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update auto trait handling

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lcnr 2021-05-07 20:00:17 +02:00 committed by Oleksandr Babak
parent b112bc5529
commit 3adedc93a9
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11 changed files with 339 additions and 78 deletions
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52
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View File

@ -124,11 +124,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.assemble_candidates_from_projected_tys(obligation, &mut candidates);
self.assemble_candidates_from_caller_bounds(stack, &mut candidates)?;
// Auto implementations have lower priority, so we only
// consider triggering a default if there is no other impl that can apply.
if candidates.vec.is_empty() {
self.assemble_candidates_from_auto_impls(obligation, &mut candidates);
}
self.assemble_candidates_from_auto_impls(obligation, &mut candidates);
}
debug!("candidate list size: {}", candidates.vec.len());
Ok(candidates)
@ -516,7 +512,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// for an example of a test case that exercises
// this path.
}
ty::Infer(ty::TyVar(_)) => {
ty::Infer(ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_)) => {
// The auto impl might apply; we don't know.
candidates.ambiguous = true;
}
@ -536,7 +532,49 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
_ => candidates.vec.push(AutoImplCandidate),
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!(
"asked to assemble auto trait candidates of unexpected type: {:?}",
self_ty
);
}
// Only consider auto impls if there are no manual impls for the root of `self_ty`.
//
// For example, we only consider auto candidates for `&i32: Auto` if no explicit impl
// for `&SomeType: Auto` exists. Due to E0321 the only crate where impls
// for `&SomeType: Auto` can be defined is the crate where `Auto` has been defined.
//
// Generally, we have to guarantee that for all `SimplifiedType`s the only crate
// which may define impls for that type is either the crate defining the type
// or the trait. This should be guaranteed by the orphan check.
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::Adt(..)
| ty::RawPtr(_)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(_)
| ty::Closure(_, _)
| ty::Generator(..)
| ty::Never
| ty::Tuple(_)
| ty::Alias(_, _)
| ty::GeneratorWitness(_)
| ty::GeneratorWitnessMIR(..) => {
let mut has_impl = false;
self.tcx().for_each_relevant_impl(def_id, self_ty, |_| has_impl = true);
if !has_impl {
candidates.vec.push(AutoImplCandidate)
}
}
ty::Error(_) => {} // do not add an auto trait impl for `ty::Error` for now.
}
}
}

25
compiler/rustc_trait_selection/src/traits/select/mod.rs
View File

@ -1814,6 +1814,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
/// candidates and prefer where-clause candidates.
///
/// See the comment for "SelectionCandidate" for more details.
#[instrument(level = "debug", skip(self))]
fn candidate_should_be_dropped_in_favor_of(
&mut self,
victim: &EvaluatedCandidate<'tcx>,
@ -1837,13 +1838,6 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
// This is a fix for #53123 and prevents winnowing from accidentally extending the
// lifetime of a variable.
match (&other.candidate, &victim.candidate) {
(_, AutoImplCandidate) | (AutoImplCandidate, _) => {
bug!(
"default implementations shouldn't be recorded \
when there are other valid candidates"
);
}
// FIXME(@jswrenn): this should probably be more sophisticated
(TransmutabilityCandidate, _) | (_, TransmutabilityCandidate) => DropVictim::No,
@ -1885,6 +1879,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
(
ParamCandidate(ref other_cand),
ImplCandidate(..)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -1912,6 +1907,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
}
(
ImplCandidate(_)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -1945,6 +1941,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
(
ObjectCandidate(_) | ProjectionCandidate(..),
ImplCandidate(..)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -1958,6 +1955,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
(
ImplCandidate(..)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -2048,6 +2046,19 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
}
}
(AutoImplCandidate, ImplCandidate(_)) | (ImplCandidate(_), AutoImplCandidate) => {
DropVictim::No
}
(AutoImplCandidate, _) | (_, AutoImplCandidate) => {
bug!(
"default implementations shouldn't be recorded \
when there are other global candidates: {:?} {:?}",
other,
victim
);
}
// Everything else is ambiguous
(
ImplCandidate(_)

