diff --git a/compiler/rustc_error_codes/src/error_codes/E0719.md b/compiler/rustc_error_codes/src/error_codes/E0719.md
index cd981db1058a6..17cbd2de49efd 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0719.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0719.md
@@ -1,4 +1,4 @@
-An associated type value was specified more than once.
+An associated item value was specified more than once in a trait object.
 
 Erroneous code example:
 
@@ -7,21 +7,15 @@ trait FooTrait {}
 trait BarTrait {}
 
 // error: associated type `Item` in trait `Iterator` is specified twice
-struct Foo<T: Iterator<Item: FooTrait, Item: BarTrait>> { f: T }
+type Foo = dyn Iterator<Item = u32, Item = u32>;
 ```
 
-`Item` in trait `Iterator` cannot be specified multiple times for struct `Foo`.
-To fix this, create a new trait that is a combination of the desired traits and
-specify the associated type with the new trait.
+To fix this, remove the duplicate specifier:
 
 Corrected example:
 
 ```
-trait FooTrait {}
-trait BarTrait {}
-trait FooBarTrait: FooTrait + BarTrait {}
-
-struct Foo<T: Iterator<Item: FooBarTrait>> { f: T } // ok!
+type Foo = dyn Iterator<Item = u32>; // ok!
 ```
 
 For more information about associated types, see [the book][bk-at]. For more
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
index 99dc8e6e52217..a8d75ba223ab3 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -362,6 +362,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         param_ty,
                         bounds,
                         predicate_filter,
+                        false,
                     );
                 }
                 hir::GenericBound::Outlives(lifetime) => {
@@ -402,7 +403,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         trait_ref: ty::PolyTraitRef<'tcx>,
         constraint: &hir::AssocItemConstraint<'tcx>,
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
-        duplicates: &mut FxIndexMap<DefId, Span>,
+        duplicates: Option<&mut FxIndexMap<DefId, Span>>,
         path_span: Span,
         predicate_filter: PredicateFilter,
     ) -> Result<(), ErrorGuaranteed> {
@@ -458,17 +459,19 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             )
             .expect("failed to find associated item");
 
-        duplicates
-            .entry(assoc_item.def_id)
-            .and_modify(|prev_span| {
-                self.dcx().emit_err(errors::ValueOfAssociatedStructAlreadySpecified {
-                    span: constraint.span,
-                    prev_span: *prev_span,
-                    item_name: constraint.ident,
-                    def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
-                });
-            })
-            .or_insert(constraint.span);
+        if let Some(duplicates) = duplicates {
+            duplicates
+                .entry(assoc_item.def_id)
+                .and_modify(|prev_span| {
+                    self.dcx().emit_err(errors::ValueOfAssociatedStructAlreadySpecified {
+                        span: constraint.span,
+                        prev_span: *prev_span,
+                        item_name: constraint.ident,
+                        def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
+                    });
+                })
+                .or_insert(constraint.span);
+        }
 
         let projection_term = if let ty::AssocTag::Fn = assoc_tag {
             let bound_vars = tcx.late_bound_vars(constraint.hir_id);
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
index c248cd7fec2e5..a4179776572d6 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
@@ -60,6 +60,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 dummy_self,
                 &mut user_written_bounds,
                 PredicateFilter::SelfOnly,
+                true,
             );
             if let Err(GenericArgCountMismatch { invalid_args, .. }) = result.correct {
                 potential_assoc_types.extend(invalid_args);
@@ -157,10 +158,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 self.dcx()
                     .struct_span_err(
                         span,
-                        format!(
-                            "conflicting associated type bounds for `{item}` when \
-                            expanding trait alias"
-                        ),
+                        format!("conflicting associated type bounds for `{item}`"),
                     )
                     .with_span_label(
                         old_proj_span,
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 9b198d044542f..0ff1fabd7b303 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -752,6 +752,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         self_ty: Ty<'tcx>,
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         predicate_filter: PredicateFilter,
+        for_dyn: bool,
     ) -> GenericArgCountResult {
         let tcx = self.tcx();
 
@@ -927,7 +928,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 poly_trait_ref,
                 constraint,
                 bounds,
-                &mut dup_constraints,
+                for_dyn.then_some(&mut dup_constraints),
                 constraint.span,
                 predicate_filter,
             );
diff --git a/tests/ui/associated-type-bounds/duplicate-bound-err.rs b/tests/ui/associated-type-bounds/duplicate-bound-err.rs
new file mode 100644
index 0000000000000..50db5de7ca768
--- /dev/null
+++ b/tests/ui/associated-type-bounds/duplicate-bound-err.rs
@@ -0,0 +1,114 @@
+//@ edition: 2024
+
+#![feature(associated_const_equality, type_alias_impl_trait, return_type_notation)]
+#![allow(refining_impl_trait_internal)]
+
+use std::iter;
+
+fn frpit1() -> impl Iterator<Item: Copy, Item: Send> {
+    iter::empty()
+    //~^ ERROR type annotations needed
+}
+fn frpit2() -> impl Iterator<Item: Copy, Item: Copy> {
+    iter::empty()
+    //~^ ERROR type annotations needed
