Rollup merge of #139789 - lcnr:opaques-auto-trait-leakage, r=compiler-errors
do not unnecessarily leak auto traits in item bounds fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/158 Not a fix for https://github.com/rust-lang/trait-system-refactor-initiative/issues/173 as you may have realized/tried yourself, cc #139788. However, fixing this feels desirable regardless and I don't see any reason not to. r? ```@compiler-errors```
This commit is contained in:
Stuart Cook
GitHub
commit
8118fca7fd
16 changed files with 285 additions and 7 deletions
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@ -164,6 +164,7 @@ where
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ecx: &mut EvalCtxt<'_, D>,
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goal: Goal<I, Self>,
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) -> Result<Candidate<I>, NoSolution> {
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let cx = ecx.cx();
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if goal.predicate.polarity != ty::PredicatePolarity::Positive {
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return Err(NoSolution);
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}
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@ -174,20 +175,37 @@ where
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// Only consider auto impls of unsafe traits when there are no unsafe
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// fields.
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if ecx.cx().trait_is_unsafe(goal.predicate.def_id())
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if cx.trait_is_unsafe(goal.predicate.def_id())
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&& goal.predicate.self_ty().has_unsafe_fields()
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{
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return Err(NoSolution);
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}
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// We only look into opaque types during analysis for opaque types
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// outside of their defining scope. Doing so for opaques in the
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// defining scope may require calling `typeck` on the same item we're
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// currently type checking, which will result in a fatal cycle that
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// ideally we want to avoid, since we can make progress on this goal
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// via an alias bound or a locally-inferred hidden type instead.
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// We leak the implemented auto traits of opaques outside of their defining scope.
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// This depends on `typeck` of the defining scope of that opaque, which may result in
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// fatal query cycles.
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//
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// We only get to this point if we're outside of the defining scope as we'd otherwise
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// be able to normalize the opaque type. We may also cycle in case `typeck` of a defining
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// scope relies on the current context, e.g. either because it also leaks auto trait
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// bounds of opaques defined in the current context or by evaluating the current item.
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//
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// To avoid this we don't try to leak auto trait bounds if they can also be proven via
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// item bounds of the opaque. These bounds are always applicable as auto traits must not
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// have any generic parameters. They would also get preferred over the impl candidate
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// when merging candidates anyways.
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//
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// See tests/ui/impl-trait/auto-trait-leakage/avoid-query-cycle-via-item-bound.rs.
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if let ty::Alias(ty::Opaque, opaque_ty) = goal.predicate.self_ty().kind() {
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debug_assert!(ecx.opaque_type_is_rigid(opaque_ty.def_id));
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for item_bound in cx.item_self_bounds(opaque_ty.def_id).skip_binder() {
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if item_bound
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.as_trait_clause()
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.is_some_and(|b| b.def_id() == goal.predicate.def_id())
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{
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return Err(NoSolution);
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}
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}
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}
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ecx.probe_and_evaluate_goal_for_constituent_tys(
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@ -0,0 +1,33 @@
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//@ check-pass
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//@ revisions: current next
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//@[next] compile-flags: -Znext-solver
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//@ ignore-compare-mode-next-solver (explicit revisions)
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// When proving auto trait bounds, make sure that we depend on auto trait
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// leakage if we can also prove it via an item bound.
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fn is_send<T: Send>(_: T) {}
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fn direct() -> impl Send {
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is_send(check(false)); // leaks auto traits, depends on `check`
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1u16
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}
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trait Indir: Send {}
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impl Indir for u32 {}
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fn indir() -> impl Indir {
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is_send(check(false)); // leaks auto traits, depends on `check`
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1u32
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}
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fn check(b: bool) -> impl Sized {
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if b {
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// must not leak auto traits, as we otherwise get a query cycle.
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is_send(direct());
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is_send(indir());
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}
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1u64
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}
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fn main() {
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check(true);
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}
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@ -0,0 +1,58 @@
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error[E0391]: cycle detected when computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::{anon_assoc#0}`
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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= note: ...which requires evaluating trait selection obligation `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo::{opaque#0}: core::marker::Send`...
