Introduce InhabitedPredicate
This commit is contained in:
Cameron Steffen
parent
0940040c04
commit
2928e9ef2c
8 changed files with 338 additions and 354 deletions
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@ -2467,42 +2467,6 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
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None
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}
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/// Determines whether the given type is inhabited. `None` means that we don't know.
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fn ty_inhabited<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<bool> {
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use rustc_type_ir::sty::TyKind::*;
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if !cx.tcx.type_uninhabited_from(cx.param_env.and(ty)).is_empty() {
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// This is definitely uninhabited from some module.
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return Some(false);
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}
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match ty.kind() {
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Never => Some(false),
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Int(_) | Uint(_) | Float(_) | Bool | Char | RawPtr(_) => Some(true),
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// Fallback for more complicated types. (Note that `&!` might be considered
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// uninhabited so references are "complicated", too.)
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_ => None,
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}
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}
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/// Determines whether a product type formed from a list of types is inhabited.
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fn tys_inhabited<'tcx>(
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cx: &LateContext<'tcx>,
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tys: impl Iterator<Item = Ty<'tcx>>,
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) -> Option<bool> {
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let mut definitely_inhabited = true; // with no fields, we are definitely inhabited.
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for ty in tys {
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match ty_inhabited(cx, ty) {
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// If any type is uninhabited, the product is uninhabited.
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Some(false) => return Some(false),
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// Otherwise go searching for a `None`.
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None => {
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// We don't know.
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definitely_inhabited = false;
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}
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Some(true) => {}
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}
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}
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if definitely_inhabited { Some(true) } else { None }
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}
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fn variant_find_init_error<'tcx>(
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cx: &LateContext<'tcx>,
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variant: &VariantDef,
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@ -2599,11 +2563,11 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
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// And now, enums.
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let span = cx.tcx.def_span(adt_def.did());
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let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
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let inhabited = tys_inhabited(
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cx,
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variant.fields.iter().map(|field| field.ty(cx.tcx, substs)),
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);
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let definitely_inhabited = match inhabited {
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let definitely_inhabited = match variant
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.inhabited_predicate(cx.tcx, *adt_def)
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.subst(cx.tcx, substs)
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.apply_any_module(cx.tcx, cx.param_env)
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{
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// Entirely skip uninhbaited variants.
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Some(false) => return None,
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// Forward the others, but remember which ones are definitely inhabited.
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@ -1653,14 +1653,13 @@ rustc_queries! {
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separate_provide_extern
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}
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/// Computes the set of modules from which this type is visibly uninhabited.
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/// To check whether a type is uninhabited at all (not just from a given module), you could
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/// check whether the forest is empty.
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query type_uninhabited_from(
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key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>
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) -> ty::inhabitedness::DefIdForest<'tcx> {
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desc { "computing the inhabitedness of `{}`", key.value }
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remap_env_constness
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query inhabited_predicate_adt(key: DefId) -> ty::inhabitedness::InhabitedPredicate<'tcx> {
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desc { "computing the uninhabited predicate of `{:?}`", key }
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}
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/// Do not call this query directly: invoke `Ty::inhabited_predicate` instead.
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query inhabited_predicate_type(key: Ty<'tcx>) -> ty::inhabitedness::InhabitedPredicate<'tcx> {
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desc { "computing the uninhabited predicate of `{}`", key }
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}
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query dep_kind(_: CrateNum) -> CrateDepKind {
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@ -1,145 +0,0 @@
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use crate::ty::context::TyCtxt;
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use crate::ty::{DefId, DefIdTree};
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use rustc_span::def_id::CRATE_DEF_ID;
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use smallvec::SmallVec;
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use std::mem;
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use DefIdForest::*;
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/// Represents a forest of `DefId`s closed under the ancestor relation. That is,
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/// if a `DefId` representing a module is contained in the forest then all
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/// `DefId`s defined in that module or submodules are also implicitly contained
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/// in the forest.
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///
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/// This is used to represent a set of modules in which a type is visibly
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/// uninhabited.
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///
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/// We store the minimal set of `DefId`s required to represent the whole set. If A and B are
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/// `DefId`s in the `DefIdForest`, and A is a parent of B, then only A will be stored. When this is
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/// used with `type_uninhabited_from`, there will very rarely be more than one `DefId` stored.
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#[derive(Copy, Clone, HashStable, Debug)]
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pub enum DefIdForest<'a> {
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Empty,
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Single(DefId),
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/// This variant is very rare.