+}
+fn frpit3() -> impl Iterator<Item: 'static, Item: 'static> {
+    iter::empty()
+    //~^ ERROR type annotations needed
+}
+
+type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
+//~^ ERROR unconstrained opaque type
+type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
+//~^ ERROR unconstrained opaque type
+type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
+//~^ ERROR unconstrained opaque type
+
+type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
+//~^ ERROR unconstrained opaque type
+type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
+//~^ ERROR unconstrained opaque type
+type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
+//~^ ERROR unconstrained opaque type
+
+fn mismatch() -> impl Iterator<Item: Copy, Item: Send> {
+    //~^ ERROR [E0277]
+    iter::empty::<*const ()>()
+}
+
+fn mismatch_2() -> impl Iterator<Item: Copy, Item: Send> {
+    //~^ ERROR [E0277]
+    iter::empty::<String>()
+}
+
+trait Trait {
+    type Gat<T>;
+
+    const ASSOC: i32;
+
+    fn foo() -> impl Sized;
+}
+
+impl Trait for () {
+    type Gat<T> = ();
+
+    const ASSOC: i32 = 3;
+
+    fn foo() {}
+}
+
+impl Trait for u32 {
+    type Gat<T> = ();
+
+    const ASSOC: i32 = 4;
+
+    fn foo() -> u32 {
+        42
+    }
+}
+
+fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+
+fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+
+fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+
+type MustFail = dyn Iterator<Item = i32, Item = u32>;
+//~^ ERROR [E0719]
+//~| ERROR conflicting associated type bounds
+
+trait Trait2 {
+    const ASSOC: u32;
+}
+
+type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+//~^ ERROR [E0719]
+//~| ERROR conflicting associated type bounds
+
+type MustFail3 = dyn Iterator<Item = i32, Item = i32>;
+//~^ ERROR [E0719]
+
+type MustFail4 = dyn Trait2<ASSOC = 3u32, ASSOC = 3u32>;
+//~^ ERROR [E0719]
+
+trait Trait3 {
+    fn foo() -> impl Iterator<Item = i32, Item = u32>;
+}
+
+impl Trait3 for () {
+    fn foo() -> impl Iterator<Item = i32, Item = u32> {
+        //~^ ERROR[E0271]
+        //~| ERROR[E0271]
+        [2u32].into_iter()
+    }
+}
+
+fn main() {
+    uncallable(iter::empty::<u32>()); //~ ERROR [E0271]
+    uncallable(iter::empty::<i32>()); //~ ERROR [E0271]
+    uncallable_const(()); //~ ERROR [E0271]
+    uncallable_const(4u32); //~ ERROR [E0271]
+    uncallable_rtn(()); //~ ERROR [E0271]
+    uncallable_rtn(17u32); //~ ERROR [E0271]
+}
diff --git a/tests/ui/associated-type-bounds/duplicate-bound-err.stderr b/tests/ui/associated-type-bounds/duplicate-bound-err.stderr
new file mode 100644
index 0000000000000..6c1dc03676c79
--- /dev/null
+++ b/tests/ui/associated-type-bounds/duplicate-bound-err.stderr
@@ -0,0 +1,268 @@
+error[E0282]: type annotations needed
+  --> $DIR/duplicate-bound-err.rs:9:5
+   |
+LL |     iter::empty()
+   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
+   |
+help: consider specifying the generic argument
+   |
+LL |     iter::empty::<T>()
+   |                +++++
+
+error[E0282]: type annotations needed
+  --> $DIR/duplicate-bound-err.rs:13:5
+   |
+LL |     iter::empty()
+   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
+   |
+help: consider specifying the generic argument
+   |
+LL |     iter::empty::<T>()
+   |                +++++
+
+error[E0282]: type annotations needed
+  --> $DIR/duplicate-bound-err.rs:17:5
+   |
+LL |     iter::empty()
+   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
+   |
+help: consider specifying the generic argument
+   |
+LL |     iter::empty::<T>()
+   |                +++++
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:21:51
+   |
+LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
+   |                                                   ^^^^^^^^^
+   |
+   = note: `ETAI1` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:23:51
+   |
+LL | type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
+   |                                                   ^^^^^^^^^
+   |
+   = note: `ETAI2` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:25:57
+   |
+LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
+   |                                                         ^^^^^^^^^
+   |
+   = note: `ETAI3` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:28:14
+   |
+LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `ETAI4` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:30:14
+   |
+LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `ETAI5` must be used in combination with a concrete type within the same crate
+
+error: unconstrained opaque type
+  --> $DIR/duplicate-bound-err.rs:32:14
+   |
+LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `ETAI6` must be used in combination with a concrete type within the same crate
+
+error[E0277]: `*const ()` cannot be sent between threads safely
+  --> $DIR/duplicate-bound-err.rs:35:18
+   |
+LL | fn mismatch() -> impl Iterator<Item: Copy, Item: Send> {
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `*const ()` cannot be sent between threads safely
+LL |
+LL |     iter::empty::<*const ()>()
+   |     -------------------------- return type was inferred to be `std::iter::Empty<*const ()>` here
+   |
+   = help: the trait `Send` is not implemented for `*const ()`
+
+error[E0277]: the trait bound `String: Copy` is not satisfied
+  --> $DIR/duplicate-bound-err.rs:40:20
+   |
+LL | fn mismatch_2() -> impl Iterator<Item: Copy, Item: Send> {
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `String`
+LL |
+LL |     iter::empty::<String>()
+   |     ----------------------- return type was inferred to be `std::iter::Empty<String>` here
+
+error[E0271]: expected `IntoIter<u32, 1>` to be an iterator that yields `i32`, but it yields `u32`
+  --> $DIR/duplicate-bound-err.rs:100:17
+   |
+LL |     fn foo() -> impl Iterator<Item = i32, Item = u32> {
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
+...
