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Rollup merge of #111132 - lcnr:nll-generalize, r=b-naber
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cleanup nll generalizer

followup to #108861
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@JohnTitor
JohnTitor authored May 5, 2023
2 parents b2ee088 + 0c5fe37 commit f5c50e3
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Showing 6 changed files with 20 additions and 113 deletions.
8 changes: 4 additions & 4 deletions compiler/rustc_borrowck/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -498,11 +498,11 @@ impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
let next_region = self.infcx.next_region_var(origin);
let vid = next_region.as_var();

if cfg!(debug_assertions) && !self.inside_canonicalization_ctxt() {
if cfg!(debug_assertions) {
debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
let ctxt = get_ctxt_fn();
let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
var_to_origin.insert(vid, ctxt);
assert_eq!(var_to_origin.insert(vid, ctxt), None);
}

next_region
Expand All @@ -520,11 +520,11 @@ impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
let next_region = self.infcx.next_nll_region_var(origin);
let vid = next_region.as_var();

if cfg!(debug_assertions) && !self.inside_canonicalization_ctxt() {
if cfg!(debug_assertions) {
debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
let ctxt = get_ctxt_fn();
let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
var_to_origin.insert(vid, ctxt);
assert_eq!(var_to_origin.insert(vid, ctxt), None);
}

next_region
Expand Down
13 changes: 9 additions & 4 deletions compiler/rustc_borrowck/src/type_check/relate_tys.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -131,9 +131,13 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
ty::BoundRegionKind::BrEnv => BoundRegionInfo::Name(sym::env),
};

if cfg!(debug_assertions) && !self.type_checker.infcx.inside_canonicalization_ctxt() {
if cfg!(debug_assertions) {
let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
var_to_origin.insert(reg.as_var(), RegionCtxt::Placeholder(reg_info));
let new = RegionCtxt::Placeholder(reg_info);
let prev = var_to_origin.insert(reg.as_var(), new);
if let Some(prev) = prev {
assert_eq!(new, prev);
}
}

reg
Expand All @@ -146,9 +150,10 @@ impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx>
universe,
);

if cfg!(debug_assertions) && !self.type_checker.infcx.inside_canonicalization_ctxt() {
if cfg!(debug_assertions) {
let mut var_to_origin = self.type_checker.infcx.reg_var_to_origin.borrow_mut();
var_to_origin.insert(reg.as_var(), RegionCtxt::Existential(None));
let prev = var_to_origin.insert(reg.as_var(), RegionCtxt::Existential(None));
assert_eq!(prev, None);
}

reg
Expand Down
3 changes: 0 additions & 3 deletions compiler/rustc_infer/src/infer/at.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,8 +30,6 @@ use super::*;
use rustc_middle::ty::relate::{Relate, TypeRelation};
use rustc_middle::ty::{Const, ImplSubject};

use std::cell::Cell;

/// Whether we should define opaque types or just treat them opaquely.
///
/// Currently only used to prevent predicate matching from matching anything
Expand Down Expand Up @@ -84,7 +82,6 @@ impl<'tcx> InferCtxt<'tcx> {
in_snapshot: self.in_snapshot.clone(),
universe: self.universe.clone(),
intercrate: self.intercrate,
inside_canonicalization_ctxt: Cell::new(self.inside_canonicalization_ctxt()),
}
}
}
Expand Down
2 changes: 0 additions & 2 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 @@ -561,8 +561,6 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
where
V: TypeFoldable<TyCtxt<'tcx>>,
{
let _inside_canonical_ctxt_guard = infcx.set_canonicalization_ctxt();

let needs_canonical_flags = if canonicalize_region_mode.any() {
TypeFlags::HAS_INFER |
TypeFlags::HAS_FREE_REGIONS | // `HAS_RE_PLACEHOLDER` implies `HAS_FREE_REGIONS`
Expand Down
32 changes: 0 additions & 32 deletions compiler/rustc_infer/src/infer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,6 @@ use rustc_span::Span;

use std::cell::{Cell, RefCell};
use std::fmt;
use std::ops::Drop;

use self::combine::CombineFields;
use self::error_reporting::TypeErrCtxt;
Expand Down Expand Up @@ -342,11 +341,6 @@ pub struct InferCtxt<'tcx> {
/// there is no type that the user could *actually name* that
/// would satisfy it. This avoids crippling inference, basically.
pub intercrate: bool,

