Auto merge of #80246 - matthewjasper:projection-cycle-caching, r=Mark-Simulacrum
Prevent caching normalization results with a cycle When normalizing a projection which results in a cycle, we would cache the result of `project_type` without the nested obligations (because they're not needed for inference). This would result in the nested obligations only being handled once in fulfill, which would avoid the cycle error. `get_paranoid_cache_value_obligation` used to add an obligation that resulted in a cycle in this case previously, but was removed by #73905. This PR makes the projection cache not cache the value of a projection if it was ever normalized in a cycle (except in a snapshot that's rolled back). Fixes #79714. r? `@nikomatsakis`
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931aa27922
@ -90,6 +90,7 @@ pub fn new(ty: ty::ProjectionTy<'tcx>) -> Self {
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pub enum ProjectionCacheEntry<'tcx> {
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InProgress,
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Ambiguous,
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Recur,
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Error,
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NormalizedTy(NormalizedTy<'tcx>),
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}
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@ -143,7 +144,12 @@ pub fn insert_ty(&mut self, key: ProjectionCacheKey<'tcx>, value: NormalizedTy<'
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"ProjectionCacheEntry::insert_ty: adding cache entry: key={:?}, value={:?}",
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key, value
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);
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let fresh_key = self.map().insert(key, ProjectionCacheEntry::NormalizedTy(value));
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let mut map = self.map();
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if let Some(ProjectionCacheEntry::Recur) = map.get(&key) {
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debug!("Not overwriting Recur");
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return;
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}
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let fresh_key = map.insert(key, ProjectionCacheEntry::NormalizedTy(value));
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assert!(!fresh_key, "never started projecting `{:?}`", key);
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}
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@ -197,6 +203,14 @@ pub fn ambiguous(&mut self, key: ProjectionCacheKey<'tcx>) {
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assert!(!fresh, "never started projecting `{:?}`", key);
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}
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/// Indicates that while trying to normalize `key`, `key` was required to
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/// be normalized again. Selection or evaluation should eventually report
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/// an error here.
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pub fn recur(&mut self, key: ProjectionCacheKey<'tcx>) {
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let fresh = self.map().insert(key, ProjectionCacheEntry::Recur);
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assert!(!fresh, "never started projecting `{:?}`", key);
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}
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/// Indicates that trying to normalize `key` resulted in
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/// error.
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pub fn error(&mut self, key: ProjectionCacheKey<'tcx>) {
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@ -496,12 +496,6 @@ fn opt_normalize_projection_type<'a, 'b, 'tcx>(
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return Ok(None);
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}
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Err(ProjectionCacheEntry::InProgress) => {
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// If while normalized A::B, we are asked to normalize
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// A::B, just return A::B itself. This is a conservative
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// answer, in the sense that A::B *is* clearly equivalent
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// to A::B, though there may be a better value we can
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// find.
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// Under lazy normalization, this can arise when
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// bootstrapping. That is, imagine an environment with a
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// where-clause like `A::B == u32`. Now, if we are asked
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@ -512,6 +506,14 @@ fn opt_normalize_projection_type<'a, 'b, 'tcx>(
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debug!("found cache entry: in-progress");
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// Cache that normalizing this projection resulted in a cycle. This
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// should ensure that, unless this happens within a snapshot that's
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// rolled back, fulfillment or evaluation will notice the cycle.
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infcx.inner.borrow_mut().projection_cache().recur(cache_key);
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return Err(InProgress);
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}
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Err(ProjectionCacheEntry::Recur) => {
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return Err(InProgress);
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}
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Err(ProjectionCacheEntry::NormalizedTy(ty)) => {
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@ -734,8 +736,15 @@ fn project_type<'cx, 'tcx>(
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if !selcx.tcx().sess.recursion_limit().value_within_limit(obligation.recursion_depth) {
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debug!("project: overflow!");
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match selcx.query_mode() {
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super::TraitQueryMode::Standard => {
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selcx.infcx().report_overflow_error(&obligation, true);
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}
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super::TraitQueryMode::Canonical => {
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return Err(ProjectionTyError::TraitSelectionError(SelectionError::Overflow));
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}
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}
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}
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let obligation_trait_ref = &obligation.predicate.trait_ref(selcx.tcx());
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@ -291,6 +291,10 @@ pub fn tcx(&self) -> TyCtxt<'tcx> {
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self.infcx.tcx
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}
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pub(super) fn query_mode(&self) -> TraitQueryMode {
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self.query_mode
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}
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///////////////////////////////////////////////////////////////////////////
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// Selection
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//
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@ -24,13 +24,13 @@ impl Tr for u32 {
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// ...but not in an impl that redefines one of the types.