+LL |         [2u32].into_iter()
+   |         ------------------ return type was inferred to be `std::array::IntoIter<u32, 1>` here
+
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate-bound-err.rs:77:42
+   |
+LL | type MustFail = dyn Iterator<Item = i32, Item = u32>;
+   |                              ----------  ^^^^^^^^^^ re-bound here
+   |                              |
+   |                              `Item` bound here first
+
+error: conflicting associated type bounds for `Item`
+  --> $DIR/duplicate-bound-err.rs:77:17
+   |
+LL | type MustFail = dyn Iterator<Item = i32, Item = u32>;
+   |                 ^^^^^^^^^^^^^----------^^----------^
+   |                              |           |
+   |                              |           `Item` is specified to be `u32` here
+   |                              `Item` is specified to be `i32` here
+
+error[E0719]: the value of the associated type `ASSOC` in trait `Trait2` is already specified
+  --> $DIR/duplicate-bound-err.rs:85:43
+   |
+LL | type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+   |                             ------------  ^^^^^^^^^^^^ re-bound here
+   |                             |
+   |                             `ASSOC` bound here first
+
+error: conflicting associated type bounds for `ASSOC`
+  --> $DIR/duplicate-bound-err.rs:85:18
+   |
+LL | type MustFail2 = dyn Trait2<ASSOC = 3u32, ASSOC = 4u32>;
+   |                  ^^^^^^^^^^^------------^^------------^
+   |                             |             |
+   |                             |             `ASSOC` is specified to be `4` here
+   |                             `ASSOC` is specified to be `3` here
+
+error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
+  --> $DIR/duplicate-bound-err.rs:89:43
+   |
+LL | type MustFail3 = dyn Iterator<Item = i32, Item = i32>;
+   |                               ----------  ^^^^^^^^^^ re-bound here
+   |                               |
+   |                               `Item` bound here first
+
+error[E0719]: the value of the associated type `ASSOC` in trait `Trait2` is already specified
+  --> $DIR/duplicate-bound-err.rs:92:43
+   |
+LL | type MustFail4 = dyn Trait2<ASSOC = 3u32, ASSOC = 3u32>;
+   |                             ------------  ^^^^^^^^^^^^ re-bound here
+   |                             |
+   |                             `ASSOC` bound here first
+
+error[E0271]: expected `impl Iterator<Item = u32>` to be an iterator that yields `i32`, but it yields `u32`
+  --> $DIR/duplicate-bound-err.rs:100:17
+   |
+LL |     fn foo() -> impl Iterator<Item = i32, Item = u32> {
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
+   |
+note: required by a bound in `Trait3::foo::{anon_assoc#0}`
+  --> $DIR/duplicate-bound-err.rs:96:31
+   |
+LL |     fn foo() -> impl Iterator<Item = i32, Item = u32>;
+   |                               ^^^^^^^^^^ required by this bound in `Trait3::foo::{anon_assoc#0}`
+
+error[E0271]: expected `Empty<u32>` to be an iterator that yields `i32`, but it yields `u32`
+  --> $DIR/duplicate-bound-err.rs:108:16
+   |
+LL |     uncallable(iter::empty::<u32>());
+   |     ---------- ^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `u32`
+   |     |
+   |     required by a bound introduced by this call
+   |
+note: required by a bound in `uncallable`
+  --> $DIR/duplicate-bound-err.rs:71:32
+   |
+LL | fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+   |                                ^^^^^^^^^^ required by this bound in `uncallable`
+
+error[E0271]: expected `Empty<i32>` to be an iterator that yields `u32`, but it yields `i32`
+  --> $DIR/duplicate-bound-err.rs:109:16
+   |
+LL |     uncallable(iter::empty::<i32>());
+   |     ---------- ^^^^^^^^^^^^^^^^^^^^ expected `u32`, found `i32`
+   |     |
+   |     required by a bound introduced by this call
+   |
+note: required by a bound in `uncallable`
+  --> $DIR/duplicate-bound-err.rs:71:44
+   |
+LL | fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+   |                                            ^^^^^^^^^^ required by this bound in `uncallable`
+
+error[E0271]: type mismatch resolving `<() as Trait>::ASSOC == 4`
+  --> $DIR/duplicate-bound-err.rs:110:22
+   |
+LL |     uncallable_const(());
+   |     ---------------- ^^ expected `4`, found `3`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `4`
+              found constant `3`
+note: required by a bound in `uncallable_const`
+  --> $DIR/duplicate-bound-err.rs:73:46
+   |
+LL | fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+   |                                              ^^^^^^^^^ required by this bound in `uncallable_const`
+
+error[E0271]: type mismatch resolving `<u32 as Trait>::ASSOC == 3`
+  --> $DIR/duplicate-bound-err.rs:111:22
+   |
+LL |     uncallable_const(4u32);
+   |     ---------------- ^^^^ expected `3`, found `4`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `3`
+              found constant `4`
+note: required by a bound in `uncallable_const`
+  --> $DIR/duplicate-bound-err.rs:73:35
+   |
+LL | fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+   |                                   ^^^^^^^^^ required by this bound in `uncallable_const`
+
+error[E0271]: type mismatch resolving `<() as Trait>::ASSOC == 4`
+  --> $DIR/duplicate-bound-err.rs:112:20
+   |
+LL |     uncallable_rtn(());
+   |     -------------- ^^ expected `4`, found `3`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `4`
+              found constant `3`
+note: required by a bound in `uncallable_rtn`
+  --> $DIR/duplicate-bound-err.rs:75:75
+   |
+LL | fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+   |                                                                           ^^^^^^^^^ required by this bound in `uncallable_rtn`
+