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note: ...which requires computing type of opaque `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo::{opaque#0}`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires borrow-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires promoting constants in MIR for `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires checking if `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo` contains FFI-unwind calls...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires building MIR for `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires match-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires type-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: ...which again requires computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::{anon_assoc#0}`, completing the cycle
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note: cycle used when checking that `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>` is well-formed
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--> $DIR/method-compatability-via-leakage-cycle.rs:17:1
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LL | impl Trait for u32 {
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| ^^^^^^^^^^^^^^^^^^
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= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
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error: aborting due to 1 previous error
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For more information about this error, try `rustc --explain E0391`.
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@ -0,0 +1,122 @@
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error[E0391]: cycle detected when computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::{anon_assoc#0}`
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo::{opaque#0}`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires computing type of opaque `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo::{opaque#0}`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires borrow-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires promoting constants in MIR for `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires checking if `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo` contains FFI-unwind calls...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires building MIR for `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires match-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires type-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: ...which again requires computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::{anon_assoc#0}`, completing the cycle
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note: cycle used when checking that `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>` is well-formed
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--> $DIR/method-compatability-via-leakage-cycle.rs:17:1
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LL | impl Trait for u32 {
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| ^^^^^^^^^^^^^^^^^^
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= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
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error[E0391]: cycle detected when computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::{anon_assoc#0}`
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires comparing an impl and trait method signature, inferring any hidden `impl Trait` types in the process...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo::{opaque#0}`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires computing type of opaque `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo::{opaque#0}`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:24
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^
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note: ...which requires borrow-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires promoting constants in MIR for `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires checking if `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo` contains FFI-unwind calls...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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|
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires building MIR for `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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|
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires match-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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|
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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note: ...which requires type-checking `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::foo`...
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--> $DIR/method-compatability-via-leakage-cycle.rs:21:5
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|
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LL | fn foo(b: bool) -> impl Sized {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: ...which again requires computing type of `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>::{anon_assoc#0}`, completing the cycle
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note: cycle used when checking that `<impl at $DIR/method-compatability-via-leakage-cycle.rs:17:1: 17:19>` is well-formed
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--> $DIR/method-compatability-via-leakage-cycle.rs:17:1
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|
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LL | impl Trait for u32 {
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| ^^^^^^^^^^^^^^^^^^
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= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
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= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0391`.
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@ -0,0 +1,30 @@
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//@ revisions: current next
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//@[next] compile-flags: -Znext-solver
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//@ ignore-compare-mode-next-solver (explicit revisions)
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//@ known-bug: #139788
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// Recursively using the trait method inside of an impl in case checking
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// method compatability relies on opaque type leakage currently causes a
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// cycle error.
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trait Trait {
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// desugars to
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// type Assoc: Sized + Send;
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// fn foo(b: bool) -> Self::Assoc;
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fn foo(b: bool) -> impl Sized + Send;
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}
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impl Trait for u32 {
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// desugars to
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// type Assoc = impl_rpit::<Self>;
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// fn foo(b: bool) -> Self::Assoc { .. }
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fn foo(b: bool) -> impl Sized {
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if b {
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u32::foo(false)
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} else {
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1u32
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}
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}
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}
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fn main() {}
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@ -0,0 +1,14 @@
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//@ check-pass
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//@ revisions: current next
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//@[next] compile-flags: -Znext-solver
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//@ ignore-compare-mode-next-solver (explicit revisions)
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trait Trait {
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fn foo() -> impl Sized + Send;
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}
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impl Trait for u32 {
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fn foo() -> impl Sized {}
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}
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fn main() {}
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@ -1,4 +1,7 @@
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//@ check-pass
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//@ revisions: current next
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//@[next] compile-flags: -Znext-solver
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//@ ignore-compare-mode-next-solver (explicit revisions)
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// Make sure that refinement checking doesn't cause a cycle in `Instance::resolve`
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// which calls `compare_impl_item`.
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