From f3dfa52fd18b0cd684ef44b409891d6cd16fe553 Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Thu, 16 Feb 2023 14:40:53 +0300
Subject: [PATCH 1/7] resolve to universal regions when possible
---
.../src/infer/canonical/canonicalizer.rs | 12 ++++-----
.../src/infer/region_constraints/mod.rs | 26 +++++--------------
compiler/rustc_infer/src/infer/resolve.rs | 15 +++++------
.../src/traits/project.rs | 4 +--
4 files changed, 19 insertions(+), 38 deletions(-)
diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index 7ffd39de781b4..c6adc88bd1210 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -352,19 +352,17 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
}
ty::ReVar(vid) => {
- let resolved_vid = self
+ let resolved = self
.infcx
.inner
.borrow_mut()
.unwrap_region_constraints()
- .opportunistic_resolve_var(vid);
+ .opportunistic_resolve_var(self.tcx, vid);
debug!(
- "canonical: region var found with vid {:?}, \
- opportunistically resolved to {:?}",
- vid, resolved_vid
+ "canonical: region var found with vid {vid:?}, \
+ opportunistically resolved to {resolved:?}",
);
- let r = self.tcx.mk_re_var(resolved_vid);
- self.canonicalize_mode.canonicalize_free_region(self, r)
+ self.canonicalize_mode.canonicalize_free_region(self, resolved)
}
ty::ReStatic
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 33514eedfc3d0..bf9e71b63fa08 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -633,29 +633,15 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
}
}
- /// Resolves the passed RegionVid to the root RegionVid in the unification table
- pub(super) fn opportunistic_resolve_var(&mut self, rid: ty::RegionVid) -> ty::RegionVid {
- self.unification_table().find(rid).vid
- }
-
- /// If the Region is a `ReVar`, then resolves it either to the root value in
- /// the unification table, if it exists, or to the root `ReVar` in the table.
- /// If the Region is not a `ReVar`, just returns the Region itself.
- pub fn opportunistic_resolve_region(
+ /// Resolves a region var to its value in the unification table, if it exists.
+ /// Otherwise, it is resolved to the root `ReVar` in the table.
+ pub fn opportunistic_resolve_var(
&mut self,
tcx: TyCtxt<'tcx>,
- region: ty::Region<'tcx>,
+ vid: ty::RegionVid,
) -> ty::Region<'tcx> {
- match *region {
- ty::ReVar(rid) => {
- let unified_region = self.unification_table().probe_value(rid);
- unified_region.0.unwrap_or_else(|| {
- let root = self.unification_table().find(rid).vid;
- tcx.mk_re_var(root)
- })
- }
- _ => region,
- }
+ let root_vid = self.unification_table().find(vid).vid;
+ self.unification_table().probe_value(root_vid).0.unwrap_or_else(|| tcx.mk_re_var(root_vid))
}
fn combine_map(&mut self, t: CombineMapType) -> &mut CombineMap<'tcx> {
diff --git a/compiler/rustc_infer/src/infer/resolve.rs b/compiler/rustc_infer/src/infer/resolve.rs
index 5bb35832930bf..4f49f4165074f 100644
--- a/compiler/rustc_infer/src/infer/resolve.rs
+++ b/compiler/rustc_infer/src/infer/resolve.rs
@@ -85,15 +85,12 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for OpportunisticRegionResolver<'a, 'tcx
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
match *r {
- ty::ReVar(rid) => {
- let resolved = self
- .infcx
- .inner
- .borrow_mut()
- .unwrap_region_constraints()
- .opportunistic_resolve_var(rid);
- TypeFolder::interner(self).mk_re_var(resolved)
- }
+ ty::ReVar(vid) => self
+ .infcx
+ .inner
+ .borrow_mut()
+ .unwrap_region_constraints()
+ .opportunistic_resolve_var(TypeFolder::interner(self), vid),
_ => r,
}
}
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 013db2edb398d..2b1db1633c756 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -871,12 +871,12 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for PlaceholderReplacer<'_, 'tcx> {
fn fold_region(&mut self, r0: ty::Region<'tcx>) -> ty::Region<'tcx> {
let r1 = match *r0 {
- ty::ReVar(_) => self
+ ty::ReVar(vid) => self
.infcx
.inner
.borrow_mut()
.unwrap_region_constraints()
- .opportunistic_resolve_region(self.infcx.tcx, r0),
+ .opportunistic_resolve_var(self.infcx.tcx, vid),
_ => r0,
};
From 79dca7b7ba7ac1c9292fadff197204169ae43630 Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Fri, 17 Feb 2023 09:27:43 +0300
Subject: [PATCH 2/7] s/unification_table/unification_table_mut
Give a more clear name.