+error[E0271]: type mismatch resolving `<u32 as Trait>::ASSOC == 3`
+  --> $DIR/duplicate-bound-err.rs:113:20
+   |
+LL |     uncallable_rtn(17u32);
+   |     -------------- ^^^^^ expected `3`, found `4`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = note: expected constant `3`
+              found constant `4`
+note: required by a bound in `uncallable_rtn`
+  --> $DIR/duplicate-bound-err.rs:75:48
+   |
+LL | fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+   |                                                ^^^^^^^^^ required by this bound in `uncallable_rtn`
+
+error: aborting due to 25 previous errors
+
+Some errors have detailed explanations: E0271, E0277, E0282, E0719.
+For more information about an error, try `rustc --explain E0271`.
diff --git a/tests/ui/associated-type-bounds/duplicate-bound.rs b/tests/ui/associated-type-bounds/duplicate-bound.rs
new file mode 100644
index 0000000000000..97b2b3905a55e
--- /dev/null
+++ b/tests/ui/associated-type-bounds/duplicate-bound.rs
@@ -0,0 +1,240 @@
+//@ edition: 2024
+//@ run-pass
+
+#![feature(associated_const_equality, return_type_notation)]
+#![allow(dead_code, refining_impl_trait_internal, type_alias_bounds)]
+
+use std::iter;
+use std::mem::ManuallyDrop;
+
+struct SI1<T: Iterator<Item: Copy, Item: Send>> {
+    f: T,
+}
+struct SI2<T: Iterator<Item: Copy, Item: Copy>> {
+    f: T,
+}
+struct SI3<T: Iterator<Item: 'static, Item: 'static>> {
+    f: T,
+}
+struct SW1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+    f: T,
+}
+struct SW2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+    f: T,
+}
+struct SW3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+    f: T,
+}
+
+enum EI1<T: Iterator<Item: Copy, Item: Send>> {
+    V(T),
+}
+enum EI2<T: Iterator<Item: Copy, Item: Copy>> {
+    V(T),
+}
+enum EI3<T: Iterator<Item: 'static, Item: 'static>> {
+    V(T),
+}
+enum EW1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+    V(T),
+}
+enum EW2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+    V(T),
+}
+enum EW3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+    V(T),
+}
+
+union UI1<T: Iterator<Item: Copy, Item: Send>> {
+    f: ManuallyDrop<T>,
+}
+union UI2<T: Iterator<Item: Copy, Item: Copy>> {
+    f: ManuallyDrop<T>,
+}
+union UI3<T: Iterator<Item: 'static, Item: 'static>> {
+    f: ManuallyDrop<T>,
+}
+union UW1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+    f: ManuallyDrop<T>,
+}
+union UW2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+    f: ManuallyDrop<T>,
+}
+union UW3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+    f: ManuallyDrop<T>,
+}
+
+fn fi1<T: Iterator<Item: Copy, Item: Send>>() {}
+fn fi2<T: Iterator<Item: Copy, Item: Copy>>() {}
+fn fi3<T: Iterator<Item: 'static, Item: 'static>>() {}
+fn fw1<T>()
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+}
+fn fw2<T>()
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+}
+fn fw3<T>()
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+}
+
+fn frpit1() -> impl Iterator<Item: Copy, Item: Send> {
+    iter::empty::<u32>()
+}
+fn frpit2() -> impl Iterator<Item: Copy, Item: Copy> {
+    iter::empty::<u32>()
+}
+fn frpit3() -> impl Iterator<Item: 'static, Item: 'static> {
+    iter::empty::<u32>()
+}
+fn fapit1(_: impl Iterator<Item: Copy, Item: Send>) {}
+fn fapit2(_: impl Iterator<Item: Copy, Item: Copy>) {}
+fn fapit3(_: impl Iterator<Item: 'static, Item: 'static>) {}
+
+type TAI1<T: Iterator<Item: Copy, Item: Send>> = T;
+type TAI2<T: Iterator<Item: Copy, Item: Copy>> = T;
+type TAI3<T: Iterator<Item: 'static, Item: 'static>> = T;
+type TAW1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+= T;
+type TAW2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+= T;
+type TAW3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+= T;
+
+trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
+trait TRI2<T: Iterator<Item: Copy, Item: Copy>> {}
+trait TRI3<T: Iterator<Item: 'static, Item: 'static>> {}
+trait TRS1: Iterator<Item: Copy, Item: Send> {}
+trait TRS2: Iterator<Item: Copy, Item: Copy> {}
+trait TRS3: Iterator<Item: 'static, Item: 'static> {}
+trait TRW1<T>
+where
+    T: Iterator<Item: Copy, Item: Send>,
+{
+}
+trait TRW2<T>
+where
+    T: Iterator<Item: Copy, Item: Copy>,
+{
+}
+trait TRW3<T>
+where
+    T: Iterator<Item: 'static, Item: 'static>,
+{
+}
+trait TRSW1
+where
+    Self: Iterator<Item: Copy, Item: Send>,
+{
+}
+trait TRSW2
+where
+    Self: Iterator<Item: Copy, Item: Copy>,
+{
+}
+trait TRSW3
+where
+    Self: Iterator<Item: 'static, Item: 'static>,
+{
+}
+trait TRA1 {
+    type A: Iterator<Item: Copy, Item: Send>;
+}
+trait TRA2 {
+    type A: Iterator<Item: Copy, Item: Copy>;
+}
+trait TRA3 {
+    type A: Iterator<Item: 'static, Item: 'static>;
+}
+
+trait Trait {
+    type Gat<T>;
+
+    const ASSOC: i32;
+
+    fn foo() -> impl Sized;
+}
+
+impl Trait for () {
+    type Gat<T> = ();
+
+    const ASSOC: i32 = 3;
+
+    fn foo() {}
+}
+
+trait Subtrait: Trait<Gat<u32> = u32, Gat<u64> = u64> {}
+
+fn f<T: Trait<Gat<i32> = (), Gat<i64> = ()>>() {
+    let _: T::Gat<i32> = ();
+    let _: T::Gat<i64> = ();
+}
+
+fn g<T: Trait<Gat<i32> = (), Gat<i64> = &'static str>>() {
+    let _: T::Gat<i32> = ();
+    let _: T::Gat<i64> = "";
+}
+
+fn uncallable(_: impl Iterator<Item = i32, Item = u32>) {}
+
+fn callable(_: impl Iterator<Item = i32, Item = i32>) {}
+
+fn uncallable_const(_: impl Trait<ASSOC = 3, ASSOC = 4>) {}
+
+fn callable_const(_: impl Trait<ASSOC = 3, ASSOC = 3>) {}
+
+fn uncallable_rtn(_: impl Trait<foo(..): Trait<ASSOC = 3>, foo(..): Trait<ASSOC = 4>>) {}
+
+fn callable_rtn(_: impl Trait<foo(..): Send, foo(..): Send, foo(..): Eq>) {}
+
+trait Trait2 {
+    const ASSOC: u32;
+}
+
+trait Trait3 {
+    fn foo() -> impl Iterator<Item = i32, Item = u32>;
+}
+
+fn main() {
+    callable(iter::empty::<i32>());
+    callable_const(());