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/// Invariant: >1 elements
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Multiple(&'a [DefId]),
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}
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/// Tests whether a slice of roots contains a given DefId.
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#[inline]
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fn slice_contains<'tcx>(tcx: TyCtxt<'tcx>, slice: &[DefId], id: DefId) -> bool {
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slice.iter().any(|root_id| tcx.is_descendant_of(id, *root_id))
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}
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impl<'tcx> DefIdForest<'tcx> {
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/// Creates an empty forest.
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pub fn empty() -> DefIdForest<'tcx> {
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DefIdForest::Empty
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}
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/// Creates a forest consisting of a single tree representing the entire
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/// crate.
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#[inline]
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pub fn full() -> DefIdForest<'tcx> {
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DefIdForest::from_id(CRATE_DEF_ID.to_def_id())
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}
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/// Creates a forest containing a `DefId` and all its descendants.
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pub fn from_id(id: DefId) -> DefIdForest<'tcx> {
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DefIdForest::Single(id)
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}
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fn as_slice(&self) -> &[DefId] {
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match self {
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Empty => &[],
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Single(id) => std::slice::from_ref(id),
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Multiple(root_ids) => root_ids,
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}
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}
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// Only allocates in the rare `Multiple` case.
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fn from_vec(tcx: TyCtxt<'tcx>, root_ids: SmallVec<[DefId; 1]>) -> DefIdForest<'tcx> {
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match &root_ids[..] {
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[] => Empty,
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[id] => Single(*id),
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_ => DefIdForest::Multiple(tcx.arena.alloc_from_iter(root_ids)),
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}
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}
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/// Tests whether the forest is empty.
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pub fn is_empty(&self) -> bool {
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match self {
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Empty => true,
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Single(..) | Multiple(..) => false,
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}
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}
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/// Iterate over the set of roots.
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fn iter(&self) -> impl Iterator<Item = DefId> + '_ {
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self.as_slice().iter().copied()
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}
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/// Tests whether the forest contains a given DefId.
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pub fn contains(&self, tcx: TyCtxt<'tcx>, id: DefId) -> bool {
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slice_contains(tcx, self.as_slice(), id)
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}
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/// Calculate the intersection of a collection of forests.
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pub fn intersection<I>(tcx: TyCtxt<'tcx>, iter: I) -> DefIdForest<'tcx>
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where
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I: IntoIterator<Item = DefIdForest<'tcx>>,
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{
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let mut iter = iter.into_iter();
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let mut ret: SmallVec<[_; 1]> = if let Some(first) = iter.next() {
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SmallVec::from_slice(first.as_slice())
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} else {
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return DefIdForest::full();
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};
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let mut next_ret: SmallVec<[_; 1]> = SmallVec::new();
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for next_forest in iter {
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// No need to continue if the intersection is already empty.
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if ret.is_empty() || next_forest.is_empty() {
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return DefIdForest::empty();
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}
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// We keep the elements in `ret` that are also in `next_forest`.
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next_ret.extend(ret.iter().copied().filter(|&id| next_forest.contains(tcx, id)));
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// We keep the elements in `next_forest` that are also in `ret`.
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next_ret.extend(next_forest.iter().filter(|&id| slice_contains(tcx, &ret, id)));
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mem::swap(&mut next_ret, &mut ret);
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next_ret.clear();
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}
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DefIdForest::from_vec(tcx, ret)
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}
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/// Calculate the union of a collection of forests.
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pub fn union<I>(tcx: TyCtxt<'tcx>, iter: I) -> DefIdForest<'tcx>
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where
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I: IntoIterator<Item = DefIdForest<'tcx>>,
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{
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let mut ret: SmallVec<[_; 1]> = SmallVec::new();
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let mut next_ret: SmallVec<[_; 1]> = SmallVec::new();
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for next_forest in iter {
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// Union with the empty set is a no-op.
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if next_forest.is_empty() {
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continue;
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}
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// We add everything in `ret` that is not in `next_forest`.
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next_ret.extend(ret.iter().copied().filter(|&id| !next_forest.contains(tcx, id)));
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// We add everything in `next_forest` that we haven't added yet.
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for id in next_forest.iter() {
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if !slice_contains(tcx, &next_ret, id) {
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next_ret.push(id);
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}
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}
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mem::swap(&mut next_ret, &mut ret);
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next_ret.clear();
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}
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DefIdForest::from_vec(tcx, ret)
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}
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}
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@ -0,0 +1,204 @@
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use crate::ty::context::TyCtxt;
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use crate::ty::{self, DefId, DefIdTree, ParamEnv, Ty};
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/// Represents whether some type is inhabited in a given context.