31
tests/ui/auto-traits/issue-83857-ub.rs Normal file
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@ -0,0 +1,31 @@
#![allow(suspicious_auto_trait_impls)]
struct Always<T, U>(T, U);
unsafe impl<T, U> Send for Always<T, U> {}
struct Foo<T, U>(Always<T, U>);
trait False {}
unsafe impl<U: False> Send for Foo<u32, U> {}
trait WithAssoc {
type Output;
}
impl<T: Send> WithAssoc for T {
type Output = Self;
}
impl WithAssoc for Foo<u32, ()> {
type Output = Box<i32>;
}
fn generic<T, U>(v: Foo<T, U>, f: fn(<Foo<T, U> as WithAssoc>::Output) -> i32) {
//~^ ERROR `Foo<T, U>` cannot be sent between threads safely
f(foo(v));
}
fn foo<T: Send>(x: T) -> <T as WithAssoc>::Output {
x
}
fn main() {
generic(Foo(Always(0, ())), |b| *b);
}

22
tests/ui/auto-traits/issue-83857-ub.stderr Normal file
View File

@ -0,0 +1,22 @@
error[E0277]: `Foo<T, U>` cannot be sent between threads safely
--> $DIR/issue-83857-ub.rs:20:38
|
LL | fn generic<T, U>(v: Foo<T, U>, f: fn(<Foo<T, U> as WithAssoc>::Output) -> i32) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo<T, U>` cannot be sent between threads safely
|
= help: the trait `Send` is not implemented for `Foo<T, U>`
note: required for `Foo<T, U>` to implement `WithAssoc`
--> $DIR/issue-83857-ub.rs:13:15
|
LL | impl<T: Send> WithAssoc for T {
| ---- ^^^^^^^^^ ^
| |
| unsatisfied trait bound introduced here
help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
|
LL | fn generic<T, U>(v: Foo<T, U>, f: fn(<Foo<T, U> as WithAssoc>::Output) -> i32) where Foo<T, U>: Send {
| +++++++++++++++++++++
error: aborting due to previous error
For more information about this error, try `rustc --explain E0277`.

6
tests/ui/generator/auto-trait-regions.rs
View File

@ -26,7 +26,7 @@ fn assert_foo<T: Foo>(f: T) {}
fn main() {
// Make sure 'static is erased for generator interiors so we can't match it in trait selection
let x: &'static _ = &OnlyFooIfStaticRef(No);
let gen = || {
let gen = move || {
let x = x;
yield;
assert_foo(x);
@ -36,7 +36,7 @@ fn main() {
// Allow impls which matches any lifetime
let x = &OnlyFooIfRef(No);
let gen = || {
let gen = move || {
let x = x;
yield;
assert_foo(x);
@ -44,7 +44,7 @@ fn main() {
assert_foo(gen); // ok
// Disallow impls which relates lifetimes in the generator interior
let gen = || {
let gen = move || {
let a = A(&mut true, &mut true, No);
//~^ temporary value dropped while borrowed
//~| temporary value dropped while borrowed

0
tests/ui/impl-trait/auto-trait-leak Normal file
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42
tests/ui/impl-trait/recursive-impl-trait-type-indirect.drop_tracking.stderr
View File