+    callable_rtn(());
+}
diff --git a/tests/ui/associated-type-bounds/duplicate.rs b/tests/ui/associated-type-bounds/duplicate.rs
deleted file mode 100644
index e9d94787e9829..0000000000000
--- a/tests/ui/associated-type-bounds/duplicate.rs
+++ /dev/null
@@ -1,278 +0,0 @@
-#![feature(type_alias_impl_trait)]
-
-use std::iter;
-use std::mem::ManuallyDrop;
-
-struct SI1<T: Iterator<Item: Copy, Item: Send>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: T,
-}
-struct SI2<T: Iterator<Item: Copy, Item: Copy>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: T,
-}
-struct SI3<T: Iterator<Item: 'static, Item: 'static>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: T,
-}
-struct SW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: T,
-}
-struct SW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: T,
-}
-struct SW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: T,
-}
-
-enum EI1<T: Iterator<Item: Copy, Item: Send>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    V(T),
-}
-enum EI2<T: Iterator<Item: Copy, Item: Copy>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    V(T),
-}
-enum EI3<T: Iterator<Item: 'static, Item: 'static>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    V(T),
-}
-enum EW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    V(T),
-}
-enum EW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    V(T),
-}
-enum EW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    V(T),
-}
-
-union UI1<T: Iterator<Item: Copy, Item: Send>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: ManuallyDrop<T>,
-}
-union UI2<T: Iterator<Item: Copy, Item: Copy>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: ManuallyDrop<T>,
-}
-union UI3<T: Iterator<Item: 'static, Item: 'static>> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    f: ManuallyDrop<T>,
-}
-union UW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: ManuallyDrop<T>,
-}
-union UW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: ManuallyDrop<T>,
-}
-union UW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-    f: ManuallyDrop<T>,
-}
-
-fn FI1<T: Iterator<Item: Copy, Item: Send>>() {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FI2<T: Iterator<Item: Copy, Item: Copy>>() {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FI3<T: Iterator<Item: 'static, Item: 'static>>() {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FW1<T>()
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-fn FW2<T>()
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-fn FW3<T>()
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-
-fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    iter::empty()
-    //~^ ERROR type annotations needed
-}
-fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    iter::empty()
-    //~^ ERROR type annotations needed
-}
-fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    iter::empty()
-    //~^ ERROR type annotations needed
-}
-fn FAPIT1(_: impl Iterator<Item: Copy, Item: Send>) {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FAPIT2(_: impl Iterator<Item: Copy, Item: Copy>) {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-fn FAPIT3(_: impl Iterator<Item: 'static, Item: 'static>) {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-
-type TAI1<T: Iterator<Item: Copy, Item: Send>> = T;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-type TAI2<T: Iterator<Item: Copy, Item: Copy>> = T;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-type TAI3<T: Iterator<Item: 'static, Item: 'static>> = T;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-type TAW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-= T;
-type TAW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-= T;
-type TAW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-= T;
-
-type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR unconstrained opaque type
-
-trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRI2<T: Iterator<Item: Copy, Item: Copy>> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRI3<T: Iterator<Item: 'static, Item: 'static>> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRS1: Iterator<Item: Copy, Item: Send> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-//~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-//~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-trait TRW1<T>
-where
-    T: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRW2<T>
-where
-    T: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRW3<T>
-where
-    T: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRSW1
-where
-    Self: Iterator<Item: Copy, Item: Send>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRSW2
-where
-    Self: Iterator<Item: Copy, Item: Copy>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRSW3
-where
-    Self: Iterator<Item: 'static, Item: 'static>,
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-{
-}
-trait TRA1 {
-    type A: Iterator<Item: Copy, Item: Send>;
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-}
-trait TRA2 {
-    type A: Iterator<Item: Copy, Item: Copy>;
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-}
-trait TRA3 {
-    type A: Iterator<Item: 'static, Item: 'static>;
-    //~^ ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-    //~| ERROR the value of the associated type `Item` in trait `Iterator` is already specified [E0719]
-}
-
-fn main() {}
diff --git a/tests/ui/associated-type-bounds/duplicate.stderr b/tests/ui/associated-type-bounds/duplicate.stderr
deleted file mode 100644
index 68fbb345f6f93..0000000000000
--- a/tests/ui/associated-type-bounds/duplicate.stderr
+++ /dev/null
@@ -1,751 +0,0 @@
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:6:36
-   |
-LL | struct SI1<T: Iterator<Item: Copy, Item: Send>> {
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:10:36