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/// Examples of uninhabited types are `!`, `enum Void {}`, or a struct
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/// containing either of those types.
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/// A type's inhabitedness may depend on the `ParamEnv` as well as what types
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/// are visible in the current module.
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#[derive(Clone, Copy, Debug, PartialEq, HashStable)]
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pub enum InhabitedPredicate<'tcx> {
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/// Inhabited
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True,
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/// Uninhabited
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False,
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/// Uninhabited when a const value is non-zero. This occurs when there is an
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/// array of uninhabited items, but the array is inhabited if it is empty.
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ConstIsZero(ty::Const<'tcx>),
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/// Uninhabited if within a certain module. This occurs when an uninhabited
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/// type has restricted visibility.
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NotInModule(DefId),
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/// Inhabited if some generic type is inhabited.
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/// These are replaced by calling [`Self::subst`].
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GenericType(Ty<'tcx>),
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/// A AND B
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And(&'tcx [InhabitedPredicate<'tcx>; 2]),
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/// A OR B
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Or(&'tcx [InhabitedPredicate<'tcx>; 2]),
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}
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impl<'tcx> InhabitedPredicate<'tcx> {
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/// Returns true if the corresponding type is inhabited in the given
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/// `ParamEnv` and module
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pub fn apply(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, module_def_id: DefId) -> bool {
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let Ok(result) = self
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.apply_inner::<!>(tcx, param_env, &|id| Ok(tcx.is_descendant_of(module_def_id, id)));
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result
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}
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/// Same as `apply`, but returns `None` if self contains a module predicate
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pub fn apply_any_module(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> {
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self.apply_inner(tcx, param_env, &|_| Err(())).ok()
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}
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fn apply_inner<E>(
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self,
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tcx: TyCtxt<'tcx>,
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param_env: ParamEnv<'tcx>,
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in_module: &impl Fn(DefId) -> Result<bool, E>,
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) -> Result<bool, E> {
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match self {
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Self::False => Ok(false),
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Self::True => Ok(true),
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Self::ConstIsZero(const_) => match const_.try_eval_usize(tcx, param_env) {
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None | Some(0) => Ok(true),
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Some(1..) => Ok(false),
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},
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Self::NotInModule(id) => in_module(id).map(|in_mod| !in_mod),
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Self::GenericType(_) => Ok(true),
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Self::And([a, b]) => try_and(a, b, |x| x.apply_inner(tcx, param_env, in_module)),
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Self::Or([a, b]) => try_or(a, b, |x| x.apply_inner(tcx, param_env, in_module)),
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}
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}
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pub fn and(self, tcx: TyCtxt<'tcx>, other: Self) -> Self {
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self.reduce_and(tcx, other).unwrap_or_else(|| Self::And(tcx.arena.alloc([self, other])))
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}
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pub fn or(self, tcx: TyCtxt<'tcx>, other: Self) -> Self {
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self.reduce_or(tcx, other).unwrap_or_else(|| Self::Or(tcx.arena.alloc([self, other])))
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}
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pub fn all(tcx: TyCtxt<'tcx>, iter: impl IntoIterator<Item = Self>) -> Self {
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let mut result = Self::True;
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for pred in iter {
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if matches!(pred, Self::False) {
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return Self::False;
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}
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result = result.and(tcx, pred);
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}
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result
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}
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pub fn any(tcx: TyCtxt<'tcx>, iter: impl IntoIterator<Item = Self>) -> Self {
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let mut result = Self::False;
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for pred in iter {
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if matches!(pred, Self::True) {
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return Self::True;
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}
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result = result.or(tcx, pred);
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}
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result
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}
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fn reduce_and(self, tcx: TyCtxt<'tcx>, other: Self) -> Option<Self> {
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match (self, other) {
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(Self::True, a) | (a, Self::True) => Some(a),
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(Self::False, _) | (_, Self::False) => Some(Self::False),
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(Self::ConstIsZero(a), Self::ConstIsZero(b)) if a == b => Some(Self::ConstIsZero(a)),