---
.../src/infer/region_constraints/mod.rs | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index bf9e71b63fa08..2723598ad6d7b 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -420,7 +420,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
// `RegionConstraintData` contains the relationship here.
if *any_unifications {
*any_unifications = false;
- self.unification_table().reset_unifications(|_| UnifiedRegion(None));
+ self.unification_table_mut().reset_unifications(|_| UnifiedRegion(None));
}
data
@@ -447,7 +447,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
) -> RegionVid {
let vid = self.var_infos.push(RegionVariableInfo { origin, universe });
- let u_vid = self.unification_table().new_key(UnifiedRegion(None));
+ let u_vid = self.unification_table_mut().new_key(UnifiedRegion(None));
assert_eq!(vid, u_vid.vid);
self.undo_log.push(AddVar(vid));
debug!("created new region variable {:?} in {:?} with origin {:?}", vid, universe, origin);
@@ -516,13 +516,13 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
match (sub, sup) {
(Region(Interned(ReVar(sub), _)), Region(Interned(ReVar(sup), _))) => {
debug!("make_eqregion: unifying {:?} with {:?}", sub, sup);
- self.unification_table().union(*sub, *sup);
+ self.unification_table_mut().union(*sub, *sup);
self.any_unifications = true;
}
(Region(Interned(ReVar(vid), _)), value)
| (value, Region(Interned(ReVar(vid), _))) => {
debug!("make_eqregion: unifying {:?} with {:?}", vid, value);
- self.unification_table().union_value(*vid, UnifiedRegion(Some(value)));
+ self.unification_table_mut().union_value(*vid, UnifiedRegion(Some(value)));
self.any_unifications = true;
}
(_, _) => {}
@@ -640,8 +640,9 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
tcx: TyCtxt<'tcx>,
vid: ty::RegionVid,
) -> ty::Region<'tcx> {
- let root_vid = self.unification_table().find(vid).vid;
- self.unification_table().probe_value(root_vid).0.unwrap_or_else(|| tcx.mk_re_var(root_vid))
+ let mut ut = self.unification_table_mut(); // FIXME(rust-lang/ena#42): unnecessary mut
+ let root_vid = ut.find(vid).vid;
+ ut.probe_value(root_vid).0.unwrap_or_else(|| tcx.mk_re_var(root_vid))
}
fn combine_map(&mut self, t: CombineMapType) -> &mut CombineMap<'tcx> {
@@ -719,7 +720,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
}
#[inline]
- fn unification_table(&mut self) -> super::UnificationTable<'_, 'tcx, RegionVidKey<'tcx>> {
+ fn unification_table_mut(&mut self) -> super::UnificationTable<'_, 'tcx, RegionVidKey<'tcx>> {
ut::UnificationTable::with_log(&mut self.storage.unification_table, self.undo_log)
}
}
From eea560494c121bf93f725eb174fc03d34b0e96f1 Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Sun, 5 Mar 2023 12:05:04 +0300
Subject: [PATCH 3/7] oops! new unsoundness
Bless tests and show an introduced unsoundness related to
exits<'a> { forall<'b> { 'a == 'b } }.
We now resolve the var ?a in U0 to the placeholder !b in U1.