-   |
-LL | struct SI2<T: Iterator<Item: Copy, Item: Copy>> {
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:14:39
-   |
-LL | struct SI3<T: Iterator<Item: 'static, Item: 'static>> {
-   |                        -------------  ^^^^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:20:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:27:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:34:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:40:34
-   |
-LL | enum EI1<T: Iterator<Item: Copy, Item: Send>> {
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:44:34
-   |
-LL | enum EI2<T: Iterator<Item: Copy, Item: Copy>> {
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:48:37
-   |
-LL | enum EI3<T: Iterator<Item: 'static, Item: 'static>> {
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:54:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:61:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:68:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:74:35
-   |
-LL | union UI1<T: Iterator<Item: Copy, Item: Send>> {
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:78:35
-   |
-LL | union UI2<T: Iterator<Item: Copy, Item: Copy>> {
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:82:38
-   |
-LL | union UI3<T: Iterator<Item: 'static, Item: 'static>> {
-   |                       -------------  ^^^^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:88:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:95:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:102:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:108:32
-   |
-LL | fn FI1<T: Iterator<Item: Copy, Item: Send>>() {}
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:110:32
-   |
-LL | fn FI2<T: Iterator<Item: Copy, Item: Copy>>() {}
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:112:35
-   |
-LL | fn FI3<T: Iterator<Item: 'static, Item: 'static>>() {}
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:116:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:122:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:128:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:133:42
-   |
-LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:139:42
-   |
-LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:145:45
-   |
-LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
-   |                              -------------  ^^^^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:151:40
-   |
-LL | fn FAPIT1(_: impl Iterator<Item: Copy, Item: Send>) {}
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:153:40
-   |
-LL | fn FAPIT2(_: impl Iterator<Item: Copy, Item: Copy>) {}
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:155:43
-   |
-LL | fn FAPIT3(_: impl Iterator<Item: 'static, Item: 'static>) {}
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:158:35
-   |
-LL | type TAI1<T: Iterator<Item: Copy, Item: Send>> = T;
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:160:35
-   |
-LL | type TAI2<T: Iterator<Item: Copy, Item: Copy>> = T;
-   |                       ----------  ^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:162:38
-   |
-LL | type TAI3<T: Iterator<Item: 'static, Item: 'static>> = T;
-   |                       -------------  ^^^^^^^^^^^^^ re-bound here
-   |                       |
-   |                       `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:166:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:171:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:176:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:180:36
-   |
-LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:183:36
-   |
-LL | type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:186:39
-   |
-LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
-   |                        -------------  ^^^^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:202:36
-   |
-LL | trait TRI1<T: Iterator<Item: Copy, Item: Send>> {}
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:204:36
-   |
-LL | trait TRI2<T: Iterator<Item: Copy, Item: Copy>> {}
-   |                        ----------  ^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:206:39
-   |
-LL | trait TRI3<T: Iterator<Item: 'static, Item: 'static>> {}
-   |                        -------------  ^^^^^^^^^^^^^ re-bound here
-   |                        |
-   |                        `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:208:34
-   |
-LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:208:34
-   |
-LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:208:34
-   |
-LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:212:34
-   |
-LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:212:34
-   |
-LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:212:34
-   |
-LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:216:37
-   |
-LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:216:37
-   |
-LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:216:37
-   |
-LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:222:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Send>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:228:29
-   |
-LL |     T: Iterator<Item: Copy, Item: Copy>,
-   |                 ----------  ^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:234:32
-   |
-LL |     T: Iterator<Item: 'static, Item: 'static>,
-   |                 -------------  ^^^^^^^^^^^^^ re-bound here
-   |                 |