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(Self::NotInModule(a), Self::NotInModule(b)) if a == b => Some(Self::NotInModule(a)),
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(Self::NotInModule(a), Self::NotInModule(b)) if tcx.is_descendant_of(a, b) => {
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Some(Self::NotInModule(b))
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}
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(Self::NotInModule(a), Self::NotInModule(b)) if tcx.is_descendant_of(b, a) => {
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Some(Self::NotInModule(a))
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}
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(Self::GenericType(a), Self::GenericType(b)) if a == b => Some(Self::GenericType(a)),
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(Self::And(&[a, b]), c) | (c, Self::And(&[a, b])) => {
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if let Some(ac) = a.reduce_and(tcx, c) {
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Some(ac.and(tcx, b))
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} else if let Some(bc) = b.reduce_and(tcx, c) {
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Some(Self::And(tcx.arena.alloc([a, bc])))
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} else {
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None
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}
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}
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_ => None,
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}
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}
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fn reduce_or(self, tcx: TyCtxt<'tcx>, other: Self) -> Option<Self> {
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match (self, other) {
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(Self::True, _) | (_, Self::True) => Some(Self::True),
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(Self::False, a) | (a, Self::False) => Some(a),
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(Self::ConstIsZero(a), Self::ConstIsZero(b)) if a == b => Some(Self::ConstIsZero(a)),
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(Self::NotInModule(a), Self::NotInModule(b)) if a == b => Some(Self::NotInModule(a)),
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(Self::NotInModule(a), Self::NotInModule(b)) if tcx.is_descendant_of(a, b) => {
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Some(Self::NotInModule(a))
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}
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(Self::NotInModule(a), Self::NotInModule(b)) if tcx.is_descendant_of(b, a) => {
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Some(Self::NotInModule(b))
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}
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(Self::GenericType(a), Self::GenericType(b)) if a == b => Some(Self::GenericType(a)),
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(Self::Or(&[a, b]), c) | (c, Self::Or(&[a, b])) => {
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if let Some(ac) = a.reduce_or(tcx, c) {
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Some(ac.or(tcx, b))
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} else if let Some(bc) = b.reduce_or(tcx, c) {
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Some(Self::Or(tcx.arena.alloc([a, bc])))
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} else {
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None
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}
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}
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_ => None,
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}
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}
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/// Replaces generic types with its corresponding predicate
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pub fn subst(self, tcx: TyCtxt<'tcx>, substs: ty::SubstsRef<'tcx>) -> Self {
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self.subst_opt(tcx, substs).unwrap_or(self)
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}
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fn subst_opt(self, tcx: TyCtxt<'tcx>, substs: ty::SubstsRef<'tcx>) -> Option<Self> {
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match self {
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Self::ConstIsZero(c) => {
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let c = ty::EarlyBinder(c).subst(tcx, substs);
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let pred = match c.kind().try_to_machine_usize(tcx) {
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Some(0) => Self::True,
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Some(1..) => Self::False,
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None => Self::ConstIsZero(c),
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};
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Some(pred)
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}
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Self::GenericType(t) => {
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Some(ty::EarlyBinder(t).subst(tcx, substs).inhabited_predicate(tcx))
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}
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Self::And(&[a, b]) => match a.subst_opt(tcx, substs) {
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None => b.subst_opt(tcx, substs).map(|b| a.and(tcx, b)),
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Some(InhabitedPredicate::False) => Some(InhabitedPredicate::False),
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Some(a) => Some(a.and(tcx, b.subst_opt(tcx, substs).unwrap_or(b))),
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},
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Self::Or(&[a, b]) => match a.subst_opt(tcx, substs) {
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None => b.subst_opt(tcx, substs).map(|b| a.or(tcx, b)),
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Some(InhabitedPredicate::True) => Some(InhabitedPredicate::True),
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||||
Some(a) => Some(a.or(tcx, b.subst_opt(tcx, substs).unwrap_or(b))),
|
||||
},
|
||||
_ => None,
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// this is basically like `f(a)? && f(b)?` but different in the case of
|
||||
// `Ok(false) && Err(_) -> Ok(false)`
|
||||
fn try_and<T, E>(a: T, b: T, f: impl Fn(T) -> Result<bool, E>) -> Result<bool, E> {
|
||||
let a = f(a);
|
||||
if matches!(a, Ok(false)) {
|
||||
return Ok(false);
|
||||
}
|
||||
match (a, f(b)) {
|
||||
(_, Ok(false)) | (Ok(false), _) => Ok(false),
|
||||
(Ok(true), Ok(true)) => Ok(true),
|
||||
(Err(e), _) | (_, Err(e)) => Err(e),
|
||||
}
|
||||
}
|
||||
|
||||
fn try_or<T, E>(a: T, b: T, f: impl Fn(T) -> Result<bool, E>) -> Result<bool, E> {
|
||||
let a = f(a);
|
||||
if matches!(a, Ok(true)) {
|
||||
return Ok(true);
|
||||
}
|
||||
match (a, f(b)) {
|
||||
(_, Ok(true)) | (Ok(true), _) => Ok(true),
|
||||
(Ok(false), Ok(false)) => Ok(false),
|
||||
(Err(e), _) | (_, Err(e)) => Err(e),
|
||||
}
|
||||
}
|
||||
|
|
@ -1,57 +1,60 @@
|
|||
pub use self::def_id_forest::DefIdForest;
|
||||
//! This module contains logic for determining whether a type is inhabited or
|
||||
//! uninhabited. The [`InhabitedPredicate`] type captures the minimum
|
||||
//! information needed to determine whether a type is inhabited given a
|
||||
//! `ParamEnv` and module ID.
