Point out if a local trait has no implementations

compiler/rustc_middle/src/ty/trait_def.rs

@@ -90,6 +90,10 @@ pub struct TraitImpls {
 }
 
 impl TraitImpls {
+    pub fn is_empty(&self) -> bool {
+        self.blanket_impls.is_empty() && self.non_blanket_impls.is_empty()
+    }
+
     pub fn blanket_impls(&self) -> &[DefId] {
         self.blanket_impls.as_slice()
     }

compiler/rustc_trait_selection/messages.ftl

@@ -40,5 +40,7 @@ trait_selection_no_value_in_rustc_on_unimplemented = this attribute must have a
     .label = expected value here
     .note = eg `#[rustc_on_unimplemented(message="foo")]`
 
+trait_selection_trait_has_no_impls = this trait has no implementations, consider adding one
+
 trait_selection_ty_alias_overflow = in case this is a recursive type alias, consider using a struct, enum, or union instead
 trait_selection_unable_to_construct_constant_value = unable to construct a constant value for the unevaluated constant {$unevaluated}

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -3009,10 +3009,10 @@ fn try_to_add_help_message(
         // Try to report a help message
         if is_fn_trait
             && let Ok((implemented_kind, params)) = self.type_implements_fn_trait(
-            obligation.param_env,
-            trait_ref.self_ty(),
-            trait_predicate.skip_binder().polarity,
-        )
+                obligation.param_env,
+                trait_ref.self_ty(),
+                trait_predicate.skip_binder().polarity,
+            )
         {
             self.add_help_message_for_fn_trait(trait_ref, err, implemented_kind, params);
         } else if !trait_ref.has_non_region_infer()
@@ -3031,6 +3031,15 @@ fn try_to_add_help_message(
                 None,
                 obligation.cause.body_id,
             );
+        } else if trait_ref.def_id().is_local()
+            && self.tcx.trait_impls_of(trait_ref.def_id()).is_empty()
+            && !self.tcx.trait_is_auto(trait_ref.def_id())
+            && !self.tcx.trait_is_alias(trait_ref.def_id())
+        {
+            err.span_help(
+                self.tcx.def_span(trait_ref.def_id()),
+                crate::fluent_generated::trait_selection_trait_has_no_impls,
+            );
         } else if !suggested && !unsatisfied_const {
             // Can't show anything else useful, try to find similar impls.
             let impl_candidates = self.find_similar_impl_candidates(*trait_predicate);
@@ -3041,7 +3050,12 @@ fn try_to_add_help_message(
                 err,
                 true,
             ) {
-                self.report_similar_impl_candidates_for_root_obligation(&obligation, *trait_predicate, body_def_id, err);
+                self.report_similar_impl_candidates_for_root_obligation(
+                    &obligation,
+                    *trait_predicate,
+                    body_def_id,
+                    err,
+                );
             }
 
             self.suggest_convert_to_slice(

tests/ui/associated-consts/associated-const-array-len.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `i32: Foo` is not satisfied
    |
 LL | const X: [i32; <i32 as Foo>::ID] = [0, 1, 2];
    |                 ^^^ the trait `Foo` is not implemented for `i32`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/associated-const-array-len.rs:1:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/associated-consts/issue-105330.stderr

@@ -51,6 +51,11 @@ error[E0277]: the trait bound `Demo: TraitWAssocConst` is not satisfied
 LL |     foo::<Demo>()();
    |           ^^^^ the trait `TraitWAssocConst` is not implemented for `Demo`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-105330.rs:1:1
+   |
+LL | pub trait TraitWAssocConst {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
 note: required by a bound in `foo`
   --> $DIR/issue-105330.rs:11:11
    |
@@ -87,6 +92,11 @@ error[E0277]: the trait bound `Demo: TraitWAssocConst` is not satisfied
 LL |     foo::<Demo>();
    |           ^^^^ the trait `TraitWAssocConst` is not implemented for `Demo`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-105330.rs:1:1
+   |
+LL | pub trait TraitWAssocConst {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
 note: required by a bound in `foo`
   --> $DIR/issue-105330.rs:11:11
    |