---
.../hrtb-exists-forall-trait-invariant.rs | 5 ++++-
.../hrtb-exists-forall-trait-invariant.stderr | 11 -----------
.../hrtb-just-for-static.stderr | 6 ------
tests/ui/traits/inductive-overflow/lifetime.rs | 6 ++----
.../ui/traits/inductive-overflow/lifetime.stderr | 14 +++++---------
tests/ui/wf/hir-wf-check-erase-regions.rs | 4 ++--
tests/ui/wf/hir-wf-check-erase-regions.stderr | 16 ++++++++--------
7 files changed, 21 insertions(+), 41 deletions(-)
delete mode 100644 tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr
diff --git a/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs b/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs
index 9b9e4496a870d..e7c3bdbbf3598 100644
--- a/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs
+++ b/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs
@@ -2,6 +2,9 @@
//
// In particular, we test this pattern in trait solving, where it is not connected
// to any part of the source code.
+//
+// check-pass
+// Oops!
use std::cell::Cell;
@@ -25,5 +28,5 @@ fn main() {
// yielding `fn(&!b u32)`, in a fresh universe U1
// - So we get `?a = !b` but the universe U0 assigned to `?a` cannot name `!b`.
- foo::<()>(); //~ ERROR implementation of `Trait` is not general enough
+ foo::<()>();
}
diff --git a/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr b/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr
deleted file mode 100644
index cb2ce8a4116aa..0000000000000
--- a/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error: implementation of `Trait` is not general enough
- --> $DIR/hrtb-exists-forall-trait-invariant.rs:28:5
- |
-LL | foo::<()>();
- | ^^^^^^^^^^^ implementation of `Trait` is not general enough
- |
- = note: `()` must implement `Trait<for<'b> fn(Cell<&'b u32>)>`
- = note: ...but it actually implements `Trait<fn(Cell<&'0 u32>)>`, for some specific lifetime `'0`
-
-error: aborting due to previous error
-
diff --git a/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr b/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
index 31e11e1283516..b4312091edb27 100644
--- a/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
+++ b/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
@@ -14,12 +14,6 @@ LL | fn give_some<'a>() {
| -- lifetime `'a` defined here
LL | want_hrtb::<&'a u32>()
| ^^^^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
- |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
- --> $DIR/hrtb-just-for-static.rs:9:15
- |
-LL | where T : for<'a> Foo<&'a isize>
- | ^^^^^^^^^^^^^^^^^^^^^^
error: implementation of `Foo` is not general enough
--> $DIR/hrtb-just-for-static.rs:30:5
diff --git a/tests/ui/traits/inductive-overflow/lifetime.rs b/tests/ui/traits/inductive-overflow/lifetime.rs
index bf536d21cf970..2f3c90dcece60 100644
--- a/tests/ui/traits/inductive-overflow/lifetime.rs
+++ b/tests/ui/traits/inductive-overflow/lifetime.rs
@@ -15,9 +15,9 @@ impl<'a> Y for C<'a> {
struct C<'a>(&'a ());
struct X<T: Y>(T::P);
-impl<T: NotAuto> NotAuto for Box<T> {} //~ NOTE: required
+impl<T: NotAuto> NotAuto for Box<T> {}
+impl<T: Y> NotAuto for X<T> where T::P: NotAuto {} //~ NOTE: required
//~^ NOTE unsatisfied trait bound introduced here
-impl<T: Y> NotAuto for X<T> where T::P: NotAuto {}
impl<'a> NotAuto for C<'a> {}
fn is_send<S: NotAuto>() {}
@@ -28,6 +28,4 @@ fn main() {
// Should only be a few notes.