|
||||
//!
|
||||
//! # Example
|
||||
//! ```rust
|
||||
//! enum Void {}
|
||||
//! mod a {
|
||||
//! pub mod b {
|
||||
//! pub struct SecretlyUninhabited {
|
||||
//! _priv: !,
|
||||
//! }
|
||||
//! }
|
||||
//! }
|
||||
//!
|
||||
//! mod c {
|
||||
//! pub struct AlsoSecretlyUninhabited {
|
||||
//! _priv: Void,
|
||||
//! }
|
||||
//! mod d {
|
||||
//! }
|
||||
//! }
|
||||
//!
|
||||
//! struct Foo {
|
||||
//! x: a::b::SecretlyUninhabited,
|
||||
//! y: c::AlsoSecretlyUninhabited,
|
||||
//! }
|
||||
//! ```
|
||||
//! In this code, the type `Foo` will only be visibly uninhabited inside the
|
||||
//! modules `b`, `c` and `d`. Calling `uninhabited_predicate` on `Foo` will
|
||||
//! return `NotInModule(b) AND NotInModule(c)`.
|
||||
//!
|
||||
//! We need this information for pattern-matching on `Foo` or types that contain
|
||||
//! `Foo`.
|
||||
//!
|
||||
//! # Example
|
||||
//! ```rust
|
||||
//! let foo_result: Result<T, Foo> = ... ;
|
||||
//! let Ok(t) = foo_result;
|
||||
//! ```
|
||||
//! This code should only compile in modules where the uninhabitedness of `Foo`
|
||||
//! is visible.
|
||||
|
||||
use crate::ty;
|
||||
use crate::ty::context::TyCtxt;
|
||||
use crate::ty::{AdtDef, FieldDef, Ty, VariantDef};
|
||||
use crate::ty::{AdtKind, Visibility};
|
||||
use crate::ty::{DefId, SubstsRef};
|
||||
use crate::ty::{self, DefId, Ty, VariantDef, Visibility};
|
||||
|
||||
use rustc_type_ir::sty::TyKind::*;
|
||||
|
||||
mod def_id_forest;
|
||||
pub mod inhabited_predicate;
|
||||
|
||||
// The methods in this module calculate `DefIdForest`s of modules in which an
|
||||
// `AdtDef`/`VariantDef`/`FieldDef` is visibly uninhabited.
|
||||
//
|
||||
// # Example
|
||||
// ```rust
|
||||
// enum Void {}
|
||||
// mod a {
|
||||
// pub mod b {
|
||||
// pub struct SecretlyUninhabited {
|
||||
// _priv: !,
|
||||
// }
|
||||
// }
|
||||
// }
|
||||
//
|
||||
// mod c {
|
||||
// pub struct AlsoSecretlyUninhabited {
|
||||
// _priv: Void,
|
||||
// }
|
||||
// mod d {
|
||||
// }
|
||||
// }
|
||||
//
|
||||
// struct Foo {
|
||||
// x: a::b::SecretlyUninhabited,
|
||||
// y: c::AlsoSecretlyUninhabited,
|
||||
// }
|
||||
// ```
|
||||
// In this code, the type `Foo` will only be visibly uninhabited inside the
|
||||
// modules `b`, `c` and `d`. Calling `uninhabited_from` on `Foo` or its `AdtDef` will
|
||||
// return the forest of modules {`b`, `c`->`d`} (represented in a `DefIdForest` by the
|
||||
// set {`b`, `c`}).
|
||||
//
|
||||
// We need this information for pattern-matching on `Foo` or types that contain
|
||||
// `Foo`.
