Rollup merge of rust-lang#48185 - michaelwoerister:recursive-cache-de…

…coding, r=nikomatsakis

incr.comp.: Don't keep RefCells in on-disk-cache borrowed in order to allow for recursive invocations.

Fixes rust-lang#47972.

r? @nikomatsakis

src/librustc/ty/maps/on_disk_cache.rs

@@ -347,22 +347,21 @@ impl<'sess> OnDiskCache<'sess> {
  return None
  };
 
- let mut cnum_map = self.cnum_map.borrow_mut();
- if cnum_map.is_none() {
+ // Initialize the cnum_map if it is not initialized yet.
+ if self.cnum_map.borrow().is_none() {
+ let mut cnum_map = self.cnum_map.borrow_mut();
  *cnum_map = Some(Self::compute_cnum_map(tcx, &self.prev_cnums[..]));
  }
-
- let mut synthetic_expansion_infos = self.synthetic_expansion_infos.borrow_mut();
- let mut file_index_to_file = self.file_index_to_file.borrow_mut();
+ let cnum_map = self.cnum_map.borrow();
 
  let mut decoder = CacheDecoder {
  tcx,
  opaque: opaque::Decoder::new(&self.serialized_data[..], pos.to_usize()),
  codemap: self.codemap,
  cnum_map: cnum_map.as_ref().unwrap(),
- file_index_to_file: &mut file_index_to_file,
+ file_index_to_file: &self.file_index_to_file,
  file_index_to_stable_id: &self.file_index_to_stable_id,
- synthetic_expansion_infos: &mut synthetic_expansion_infos,
+ synthetic_expansion_infos: &self.synthetic_expansion_infos,
  };
 
  match decode_tagged(&mut decoder, dep_node_index) {
@@ -421,21 +420,21 @@ struct CacheDecoder<'a, 'tcx: 'a, 'x> {
  opaque: opaque::Decoder<'x>,
  codemap: &'x CodeMap,
  cnum_map: &'x IndexVec<CrateNum, Option<CrateNum>>,
- synthetic_expansion_infos: &'x mut FxHashMap<AbsoluteBytePos, SyntaxContext>,
- file_index_to_file: &'x mut FxHashMap<FileMapIndex, Rc<FileMap>>,
+ synthetic_expansion_infos: &'x RefCell<FxHashMap<AbsoluteBytePos, SyntaxContext>>,
+ file_index_to_file: &'x RefCell<FxHashMap<FileMapIndex, Rc<FileMap>>>,
  file_index_to_stable_id: &'x FxHashMap<FileMapIndex, StableFilemapId>,
 }
 
 impl<'a, 'tcx, 'x> CacheDecoder<'a, 'tcx, 'x> {
- fn file_index_to_file(&mut self, index: FileMapIndex) -> Rc<FileMap> {
+ fn file_index_to_file(&self, index: FileMapIndex) -> Rc<FileMap> {
  let CacheDecoder {
- ref mut file_index_to_file,
+ ref file_index_to_file,
  ref file_index_to_stable_id,
  ref codemap,
  ..
  } = *self;
 
- file_index_to_file.entry(index).or_insert_with(|| {
+ file_index_to_file.borrow_mut().entry(index).or_insert_with(|| {
  let stable_id = file_index_to_stable_id[&index];
  codemap.filemap_by_stable_id(stable_id)
  .expect("Failed to lookup FileMap in new context.")
@@ -572,19 +571,24 @@ impl<'a, 'tcx, 'x> SpecializedDecoder<Span> for CacheDecoder<'a, 'tcx, 'x> {
  let pos = AbsoluteBytePos::new(self.opaque.position());
  let expn_info: ExpnInfo = Decodable::decode(self)?;
  let ctxt = SyntaxContext::allocate_directly(expn_info);
- self.synthetic_expansion_infos.insert(pos, ctxt);
+ self.synthetic_expansion_infos.borrow_mut().insert(pos, ctxt);
  ctxt
  }
  TAG_EXPANSION_INFO_SHORTHAND => {
  let pos = AbsoluteBytePos::decode(self)?;
- if let Some(ctxt) = self.synthetic_expansion_infos.get(&pos).cloned() {
+ let cached_ctxt = self.synthetic_expansion_infos
+ .borrow()
+ .get(&pos)
+ .cloned();
+
+ if let Some(ctxt) = cached_ctxt {
  ctxt
  } else {
  let expn_info = self.with_position(pos.to_usize(), |this| {
  ExpnInfo::decode(this)
  })?;
  let ctxt = SyntaxContext::allocate_directly(expn_info);
- self.synthetic_expansion_infos.insert(pos, ctxt);
+ self.synthetic_expansion_infos.borrow_mut().insert(pos, ctxt);
  ctxt
  }
  }