is_send::<X<C<'static>>>();
//~^ ERROR overflow evaluating
- //~| 3 redundant requirements hidden
- //~| required for
}
diff --git a/tests/ui/traits/inductive-overflow/lifetime.stderr b/tests/ui/traits/inductive-overflow/lifetime.stderr
index 357e59991a3d4..7ab2864a8cfdc 100644
--- a/tests/ui/traits/inductive-overflow/lifetime.stderr
+++ b/tests/ui/traits/inductive-overflow/lifetime.stderr
@@ -1,18 +1,14 @@
-error[E0275]: overflow evaluating the requirement `X<C<'_>>: NotAuto`
+error[E0275]: overflow evaluating the requirement `Box<X<C<'static>>>: NotAuto`
--> $DIR/lifetime.rs:29:5
|
LL | is_send::<X<C<'static>>>();
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
-note: required for `Box<X<C<'_>>>` to implement `NotAuto`
- --> $DIR/lifetime.rs:18:18
+note: required for `X<C<'static>>` to implement `NotAuto`
+ --> $DIR/lifetime.rs:19:12
|
-LL | impl<T: NotAuto> NotAuto for Box<T> {}
- | ------- ^^^^^^^ ^^^^^^
- | |
- | unsatisfied trait bound introduced here
- = note: 3 redundant requirements hidden
- = note: required for `X<C<'static>>` to implement `NotAuto`
+LL | impl<T: Y> NotAuto for X<T> where T::P: NotAuto {}
+ | ^^^^^^^ ^^^^ ------- unsatisfied trait bound introduced here
note: required by a bound in `is_send`
--> $DIR/lifetime.rs:23:15
|
diff --git a/tests/ui/wf/hir-wf-check-erase-regions.rs b/tests/ui/wf/hir-wf-check-erase-regions.rs
index 2b4b480df0acf..3855f2c35c1fb 100644
--- a/tests/ui/wf/hir-wf-check-erase-regions.rs
+++ b/tests/ui/wf/hir-wf-check-erase-regions.rs
@@ -4,10 +4,10 @@
pub struct Table<T, const N: usize>([Option<T>; N]);
impl<'a, T, const N: usize> IntoIterator for &'a Table<T, N> {
- type IntoIter = std::iter::Flatten<std::slice::Iter<'a, T>>; //~ ERROR `&T` is not an iterator
+ type IntoIter = std::iter::Flatten<std::slice::Iter<'a, T>>; //~ ERROR `&'a T` is not an iterator
type Item = &'a T;
- fn into_iter(self) -> Self::IntoIter { //~ ERROR `&T` is not an iterator
+ fn into_iter(self) -> Self::IntoIter { //~ ERROR `&'a T` is not an iterator
unimplemented!()
}
}
diff --git a/tests/ui/wf/hir-wf-check-erase-regions.stderr b/tests/ui/wf/hir-wf-check-erase-regions.stderr
index 7bc19dd2e2162..2843983c716a6 100644
--- a/tests/ui/wf/hir-wf-check-erase-regions.stderr
+++ b/tests/ui/wf/hir-wf-check-erase-regions.stderr
@@ -1,24 +1,24 @@
-error[E0277]: `&T` is not an iterator
+error[E0277]: `&'a T` is not an iterator
--> $DIR/hir-wf-check-erase-regions.rs:7:21
|
LL | type IntoIter = std::iter::Flatten<std::slice::Iter<'a, T>>;
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `&T` is not an iterator
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `&'a T` is not an iterator
|
- = help: the trait `Iterator` is not implemented for `&T`
+ = help: the trait `Iterator` is not implemented for `&'a T`
= help: the trait `Iterator` is implemented for `&mut I`
- = note: required for `&T` to implement `IntoIterator`
+ = note: required for `&'a T` to implement `IntoIterator`
note: required by a bound in `Flatten`
--> $SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL
-error[E0277]: `&T` is not an iterator
+error[E0277]: `&'a T` is not an iterator
--> $DIR/hir-wf-check-erase-regions.rs:10:27
|
LL | fn into_iter(self) -> Self::IntoIter {
- | ^^^^^^^^^^^^^^ `&T` is not an iterator
+ | ^^^^^^^^^^^^^^ `&'a T` is not an iterator
|
- = help: the trait `Iterator` is not implemented for `&T`
+ = help: the trait `Iterator` is not implemented for `&'a T`