/// Flag that is set when we enter canonicalization. Used for debugging to ensure
/// that we only collect region information for `BorrowckInferCtxt::reg_var_to_origin`
/// inside non-canonicalization contexts.
inside_canonicalization_ctxt: Cell<bool>,
}

/// See the `error_reporting` module for more details.
Expand Down Expand Up @@ -638,7 +632,6 @@ impl<'tcx> InferCtxtBuilder<'tcx> {
skip_leak_check: Cell::new(false),
universe: Cell::new(ty::UniverseIndex::ROOT),
intercrate,
inside_canonicalization_ctxt: Cell::new(false),
}
}
}
Expand Down Expand Up @@ -1636,31 +1629,6 @@ impl<'tcx> InferCtxt<'tcx> {
}
}
}

pub fn inside_canonicalization_ctxt(&self) -> bool {
self.inside_canonicalization_ctxt.get()
}

pub fn set_canonicalization_ctxt(&self) -> CanonicalizationCtxtGuard<'_, 'tcx> {
let prev_ctxt = self.inside_canonicalization_ctxt();
self.inside_canonicalization_ctxt.set(true);
CanonicalizationCtxtGuard { prev_ctxt, infcx: self }
}

fn set_canonicalization_ctxt_to(&self, ctxt: bool) {
self.inside_canonicalization_ctxt.set(ctxt);
}
}

pub struct CanonicalizationCtxtGuard<'cx, 'tcx> {
prev_ctxt: bool,
infcx: &'cx InferCtxt<'tcx>,
}

impl<'cx, 'tcx> Drop for CanonicalizationCtxtGuard<'cx, 'tcx> {
fn drop(&mut self) {
self.infcx.set_canonicalization_ctxt_to(self.prev_ctxt)
}
}

impl<'tcx> TypeErrCtxt<'_, 'tcx> {
Expand Down
75 changes: 7 additions & 68 deletions compiler/rustc_infer/src/infer/nll_relate/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,11 +30,10 @@ use rustc_middle::traits::ObligationCause;
use rustc_middle::ty::error::TypeError;
use rustc_middle::ty::fold::FnMutDelegate;
use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
use rustc_middle::ty::visit::TypeVisitableExt;
use rustc_middle::ty::{self, InferConst, Ty, TyCtxt};
use rustc_span::{Span, Symbol};
use std::fmt::Debug;
use std::ops::ControlFlow;

use super::combine::ObligationEmittingRelation;

Expand Down Expand Up @@ -115,11 +114,6 @@ pub trait TypeRelatingDelegate<'tcx> {
fn forbid_inference_vars() -> bool;
}

#[derive(Clone, Debug, Default)]
struct BoundRegionScope<'tcx> {
map: FxHashMap<ty::BoundRegion, ty::Region<'tcx>>,
}

#[derive(Copy, Clone)]
struct UniversallyQuantified(bool);

Expand Down Expand Up @@ -230,10 +224,13 @@ where
) -> RelateResult<'tcx, T> {
let universe = self.infcx.probe_ty_var(for_vid).unwrap_err();

if value.has_escaping_bound_vars() {
bug!("trying to instantiate {for_vid:?} with escaping bound vars: {value:?}");
}

let mut generalizer = TypeGeneralizer {
infcx: self.infcx,
delegate: &mut self.delegate,
first_free_index: ty::INNERMOST,
ambient_variance: self.ambient_variance,
for_vid_sub_root: self.infcx.inner.borrow_mut().type_variables().sub_root_var(for_vid),
universe,
Expand Down Expand Up @@ -488,13 +485,7 @@ where
}

if a == b {
// Subtle: if a or b has a bound variable that we are lazily
// substituting, then even if a == b, it could be that the values we
// will substitute for those bound variables are *not* the same, and
// hence returning `Ok(a)` is incorrect.
if !a.has_escaping_bound_vars() && !b.has_escaping_bound_vars() {
return Ok(a);
}
return Ok(a);
}

match (a.kind(), b.kind()) {
Expand Down Expand Up @@ -726,47 +717,6 @@ where
}
}

