diff options
Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_middle/src/ty/inhabitedness/def_id_forest.rs | 145 |
1 files changed, 0 insertions, 145 deletions
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/def_id_forest.rs b/compiler/rustc_middle/src/ty/inhabitedness/def_id_forest.rs deleted file mode 100644 index c4ad698ba..000000000 --- a/compiler/rustc_middle/src/ty/inhabitedness/def_id_forest.rs +++ /dev/null @@ -1,145 +0,0 @@ -use crate::ty::context::TyCtxt; -use crate::ty::{DefId, DefIdTree}; -use rustc_span::def_id::CRATE_DEF_ID; -use smallvec::SmallVec; -use std::mem; - -use DefIdForest::*; - -/// Represents a forest of `DefId`s closed under the ancestor relation. That is, -/// if a `DefId` representing a module is contained in the forest then all -/// `DefId`s defined in that module or submodules are also implicitly contained -/// in the forest. -/// -/// This is used to represent a set of modules in which a type is visibly -/// uninhabited. -/// -/// We store the minimal set of `DefId`s required to represent the whole set. If A and B are -/// `DefId`s in the `DefIdForest`, and A is a parent of B, then only A will be stored. When this is -/// used with `type_uninhabited_from`, there will very rarely be more than one `DefId` stored. -#[derive(Copy, Clone, HashStable, Debug)] -pub enum DefIdForest<'a> { - Empty, - Single(DefId), - /// This variant is very rare. - /// Invariant: >1 elements - Multiple(&'a [DefId]), -} - -/// Tests whether a slice of roots contains a given DefId. -#[inline] -fn slice_contains<'tcx>(tcx: TyCtxt<'tcx>, slice: &[DefId], id: DefId) -> bool { - slice.iter().any(|root_id| tcx.is_descendant_of(id, *root_id)) -} - -impl<'tcx> DefIdForest<'tcx> { - /// Creates an empty forest. - pub fn empty() -> DefIdForest<'tcx> { - DefIdForest::Empty - } - - /// Creates a forest consisting of a single tree representing the entire - /// crate. - #[inline] - pub fn full() -> DefIdForest<'tcx> { - DefIdForest::from_id(CRATE_DEF_ID.to_def_id()) - } - - /// Creates a forest containing a `DefId` and all its descendants. - pub fn from_id(id: DefId) -> DefIdForest<'tcx> { - DefIdForest::Single(id) - } - - fn as_slice(&self) -> &[DefId] { - match self { - Empty => &[], - Single(id) => std::slice::from_ref(id), - Multiple(root_ids) => root_ids, - } - } - - // Only allocates in the rare `Multiple` case. - fn from_vec(tcx: TyCtxt<'tcx>, root_ids: SmallVec<[DefId; 1]>) -> DefIdForest<'tcx> { - match &root_ids[..] { - [] => Empty, - [id] => Single(*id), - _ => DefIdForest::Multiple(tcx.arena.alloc_from_iter(root_ids)), - } - } - - /// Tests whether the forest is empty. - pub fn is_empty(&self) -> bool { - match self { - Empty => true, - Single(..) | Multiple(..) => false, - } - } - - /// Iterate over the set of roots. - fn iter(&self) -> impl Iterator<Item = DefId> + '_ { - self.as_slice().iter().copied() - } - - /// Tests whether the forest contains a given DefId. - pub fn contains(&self, tcx: TyCtxt<'tcx>, id: DefId) -> bool { - slice_contains(tcx, self.as_slice(), id) - } - - /// Calculate the intersection of a collection of forests. - pub fn intersection<I>(tcx: TyCtxt<'tcx>, iter: I) -> DefIdForest<'tcx> - where - I: IntoIterator<Item = DefIdForest<'tcx>>, - { - let mut iter = iter.into_iter(); - let mut ret: SmallVec<[_; 1]> = if let Some(first) = iter.next() { - SmallVec::from_slice(first.as_slice()) - } else { - return DefIdForest::full(); - }; - - let mut next_ret: SmallVec<[_; 1]> = SmallVec::new(); - for next_forest in iter { - // No need to continue if the intersection is already empty. - if ret.is_empty() || next_forest.is_empty() { - return DefIdForest::empty(); - } - - // We keep the elements in `ret` that are also in `next_forest`. - next_ret.extend(ret.iter().copied().filter(|&id| next_forest.contains(tcx, id))); - // We keep the elements in `next_forest` that are also in `ret`. - next_ret.extend(next_forest.iter().filter(|&id| slice_contains(tcx, &ret, id))); - - mem::swap(&mut next_ret, &mut ret); - next_ret.clear(); - } - DefIdForest::from_vec(tcx, ret) - } - - /// Calculate the union of a collection of forests. - pub fn union<I>(tcx: TyCtxt<'tcx>, iter: I) -> DefIdForest<'tcx> - where - I: IntoIterator<Item = DefIdForest<'tcx>>, - { - let mut ret: SmallVec<[_; 1]> = SmallVec::new(); - let mut next_ret: SmallVec<[_; 1]> = SmallVec::new(); - for next_forest in iter { - // Union with the empty set is a no-op. - if next_forest.is_empty() { - continue; - } - - // We add everything in `ret` that is not in `next_forest`. - next_ret.extend(ret.iter().copied().filter(|&id| !next_forest.contains(tcx, id))); - // We add everything in `next_forest` that we haven't added yet. - for id in next_forest.iter() { - if !slice_contains(tcx, &next_ret, id) { - next_ret.push(id); - } - } - - mem::swap(&mut next_ret, &mut ret); - next_ret.clear(); - } - DefIdForest::from_vec(tcx, ret) - } -} |