-   |                 `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:240:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Send>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:240:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Send>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:240:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Send>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:248:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Copy>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:248:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Copy>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:248:32
-   |
-LL |     Self: Iterator<Item: Copy, Item: Copy>,
-   |                    ----------  ^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:256:35
-   |
-LL |     Self: Iterator<Item: 'static, Item: 'static>,
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:256:35
-   |
-LL |     Self: Iterator<Item: 'static, Item: 'static>,
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:256:35
-   |
-LL |     Self: Iterator<Item: 'static, Item: 'static>,
-   |                    -------------  ^^^^^^^^^^^^^ re-bound here
-   |                    |
-   |                    `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:263:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Send>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:263:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Send>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:268:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Copy>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:268:34
-   |
-LL |     type A: Iterator<Item: Copy, Item: Copy>;
-   |                      ----------  ^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:273:37
-   |
-LL |     type A: Iterator<Item: 'static, Item: 'static>;
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:273:37
-   |
-LL |     type A: Iterator<Item: 'static, Item: 'static>;
-   |                      -------------  ^^^^^^^^^^^^^ re-bound here
-   |                      |
-   |                      `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:133:42
-   |
-LL | fn FRPIT1() -> impl Iterator<Item: Copy, Item: Send> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0282]: type annotations needed
-  --> $DIR/duplicate.rs:136:5
-   |
-LL |     iter::empty()
-   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
-   |
-help: consider specifying the generic argument
-   |
-LL |     iter::empty::<T>()
-   |                +++++
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:139:42
-   |
-LL | fn FRPIT2() -> impl Iterator<Item: Copy, Item: Copy> {
-   |                              ----------  ^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0282]: type annotations needed
-  --> $DIR/duplicate.rs:142:5
-   |
-LL |     iter::empty()
-   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
-   |
-help: consider specifying the generic argument
-   |
-LL |     iter::empty::<T>()
-   |                +++++
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:145:45
-   |
-LL | fn FRPIT3() -> impl Iterator<Item: 'static, Item: 'static> {
-   |                              -------------  ^^^^^^^^^^^^^ re-bound here
-   |                              |
-   |                              `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0282]: type annotations needed
-  --> $DIR/duplicate.rs:148:5
-   |
-LL |     iter::empty()
-   |     ^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `empty`
-   |
-help: consider specifying the generic argument
-   |
-LL |     iter::empty::<T>()
-   |                +++++
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:180:51
-   |
-LL | type ETAI1<T: Iterator<Item: Copy, Item: Send>> = impl Copy;
-   |                                                   ^^^^^^^^^
-   |
-   = note: `ETAI1` must be used in combination with a concrete type within the same crate
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:183:51
-   |
-LL | type ETAI2<T: Iterator<Item: Copy, Item: Copy>> = impl Copy;
-   |                                                   ^^^^^^^^^
-   |
-   = note: `ETAI2` must be used in combination with a concrete type within the same crate
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:186:57
-   |
-LL | type ETAI3<T: Iterator<Item: 'static, Item: 'static>> = impl Copy;
-   |                                                         ^^^^^^^^^
-   |
-   = note: `ETAI3` must be used in combination with a concrete type within the same crate
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:189:14
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `ETAI4` must be used in combination with a concrete type within the same crate
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:189:40
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:189:40
-   |
-LL | type ETAI4 = impl Iterator<Item: Copy, Item: Send>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:193:14
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `ETAI5` must be used in combination with a concrete type within the same crate
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:193:40
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:193:40
-   |
-LL | type ETAI5 = impl Iterator<Item: Copy, Item: Copy>;
-   |                            ----------  ^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: unconstrained opaque type
-  --> $DIR/duplicate.rs:197:14
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `ETAI6` must be used in combination with a concrete type within the same crate
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:197:43
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/duplicate.rs:197:43
-   |
-LL | type ETAI6 = impl Iterator<Item: 'static, Item: 'static>;
-   |                            -------------  ^^^^^^^^^^^^^ re-bound here
-   |                            |
-   |                            `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error: aborting due to 87 previous errors
-
-Some errors have detailed explanations: E0282, E0719.
