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remove unnecessary sized checks

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This commit is contained in:
Lukas Markeffsky 2024-03-13 23:35:24 +01:00
parent 8ad94111ad
commit 8fe99f57a4
4 changed files with 15 additions and 11 deletions
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8
compiler/rustc_const_eval/src/interpret/eval_context.rs
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@ -1034,8 +1034,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
) -> InterpResult<'tcx> {
trace!("{:?} is now live", local);
// We avoid `ty.is_trivially_sized` since that (a) cannot assume WF, so it recurses through
// all fields of a tuple, and (b) does something expensive for ADTs.
// We avoid `ty.is_trivially_sized` since that does something expensive for ADTs.
fn is_very_trivially_sized(ty: Ty<'_>) -> bool {
match ty.kind() {
ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
@ -1054,9 +1053,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Never
| ty::Error(_) => true,
| ty::Error(_)
| ty::Dynamic(_, _, ty::DynStar) => true,
ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
ty::Str | ty::Slice(_) | ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => false,
ty::Tuple(tys) => tys.last().iter().all(|ty| is_very_trivially_sized(**ty)),

11
compiler/rustc_middle/src/ty/sty.rs
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@ -2484,13 +2484,16 @@ impl<'tcx> Ty<'tcx> {
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Never
| ty::Error(_) => true,
| ty::Error(_)
| ty::Dynamic(_, _, ty::DynStar) => true,
ty::Str | ty::Slice(_) | ty::Dynamic(..) | ty::Foreign(..) => false,
ty::Str | ty::Slice(_) | ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => false,
ty::Tuple(tys) => tys.iter().all(|ty| ty.is_trivially_sized(tcx)),
ty::Tuple(tys) => tys.last().map_or(true, |ty| ty.is_trivially_sized(tcx)),
ty::Adt(def, _args) => def.sized_constraint(tcx).is_none(),
ty::Adt(def, args) => def
.sized_constraint(tcx)
.map_or(true, |ty| ty.instantiate(tcx, args).is_trivially_sized(tcx)),
ty::Alias(..) | ty::Param(_) | ty::Placeholder(..) | ty::Bound(..) => false,

2
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
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@ -128,7 +128,7 @@ pub(super) trait GoalKind<'tcx>:
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
/// A type is `Copy` or `Clone` if its components are `Sized`.
/// A type is `Sized` if its tail component is `Sized`.
///
/// These components are given by built-in rules from
/// [`structural_traits::instantiate_constituent_tys_for_sized_trait`].

5
compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
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@ -154,8 +154,9 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>(
bug!("unexpected type `{ty}`")
}
// impl Sized for (T1, T2, .., Tn) where T1: Sized, T2: Sized, .. Tn: Sized
ty::Tuple(tys) => Ok(tys.iter().map(ty::Binder::dummy).collect()),
// impl Sized for ()
// impl Sized for (T1, T2, .., Tn) where Tn: Sized if n >= 1
ty::Tuple(tys) => Ok(tys.last().map_or_else(Vec::new, |&ty| vec![ty::Binder::dummy(ty)])),
// impl Sized for Adt<Args...> where sized_constraint(Adt)<Args...>: Sized
// `sized_constraint(Adt)` is the deepest struct trail that can be determined