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review, small cleanup

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This commit is contained in:
Bastian Kauschke 2020-09-18 17:11:17 +02:00
parent 1b275d08ad
commit 09e6254496
1 changed files with 21 additions and 18 deletions
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39
compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
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@ -30,24 +30,24 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
span: Span,
) -> Result<(), ErrorHandled> {
debug!("is_const_evaluatable({:?}, {:?})", def, substs);
if infcx.tcx.features().const_evaluatable_checked {
if let Some(ct) = AbstractConst::new(infcx.tcx, def, substs) {
for pred in param_env.caller_bounds() {
match pred.skip_binders() {
ty::PredicateAtom::ConstEvaluatable(b_def, b_substs) => {
debug!("is_const_evaluatable: caller_bound={:?}, {:?}", b_def, b_substs);
if b_def == def && b_substs == substs {
debug!("is_const_evaluatable: caller_bound ~~> ok");
return Ok(());
} else if AbstractConst::new(infcx.tcx, b_def, b_substs)
.map_or(false, |b_ct| try_unify(infcx.tcx, ct, b_ct))
{
debug!("is_const_evaluatable: abstract_const ~~> ok");
return Ok(());
}
// `AbstractConst::new` already returns `None` if `const_evaluatable_checked`
// is not active, so we don't have to explicitly check for this here.
if let Some(ct) = AbstractConst::new(infcx.tcx, def, substs) {
for pred in param_env.caller_bounds() {
match pred.skip_binders() {
ty::PredicateAtom::ConstEvaluatable(b_def, b_substs) => {
debug!("is_const_evaluatable: caller_bound={:?}, {:?}", b_def, b_substs);
if b_def == def && b_substs == substs {
debug!("is_const_evaluatable: caller_bound ~~> ok");
return Ok(());
} else if AbstractConst::new(infcx.tcx, b_def, b_substs)
.map_or(false, |b_ct| try_unify(infcx.tcx, ct, b_ct))
{
debug!("is_const_evaluatable: abstract_const ~~> ok");
return Ok(());
}
_ => {} // don't care
}
_ => {} // don't care
}
}
}
@ -394,14 +394,17 @@ pub(super) fn try_unify<'tcx>(
let a_ct = a_ct.subst(tcx, a.substs);
let b_ct = b_ct.subst(tcx, b.substs);
match (a_ct.val, b_ct.val) {
// We can just unify errors with everything to reduce the amount of
// emitted errors here.
(ty::ConstKind::Error(_), _) | (_, ty::ConstKind::Error(_)) => true,
(ty::ConstKind::Param(a_param), ty::ConstKind::Param(b_param)) => {
a_param == b_param
}
(ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => a_val == b_val,
// If we have `fn a<const N: usize>() -> [u8; N + 1]` and `fn b<const M: usize>() -> [u8; 1 + M]`
// we do not want to use `assert_eq!(a(), b())` to infer that `N` and `M` have to be `1`. This
// means that we can't do anything with inference variables here.
(ty::ConstKind::Infer(_), _) | (_, ty::ConstKind::Infer(_)) => false,
// means that we only allow inference variables if they are equal.
(ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val,
// FIXME(const_evaluatable_checked): We may want to either actually try
// to evaluate `a_ct` and `b_ct` if they are are fully concrete or something like
// this, for now we just return false here.