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https://github.com/rust-lang/rust
synced 2024-10-19 06:54:02 +00:00
use abstract consts when unifying ConstKind::Unevaluated
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@ -263,6 +263,16 @@ fn describe_as_module(def_id: LocalDefId, tcx: TyCtxt<'_>) -> String {
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}
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}
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query try_unify_abstract_consts(key: (
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(ty::WithOptConstParam<DefId>, SubstsRef<'tcx>),
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(ty::WithOptConstParam<DefId>, SubstsRef<'tcx>)
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)) -> bool {
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desc {
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|tcx| "trying to unify the generic constants {} and {}",
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tcx.def_path_str(key.0.0.did), tcx.def_path_str(key.1.0.did)
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}
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}
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query mir_drops_elaborated_and_const_checked(
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key: ty::WithOptConstParam<LocalDefId>
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) -> &'tcx Steal<mir::Body<'tcx>> {
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@ -193,6 +193,22 @@ fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
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}
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}
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impl<'tcx> Key
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for (
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(ty::WithOptConstParam<DefId>, SubstsRef<'tcx>),
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(ty::WithOptConstParam<DefId>, SubstsRef<'tcx>),
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)
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{
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type CacheSelector = DefaultCacheSelector;
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fn query_crate(&self) -> CrateNum {
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(self.0).0.did.krate
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}
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fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
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(self.0).0.did.default_span(tcx)
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}
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}
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impl<'tcx> Key for (LocalDefId, DefId, SubstsRef<'tcx>) {
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type CacheSelector = DefaultCacheSelector;
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@ -576,7 +576,20 @@ pub fn super_relate_consts<R: TypeRelation<'tcx>>(
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new_val.map(ty::ConstKind::Value)
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}
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// FIXME(const_generics): this is wrong, as it is a projection
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(
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ty::ConstKind::Unevaluated(a_def, a_substs, None),
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ty::ConstKind::Unevaluated(b_def, b_substs, None),
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) if tcx.features().const_evaluatable_checked => {
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if tcx.try_unify_abstract_consts(((a_def, a_substs), (b_def, b_substs))) {
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Ok(a.val)
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} else {
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Err(TypeError::ConstMismatch(expected_found(relation, a, b)))
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}
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}
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// While this is slightly incorrect, it shouldn't matter for `min_const_generics`
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// and is the better alternative to waiting until `const_evaluatable_checked` can
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// be stabilized.
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(
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ty::ConstKind::Unevaluated(a_def, a_substs, a_promoted),
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ty::ConstKind::Unevaluated(b_def, b_substs, b_promoted),
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@ -269,7 +269,27 @@ pub(super) fn mir_abstract_const<'tcx>(
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}
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}
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pub fn try_unify<'tcx>(tcx: TyCtxt<'tcx>, a: AbstractConst<'tcx>, b: AbstractConst<'tcx>) -> bool {
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pub(super) fn try_unify_abstract_consts<'tcx>(
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tcx: TyCtxt<'tcx>,
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((a, a_substs), (b, b_substs)): (
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(ty::WithOptConstParam<DefId>, SubstsRef<'tcx>),
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(ty::WithOptConstParam<DefId>, SubstsRef<'tcx>),
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),
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) -> bool {
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if let Some(a) = AbstractConst::new(tcx, a, a_substs) {
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if let Some(b) = AbstractConst::new(tcx, b, b_substs) {
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return try_unify(tcx, a, b);
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}
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}
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false
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}
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pub(super) fn try_unify<'tcx>(
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tcx: TyCtxt<'tcx>,
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a: AbstractConst<'tcx>,
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b: AbstractConst<'tcx>,
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) -> bool {
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match (a.root(), b.root()) {
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(Node::Leaf(a_ct), Node::Leaf(b_ct)) => {
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let a_ct = a_ct.subst(tcx, a.substs);
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@ -476,6 +476,25 @@ fn process_obligation(
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ty::PredicateAtom::ConstEquate(c1, c2) => {
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debug!("equating consts: c1={:?} c2={:?}", c1, c2);
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if self.selcx.tcx().features().const_evaluatable_checked {
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// FIXME: we probably should only try to unify abstract constants
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// if the constants depend on generic parameters.
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//
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// Let's just see where this breaks :shrug:
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if let (
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ty::ConstKind::Unevaluated(a_def, a_substs, None),
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ty::ConstKind::Unevaluated(b_def, b_substs, None),
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) = (c1.val, c2.val)
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{
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if self
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.selcx
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.tcx()
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.try_unify_abstract_consts(((a_def, a_substs), (b_def, b_substs)))
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{
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return ProcessResult::Changed(vec![]);
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}
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}
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}
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let stalled_on = &mut pending_obligation.stalled_on;
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@ -566,6 +566,7 @@ pub fn provide(providers: &mut ty::query::Providers) {
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ty::WithOptConstParam { did, const_param_did: Some(param_did) },
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)
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},
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try_unify_abstract_consts: const_evaluatable::try_unify_abstract_consts,
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..*providers
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};
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}
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@ -1,10 +1,18 @@
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error: generic parameters must not be used inside of non trivial constant values
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--> $DIR/simple.rs:8:33
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--> $DIR/simple.rs:8:53
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LL | type Arr<const N: usize> = [u8; N - 1];
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| ^ non-trivial anonymous constants must not depend on the parameter `N`
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LL | fn test<const N: usize>() -> [u8; N - 1] where [u8; N - 1]: Default {
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| ^ non-trivial anonymous constants must not depend on the parameter `N`
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= help: it is currently only allowed to use either `N` or `{ N }` as generic constants
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error: aborting due to previous error
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error: generic parameters must not be used inside of non trivial constant values
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--> $DIR/simple.rs:8:35
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LL | fn test<const N: usize>() -> [u8; N - 1] where [u8; N - 1]: Default {
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| ^ non-trivial anonymous constants must not depend on the parameter `N`
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= help: it is currently only allowed to use either `N` or `{ N }` as generic constants
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error: aborting due to 2 previous errors
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@ -5,10 +5,9 @@
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#![feature(const_evaluatable_checked)]
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#![allow(incomplete_features)]
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type Arr<const N: usize> = [u8; N - 1];
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//[min]~^ ERROR generic parameters must not be used inside of non trivial constant values
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fn test<const N: usize>() -> Arr<N> where Arr<N>: Default {
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fn test<const N: usize>() -> [u8; N - 1] where [u8; N - 1]: Default {
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//[min]~^ ERROR generic parameters
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//[min]~| ERROR generic parameters
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Default::default()
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}
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