diff options
| -rw-r--r-- | src/librustc/ty/structural_impls.rs | 52 |
1 files changed, 35 insertions, 17 deletions
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs index 25f9dc5b0c7..c1ae4d9fe17 100644 --- a/src/librustc/ty/structural_impls.rs +++ b/src/librustc/ty/structural_impls.rs @@ -805,8 +805,7 @@ impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<T> { impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::ExistentialPredicate<'tcx>> { fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self { - let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>(); - folder.tcx().intern_existential_predicates(&v) + fold_list(*self, folder, |tcx, v| tcx.intern_existential_predicates(v)) } fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool { @@ -816,8 +815,7 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::ExistentialPredicate<'tcx>> impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> { fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self { - let v = self.iter().map(|t| t.fold_with(folder)).collect::<SmallVec<[_; 8]>>(); - folder.tcx().intern_type_list(&v) + fold_list(*self, folder, |tcx, v| tcx.intern_type_list(v)) } fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool { @@ -827,8 +825,7 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> { impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> { fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self { - let v = self.iter().map(|t| t.fold_with(folder)).collect::<SmallVec<[_; 8]>>(); - folder.tcx().intern_projs(&v) + fold_list(*self, folder, |tcx, v| tcx.intern_projs(v)) } fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool { @@ -992,17 +989,7 @@ impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> { impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> { fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self { - // This code is hot enough that it's worth specializing for a list of - // length 0. (No other length is common enough to be worth singling - // out). - if self.len() == 0 { - self - } else { - // Don't bother interning if nothing changed, which is the common - // case. - let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>(); - if v[..] == self[..] { self } else { folder.tcx().intern_predicates(&v) } - } + fold_list(*self, folder, |tcx, v| tcx.intern_predicates(v)) } fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool { @@ -1075,3 +1062,34 @@ impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> { false } } + +// Does the equivalent of +// ``` +// let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>(); +// folder.tcx().intern_*(&v) +// ``` +fn fold_list<'tcx, F, T>( + list: &'tcx ty::List<T>, + folder: &mut F, + intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>, +) -> &'tcx ty::List<T> +where + F: TypeFolder<'tcx>, + T: TypeFoldable<'tcx> + PartialEq + Copy, +{ + let mut iter = list.iter(); + // Look for the first element that changed + if let Some((i, new_t)) = iter.by_ref().enumerate().find_map(|(i, t)| { + let new_t = t.fold_with(folder); + if new_t == *t { None } else { Some((i, new_t)) } + }) { + // An element changed, prepare to intern the resulting list + let mut new_list = SmallVec::<[_; 8]>::with_capacity(list.len()); + new_list.extend_from_slice(&list[..i]); + new_list.push(new_t); + new_list.extend(iter.map(|t| t.fold_with(folder))); + intern(folder.tcx(), &new_list) + } else { + list + } +} |