tests/ui/associated-types/associated-types-ICE-when-projecting-out-of-err.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `(): Add<A>` is not satisfied
    |
 LL |     r = r + a;
    |           ^ the trait `Add<A>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/associated-types-ICE-when-projecting-out-of-err.rs:15:1
+   |
+LL | trait Add<RHS=Self> {
+   | ^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/associated-types/associated-types-no-suitable-supertrait.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `(T, U): Get` is not satisfied
    |
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <(T, U) as Get>::Value) {}
    |                                        ^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `(T, U)`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/associated-types-no-suitable-supertrait.rs:12:1
+   |
+LL | trait Get {
+   | ^^^^^^^^^
 
 error[E0277]: the trait bound `Self: Get` is not satisfied
   --> $DIR/associated-types-no-suitable-supertrait.rs:17:40

tests/ui/associated-types/defaults-suitability.stderr

@@ -58,6 +58,11 @@ error[E0277]: the trait bound `(): Foo<Self>` is not satisfied
 LL |     type Assoc: Foo<Self> = ();
    |                             ^^ the trait `Foo<Self>` is not implemented for `()`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/defaults-suitability.rs:27:1
+   |
+LL | trait Foo<T> {
+   | ^^^^^^^^^^^^
 note: required by a bound in `Bar::Assoc`
   --> $DIR/defaults-suitability.rs:34:17
    |

tests/ui/associated-types/issue-59324.stderr

@@ -48,6 +48,12 @@ error[E0277]: the trait bound `(): Foo` is not satisfied
    |
 LL | fn with_factory<H>(factory: dyn ThriftService<()>) {}
    |                             ^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-59324.rs:3:1
+   |
+LL | pub trait Foo: NotFoo {
+   | ^^^^^^^^^^^^^^^^^^^^^
 
 error[E0277]: the trait bound `Bug: Foo` is not satisfied
   --> $DIR/issue-59324.rs:19:10

tests/ui/associated-types/issue-64855.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `Bar<T>: Foo` is not satisfied
    |
 LL | pub struct Bar<T>(<Self as Foo>::Type) where Self: ;
    |                   ^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `Bar<T>`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-64855.rs:1:1
+   |
+LL | pub trait Foo {
+   | ^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/associated-types/point-at-type-on-obligation-failure-2.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `bool: Bar` is not satisfied
 LL |     type Assoc = bool;
    |                  ^^^^ the trait `Bar` is not implemented for `bool`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/point-at-type-on-obligation-failure-2.rs:1:1
+   |
+LL | trait Bar {}
+   | ^^^^^^^^^
 note: required by a bound in `Foo::Assoc`
   --> $DIR/point-at-type-on-obligation-failure-2.rs:4:17
    |
@@ -16,6 +21,11 @@ error[E0277]: the trait bound `bool: Bar` is not satisfied
 LL |     type Assoc = bool;
    |                  ^^^^ the trait `Bar` is not implemented for `bool`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/point-at-type-on-obligation-failure-2.rs:1:1
+   |
+LL | trait Bar {}
+   | ^^^^^^^^^
 note: required by a bound in `Baz::Assoc`
   --> $DIR/point-at-type-on-obligation-failure-2.rs:13:18
    |
@@ -31,6 +41,11 @@ error[E0277]: the trait bound `bool: Bar` is not satisfied
 LL |     type Assoc = bool;
    |                  ^^^^ the trait `Bar` is not implemented for `bool`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/point-at-type-on-obligation-failure-2.rs:1:1
+   |
+LL | trait Bar {}
+   | ^^^^^^^^^
 note: required by a bound in `Bat::Assoc`
   --> $DIR/point-at-type-on-obligation-failure-2.rs:24:27
    |

tests/ui/coherence/coherence-unsafe-trait-object-impl.stderr

@@ -6,6 +6,11 @@ LL |     takes_t(t);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/coherence-unsafe-trait-object-impl.rs:6:1
+   |
+LL | trait Trait: Sized {
+   | ^^^^^^^^^^^^^^^^^^
 note: required by a bound in `takes_t`
   --> $DIR/coherence-unsafe-trait-object-impl.rs:10:15
    |

tests/ui/const-generics/dont-evaluate-array-len-on-err-1.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `[Adt; std::mem::size_of::<Self::Assoc>()]: Foo` i
    |
 LL |         <[Adt; std::mem::size_of::<Self::Assoc>()] as Foo>::bar()
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `[Adt; std::mem::size_of::<Self::Assoc>()]`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-evaluate-array-len-on-err-1.rs:9:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/const-generics/generic_const_exprs/issue-85848.stderr