= help: the trait `Iterator` is implemented for `&mut I`
- = note: required for `&T` to implement `IntoIterator`
+ = note: required for `&'a T` to implement `IntoIterator`
note: required by a bound in `Flatten`
--> $SRC_DIR/core/src/iter/adapters/flatten.rs:LL:COL
From bfd35016e41724a370828dc400e6b12e1aaf9201 Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Sun, 5 Mar 2023 11:54:57 +0300
Subject: [PATCH 4/7] fix the new unsoundness
---
.../rustc_infer/src/infer/region_constraints/mod.rs | 9 ++++++++-
.../hrtb-exists-forall-trait-invariant.rs | 5 +----
.../hrtb-exists-forall-trait-invariant.stderr | 11 +++++++++++
.../hrtb-just-for-static.stderr | 6 ++++++
4 files changed, 26 insertions(+), 5 deletions(-)
create mode 100644 tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 2723598ad6d7b..022f435b9cb6d 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -642,7 +642,14 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
) -> ty::Region<'tcx> {
let mut ut = self.unification_table_mut(); // FIXME(rust-lang/ena#42): unnecessary mut
let root_vid = ut.find(vid).vid;
- ut.probe_value(root_vid).0.unwrap_or_else(|| tcx.mk_re_var(root_vid))
+ let resolved = ut.probe_value(root_vid).0.unwrap_or_else(|| tcx.mk_re_var(root_vid));
+
+ // Don't resolve a variable to a region that it cannot name.
+ if self.var_universe(vid).can_name(self.universe(resolved)) {
+ resolved
+ } else {
+ tcx.mk_re_var(vid)
+ }
}
fn combine_map(&mut self, t: CombineMapType) -> &mut CombineMap<'tcx> {
diff --git a/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs b/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs
index e7c3bdbbf3598..9b9e4496a870d 100644
--- a/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs
+++ b/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs
@@ -2,9 +2,6 @@
//
// In particular, we test this pattern in trait solving, where it is not connected
// to any part of the source code.
-//
-// check-pass
-// Oops!
use std::cell::Cell;
@@ -28,5 +25,5 @@ fn main() {
// yielding `fn(&!b u32)`, in a fresh universe U1
// - So we get `?a = !b` but the universe U0 assigned to `?a` cannot name `!b`.
- foo::<()>();
+ foo::<()>(); //~ ERROR implementation of `Trait` is not general enough
}
diff --git a/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr b/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr
new file mode 100644
index 0000000000000..cb2ce8a4116aa
--- /dev/null
+++ b/tests/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.stderr
@@ -0,0 +1,11 @@
+error: implementation of `Trait` is not general enough
+ --> $DIR/hrtb-exists-forall-trait-invariant.rs:28:5
+ |
+LL | foo::<()>();
+ | ^^^^^^^^^^^ implementation of `Trait` is not general enough
+ |
+ = note: `()` must implement `Trait<for<'b> fn(Cell<&'b u32>)>`
+ = note: ...but it actually implements `Trait<fn(Cell<&'0 u32>)>`, for some specific lifetime `'0`
+
+error: aborting due to previous error
+
diff --git a/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr b/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
index b4312091edb27..31e11e1283516 100644
--- a/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
+++ b/tests/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
@@ -14,6 +14,12 @@ LL | fn give_some<'a>() {
| -- lifetime `'a` defined here
LL | want_hrtb::<&'a u32>()
| ^^^^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
+ |
+note: due to current limitations in the borrow checker, this implies a `'static` lifetime