|
||||
//
|
||||
// # Example
|
||||
// ```rust
|
||||
// let foo_result: Result<T, Foo> = ... ;
|
||||
// let Ok(t) = foo_result;
|
||||
// ```
|
||||
// This code should only compile in modules where the uninhabitedness of `Foo` is
|
||||
// visible.
|
||||
pub use inhabited_predicate::InhabitedPredicate;
|
||||
|
||||
pub(crate) fn provide(providers: &mut ty::query::Providers) {
|
||||
*providers =
|
||||
ty::query::Providers { inhabited_predicate_adt, inhabited_predicate_type, ..*providers };
|
||||
}
|
||||
|
||||
impl<'tcx> TyCtxt<'tcx> {
|
||||
/// Checks whether a type is visibly uninhabited from a particular module.
|
||||
|
|
@ -100,131 +103,92 @@ impl<'tcx> TyCtxt<'tcx> {
|
|||
ty: Ty<'tcx>,
|
||||
param_env: ty::ParamEnv<'tcx>,
|
||||
) -> bool {
|
||||
// To check whether this type is uninhabited at all (not just from the
|
||||
// given node), you could check whether the forest is empty.
|
||||
// ```
|
||||
// forest.is_empty()
|
||||
// ```
|
||||
ty.uninhabited_from(self, param_env).contains(self, module)
|
||||
!ty.inhabited_predicate(self).apply(self, param_env, module)
|
||||
}
|
||||
}
|
||||
|
||||
impl<'tcx> AdtDef<'tcx> {
|
||||
/// Calculates the forest of `DefId`s from which this ADT is visibly uninhabited.
|
||||
fn uninhabited_from(
|
||||
self,
|
||||
tcx: TyCtxt<'tcx>,
|
||||
substs: SubstsRef<'tcx>,
|
||||
param_env: ty::ParamEnv<'tcx>,
|
||||
) -> DefIdForest<'tcx> {
|
||||
// Non-exhaustive ADTs from other crates are always considered inhabited.
|
||||
if self.is_variant_list_non_exhaustive() && !self.did().is_local() {
|
||||
DefIdForest::empty()
|
||||
} else {
|
||||
DefIdForest::intersection(
|
||||
tcx,
|
||||
self.variants()
|
||||
.iter()
|
||||
.map(|v| v.uninhabited_from(tcx, substs, self.adt_kind(), param_env)),
|
||||
)
|
||||
/// Returns an `InhabitedPredicate` that is generic over type parameters and
|
||||
/// requires calling [`InhabitedPredicate::subst`]
|
||||
fn inhabited_predicate_adt(tcx: TyCtxt<'_>, def_id: DefId) -> InhabitedPredicate<'_> {
|
||||
if let Some(def_id) = def_id.as_local() {
|
||||
if matches!(tcx.representability(def_id), ty::Representability::Infinite) {
|
||||
return InhabitedPredicate::True;
|
||||
}
|
||||
}
|
||||
let adt = tcx.adt_def(def_id);
|
||||
InhabitedPredicate::any(
|
||||
tcx,
|
||||
adt.variants().iter().map(|variant| variant.inhabited_predicate(tcx, adt)),
|
||||
)
|
||||
}
|
||||
|
||||
impl<'tcx> VariantDef {
|
||||
/// Calculates the forest of `DefId`s from which this variant is visibly uninhabited.
|
||||
pub fn uninhabited_from(
|
||||
pub fn inhabited_predicate(
|
||||
&self,
|
||||
tcx: TyCtxt<'tcx>,
|
||||
substs: SubstsRef<'tcx>,
|
||||
adt_kind: AdtKind,
|
||||
param_env: ty::ParamEnv<'tcx>,
|
||||
) -> DefIdForest<'tcx> {
|
||||
let is_enum = match adt_kind {
|
||||
// For now, `union`s are never considered uninhabited.
|
||||
// The precise semantics of inhabitedness with respect to unions is currently undecided.
|
||||
AdtKind::Union => return DefIdForest::empty(),
|
||||
AdtKind::Enum => true,
|
||||
AdtKind::Struct => false,
|
||||
};
|
||||
// Non-exhaustive variants from other crates are always considered inhabited.
|
||||
adt: ty::AdtDef<'_>,
|
||||
) -> InhabitedPredicate<'tcx> {
|
||||
debug_assert!(!adt.is_union());
|
||||
if self.is_field_list_non_exhaustive() && !self.def_id.is_local() {
|
||||
DefIdForest::empty()
|
||||
} else {
|
||||
DefIdForest::union(
|
||||
tcx,
|
||||
self.fields.iter().map(|f| f.uninhabited_from(tcx, substs, is_enum, param_env)),
|
||||
)
|
||||
// Non-exhaustive variants from other crates are always considered inhabited.