@@ -6,7 +6,11 @@ LL |     writes_to_specific_path(&cap);
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the trait `Delegates<U>` is implemented for `T`
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-85848.rs:4:1
+   |
+LL | trait _Contains<T> {
+   | ^^^^^^^^^^^^^^^^^^
 note: required for `&C` to implement `Contains<(), true>`
   --> $DIR/issue-85848.rs:21:12
    |

tests/ui/const-generics/issues/issue-86530.stderr

@@ -6,6 +6,11 @@ LL |     z(" ");
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-86530.rs:4:1
+   |
+LL | pub trait X {
+   | ^^^^^^^^^^^
 note: required by a bound in `z`
   --> $DIR/issue-86530.rs:10:8
    |

tests/ui/cross/cross-fn-cache-hole.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `i32: Bar<u32>` is not satisfied
 LL |     where i32: Foo<u32, A>
    |           ^^^^^^^^^^^^^^^^ the trait `Bar<u32>` is not implemented for `i32`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/cross-fn-cache-hole.rs:11:1
+   |
+LL | trait Bar<X> { }
+   | ^^^^^^^^^^^^
    = help: see issue #48214
    = help: add `#![feature(trivial_bounds)]` to the crate attributes to enable
 

tests/ui/dst/dst-bad-coerce1.stderr

@@ -15,6 +15,11 @@ error[E0277]: the trait bound `Foo: Bar` is not satisfied
 LL |     let f3: &Fat<dyn Bar> = f2;
    |                             ^^ the trait `Bar` is not implemented for `Foo`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dst-bad-coerce1.rs:10:1
+   |
+LL | trait Bar { fn bar(&self) {} }
+   | ^^^^^^^^^
    = note: required for the cast from `&Fat<Foo>` to `&Fat<dyn Bar>`
 
 error[E0308]: mismatched types
@@ -34,6 +39,11 @@ error[E0277]: the trait bound `Foo: Bar` is not satisfied
 LL |     let f3: &(dyn Bar,) = f2;
    |                           ^^ the trait `Bar` is not implemented for `Foo`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dst-bad-coerce1.rs:10:1
+   |
+LL | trait Bar { fn bar(&self) {} }
+   | ^^^^^^^^^
    = note: required for the cast from `&(Foo,)` to `&(dyn Bar,)`
 
 error: aborting due to 4 previous errors

tests/ui/dyn-star/error.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `{integer}: Foo` is not satisfied
    |
 LL |     let dyn_i: dyn* Foo = i;
    |                           ^ the trait `Foo` is not implemented for `{integer}`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/error.rs:6:1
+   |
+LL | trait Foo {}
+   | ^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/error-codes/E0277.stderr

@@ -21,6 +21,11 @@ LL |     some_func(5i32);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/E0277.rs:3:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 note: required by a bound in `some_func`
   --> $DIR/E0277.rs:7:17
    |

tests/ui/generic-associated-types/issue-101020.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `for<'a> &'a mut (): Foo<&'a mut ()>` is not satis
 LL |     (&mut EmptyIter).consume(());
    |                      ^^^^^^^ the trait `for<'a> Foo<&'a mut ()>` is not implemented for `&'a mut ()`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-101020.rs:28:1
+   |
+LL | trait Foo<T> {}
+   | ^^^^^^^^^^^^
 note: required for `&'a mut ()` to implement `for<'a> FuncInput<'a, &'a mut ()>`
   --> $DIR/issue-101020.rs:27:20
    |

