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Auto merge of #127404 - compiler-errors:rpitit-entailment-false-positive, r=oli-obk
Don't try to label `ObligationCauseCode::CompareImplItem` for an RPITIT, since it has no name The old (current) trait solver has a limitation that when a where clause in param-env must be normalized using the same where clause, then we get spurious errors in `normalize_param_env_or_error`. I don't think there's an issue tracking it, but it's the root cause for many of the "fixed-by-next-solver" labeled issues. Specifically, these errors may occur when checking predicate entailment of the GAT that comes out of desugaring RPITITs. Since we use `ObligationCauseCode::CompareImplItem` for these predicates, we try calling `item_name` on an RPITIT which fails, since the RPITIT has no name. We simply suppress this logic when we're reporting a predicate entailment error for an RPITIT. RPITITs should never have predicate entailment errors, *by construction*, but they may due to this bug in the old solver. Addresses the ICE in #127331, though doesn't fix the underlying issue (which is fundamental to the old solver). r? types
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Diff for: ‎compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

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@@ -3472,6 +3472,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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)
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});
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}
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// Suppress `compare_type_predicate_entailment` errors for RPITITs, since they
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// should be implied by the parent method.
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ObligationCauseCode::CompareImplItem { trait_item_def_id, .. }
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if tcx.is_impl_trait_in_trait(trait_item_def_id) => {}
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ObligationCauseCode::CompareImplItem { trait_item_def_id, kind, .. } => {
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let item_name = tcx.item_name(trait_item_def_id);
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let msg = format!(

Diff for: ‎tests/crashes/125099.rs

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This file was deleted.

Diff for: ‎tests/ui/impl-trait/in-trait/false-positive-predicate-entailment-error.current.stderr

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error[E0277]: the trait bound `F: MyFn<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:36:5
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|
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LL | / fn autobatch<F>(self) -> impl Trait
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LL | |
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LL | |
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LL | |
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... |
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LL | | where
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LL | | F: Callback<Self::CallbackArg>,
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| |_______________________________________^ the trait `MyFn<i32>` is not implemented for `F`, which is required by `F: Callback<i32>`
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|
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note: required for `F` to implement `Callback<i32>`
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--> $DIR/false-positive-predicate-entailment-error.rs:14:21
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|
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LL | impl<A, F: MyFn<A>> Callback<A> for F {
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| ------- ^^^^^^^^^^^ ^
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| |
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| unsatisfied trait bound introduced here
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help: consider further restricting this bound
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|
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LL | F: Callback<Self::CallbackArg> + MyFn<i32>,
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| +++++++++++
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error[E0277]: the trait bound `F: MyFn<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:36:30
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|
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LL | fn autobatch<F>(self) -> impl Trait
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| ^^^^^^^^^^ the trait `MyFn<i32>` is not implemented for `F`, which is required by `F: Callback<i32>`
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|
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note: required for `F` to implement `Callback<i32>`
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--> $DIR/false-positive-predicate-entailment-error.rs:14:21
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|
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LL | impl<A, F: MyFn<A>> Callback<A> for F {
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| ------- ^^^^^^^^^^^ ^
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| |
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| unsatisfied trait bound introduced here
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note: required by a bound in `<Sender as ChannelSender>::autobatch`
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--> $DIR/false-positive-predicate-entailment-error.rs:43:12
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|
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LL | fn autobatch<F>(self) -> impl Trait
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| --------- required by a bound in this associated function
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...
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LL | F: Callback<Self::CallbackArg>,
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `<Sender as ChannelSender>::autobatch`
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help: consider further restricting this bound
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|
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LL | F: Callback<Self::CallbackArg> + MyFn<i32>,
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| +++++++++++
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error[E0277]: the trait bound `F: MyFn<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:36:5
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|
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LL | / fn autobatch<F>(self) -> impl Trait
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LL | |
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LL | |
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LL | |
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... |
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LL | | where
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LL | | F: Callback<Self::CallbackArg>,
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| |_______________________________________^ the trait `MyFn<i32>` is not implemented for `F`, which is required by `F: Callback<i32>`
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|
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note: required for `F` to implement `Callback<i32>`
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--> $DIR/false-positive-predicate-entailment-error.rs:14:21
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|
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LL | impl<A, F: MyFn<A>> Callback<A> for F {
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| ------- ^^^^^^^^^^^ ^
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| |
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| unsatisfied trait bound introduced here
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= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
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help: consider further restricting this bound
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|
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LL | F: Callback<Self::CallbackArg> + MyFn<i32>,
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| +++++++++++
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error[E0277]: the trait bound `F: Callback<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:43:12
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|
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LL | F: Callback<Self::CallbackArg>,
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `MyFn<i32>` is not implemented for `F`, which is required by `F: Callback<i32>`
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|
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note: required for `F` to implement `Callback<i32>`
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--> $DIR/false-positive-predicate-entailment-error.rs:14:21
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|
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LL | impl<A, F: MyFn<A>> Callback<A> for F {
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| ------- ^^^^^^^^^^^ ^
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| |
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| unsatisfied trait bound introduced here
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note: the requirement `F: Callback<i32>` appears on the `impl`'s method `autobatch` but not on the corresponding trait's method
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--> $DIR/false-positive-predicate-entailment-error.rs:25:8
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|
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LL | trait ChannelSender {
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| ------------- in this trait
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...
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LL | fn autobatch<F>(self) -> impl Trait
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| ^^^^^^^^^ this trait's method doesn't have the requirement `F: Callback<i32>`
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help: consider further restricting this bound
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|
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LL | F: Callback<Self::CallbackArg> + MyFn<i32>,
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| +++++++++++
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error[E0277]: the trait bound `F: MyFn<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:36:30
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|
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LL | fn autobatch<F>(self) -> impl Trait
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| ^^^^^^^^^^ the trait `MyFn<i32>` is not implemented for `F`, which is required by `F: Callback<i32>`
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|
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note: required for `F` to implement `Callback<i32>`
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--> $DIR/false-positive-predicate-entailment-error.rs:14:21
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|
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LL | impl<A, F: MyFn<A>> Callback<A> for F {
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| ------- ^^^^^^^^^^^ ^
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| |
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| unsatisfied trait bound introduced here
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error[E0277]: the trait bound `F: Callback<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:27:12
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|
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LL | F: Callback<Self::CallbackArg>;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `MyFn<i32>` is not implemented for `F`, which is required by `F: Callback<i32>`
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|
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note: required for `F` to implement `Callback<i32>`
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--> $DIR/false-positive-predicate-entailment-error.rs:14:21
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|
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LL | impl<A, F: MyFn<A>> Callback<A> for F {
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| ------- ^^^^^^^^^^^ ^
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| |
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| unsatisfied trait bound introduced here
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error[E0277]: the trait bound `F: MyFn<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:36:5
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|
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LL | / fn autobatch<F>(self) -> impl Trait
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LL | |
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LL | |
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LL | |
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... |
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LL | | where
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LL | | F: Callback<Self::CallbackArg>,
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| |_______________________________________^ the trait `MyFn<i32>` is not implemented for `F`, which is required by `F: Callback<i32>`
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|
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note: required for `F` to implement `Callback<i32>`
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--> $DIR/false-positive-predicate-entailment-error.rs:14:21
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|
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LL | impl<A, F: MyFn<A>> Callback<A> for F {
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| ------- ^^^^^^^^^^^ ^
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| |
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| unsatisfied trait bound introduced here
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= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
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help: consider further restricting this bound
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|
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LL | F: Callback<Self::CallbackArg> + MyFn<i32>,
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| +++++++++++
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error[E0277]: the trait bound `F: MyFn<i32>` is not satisfied
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--> $DIR/false-positive-predicate-entailment-error.rs:43:12
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|
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LL | F: Callback<Self::CallbackArg>,
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `MyFn<i32>` is not implemented for `F`
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|
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note: required by a bound in `Callback`
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--> $DIR/false-positive-predicate-entailment-error.rs:10:20
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|
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LL | trait Callback<A>: MyFn<A, Output = Self::Ret> {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Callback`
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help: consider further restricting this bound
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|
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LL | F: Callback<Self::CallbackArg> + MyFn<i32>,
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| +++++++++++
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error: aborting due to 8 previous errors
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For more information about this error, try `rustc --explain E0277`.

