintaining a list of `xref` instances, which are used to extract
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//! common data so it is not re-serialized.
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//!
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//! `ItemContentBuilder` is a distinct type which does not offer the
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//! `record` method, so that we can ensure that `common::data_item` elements
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//! are never nested.
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//!
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//! In addition, while the `callback_fn` is executing, we will push a
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//! task `MetaData(some_def_id)`, which can then observe the
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//! reads/writes that occur in the task. For this reason, the `data`
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//! argument that is given to the `callback_fn` must implement the
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//! trait `DepGraphRead`, which indicates how to register reads on the
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//! data in this new task (note that many types of data, such as
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//! `DefId`, do not currently require any reads to be registered,
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//! since they are not derived from a HIR node). This is also why we
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//! give a callback fn, rather than taking a closure: it allows us to
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//! easily control precisely what data is given to that fn.
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use common::tag_items_data_item;
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use encoder::EncodeContext;
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use index::IndexData;
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use rbml::writer::Encoder;
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use rustc::dep_graph::DepNode;
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use rustc::hir;
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use rustc::hir::def_id::DefId;
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use rustc::ty::{self, TyCtxt};
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use rustc_data_structures::fnv::FnvHashMap;
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use syntax::ast;
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/// Builder that can encode new items, adding them into the index.
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/// Item encoding cannot be nested.
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pub struct IndexBuilder<'a, 'tcx: 'a, 'encoder: 'a> {
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items: IndexData,
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builder: ItemContentBuilder<'a, 'tcx, 'encoder>,
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}
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/// Builder that can encode the content of items, but can't start a
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/// new item itself. Most code is attached to here.
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pub struct ItemContentBuilder<'a, 'tcx: 'a, 'encoder: 'a> {
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xrefs: FnvHashMap<XRef<'tcx>, u32>, // sequentially-assigned
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pub ecx: &'a EncodeContext<'a, 'tcx>,
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pub rbml_w: &'a mut Encoder<'encoder>,
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}
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/// "interned" entries referenced by id
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#[derive(PartialEq, Eq, Hash)]
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pub enum XRef<'tcx> { Predicate(ty::Predicate<'tcx>) }
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impl<'a, 'tcx, 'encoder> IndexBuilder<'a, 'tcx, 'encoder> {
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pub fn new(ecx: &'a EncodeContext<'a, 'tcx>,
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rbml_w: &'a mut Encoder<'encoder>)
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-> Self {
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IndexBuilder {
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items: IndexData::new(ecx.tcx.map.num_local_def_ids()),
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builder: ItemContentBuilder {
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ecx: ecx,
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xrefs: FnvHashMap(),
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rbml_w: rbml_w,
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},
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}
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}
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pub fn ecx(&self) -> &'a EncodeContext<'a, 'tcx> {
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self.builder.ecx()
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}
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/// Emit the data for a def-id to the metadata. The function to
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/// emit the data is `op`, and it will be given `data` as
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/// arguments. This `record` function will start/end an RBML tag
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/// and record the current offset for use in the index, calling
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/// `op` to generate the data in the RBML tag.
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///
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/// In addition, it will setup a dep-graph task to track what data
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/// `op` accesses to generate the metadata, which is later used by
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/// incremental compilation to compute a hash for the metadata and
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/// track changes.
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///
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/// The reason that `op` is a function pointer, and not a closure,
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/// is that we want to be able to completely track all data it has
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/// access to, so that we can be sure that `DATA: DepGraphRead`
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/// holds, and that it is therefore not gaining "secret" access to
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/// bits of HIR or other state that would not be trackd by the
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/// content system.