@ -123,30 +123,32 @@ LL | | x;
LL | | }
| |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:78:5: 78:12]`
error[E0720]: cannot resolve opaque type
error[E0391]: cycle detected when computing type of `mutual_recursion::{opaque#0}`
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| ^^^^^^^^^ recursive opaque type
LL |
LL | mutual_recursion_b()
| -------------------- returning here with type `impl Sized`
...
LL | fn mutual_recursion_b() -> impl Sized {
| ---------- returning this opaque type `impl Sized`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:95:28
| ^^^^^^^^^
|
note: ...which requires type-checking `mutual_recursion`...
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| --------- returning this opaque type `impl Sync`
...
LL | fn mutual_recursion_b() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | mutual_recursion()
| ------------------ returning here with type `impl Sync`
| ^^^^^^^^^
= note: ...which requires evaluating trait selection obligation `mutual_recursion_b::{opaque#0}: core::marker::Sync`...
= note: ...which again requires computing type of `mutual_recursion::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/recursive-impl-trait-type-indirect.rs:8:1
|
LL | / #![feature(generators)]
LL | | #![allow(unconditional_recursion)]
LL | |
LL | | fn option(i: i32) -> impl Sized {
... |
LL | |
LL | | fn main() {}
| |____________^
error: aborting due to 14 previous errors
error: aborting due to 13 previous errors
For more information about this error, try `rustc --explain E0720`.
Some errors have detailed explanations: E0391, E0720.
For more information about an error, try `rustc --explain E0391`.

42
tests/ui/impl-trait/recursive-impl-trait-type-indirect.drop_tracking_mir.stderr
View File

@ -118,30 +118,32 @@ LL | fn generator_hold() -> impl Sized {
LL | let x = generator_hold();
| - generator captures itself here
error[E0720]: cannot resolve opaque type
error[E0391]: cycle detected when computing type of `mutual_recursion::{opaque#0}`
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| ^^^^^^^^^ recursive opaque type
LL |
LL | mutual_recursion_b()
| -------------------- returning here with type `impl Sized`
...
LL | fn mutual_recursion_b() -> impl Sized {
| ---------- returning this opaque type `impl Sized`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:95:28
| ^^^^^^^^^
|
note: ...which requires type-checking `mutual_recursion`...
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| --------- returning this opaque type `impl Sync`
...
LL | fn mutual_recursion_b() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | mutual_recursion()
| ------------------ returning here with type `impl Sync`
| ^^^^^^^^^
= note: ...which requires evaluating trait selection obligation `mutual_recursion_b::{opaque#0}: core::marker::Sync`...
= note: ...which again requires computing type of `mutual_recursion::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/recursive-impl-trait-type-indirect.rs:8:1
|
LL | / #![feature(generators)]
LL | | #![allow(unconditional_recursion)]
LL | |
LL | | fn option(i: i32) -> impl Sized {
... |
LL | |
LL | | fn main() {}
| |____________^
error: aborting due to 14 previous errors
error: aborting due to 13 previous errors
For more information about this error, try `rustc --explain E0720`.
Some errors have detailed explanations: E0391, E0720.
For more information about an error, try `rustc --explain E0391`.

42
tests/ui/impl-trait/recursive-impl-trait-type-indirect.no_drop_tracking.stderr
View File

@ -123,30 +123,32 @@ LL | | x;
LL | | }
| |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:78:5: 78:12]`
error[E0720]: cannot resolve opaque type
error[E0391]: cycle detected when computing type of `mutual_recursion::{opaque#0}`
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| ^^^^^^^^^ recursive opaque type
LL |
LL | mutual_recursion_b()
| -------------------- returning here with type `impl Sized`
...
LL | fn mutual_recursion_b() -> impl Sized {
| ---------- returning this opaque type `impl Sized`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:95:28
| ^^^^^^^^^
|
note: ...which requires type-checking `mutual_recursion`...
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| --------- returning this opaque type `impl Sync`
...
LL | fn mutual_recursion_b() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | mutual_recursion()
| ------------------ returning here with type `impl Sync`
| ^^^^^^^^^
= note: ...which requires evaluating trait selection obligation `mutual_recursion_b::{opaque#0}: core::marker::Sync`...
= note: ...which again requires computing type of `mutual_recursion::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/recursive-impl-trait-type-indirect.rs:8:1
|
LL | / #![feature(generators)]
LL | | #![allow(unconditional_recursion)]
LL | |
LL | | fn option(i: i32) -> impl Sized {
... |
LL | |
LL | | fn main() {}
| |____________^
error: aborting due to 14 previous errors
error: aborting due to 13 previous errors
For more information about this error, try `rustc --explain E0720`.
Some errors have detailed explanations: E0391, E0720.
For more information about an error, try `rustc --explain E0391`.