-For more information about an error, try `rustc --explain E0282`.
diff --git a/tests/ui/associated-types/associated-types-overridden-binding-2.stderr b/tests/ui/associated-types/associated-types-overridden-binding-2.stderr
index 71a4a2610aac4..e96a2446b6ce0 100644
--- a/tests/ui/associated-types/associated-types-overridden-binding-2.stderr
+++ b/tests/ui/associated-types/associated-types-overridden-binding-2.stderr
@@ -1,4 +1,4 @@
-error: conflicting associated type bounds for `Item` when expanding trait alias
+error: conflicting associated type bounds for `Item`
   --> $DIR/associated-types-overridden-binding-2.rs:6:13
    |
 LL | trait I32Iterator = Iterator<Item = i32>;
diff --git a/tests/ui/associated-types/associated-types-overridden-binding.stderr b/tests/ui/associated-types/associated-types-overridden-binding.stderr
index 3b20015dfcab3..08ab9b63ee9fd 100644
--- a/tests/ui/associated-types/associated-types-overridden-binding.stderr
+++ b/tests/ui/associated-types/associated-types-overridden-binding.stderr
@@ -22,7 +22,7 @@ note: required by a bound in `I32Iterator`
 LL | trait I32Iterator = Iterator<Item = i32>;
    |                              ^^^^^^^^^^ required by this bound in `I32Iterator`
 
-error: conflicting associated type bounds for `Item` when expanding trait alias
+error: conflicting associated type bounds for `Item`
   --> $DIR/associated-types-overridden-binding.rs:10:13
    |
 LL | trait I32Iterator = Iterator<Item = i32>;
diff --git a/tests/ui/error-codes/E0719.rs b/tests/ui/error-codes/E0719.rs
index 0ea6d19000bd3..d7b4b876d1b78 100644
--- a/tests/ui/error-codes/E0719.rs
+++ b/tests/ui/error-codes/E0719.rs
@@ -1,8 +1,3 @@
-trait Foo: Iterator<Item = i32, Item = i32> {}
-//~^ ERROR is already specified
-//~| ERROR is already specified
-//~| ERROR is already specified
-
 type Unit = ();
 
 fn test() -> Box<dyn Iterator<Item = (), Item = Unit>> {
diff --git a/tests/ui/error-codes/E0719.stderr b/tests/ui/error-codes/E0719.stderr
index 7e8329db1f48f..f48175689249e 100644
--- a/tests/ui/error-codes/E0719.stderr
+++ b/tests/ui/error-codes/E0719.stderr
@@ -1,33 +1,5 @@
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:1:33
-   |
-LL | trait Foo: Iterator<Item = i32, Item = i32> {}
-   |                     ----------  ^^^^^^^^^^ re-bound here
-   |                     |
-   |                     `Item` bound here first
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:1:33
-   |
-LL | trait Foo: Iterator<Item = i32, Item = i32> {}
-   |                     ----------  ^^^^^^^^^^ re-bound here
-   |                     |
-   |                     `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:1:33
-   |
-LL | trait Foo: Iterator<Item = i32, Item = i32> {}
-   |                     ----------  ^^^^^^^^^^ re-bound here
-   |                     |
-   |                     `Item` bound here first
-   |
-   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
-
-error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:8:42
+  --> $DIR/E0719.rs:3:42
    |
 LL | fn test() -> Box<dyn Iterator<Item = (), Item = Unit>> {
    |                               ---------  ^^^^^^^^^^^ re-bound here
@@ -35,13 +7,13 @@ LL | fn test() -> Box<dyn Iterator<Item = (), Item = Unit>> {
    |                               `Item` bound here first
 
 error[E0719]: the value of the associated type `Item` in trait `Iterator` is already specified
-  --> $DIR/E0719.rs:14:38
+  --> $DIR/E0719.rs:9:38
    |
 LL |     let _: &dyn Iterator<Item = i32, Item = i32>;
    |                          ----------  ^^^^^^^^^^ re-bound here
    |                          |
    |                          `Item` bound here first
 
-error: aborting due to 5 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0719`.