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Make normalize_generic_arg_after_erasing_regions return a Result #85485

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Make normalize_generic_arg_after_erasing_regions return a Result #85485

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c24e995
Make `TypeFolder::fold_*` return `Result`
LeSeulArtichaut May 19, 2021
0cb4a67
Make `TypeFoldable` implementors short-circuit on error
LeSeulArtichaut May 19, 2021
7308b76
Adapt `TypeFolder` implementors to return a `Result`
LeSeulArtichaut May 19, 2021
85a1572
Unwrap the results of type folders
LeSeulArtichaut May 19, 2021
fbae9ba
Make `normalize_generic_arg_after_erasing_regions` return a `Result`
LeSeulArtichaut May 19, 2021
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70 changes: 69 additions & 1 deletion compiler/rustc_data_structures/src/functor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,16 @@ use rustc_index::vec::{Idx, IndexVec};
use std::mem;
use std::ptr;

pub trait IdFunctor {
pub trait IdFunctor: Sized {
type Inner;

fn map_id<F>(self, f: F) -> Self
where
F: FnMut(Self::Inner) -> Self::Inner;

fn try_map_id<F, E>(self, f: F) -> Result<Self, E>
where
F: FnMut(Self::Inner) -> Result<Self::Inner, E>;
}

impl<T> IdFunctor for Box<T> {
Expand All @@ -31,6 +35,25 @@ impl<T> IdFunctor for Box<T> {
raw.assume_init()
}
}

#[inline]
fn try_map_id<F, E>(self, mut f: F) -> Result<Self, E>
where
F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
{
let raw = Box::into_raw(self);
Ok(unsafe {
// SAFETY: The raw pointer points to a valid value of type `T`.
let value = ptr::read(raw);
// SAFETY: Converts `Box<T>` to `Box<MaybeUninit<T>>` which is the
// inverse of `Box::assume_init()` and should be safe.
let mut raw: Box<mem::MaybeUninit<T>> = Box::from_raw(raw.cast());
// SAFETY: Write the mapped value back into the `Box`.
ptr::write(raw.as_mut_ptr(), f(value)?);
// SAFETY: We just initialized `raw`.
raw.assume_init()
})
}
}

impl<T> IdFunctor for Vec<T> {
Expand All @@ -55,6 +78,35 @@ impl<T> IdFunctor for Vec<T> {
}
self
}

#[inline]
fn try_map_id<F, E>(mut self, mut f: F) -> Result<Self, E>
where
F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
{
// FIXME: We don't really care about panics here and leak
// far more than we should, but that should be fine for now.
let len = self.len();
let mut error = Ok(());
unsafe {
self.set_len(0);
let start = self.as_mut_ptr();
for i in 0..len {
let p = start.add(i);
match f(ptr::read(p)) {
Ok(value) => ptr::write(p, value),
Err(err) => {
error = Err(err);
break;
}
}
}
// Even if we encountered an error, set the len back
// so we don't leak memory.
self.set_len(len);
}
error.map(|()| self)
}
}

impl<T> IdFunctor for Box<[T]> {
Expand All @@ -67,6 +119,14 @@ impl<T> IdFunctor for Box<[T]> {
{
Vec::from(self).map_id(f).into()
}

#[inline]
fn try_map_id<F, E>(self, f: F) -> Result<Self, E>
where
F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
{
Vec::from(self).try_map_id(f).map(Into::into)
}
}

impl<I: Idx, T> IdFunctor for IndexVec<I, T> {
Expand All @@ -79,4 +139,12 @@ impl<I: Idx, T> IdFunctor for IndexVec<I, T> {
{
IndexVec::from_raw(self.raw.map_id(f))
}

#[inline]
fn try_map_id<F, E>(self, f: F) -> Result<Self, E>
where
F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
{
self.raw.try_map_id(f).map(IndexVec::from_raw)
}
}
57 changes: 30 additions & 27 deletions compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -293,7 +293,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
self.tcx
}

fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> Result<ty::Binder<'tcx, T>, Self::Error>
where
T: TypeFoldable<'tcx>,
{
Expand All @@ -303,13 +303,13 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
t
}

fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
fn fold_region(&mut self, r: ty::Region<'tcx>) -> Result<ty::Region<'tcx>, Self::Error> {
match *r {
ty::ReLateBound(index, ..) => {
if index >= self.binder_index {
bug!("escaping late-bound region during canonicalization");
} else {
r
Ok(r)
}
}