+ --> $DIR/hrtb-just-for-static.rs:9:15
+ |
+LL | where T : for<'a> Foo<&'a isize>
+ | ^^^^^^^^^^^^^^^^^^^^^^
error: implementation of `Foo` is not general enough
--> $DIR/hrtb-just-for-static.rs:30:5
From 095b5fae1c5fb1ff2433e6c15a092e7f267415ec Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Sun, 5 Mar 2023 14:41:35 +0300
Subject: [PATCH 5/7] bless rustdoc tests
---
tests/rustdoc/normalize-assoc-item.rs | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tests/rustdoc/normalize-assoc-item.rs b/tests/rustdoc/normalize-assoc-item.rs
index af7b2f955fd4e..c6fd5e1101ef5 100644
--- a/tests/rustdoc/normalize-assoc-item.rs
+++ b/tests/rustdoc/normalize-assoc-item.rs
@@ -63,12 +63,12 @@ impl<'a> Lifetimes<'a> for usize {
type Y = &'a isize;
}
-// @has 'normalize_assoc_item/fn.g.html' '//pre[@class="rust item-decl"]' "pub fn g() -> &isize"
+// @has 'normalize_assoc_item/fn.g.html' '//pre[@class="rust item-decl"]' "pub fn g() -> &'static isize"
pub fn g() -> <usize as Lifetimes<'static>>::Y {
&0
}
-// @has 'normalize_assoc_item/constant.A.html' '//pre[@class="rust item-decl"]' "pub const A: &isize"
+// @has 'normalize_assoc_item/constant.A.html' '//pre[@class="rust item-decl"]' "pub const A: &'static isize"
pub const A: <usize as Lifetimes<'static>>::Y = &0;
// test cross-crate re-exports
From 228f40820d91423babd3ac2e5184c5a12109dc9b Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Wed, 8 Mar 2023 14:03:20 +0300
Subject: [PATCH 6/7] address review comment
---
.../src/infer/region_constraints/mod.rs | 11 +++++++----
compiler/rustc_middle/src/infer/unify_key.rs | 19 ++++++++++++++++---
2 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 022f435b9cb6d..21bd9243ad6a0 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -420,7 +420,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
// `RegionConstraintData` contains the relationship here.
if *any_unifications {
*any_unifications = false;
- self.unification_table_mut().reset_unifications(|_| UnifiedRegion(None));
+ self.unification_table_mut().reset_unifications(|_| UnifiedRegion::new(None));
}
data
@@ -447,7 +447,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
) -> RegionVid {
let vid = self.var_infos.push(RegionVariableInfo { origin, universe });
- let u_vid = self.unification_table_mut().new_key(UnifiedRegion(None));
+ let u_vid = self.unification_table_mut().new_key(UnifiedRegion::new(None));
assert_eq!(vid, u_vid.vid);
self.undo_log.push(AddVar(vid));
debug!("created new region variable {:?} in {:?} with origin {:?}", vid, universe, origin);
@@ -522,7 +522,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
(Region(Interned(ReVar(vid), _)), value)
| (value, Region(Interned(ReVar(vid), _))) => {
debug!("make_eqregion: unifying {:?} with {:?}", vid, value);
- self.unification_table_mut().union_value(*vid, UnifiedRegion(Some(value)));
+ self.unification_table_mut().union_value(*vid, UnifiedRegion::new(Some(value)));
self.any_unifications = true;
}
(_, _) => {}
@@ -642,7 +642,10 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
) -> ty::Region<'tcx> {
let mut ut = self.unification_table_mut(); // FIXME(rust-lang/ena#42): unnecessary mut
let root_vid = ut.find(vid).vid;
- let resolved = ut.probe_value(root_vid).0.unwrap_or_else(|| tcx.mk_re_var(root_vid));
+ let resolved = ut
+ .probe_value(root_vid)
+ .get_value_ignoring_universes()
+ .unwrap_or_else(|| tcx.mk_re_var(root_vid));
// Don't resolve a variable to a region that it cannot name.