|
||||
return InhabitedPredicate::True;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl<'tcx> FieldDef {
|
||||
/// Calculates the forest of `DefId`s from which this field is visibly uninhabited.
|
||||
fn uninhabited_from(
|
||||
&self,
|
||||
tcx: TyCtxt<'tcx>,
|
||||
substs: SubstsRef<'tcx>,
|
||||
is_enum: bool,
|
||||
param_env: ty::ParamEnv<'tcx>,
|
||||
) -> DefIdForest<'tcx> {
|
||||
let data_uninhabitedness = move || self.ty(tcx, substs).uninhabited_from(tcx, param_env);
|
||||
if is_enum {
|
||||
data_uninhabitedness()
|
||||
} else {
|
||||
match self.vis {
|
||||
Visibility::Restricted(from) => {
|
||||
let forest = DefIdForest::from_id(from);
|
||||
let iter = Some(forest).into_iter().chain(Some(data_uninhabitedness()));
|
||||
DefIdForest::intersection(tcx, iter)
|
||||
InhabitedPredicate::all(
|
||||
tcx,
|
||||
self.fields.iter().map(|field| {
|
||||
let pred = tcx.type_of(field.did).inhabited_predicate(tcx);
|
||||
if adt.is_enum() {
|
||||
return pred;
|
||||
}
|
||||
Visibility::Public => data_uninhabitedness(),
|
||||
}
|
||||
}
|
||||
match field.vis {
|
||||
Visibility::Public => pred,
|
||||
Visibility::Restricted(from) => {
|
||||
pred.or(tcx, InhabitedPredicate::NotInModule(from))
|
||||
}
|
||||
}
|
||||
}),
|
||||
)
|
||||
}
|
||||
}
|
||||
|
||||
impl<'tcx> Ty<'tcx> {
|
||||
/// Calculates the forest of `DefId`s from which this type is visibly uninhabited.
|
||||
fn uninhabited_from(
|
||||
self,
|
||||
tcx: TyCtxt<'tcx>,
|
||||
param_env: ty::ParamEnv<'tcx>,
|
||||
) -> DefIdForest<'tcx> {
|
||||
tcx.type_uninhabited_from(param_env.and(self))
|
||||
pub fn inhabited_predicate(self, tcx: TyCtxt<'tcx>) -> InhabitedPredicate<'tcx> {
|
||||
match self.kind() {
|
||||
// For now, union`s are always considered inhabited
|
||||
Adt(adt, _) if adt.is_union() => InhabitedPredicate::True,
|
||||
// Non-exhaustive ADTs from other crates are always considered inhabited
|
||||
Adt(adt, _) if adt.is_variant_list_non_exhaustive() && !adt.did().is_local() => {
|
||||
InhabitedPredicate::True
|
||||
}
|
||||
Never => InhabitedPredicate::False,
|
||||
Param(_) | Projection(_) => InhabitedPredicate::GenericType(self),
|
||||
Tuple(tys) if tys.is_empty() => InhabitedPredicate::True,
|
||||
// use a query for more complex cases
|
||||
Adt(..) | Array(..) | Tuple(_) => tcx.inhabited_predicate_type(self),
|
||||
// references and other types are inhabited
|
||||
_ => InhabitedPredicate::True,
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Query provider for `type_uninhabited_from`.
|
||||
pub(crate) fn type_uninhabited_from<'tcx>(
|
||||
tcx: TyCtxt<'tcx>,
|
||||
key: ty::ParamEnvAnd<'tcx, Ty<'tcx>>,
|
||||
) -> DefIdForest<'tcx> {
|
||||
let ty = key.value;
|
||||
let param_env = key.param_env;
|
||||
/// N.B. this query should only be called through `Ty::inhabited_predicate`
|
||||
fn inhabited_predicate_type<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> InhabitedPredicate<'tcx> {
|
||||
match *ty.kind() {
|
||||
Adt(def, substs) => def.uninhabited_from(tcx, substs, param_env),
|
||||
Adt(adt, substs) => tcx.inhabited_predicate_adt(adt.did()).subst(tcx, substs),
|
||||
|
||||
Never => DefIdForest::full(),
|
||||
|
||||
Tuple(ref tys) => {
|
||||
DefIdForest::union(tcx, tys.iter().map(|ty| ty.uninhabited_from(tcx, param_env)))
|
||||
Tuple(tys) => {
|
||||
InhabitedPredicate::all(tcx, tys.iter().map(|ty| ty.inhabited_predicate(tcx)))
|
||||
}
|
||||
|
||||
Array(ty, len) => match len.try_eval_usize(tcx, param_env) {
|
||||
Some(0) | None => DefIdForest::empty(),
|
||||
// If the array is definitely non-empty, it's uninhabited if
|
||||
// the type of its elements is uninhabited.