Diff for: ‎tests/ui/impl-trait/in-trait/false-positive-predicate-entailment-error.rs

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//@ revisions: current next
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//@ ignore-compare-mode-next-solver (explicit revisions)
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//@[next] compile-flags: -Znext-solver
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//@[next] check-pass
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trait MyFn<T> {
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type Output;
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}
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trait Callback<A>: MyFn<A, Output = Self::Ret> {
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type Ret;
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}
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impl<A, F: MyFn<A>> Callback<A> for F {
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type Ret = F::Output;
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}
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struct Thing;
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trait Trait {}
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impl Trait for Thing {}
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trait ChannelSender {
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type CallbackArg;
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fn autobatch<F>(self) -> impl Trait
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where
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F: Callback<Self::CallbackArg>;
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//[current]~^ ERROR the trait bound `F: Callback<i32>` is not satisfied
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}
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struct Sender;
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impl ChannelSender for Sender {
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type CallbackArg = i32;
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fn autobatch<F>(self) -> impl Trait
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//[current]~^ ERROR the trait bound `F: MyFn<i32>` is not satisfied
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//[current]~| ERROR the trait bound `F: MyFn<i32>` is not satisfied
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//[current]~| ERROR the trait bound `F: MyFn<i32>` is not satisfied
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//[current]~| ERROR the trait bound `F: MyFn<i32>` is not satisfied
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//[current]~| ERROR the trait bound `F: MyFn<i32>` is not satisfied
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where
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F: Callback<Self::CallbackArg>,
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//[current]~^ ERROR the trait bound `F: Callback<i32>` is not satisfied
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//[current]~| ERROR the trait bound `F: MyFn<i32>` is not satisfied
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{
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Thing
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}
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}
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fn main() {}

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