/// When we encounter a binder like `for<..> fn(..)`, we actually have
/// to walk the `fn` value to find all the values bound by the `for`
/// (these are not explicitly present in the ty representation right
/// now). This visitor handles that: it descends the type, tracking
/// binder depth, and finds late-bound regions targeting the
/// `for<..`>. For each of those, it creates an entry in
/// `bound_region_scope`.
struct ScopeInstantiator<'me, 'tcx> {
next_region: &'me mut dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
// The debruijn index of the scope we are instantiating.
target_index: ty::DebruijnIndex,
bound_region_scope: &'me mut BoundRegionScope<'tcx>,
}

impl<'me, 'tcx> TypeVisitor<TyCtxt<'tcx>> for ScopeInstantiator<'me, 'tcx> {
fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
&mut self,
t: &ty::Binder<'tcx, T>,
) -> ControlFlow<Self::BreakTy> {
self.target_index.shift_in(1);
t.super_visit_with(self);
self.target_index.shift_out(1);

ControlFlow::Continue(())
}

fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
let ScopeInstantiator { bound_region_scope, next_region, .. } = self;

match *r {
ty::ReLateBound(debruijn, br) if debruijn == self.target_index => {
bound_region_scope.map.entry(br).or_insert_with(|| next_region(br));
}

_ => {}
}

ControlFlow::Continue(())
}
}

/// The "type generalizer" is used when handling inference variables.
///
/// The basic strategy for handling a constraint like `?A <: B` is to
Expand All @@ -780,11 +730,6 @@ impl<'me, 'tcx> TypeVisitor<TyCtxt<'tcx>> for ScopeInstantiator<'me, 'tcx> {
/// value of `A`. Finally, we relate `&'0 u32 <: &'x u32`, which
/// establishes `'0: 'x` as a constraint.
///
/// As a side-effect of this generalization procedure, we also replace
/// all the bound regions that we have traversed with concrete values,
/// so that the resulting generalized type is independent from the
/// scopes.
///
/// [blog post]: https://is.gd/0hKvIr
struct TypeGeneralizer<'me, 'tcx, D>
where
Expand All @@ -798,8 +743,6 @@ where
/// some other type. What will be the variance at this point?
ambient_variance: ty::Variance,

first_free_index: ty::DebruijnIndex,

/// The vid of the type variable that is in the process of being
/// instantiated. If we find this within the value we are folding,
/// that means we would have created a cyclic value.
Expand Down Expand Up @@ -939,7 +882,7 @@ where
) -> RelateResult<'tcx, ty::Region<'tcx>> {
debug!("TypeGeneralizer::regions(a={:?})", a);

if let ty::ReLateBound(debruijn, _) = *a && debruijn < self.first_free_index {
if let ty::ReLateBound(..) = *a {
return Ok(a);
}

Expand All @@ -958,7 +901,6 @@ where
// FIXME(#54105) -- if the ambient variance is bivariant,
// though, we may however need to check well-formedness or
// risk a problem like #41677 again.

let replacement_region_vid = self.delegate.generalize_existential(self.universe);

Ok(replacement_region_vid)
Expand Down Expand Up @@ -1002,10 +944,7 @@ where
T: Relate<'tcx>,
{
debug!("TypeGeneralizer::binders(a={:?})", a);

self.first_free_index.shift_in(1);
let result = self.relate(a.skip_binder(), a.skip_binder())?;
self.first_free_index.shift_out(1);
Ok(a.rebind(result))
}
}

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