|
||||
Some(1..) => ty.uninhabited_from(tcx, param_env),
|
||||
// If we can evaluate the array length before having a `ParamEnv`, then
|
||||
// we can simplify the predicate. This is an optimization.
|
||||
Array(ty, len) => match len.kind().try_to_machine_usize(tcx) {
|
||||
Some(0) => InhabitedPredicate::True,
|
||||
Some(1..) => ty.inhabited_predicate(tcx),
|
||||
None => ty.inhabited_predicate(tcx).or(tcx, InhabitedPredicate::ConstIsZero(len)),
|
||||
},
|
||||
|
||||
// References to uninitialised memory are valid for any type, including
|
||||
// uninhabited types, in unsafe code, so we treat all references as
|
||||
// inhabited.
|
||||
// The precise semantics of inhabitedness with respect to references is currently
|
||||
// undecided.
|
||||
Ref(..) => DefIdForest::empty(),
|
||||
|
||||
_ => DefIdForest::empty(),
|
||||
_ => bug!("unexpected TyKind, use `Ty::inhabited_predicate`"),
|
||||
}
|
||||
}
|
||||
|
|
|
|||
|
|
@ -2694,6 +2694,7 @@ pub fn provide(providers: &mut ty::query::Providers) {
|
|||
closure::provide(providers);
|
||||
context::provide(providers);
|
||||
erase_regions::provide(providers);
|
||||
inhabitedness::provide(providers);
|
||||
util::provide(providers);
|
||||
print::provide(providers);
|
||||
super::util::bug::provide(providers);
|
||||
|
|
@ -2701,7 +2702,6 @@ pub fn provide(providers: &mut ty::query::Providers) {
|
|||
*providers = ty::query::Providers {
|
||||
trait_impls_of: trait_def::trait_impls_of_provider,
|
||||
incoherent_impls: trait_def::incoherent_impls_provider,
|
||||
type_uninhabited_from: inhabitedness::type_uninhabited_from,
|
||||
const_param_default: consts::const_param_default,
|
||||
vtable_allocation: vtable::vtable_allocation_provider,
|
||||
..*providers
|
||||
|
|
|
|||
|
|
@ -264,14 +264,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
|
|||
let irrefutable = adt_def.variants().iter_enumerated().all(|(i, v)| {
|
||||
i == variant_index || {
|
||||
self.tcx.features().exhaustive_patterns
|
||||
&& !v
|
||||
.uninhabited_from(
|
||||
self.tcx,
|
||||
substs,
|
||||
adt_def.adt_kind(),
|
||||
self.param_env,
|
||||
)
|
||||
.is_empty()
|
||||
&& v.inhabited_predicate(self.tcx, adt_def)
|
||||
.subst(self.tcx, substs)
|
||||
.apply_any_module(self.tcx, self.param_env)
|
||||
!= Some(true)
|
||||
}
|
||||
}) && (adt_def.did().is_local()
|
||||
|| !adt_def.is_variant_list_non_exhaustive());
|
||||
|
|
|
|||
|
|
@ -988,10 +988,12 @@ impl<'tcx> SplitWildcard<'tcx> {
|
|||
.filter(|(_, v)| {
|
||||
// If `exhaustive_patterns` is enabled, we exclude variants known to be
|
||||
// uninhabited.
|
||||
let is_uninhabited = is_exhaustive_pat_feature
|
||||
&& v.uninhabited_from(cx.tcx, substs, def.adt_kind(), cx.param_env)
|
||||
.contains(cx.tcx, cx.module);
|
||||
!is_uninhabited
|
||||
!is_exhaustive_pat_feature
|
||||
|| v.inhabited_predicate(cx.tcx, *def).subst(cx.tcx, substs).apply(
|
||||
cx.tcx,
|
||||
cx.param_env,
|
||||
cx.module,
|
||||
)
|
||||
})
|
||||
.map(|(idx, _)| Variant(idx))
|
||||
.collect();
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue