Auto merge of #62221 - jonas-schievink:normalize-impl-trait, r=nikomatsakis
Normalize projections appearing in `impl Trait` Fixes #60414 This does not try to do the same for `existential type`s (which have the same bug), since that always seems to lead to cycle errors.
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0b680cfce5
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@ -1111,6 +1111,12 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
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let predicates_of = tcx.predicates_of(def_id);
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let predicates_of = tcx.predicates_of(def_id);
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debug!("instantiate_opaque_types: predicates={:#?}", predicates_of,);
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debug!("instantiate_opaque_types: predicates={:#?}", predicates_of,);
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let bounds = predicates_of.instantiate(tcx, substs);
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let bounds = predicates_of.instantiate(tcx, substs);
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let param_env = tcx.param_env(def_id);
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let InferOk { value: bounds, obligations } =
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infcx.partially_normalize_associated_types_in(span, self.body_id, param_env, &bounds);
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self.obligations.extend(obligations);
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debug!("instantiate_opaque_types: bounds={:?}", bounds);
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debug!("instantiate_opaque_types: bounds={:?}", bounds);
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let required_region_bounds = tcx.required_region_bounds(ty, bounds.predicates.clone());
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let required_region_bounds = tcx.required_region_bounds(ty, bounds.predicates.clone());
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@ -1065,6 +1065,7 @@ fn check_fn<'a, 'tcx>(
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&declared_ret_ty,
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&declared_ret_ty,
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decl.output.span(),
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decl.output.span(),
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);
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);
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debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
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fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
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fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
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fn_sig = fcx.tcx.mk_fn_sig(
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fn_sig = fcx.tcx.mk_fn_sig(
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fn_sig.inputs().iter().cloned(),
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fn_sig.inputs().iter().cloned(),
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@ -0,0 +1,16 @@
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// check-pass
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// edition:2018
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#![feature(async_await)]
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// See issue 60414
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trait Trait {
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type Assoc;
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}
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async fn foo<T: Trait<Assoc=()>>() -> T::Assoc {
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()
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}
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fn main() {}
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@ -0,0 +1,53 @@
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// compile-fail
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// edition:2018
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#![feature(async_await)]
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#![feature(existential_type)]
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#![feature(impl_trait_in_bindings)]
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//~^ WARNING the feature `impl_trait_in_bindings` is incomplete
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// See issue 60414
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/////////////////////////////////////////////
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// Reduction to `impl Trait`
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struct Foo<T>(T);
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trait FooLike { type Output; }
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impl<T> FooLike for Foo<T> {
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type Output = T;
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}
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mod impl_trait {
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use super::*;
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trait Trait {
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type Assoc;
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}
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/// `T::Assoc` can't be normalized any further here.
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fn foo_fail<T: Trait>() -> impl FooLike<Output=T::Assoc> {
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//~^ ERROR: type mismatch
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Foo(())
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}
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}
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/////////////////////////////////////////////
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// Same with lifetimes in the trait
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mod lifetimes {
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use super::*;
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trait Trait<'a> {
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type Assoc;
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}
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/// Missing bound constraining `Assoc`, `T::Assoc` can't be normalized further.
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fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output=T::Assoc> {
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//~^ ERROR: type mismatch
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Foo(())
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}
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}
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fn main() {}
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@ -0,0 +1,29 @@
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warning: the feature `impl_trait_in_bindings` is incomplete and may cause the compiler to crash
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--> $DIR/bound-normalization-fail.rs:6:12
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LL | #![feature(impl_trait_in_bindings)]
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| ^^^^^^^^^^^^^^^^^^^^^^
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error[E0271]: type mismatch resolving `<Foo<()> as FooLike>::Output == <T as impl_trait::Trait>::Assoc`
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--> $DIR/bound-normalization-fail.rs:30:32
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LL | fn foo_fail<T: Trait>() -> impl FooLike<Output=T::Assoc> {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found associated type
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= note: expected type `()`
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found type `<T as impl_trait::Trait>::Assoc`
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= note: the return type of a function must have a statically known size
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error[E0271]: type mismatch resolving `<Foo<()> as FooLike>::Output == <T as lifetimes::Trait<'static>>::Assoc`
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--> $DIR/bound-normalization-fail.rs:47:41
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LL | fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output=T::Assoc> {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected (), found associated type
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= note: expected type `()`
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found type `<T as lifetimes::Trait<'static>>::Assoc`
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= note: the return type of a function must have a statically known size
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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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@ -0,0 +1,109 @@
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// check-pass
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// edition:2018
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#![feature(async_await)]
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#![feature(existential_type)]
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#![feature(impl_trait_in_bindings)]
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//~^ WARNING the feature `impl_trait_in_bindings` is incomplete
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// See issue 60414
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/////////////////////////////////////////////
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// Reduction to `impl Trait`
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struct Foo<T>(T);
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trait FooLike { type Output; }
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impl<T> FooLike for Foo<T> {
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type Output = T;
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}
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mod impl_trait {
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use super::*;
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trait Trait {
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type Assoc;
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}
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/// `T::Assoc` should be normalized to `()` here.
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fn foo_pass<T: Trait<Assoc=()>>() -> impl FooLike<Output=T::Assoc> {
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Foo(())
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}
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}
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/////////////////////////////////////////////
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// Same with lifetimes in the trait
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mod lifetimes {
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use super::*;
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trait Trait<'a> {
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type Assoc;
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}
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/// Like above.
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///
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/// FIXME(#51525) -- the shorter notation `T::Assoc` winds up referencing `'static` here
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fn foo2_pass<'a, T: Trait<'a, Assoc=()> + 'a>(
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) -> impl FooLike<Output=<T as Trait<'a>>::Assoc> + 'a {
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Foo(())
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}
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/// Normalization to type containing bound region.
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///
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/// FIXME(#51525) -- the shorter notation `T::Assoc` winds up referencing `'static` here
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fn foo2_pass2<'a, T: Trait<'a, Assoc=&'a ()> + 'a>(
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) -> impl FooLike<Output=<T as Trait<'a>>::Assoc> + 'a {
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Foo(&())
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}
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}
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/////////////////////////////////////////////
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// Reduction using `impl Trait` in bindings
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mod impl_trait_in_bindings {
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struct Foo;
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trait FooLike { type Output; }
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impl FooLike for Foo {
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type Output = u32;
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}
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trait Trait {
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type Assoc;
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}
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fn foo<T: Trait<Assoc=u32>>() {
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let _: impl FooLike<Output=T::Assoc> = Foo;
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}
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}
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/////////////////////////////////////////////
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// The same applied to `existential type`s
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mod existential_types {
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trait Implemented {
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type Assoc;
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}
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impl<T> Implemented for T {
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type Assoc = u8;
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}
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trait Trait {
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type Out;
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}
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impl Trait for () {
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type Out = u8;
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}
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existential type Ex: Trait<Out = <() as Implemented>::Assoc>;
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fn define() -> Ex {
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()
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}
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}
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fn main() {}
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@ -0,0 +1,6 @@
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warning: the feature `impl_trait_in_bindings` is incomplete and may cause the compiler to crash
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--> $DIR/bound-normalization-pass.rs:6:12
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LL | #![feature(impl_trait_in_bindings)]
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| ^^^^^^^^^^^^^^^^^^^^^^
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