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impl Tr for bool {
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type A = Box<Self::B>;
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//~^ ERROR type mismatch resolving `<bool as Tr>::B == _`
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//~^ ERROR overflow evaluating the requirement `<bool as Tr>::B == _`
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}
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// (the error is shown twice for some reason)
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impl Tr for usize {
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type B = &'static Self::A;
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//~^ ERROR type mismatch resolving `<usize as Tr>::A == _`
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//~^ ERROR overflow evaluating the requirement `<usize as Tr>::A == _`
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}
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fn main() {
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@ -1,15 +1,15 @@
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error[E0271]: type mismatch resolving `<bool as Tr>::B == _`
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error[E0275]: overflow evaluating the requirement `<bool as Tr>::B == _`
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--> $DIR/defaults-cyclic-fail-1.rs:26:5
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LL | type A = Box<Self::B>;
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| ^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
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| ^^^^^^^^^^^^^^^^^^^^^^
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error[E0271]: type mismatch resolving `<usize as Tr>::A == _`
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error[E0275]: overflow evaluating the requirement `<usize as Tr>::A == _`
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--> $DIR/defaults-cyclic-fail-1.rs:32:5
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LL | type B = &'static Self::A;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0271`.
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For more information about this error, try `rustc --explain E0275`.
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@ -25,13 +25,13 @@ impl Tr for u32 {
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impl Tr for bool {
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type A = Box<Self::B>;
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//~^ ERROR type mismatch resolving `<bool as Tr>::B == _`
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//~^ ERROR overflow evaluating the requirement `<bool as Tr>::B == _`
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}
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// (the error is shown twice for some reason)
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impl Tr for usize {
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type B = &'static Self::A;
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//~^ ERROR type mismatch resolving `<usize as Tr>::A == _`
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//~^ ERROR overflow evaluating the requirement `<usize as Tr>::A == _`
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}
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fn main() {
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@ -1,15 +1,15 @@
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error[E0271]: type mismatch resolving `<bool as Tr>::B == _`
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error[E0275]: overflow evaluating the requirement `<bool as Tr>::B == _`
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--> $DIR/defaults-cyclic-fail-2.rs:27:5
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LL | type A = Box<Self::B>;
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| ^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
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| ^^^^^^^^^^^^^^^^^^^^^^
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error[E0271]: type mismatch resolving `<usize as Tr>::A == _`
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error[E0275]: overflow evaluating the requirement `<usize as Tr>::A == _`
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--> $DIR/defaults-cyclic-fail-2.rs:33:5
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LL | type B = &'static Self::A;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0271`.
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For more information about this error, try `rustc --explain E0275`.
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29
src/test/ui/associated-types/impl-wf-cycle-1.rs
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29
src/test/ui/associated-types/impl-wf-cycle-1.rs
Normal file
@ -0,0 +1,29 @@
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// Regression test for #79714
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trait Baz {}
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impl Baz for () {}
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impl<T> Baz for (T,) {}
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trait Fiz {}
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impl Fiz for bool {}
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trait Grault {
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type A;
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type B;
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}
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impl<T: Grault> Grault for (T,)
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where
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Self::A: Baz,
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Self::B: Fiz,
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{
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type A = ();
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//~^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
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type B = bool;
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//~^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
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}
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//~^^^^^^^^^^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
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fn main() {
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let x: <(_,) as Grault>::A = ();
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}
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39
src/test/ui/associated-types/impl-wf-cycle-1.stderr
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39
src/test/ui/associated-types/impl-wf-cycle-1.stderr
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@ -0,0 +1,39 @@
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error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
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--> $DIR/impl-wf-cycle-1.rs:15:1
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LL | / impl<T: Grault> Grault for (T,)
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LL | | where
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LL | | Self::A: Baz,
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LL | | Self::B: Fiz,
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... |
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LL | |
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LL | | }
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| |_^
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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= note: 1 redundant requirements hidden
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
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--> $DIR/impl-wf-cycle-1.rs:20:5
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LL | type A = ();
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| ^^^^^^^^^^^^
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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= note: 1 redundant requirements hidden
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
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--> $DIR/impl-wf-cycle-1.rs:22:5
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LL | type B = bool;
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| ^^^^^^^^^^^^^^
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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= note: 1 redundant requirements hidden
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0275`.
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16
src/test/ui/associated-types/impl-wf-cycle-2.rs
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16
src/test/ui/associated-types/impl-wf-cycle-2.rs
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@ -0,0 +1,16 @@
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// Regression test for #79714
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trait Grault {
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type A;
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}
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impl<T: Grault> Grault for (T,)
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where
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Self::A: Copy,
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{
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type A = ();
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//~^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
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}
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//~^^^^^^^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
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fn main() {}
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25
src/test/ui/associated-types/impl-wf-cycle-2.stderr
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25
src/test/ui/associated-types/impl-wf-cycle-2.stderr
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@ -0,0 +1,25 @@
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error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
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--> $DIR/impl-wf-cycle-2.rs:7:1
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LL | / impl<T: Grault> Grault for (T,)
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LL | | where
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LL | | Self::A: Copy,
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LL | | {
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LL | | type A = ();
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LL | |
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LL | | }
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| |_^
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
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--> $DIR/impl-wf-cycle-2.rs:11:5
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LL | type A = ();
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| ^^^^^^^^^^^^
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= note: required because of the requirements on the impl of `Grault` for `(T,)`
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0275`.
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@ -1,11 +1,10 @@
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error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next: Sized`
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error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next`
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--> $DIR/issue-23122-2.rs:9:5
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LL | type Next = <GetNext<T::Next> as Next>::Next;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: consider adding a `#![recursion_limit="256"]` attribute to your crate (`issue_23122_2`)
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= note: required because of the requirements on the impl of `Next` for `GetNext<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next>`
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error: aborting due to previous error
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