1
tests/ui/impl-trait/recursive-impl-trait-type-indirect.rs
View File

@ -93,7 +93,6 @@ fn mutual_recursion() -> impl Sync {
}
fn mutual_recursion_b() -> impl Sized {
//~^ ERROR
mutual_recursion()
}

154
tests/ui/impl-traitrecursive-impl-trait-type-indirect.no_drop_tracking.stderr Normal file
View File

@ -0,0 +1,154 @@
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:11:22
|
LL | fn option(i: i32) -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | if i < 0 { None } else { Some((option(i - 1), i)) }
| ---- ------------------------ returning here with type `Option<(impl Sized, i32)>`
| |
| returning here with type `Option<(impl Sized, i32)>`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:16:15
|
LL | fn tuple() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | (tuple(),)
| ---------- returning here with type `(impl Sized,)`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:21:15
|
LL | fn array() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | [array()]
| --------- returning here with type `[impl Sized; 1]`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:26:13
|
LL | fn ptr() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | &ptr() as *const _
| ------------------ returning here with type `*const impl Sized`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:31:16
|
LL | fn fn_ptr() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | fn_ptr as fn() -> _
| ------------------- returning here with type `fn() -> impl Sized`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:36:25
|
LL | fn closure_capture() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
...
LL | / move || {
LL | | x;
| | - closure captures itself here
LL | | }
| |_____- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:39:5: 39:12]`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:44:29
|
LL | fn closure_ref_capture() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
...
LL | / move || {
LL | | &x;
| | - closure captures itself here
LL | | }
| |_____- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:47:5: 47:12]`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:52:21
|
LL | fn closure_sig() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | || closure_sig()
| ---------------- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:54:5: 54:7]`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:57:23
|
LL | fn generator_sig() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | || generator_sig()
| ------------------ returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:59:5: 59:7]`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:62:27
|
LL | fn generator_capture() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
...
LL | / move || {
LL | | yield;
LL | | x;
| | - generator captures itself here
LL | | }
| |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:65:5: 65:12]`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:71:35
|
LL | fn substs_change<T: 'static>() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | (substs_change::<&T>(),)
| ------------------------ returning here with type `(impl Sized,)`
error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:76:24
|
LL | fn generator_hold() -> impl Sized {
| ^^^^^^^^^^ recursive opaque type
LL |
LL | / move || {
LL | | let x = generator_hold();
| | - generator captures itself here
LL | | yield;
LL | | x;
LL | | }
| |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:78:5: 78:12]`
error[E0391]: cycle detected when computing type of `mutual_recursion::{opaque#0}`
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| ^^^^^^^^^
|
note: ...which requires type-checking `mutual_recursion`...
--> $DIR/recursive-impl-trait-type-indirect.rs:90:26
|
LL | fn mutual_recursion() -> impl Sync {
| ^^^^^^^^^
= note: ...which requires evaluating trait selection obligation `mutual_recursion_b::{opaque#0}: core::marker::Sync`...
= note: ...which again requires computing type of `mutual_recursion::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/recursive-impl-trait-type-indirect.rs:8:1
|
LL | / #![feature(generators)]
LL | | #![allow(unconditional_recursion)]
LL | |
LL | | fn option(i: i32) -> impl Sized {
... |
LL | |
LL | | fn main() {}
| |____________^
error: aborting due to 13 previous errors
Some errors have detailed explanations: E0391, E0720.
For more information about an error, try `rustc --explain E0391`.