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Fix #46112: visible_parent_map construction needs a BFS over whole crate forest.

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This commit is contained in:
Felix S. Klock II 2017-12-12 19:05:12 -06:00
parent 6a36019440
commit 43406d2681
1 changed files with 19 additions and 5 deletions
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24
src/librustc_metadata/cstore_impl.rs
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@ -294,13 +294,31 @@ pub fn provide<'tcx>(providers: &mut Providers<'tcx>) {
assert_eq!(cnum, LOCAL_CRATE);
let mut visible_parent_map: DefIdMap<DefId> = DefIdMap();
// Issue 46112: We want the map to prefer the shortest
// paths when reporting the path to an item. Therefore we
// build up the map via a breadth-first search (BFS),
// which naturally yields minimal-length paths.
//
// Note that it needs to be a BFS over the whole forest of
// crates, not just each individual crate; otherwise you
// only get paths that are locally minimal with respect to
// whatever crate we happened to encounter first in this
// traversal, but not globally minimal across all crates.
let bfs_queue = &mut VecDeque::new();
for &cnum in tcx.crates().iter() {
// Ignore crates without a corresponding local `extern crate` item.
if tcx.missing_extern_crate_item(cnum) {
continue
}
let bfs_queue = &mut VecDeque::new();
bfs_queue.push_back(DefId {
krate: cnum,
index: CRATE_DEF_INDEX
});
}
// (restrict scope of mutable-borrow of `visible_parent_map`)
{
let visible_parent_map = &mut visible_parent_map;
let mut add_child = |bfs_queue: &mut VecDeque<_>,
child: &def::Export,
@ -326,10 +344,6 @@ pub fn provide<'tcx>(providers: &mut Providers<'tcx>) {
}
};
bfs_queue.push_back(DefId {
krate: cnum,
index: CRATE_DEF_INDEX
});
while let Some(def) = bfs_queue.pop_front() {
for child in tcx.item_children(def).iter() {
add_child(bfs_queue, child, def);