bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Rollup merge of #99618 - compiler-errors:uhh-idk, r=lcnr

Browse source 
handle consts with param/infer in `const_eval_resolve` better

This PR addresses [this thread here](https://github.com/rust-lang/rust/pull/99449#discussion_r924141230). Was this the change you were looking for ``@lcnr?``

Interestingly, one test has begun to pass. Was that expected?

r? ``@lcnr``
This commit is contained in:
Dylan DPC 2022-07-26 14:26:56 +05:30 • committed by GitHub
commit a39c00ee8d
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
4 changed files with 61 additions and 62 deletions
Download patch file Download diff file Expand all files Collapse all files

61
compiler/rustc_infer/src/infer/mod.rs
View file

@ -21,7 +21,7 @@ use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue};
use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType};
use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
use rustc_middle::traits::select;
use rustc_middle::ty::abstract_const::AbstractConst;
use rustc_middle::ty::abstract_const::{AbstractConst, FailureKind};
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::relate::RelateResult;
@ -1675,7 +1675,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
#[instrument(skip(self), level = "debug")]
pub fn const_eval_resolve(
&self,
param_env: ty::ParamEnv<'tcx>,
mut param_env: ty::ParamEnv<'tcx>,
unevaluated: ty::Unevaluated<'tcx>,
span: Option<Span>,
) -> EvalToValTreeResult<'tcx> {
@ -1686,10 +1686,19 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
// variables
if substs.has_infer_types_or_consts() {
let ac = AbstractConst::new(self.tcx, unevaluated.shrink());
if let Ok(None) = ac {
substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did);
} else {
return Err(ErrorHandled::TooGeneric);
match ac {
Ok(None) => {
substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did);
param_env = self.tcx.param_env(unevaluated.def.did);
}
Ok(Some(ct)) => {
if ct.unify_failure_kind(self.tcx) == FailureKind::Concrete {
substs = replace_param_and_infer_substs_with_placeholder(self.tcx, substs);
} else {
return Err(ErrorHandled::TooGeneric);
}
}
Err(guar) => return Err(ErrorHandled::Reported(guar)),
}
}
@ -2000,3 +2009,43 @@ impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
)
}
}
/// Replaces substs that reference param or infer variables with suitable
/// placeholders. This function is meant to remove these param and infer
/// substs when they're not actually needed to evaluate a constant.
fn replace_param_and_infer_substs_with_placeholder<'tcx>(
tcx: TyCtxt<'tcx>,
substs: SubstsRef<'tcx>,
) -> SubstsRef<'tcx> {
tcx.mk_substs(substs.iter().enumerate().map(|(idx, arg)| {
match arg.unpack() {
GenericArgKind::Type(_)
if arg.has_param_types_or_consts() || arg.has_infer_types_or_consts() =>
{
tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
universe: ty::UniverseIndex::ROOT,
name: ty::BoundVar::from_usize(idx),
}))
.into()
}
GenericArgKind::Const(ct)
if ct.has_infer_types_or_consts() || ct.has_param_types_or_consts() =>
{
let ty = ct.ty();
// If the type references param or infer, replace that too...
if ty.has_param_types_or_consts() || ty.has_infer_types_or_consts() {
bug!("const `{ct}`'s type should not reference params or types");
}
tcx.mk_const(ty::ConstS {
ty,
kind: ty::ConstKind::Placeholder(ty::PlaceholderConst {
universe: ty::UniverseIndex::ROOT,
name: ty::BoundConst { ty, var: ty::BoundVar::from_usize(idx) },
}),
})
.into()
}
_ => arg,
}
}))
}