Expand All @@ -327,19 +327,19 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
vid, r
);
let r = self.tcx.reuse_or_mk_region(r, ty::ReVar(resolved_vid));
self.canonicalize_region_mode.canonicalize_free_region(self, r)
Ok(self.canonicalize_region_mode.canonicalize_free_region(self, r))
}

ty::ReStatic
| ty::ReEarlyBound(..)
| ty::ReFree(_)
| ty::ReEmpty(_)
| ty::RePlaceholder(..)
| ty::ReErased => self.canonicalize_region_mode.canonicalize_free_region(self, r),
| ty::ReErased => Ok(self.canonicalize_region_mode.canonicalize_free_region(self, r)),
}
}

fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
fn fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
match *t.kind() {
ty::Infer(ty::TyVar(vid)) => {
debug!("canonical: type var found with vid {:?}", vid);
Expand All @@ -355,40 +355,40 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
Err(mut ui) => {
// FIXME: perf problem described in #55921.
ui = ty::UniverseIndex::ROOT;
self.canonicalize_ty_var(
Ok(self.canonicalize_ty_var(
CanonicalVarInfo {
kind: CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui)),
},
t,
)
))
}
}
}

ty::Infer(ty::IntVar(_)) => self.canonicalize_ty_var(
ty::Infer(ty::IntVar(_)) => Ok(self.canonicalize_ty_var(
CanonicalVarInfo { kind: CanonicalVarKind::Ty(CanonicalTyVarKind::Int) },
t,
),
)),

ty::Infer(ty::FloatVar(_)) => self.canonicalize_ty_var(
ty::Infer(ty::FloatVar(_)) => Ok(self.canonicalize_ty_var(
CanonicalVarInfo { kind: CanonicalVarKind::Ty(CanonicalTyVarKind::Float) },
t,
),
)),

ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!("encountered a fresh type during canonicalization")
}

ty::Placeholder(placeholder) => self.canonicalize_ty_var(
ty::Placeholder(placeholder) => Ok(self.canonicalize_ty_var(
CanonicalVarInfo { kind: CanonicalVarKind::PlaceholderTy(placeholder) },
t,
),
)),

ty::Bound(debruijn, _) => {
if debruijn >= self.binder_index {
bug!("escaping bound type during canonicalization")
} else {
t
Ok(t)
}
}

Expand Down Expand Up @@ -419,13 +419,16 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
if t.flags().intersects(self.needs_canonical_flags) {
t.super_fold_with(self)
} else {
t
Ok(t)
}
}
}
}

fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
fn fold_const(
&mut self,
ct: &'tcx ty::Const<'tcx>,
) -> Result<&'tcx ty::Const<'tcx>, Self::Error> {
match ct.val {
ty::ConstKind::Infer(InferConst::Var(vid)) => {
debug!("canonical: const var found with vid {:?}", vid);
Expand All @@ -440,10 +443,10 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
Err(mut ui) => {
// FIXME: perf problem described in #55921.
ui = ty::UniverseIndex::ROOT;
return self.canonicalize_const_var(
return Ok(self.canonicalize_const_var(
CanonicalVarInfo { kind: CanonicalVarKind::Const(ui) },
ct,
);
));
}
}
}
Expand All @@ -454,20 +457,20 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
if debruijn >= self.binder_index {
bug!("escaping bound type during canonicalization")
} else {
return ct;
return Ok(ct);
}
}
ty::ConstKind::Placeholder(placeholder) => {
return self.canonicalize_const_var(
return Ok(self.canonicalize_const_var(
CanonicalVarInfo { kind: CanonicalVarKind::PlaceholderConst(placeholder) },
ct,
);
));
}
_ => {}
}

let flags = FlagComputation::for_const(ct);
if flags.intersects(self.needs_canonical_flags) { ct.super_fold_with(self) } else { ct }
if flags.intersects(self.needs_canonical_flags) { ct.super_fold_with(self) } else { Ok(ct) }
}
}

Expand Down Expand Up @@ -516,7 +519,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
indices: FxHashMap::default(),
binder_index: ty::INNERMOST,
};
let out_value = value.fold_with(&mut canonicalizer);
let out_value = value.fold_with(&mut canonicalizer).into_ok();

// Once we have canonicalized `out_value`, it should not
// contain anything that ties it to this inference context
Expand Down Expand Up @@ -634,7 +637,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
let infcx = self.infcx.expect("encountered ty-var without infcx");
let bound_to = infcx.shallow_resolve(ty_var);
if bound_to != ty_var {
self.fold_ty(bound_to)
self.fold_ty(bound_to).into_ok()
} else {
let var = self.canonical_var(info, ty_var.into());
self.tcx().mk_ty(ty::Bound(self.binder_index, var.into()))
Expand All @@ -653,12 +656,12 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
let infcx = self.infcx.expect("encountered const-var without infcx");
let bound_to = infcx.shallow_resolve(const_var);
if bound_to != const_var {
self.fold_const(bound_to)
self.fold_const(bound_to).into_ok()
} else {
let var = self.canonical_var(info, const_var.into());
self.tcx().mk_const(ty::Const {
val: ty::ConstKind::Bound(self.binder_index, var),
ty: self.fold_ty(const_var.ty),
ty: self.fold_ty(const_var.ty).into_ok(),
})
}
}
Expand Down
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