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fix previous failures and address review

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This commit is contained in:
b-naber 2022-03-22 10:38:46 +01:00
parent 6cf3409e16
commit 8ff1edbe5e
9 changed files with 212 additions and 174 deletions
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222
compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
View file

@ -569,6 +569,18 @@ pub(super) fn thir_abstract_const<'tcx>(
}
}
/// Tries to unify two abstract constants using structural equality.
#[instrument(skip(tcx), level = "debug")]
pub(super) fn try_unify<'tcx>(
tcx: TyCtxt<'tcx>,
a: AbstractConst<'tcx>,
b: AbstractConst<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> bool {
let const_unify_ctxt = ConstUnifyCtxt::new(tcx, param_env);
const_unify_ctxt.try_unify_inner(a, b)
}
pub(super) fn try_unify_abstract_consts<'tcx>(
tcx: TyCtxt<'tcx>,
(a, b): (ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>),
@ -622,115 +634,119 @@ where
recurse(tcx, ct, &mut f)
}
// Substitutes generics repeatedly to allow AbstractConsts to unify where a
// ConstKind::Unevalated could be turned into an AbstractConst that would unify e.g.
// Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])]
#[inline]
#[instrument(skip(tcx), level = "debug")]
fn try_replace_substs_in_root<'tcx>(
pub(super) struct ConstUnifyCtxt<'tcx> {
tcx: TyCtxt<'tcx>,
mut abstr_const: AbstractConst<'tcx>,
) -> Option<AbstractConst<'tcx>> {
while let Node::Leaf(ct) = abstr_const.root(tcx) {
match AbstractConst::from_const(tcx, ct) {
Ok(Some(act)) => abstr_const = act,
Ok(None) => break,
Err(_) => return None,
}
}
Some(abstr_const)
}
/// Tries to unify two abstract constants using structural equality.
#[instrument(skip(tcx), level = "debug")]
pub(super) fn try_unify<'tcx>(
tcx: TyCtxt<'tcx>,
a: AbstractConst<'tcx>,
b: AbstractConst<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> bool {
let a = match try_replace_substs_in_root(tcx, a) {
Some(a) => a,
None => {
return true;
}
};
}
let b = match try_replace_substs_in_root(tcx, b) {
Some(b) => b,
None => {
return true;
}
};
impl<'tcx> ConstUnifyCtxt<'tcx> {
pub(super) fn new(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Self {
ConstUnifyCtxt { tcx, param_env }
}
let a_root = a.root(tcx);
let b_root = b.root(tcx);
debug!(?a_root, ?b_root);
match (a_root, b_root) {
(Node::Leaf(a_ct), Node::Leaf(b_ct)) => {
let a_ct = a_ct.eval(tcx, param_env);
debug!("a_ct evaluated: {:?}", a_ct);
let b_ct = b_ct.eval(tcx, param_env);
debug!("b_ct evaluated: {:?}", b_ct);
if a_ct.ty() != b_ct.ty() {
return false;
}
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 only allow inference variables if they are equal.
(ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val,
// We expand generic anonymous constants at the start of this function, so this
// branch should only be taking when dealing with associated constants, at
// which point directly comparing them seems like the desired behavior.
//
// FIXME(generic_const_exprs): This isn't actually the case.
// We also take this branch for concrete anonymous constants and
// expand generic anonymous constants with concrete substs.
(ty::ConstKind::Unevaluated(a_uv), ty::ConstKind::Unevaluated(b_uv)) => {
a_uv == b_uv
}
// FIXME(generic_const_exprs): 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.
_ => false,
// Substitutes generics repeatedly to allow AbstractConsts to unify where a
// ConstKind::Unevalated could be turned into an AbstractConst that would unify e.g.
// Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])]
#[inline]
#[instrument(skip(self), level = "debug")]
pub(super) fn try_replace_substs_in_root(
&self,
mut abstr_const: AbstractConst<'tcx>,
) -> Option<AbstractConst<'tcx>> {
while let Node::Leaf(ct) = abstr_const.root(self.tcx) {
match AbstractConst::from_const(self.tcx, ct) {
Ok(Some(act)) => abstr_const = act,
Ok(None) => break,
Err(_) => return None,
}
}
(Node::Binop(a_op, al, ar), Node::Binop(b_op, bl, br)) if a_op == b_op => {
try_unify(tcx, a.subtree(al), b.subtree(bl), param_env)
&& try_unify(tcx, a.subtree(ar), b.subtree(br), param_env)
Some(abstr_const)
}
/// Tries to unify two abstract constants using structural equality.
#[instrument(skip(self), level = "debug")]
fn try_unify_inner(&self, a: AbstractConst<'tcx>, b: AbstractConst<'tcx>) -> bool {
let a = if let Some(a) = self.try_replace_substs_in_root(a) {
a
} else {
return true;
};
let b = if let Some(b) = self.try_replace_substs_in_root(b) {
b
} else {
return true;
};
let a_root = a.root(self.tcx);
let b_root = b.root(self.tcx);
debug!(?a_root, ?b_root);
match (a_root, b_root) {
(Node::Leaf(a_ct), Node::Leaf(b_ct)) => {
let a_ct = a_ct.eval(self.tcx, self.param_env);
debug!("a_ct evaluated: {:?}", a_ct);
let b_ct = b_ct.eval(self.tcx, self.param_env);
debug!("b_ct evaluated: {:?}", b_ct);
if a_ct.ty() != b_ct.ty() {
return false;
}
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 only allow inference variables if they are equal.
(ty::ConstKind::Infer(a_val), ty::ConstKind::Infer(b_val)) => a_val == b_val,
// We expand generic anonymous constants at the start of this function, so this
// branch should only be taking when dealing with associated constants, at
// which point directly comparing them seems like the desired behavior.
//
// FIXME(generic_const_exprs): This isn't actually the case.
// We also take this branch for concrete anonymous constants and
// expand generic anonymous constants with concrete substs.
(ty::ConstKind::Unevaluated(a_uv), ty::ConstKind::Unevaluated(b_uv)) => {
a_uv == b_uv
}
// FIXME(generic_const_exprs): 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.
_ => false,
}
}
(Node::Binop(a_op, al, ar), Node::Binop(b_op, bl, br)) if a_op == b_op => {
self.try_unify_inner(a.subtree(al), b.subtree(bl))
&& self.try_unify_inner(a.subtree(ar), b.subtree(br))
}
(Node::UnaryOp(a_op, av), Node::UnaryOp(b_op, bv)) if a_op == b_op => {
self.try_unify_inner(a.subtree(av), b.subtree(bv))
}
(Node::FunctionCall(a_f, a_args), Node::FunctionCall(b_f, b_args))
if a_args.len() == b_args.len() =>
{
self.try_unify_inner(a.subtree(a_f), b.subtree(b_f))
&& iter::zip(a_args, b_args)
.all(|(&an, &bn)| self.try_unify_inner(a.subtree(an), b.subtree(bn)))
}
(Node::Cast(a_kind, a_operand, a_ty), Node::Cast(b_kind, b_operand, b_ty))
if (a_ty == b_ty) && (a_kind == b_kind) =>
{
self.try_unify_inner(a.subtree(a_operand), b.subtree(b_operand))
}
// use this over `_ => false` to make adding variants to `Node` less error prone
(Node::Cast(..), _)
| (Node::FunctionCall(..), _)
| (Node::UnaryOp(..), _)
| (Node::Binop(..), _)
| (Node::Leaf(..), _) => false,
}
(Node::UnaryOp(a_op, av), Node::UnaryOp(b_op, bv)) if a_op == b_op => {
try_unify(tcx, a.subtree(av), b.subtree(bv), param_env)
}
(Node::FunctionCall(a_f, a_args), Node::FunctionCall(b_f, b_args))
if a_args.len() == b_args.len() =>
{
try_unify(tcx, a.subtree(a_f), b.subtree(b_f), param_env)
&& iter::zip(a_args, b_args)
.all(|(&an, &bn)| try_unify(tcx, a.subtree(an), b.subtree(bn), param_env))
}
(Node::Cast(a_kind, a_operand, a_ty), Node::Cast(b_kind, b_operand, b_ty))
if (a_ty == b_ty) && (a_kind == b_kind) =>
{
try_unify(tcx, a.subtree(a_operand), b.subtree(b_operand), param_env)
}
// use this over `_ => false` to make adding variants to `Node` less error prone
(Node::Cast(..), _)
| (Node::FunctionCall(..), _)
| (Node::UnaryOp(..), _)
| (Node::Binop(..), _)
| (Node::Leaf(..), _) => false,
}
}

