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support Expr in is_const_evaluatable and compute

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This commit is contained in:
Boxy
2022-12-05 23:17:55 +00:00
parent 344889e963
commit c9bab74fb2
4 changed files with 99 additions and 20 deletions
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58
compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
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@@ -25,15 +25,13 @@ use crate::traits::ObligationCtxt;
#[instrument(skip(infcx), level = "debug")]
pub fn is_const_evaluatable<'tcx>(
infcx: &InferCtxt<'tcx>,
ct: ty::Const<'tcx>,
unexpanded_ct: ty::Const<'tcx>,
param_env: ty::ParamEnv<'tcx>,
span: Span,
) -> Result<(), NotConstEvaluatable> {
let tcx = infcx.tcx;
let uv = match ct.kind() {
ty::ConstKind::Unevaluated(uv) => uv,
// FIXME(generic_const_exprs): this seems wrong but I couldn't find a way to get this to trigger
ty::ConstKind::Expr(_) => bug!("unexpected expr in `is_const_evaluatable: {ct:?}"),
match unexpanded_ct.kind() {
ty::ConstKind::Unevaluated(_) | ty::ConstKind::Expr(_) => (),
ty::ConstKind::Param(_)
| ty::ConstKind::Bound(_, _)
| ty::ConstKind::Placeholder(_)
@@ -43,7 +41,7 @@ pub fn is_const_evaluatable<'tcx>(
};
if tcx.features().generic_const_exprs {
let ct = tcx.expand_abstract_consts(ct);
let ct = tcx.expand_abstract_consts(unexpanded_ct);
let is_anon_ct = if let ty::ConstKind::Unevaluated(uv) = ct.kind() {
tcx.def_kind(uv.def.did) == DefKind::AnonConst
@@ -62,18 +60,40 @@ pub fn is_const_evaluatable<'tcx>(
}
}
let concrete = infcx.const_eval_resolve(param_env, uv, Some(span));
match concrete {
Err(ErrorHandled::TooGeneric) => Err(NotConstEvaluatable::Error(
infcx
.tcx
.sess
.delay_span_bug(span, "Missing value for constant, but no error reported?"),
)),
Err(ErrorHandled::Reported(e)) => Err(NotConstEvaluatable::Error(e)),
Ok(_) => Ok(()),
match unexpanded_ct.kind() {
ty::ConstKind::Expr(_) => {
// FIXME(generic_const_exprs): we have a `ConstKind::Expr` which is fully concrete, but
// currently it is not possible to evaluate `ConstKind::Expr` so we are unable to tell if it
// is evaluatable or not. For now we just ICE until this is implemented this.
Err(NotConstEvaluatable::Error(tcx.sess.delay_span_bug(
span,
"evaluating `ConstKind::Expr` is not currently supported",
)))
}
ty::ConstKind::Unevaluated(uv) => {
let concrete = infcx.const_eval_resolve(param_env, uv, Some(span));
match concrete {
Err(ErrorHandled::TooGeneric) => {
Err(NotConstEvaluatable::Error(infcx.tcx.sess.delay_span_bug(
span,
"Missing value for constant, but no error reported?",
)))
}
Err(ErrorHandled::Reported(e)) => Err(NotConstEvaluatable::Error(e)),
Ok(_) => Ok(()),
}
}
_ => bug!("unexpected constkind in `is_const_evalautable: {unexpanded_ct:?}`"),
}
} else {
let uv = match unexpanded_ct.kind() {
ty::ConstKind::Unevaluated(uv) => uv,
ty::ConstKind::Expr(_) => {
bug!("`ConstKind::Expr` without `feature(generic_const_exprs)` enabled")
}
_ => bug!("unexpected constkind in `is_const_evalautable: {unexpanded_ct:?}`"),
};
// FIXME: We should only try to evaluate a given constant here if it is fully concrete
// as we don't want to allow things like `[u8; std::mem::size_of::<*mut T>()]`.
//
@@ -92,7 +112,7 @@ pub fn is_const_evaluatable<'tcx>(
&& satisfied_from_param_env(
tcx,
infcx,
tcx.expand_abstract_consts(ct),
tcx.expand_abstract_consts(unexpanded_ct),
param_env,
) =>
{
@@ -152,6 +172,7 @@ fn satisfied_from_param_env<'tcx>(
impl<'a, 'tcx> TypeVisitor<'tcx> for Visitor<'a, 'tcx> {
type BreakTy = ();
fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
debug!("is_const_evaluatable: candidate={:?}", c);
if let Ok(()) = self.infcx.commit_if_ok(|_| {
let ocx = ObligationCtxt::new_in_snapshot(self.infcx);
if let Ok(()) = ocx.eq(&ObligationCause::dummy(), self.param_env, c.ty(), self.ct.ty())
@@ -187,7 +208,7 @@ fn satisfied_from_param_env<'tcx>(
let result = b_ct.visit_with(&mut v);
if let ControlFlow::Break(()) = result {
debug!("is_const_evaluatable: abstract_const ~~> ok");
debug!("is_const_evaluatable: yes");
return true;
}
}
@@ -195,5 +216,6 @@ fn satisfied_from_param_env<'tcx>(
}
}
debug!("is_const_evaluatable: no");
false
}