if self.var_universe(vid).can_name(self.universe(resolved)) {
diff --git a/compiler/rustc_middle/src/infer/unify_key.rs b/compiler/rustc_middle/src/infer/unify_key.rs
index 41d8c7ffdb945..2ef6cf6f32d33 100644
--- a/compiler/rustc_middle/src/infer/unify_key.rs
+++ b/compiler/rustc_middle/src/infer/unify_key.rs
@@ -1,4 +1,4 @@
-use crate::ty::{self, Ty, TyCtxt};
+use crate::ty::{self, Region, Ty, TyCtxt};
use rustc_data_structures::unify::{NoError, UnifyKey, UnifyValue};
use rustc_span::def_id::DefId;
use rustc_span::symbol::Symbol;
@@ -11,7 +11,20 @@ pub trait ToType {
}
#[derive(PartialEq, Copy, Clone, Debug)]
-pub struct UnifiedRegion<'tcx>(pub Option<ty::Region<'tcx>>);
+pub struct UnifiedRegion<'tcx> {
+ value: Option<ty::Region<'tcx>>,
+}
+
+impl<'tcx> UnifiedRegion<'tcx> {
+ pub fn new(value: Option<Region<'tcx>>) -> Self {
+ Self { value }
+ }
+
+ /// The caller is responsible for checking universe compatibility before using this value.
+ pub fn get_value_ignoring_universes(self) -> Option<Region<'tcx>> {
+ self.value
+ }
+}
#[derive(PartialEq, Copy, Clone, Debug)]
pub struct RegionVidKey<'tcx> {
@@ -44,7 +57,7 @@ impl<'tcx> UnifyValue for UnifiedRegion<'tcx> {
type Error = NoError;
fn unify_values(value1: &Self, value2: &Self) -> Result<Self, NoError> {
- Ok(match (value1.0, value2.0) {
+ Ok(match (value1.value, value2.value) {
// Here we can just pick one value, because the full constraints graph
// will be handled later. Ideally, we might want a `MultipleValues`
// variant or something. For now though, this is fine.
From 0b232d022ff283d4c7118c0d205000a937121a02 Mon Sep 17 00:00:00 2001
From: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>
Date: Wed, 8 Mar 2023 14:17:58 +0300
Subject: [PATCH 7/7] prefer universal from lower universe
In case a variable is unified with two universal regions from different
universes, use the one with the lower universe as it has a higher chance
of being compatible with the variable.
---
compiler/rustc_middle/src/infer/unify_key.rs | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/compiler/rustc_middle/src/infer/unify_key.rs b/compiler/rustc_middle/src/infer/unify_key.rs
index 2ef6cf6f32d33..d83a587a86ae6 100644
--- a/compiler/rustc_middle/src/infer/unify_key.rs
+++ b/compiler/rustc_middle/src/infer/unify_key.rs
@@ -57,11 +57,27 @@ impl<'tcx> UnifyValue for UnifiedRegion<'tcx> {
type Error = NoError;
fn unify_values(value1: &Self, value2: &Self) -> Result<Self, NoError> {
+ // We pick the value of the least universe because it is compatible with more variables.
+ // This is *not* neccessary for soundness, but it allows more region variables to be
+ // resolved to the said value.
+ #[cold]
+ fn min_universe<'tcx>(r1: Region<'tcx>, r2: Region<'tcx>) -> Region<'tcx> {
+ cmp::min_by_key(r1, r2, |r| match r.kind() {
+ ty::ReStatic
+ | ty::ReErased
+ | ty::ReFree(..)
+ | ty::ReEarlyBound(..)
+ | ty::ReError(_) => ty::UniverseIndex::ROOT,
+ ty::RePlaceholder(placeholder) => placeholder.universe,
+ ty::ReVar(..) | ty::ReLateBound(..) => bug!("not a universal region"),
+ })
+ }
+
Ok(match (value1.value, value2.value) {
// Here we can just pick one value, because the full constraints graph
// will be handled later. Ideally, we might want a `MultipleValues`
// variant or something. For now though, this is fine.
- (Some(_), Some(_)) => *value1,
+ (Some(val1), Some(val2)) => Self { value: Some(min_universe(val1, val2)) },
(Some(_), _) => *value1,
(_, Some(_)) => *value2,