6
compiler/rustc_trait_selection/src/traits/fulfill.rs
View file

@ -581,7 +581,11 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
if let (ty::ConstKind::Unevaluated(a), ty::ConstKind::Unevaluated(b)) =
(c1.val(), c2.val())
{
if infcx.try_unify_abstract_consts(a.shrink(), b.shrink()) {
if infcx.try_unify_abstract_consts(
a.shrink(),
b.shrink(),
obligation.param_env,
) {
return ProcessResult::Changed(vec![]);
}
}

5
compiler/rustc_trait_selection/src/traits/mod.rs
View file

@ -860,7 +860,10 @@ pub fn provide(providers: &mut ty::query::Providers) {
ty::WithOptConstParam { did, const_param_did: Some(param_did) },
)
},
try_unify_abstract_consts: const_evaluatable::try_unify_abstract_consts,
try_unify_abstract_consts: |tcx, param_env_and| {
let (param_env, (a, b)) = param_env_and.into_parts();
const_evaluatable::try_unify_abstract_consts(tcx, (a, b), param_env)
},
..*providers
};
}

6
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -643,7 +643,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
if let (ty::ConstKind::Unevaluated(a), ty::ConstKind::Unevaluated(b)) =
(c1.val(), c2.val())
{
if self.infcx.try_unify_abstract_consts(a.shrink(), b.shrink()) {
if self.infcx.try_unify_abstract_consts(
a.shrink(),
b.shrink(),
obligation.param_env,
) {
return Ok(EvaluatedToOk);
}
}