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pub fn record<DATA>(&mut self,
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id: DefId,
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op: fn(&mut ItemContentBuilder<'a, 'tcx, 'encoder>, DATA),
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data: DATA)
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where DATA: DepGraphRead
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{
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let position = self.builder.rbml_w.mark_stable_position();
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self.items.record(id, position);
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let _task = self.ecx().tcx.dep_graph.in_task(DepNode::MetaData(id));
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self.builder.rbml_w.start_tag(tag_items_data_item).unwrap();
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data.read(self.ecx().tcx);
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op(&mut self.builder, data);
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self.builder.rbml_w.end_tag().unwrap();
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}
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pub fn into_fields(self) -> (IndexData, FnvHashMap<XRef<'tcx>, u32>) {
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(self.items, self.builder.xrefs)
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}
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}
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impl<'a, 'tcx, 'encoder> ItemContentBuilder<'a, 'tcx, 'encoder> {
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pub fn ecx(&self) -> &'a EncodeContext<'a, 'tcx> {
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self.ecx
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}
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pub fn add_xref(&mut self, xref: XRef<'tcx>) -> u32 {
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let old_len = self.xrefs.len() as u32;
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*self.xrefs.entry(xref).or_insert(old_len)
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}
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}
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/// Trait used for data that can be passed from outside a dep-graph
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/// task. The data must either be of some safe type, such as a
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/// `DefId` index, or implement the `read` method so that it can add
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/// a read of whatever dep-graph nodes are appropriate.
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pub trait DepGraphRead {
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fn read(&self, tcx: TyCtxt);
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}
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impl DepGraphRead for DefId {
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fn read(&self, _tcx: TyCtxt) { }
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}
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impl DepGraphRead for ast::NodeId {
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fn read(&self, _tcx: TyCtxt) { }
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}
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impl<T> DepGraphRead for Option<T>
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where T: DepGraphRead
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{
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fn read(&self, tcx: TyCtxt) {
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match *self {
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Some(ref v) => v.read(tcx),
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None => (),
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}
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}
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}
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impl<T> DepGraphRead for [T]
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where T: DepGraphRead
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{
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fn read(&self, tcx: TyCtxt) {
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for i in self {
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i.read(tcx);
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}
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}
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}
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macro_rules! read_tuple {
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($($name:ident),*) => {
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impl<$($name),*> DepGraphRead for ($($name),*)
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where $($name: DepGraphRead),*
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{
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#[allow(non_snake_case)]
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fn read(&self, tcx: TyCtxt) {
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let &($(ref $name),*) = self;
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$($name.read(tcx);)*
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}
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}
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}
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}
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read_tuple!(A,B);
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read_tuple!(A,B,C);
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macro_rules! read_hir {
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($t:ty) => {
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impl<'tcx> DepGraphRead for &'tcx $t {
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fn read(&self, tcx: TyCtxt) {
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tcx.map.read(self.id);
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}
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}
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}
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}
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read_hir!(hir::Item);
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read_hir!(hir::ImplItem);
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read_hir!(hir::TraitItem);
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read_hir!(hir::ForeignItem);
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/// Leaks access to a value of type T without any tracking. This is
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/// suitable for ambiguous types like `usize`, which *could* represent
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/// tracked data (e.g., if you read it out of a HIR node) or might not
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/// (e.g., if it's an index). Adding in an `Untracked` is an
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/// assertion, essentially, that the data does not need to be tracked
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/// (or that read edges will be added by some other way).
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///
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/// A good idea is to add to each use of `Untracked` an explanation of
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/// why this value is ok.
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pub struct Untracked<T>(pub T);
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impl<T> DepGraphRead for Untracked<T> {
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fn read(&self, _tcx: TyCtxt) { }
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}
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/// Newtype that can be used to package up misc data extracted from a
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/// HIR node that doesn't carry its own id. This will allow an
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/// arbitrary `T` to be passed in, but register a read on the given
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/// node-id.
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pub struct FromId<T>(pub ast::NodeId, pub T);
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impl<T> DepGraphRead for FromId<T> {
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fn read(&self, tcx: TyCtxt) {
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tcx.map.read(self.0);
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}
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}
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