tests/ui/higher-ranked/trait-bounds/normalize-under-binder/issue-89118.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `for<'a> &'a (): BufferMut` is not satisfied
 LL |     C: StackContext,
    |        ^^^^^^^^^^^^ the trait `for<'a> BufferMut` is not implemented for `&'a ()`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-89118.rs:1:1
+   |
+LL | trait BufferMut {}
+   | ^^^^^^^^^^^^^^^
 note: required for `Ctx<()>` to implement `for<'a> BufferUdpStateContext<&'a ()>`
   --> $DIR/issue-89118.rs:5:23
    |
@@ -26,6 +31,11 @@ error[E0277]: the trait bound `for<'a> &'a (): BufferMut` is not satisfied
 LL | impl<C> EthernetWorker<C> {}
    |         ^^^^^^^^^^^^^^^^^ the trait `for<'a> BufferMut` is not implemented for `&'a ()`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-89118.rs:1:1
+   |
+LL | trait BufferMut {}
+   | ^^^^^^^^^^^^^^^
 note: required for `Ctx<()>` to implement `for<'a> BufferUdpStateContext<&'a ()>`
   --> $DIR/issue-89118.rs:5:23
    |
@@ -48,6 +58,11 @@ error[E0277]: the trait bound `for<'a> &'a (): BufferMut` is not satisfied
 LL |     type Handler = Ctx<C::Dispatcher>;
    |                    ^^^^^^^^^^^^^^^^^^ the trait `for<'a> BufferMut` is not implemented for `&'a ()`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-89118.rs:1:1
+   |
+LL | trait BufferMut {}
+   | ^^^^^^^^^^^^^^^
 note: required for `Ctx<()>` to implement `for<'a> BufferUdpStateContext<&'a ()>`
   --> $DIR/issue-89118.rs:5:23
    |

tests/ui/issues/issue-18611.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `isize: HasState` is not satisfied
    |
 LL | fn add_state(op: <isize as HasState>::State) {
    |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `HasState` is not implemented for `isize`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-18611.rs:5:1
+   |
+LL | trait HasState {
+   | ^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/issues/issue-25076.stderr

@@ -6,6 +6,11 @@ LL |     do_fold(bot(), ());
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-25076.rs:3:1
+   |
+LL | trait InOut<T> { type Out; }
+   | ^^^^^^^^^^^^^^
 note: required by a bound in `do_fold`
   --> $DIR/issue-25076.rs:5:18
    |

tests/ui/issues/issue-35570.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `for<'a> (): Trait2<'a>` is not satisfied
    |
 LL | fn _ice(param: Box<dyn for <'a> Trait1<<() as Trait2<'a>>::Ty>>) {
    |                                        ^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> Trait2<'a>` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-35570.rs:4:1
+   |
+LL | trait Trait2<'a> {
+   | ^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/issues/issue-60218.stderr

@@ -6,6 +6,11 @@ LL |     trigger_error(vec![], |x: &u32| x)
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-60218.rs:7:1
+   |
+LL | pub trait Foo {}
+   | ^^^^^^^^^^^^^
 note: required by a bound in `trigger_error`
   --> $DIR/issue-60218.rs:13:72
    |

tests/ui/issues/issue-66353.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `(): _A` is not satisfied
    |
 LL |     _Func::< <() as _A>::AssocT >::func(());
    |               ^^ the trait `_A` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-66353.rs:7:1
+   |
+LL | trait _A {
+   | ^^^^^^^^
 
 error[E0277]: the trait bound `(): _Func<_>` is not satisfied
   --> $DIR/issue-66353.rs:12:41
@@ -11,6 +17,12 @@ LL |     _Func::< <() as _A>::AssocT >::func(());
    |     ----------------------------------- ^^ the trait `_Func<_>` is not implemented for `()`
    |     |
    |     required by a bound introduced by this call
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-66353.rs:3:1
+   |
+LL | trait _Func<T> {
+   | ^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 

tests/ui/lifetimes/lifetime-elision-return-type-trait.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `Result<(), _>: Future` is not satisfied
    |
 LL | fn foo() -> impl Future<Item=(), Error=Box<dyn Error>> {
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Future` is not implemented for `Result<(), _>`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/lifetime-elision-return-type-trait.rs:1:1
+   |
+LL | trait Future {
+   | ^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/namespace/namespace-mix.stderr

@@ -114,6 +114,11 @@ LL |     check(m1::S{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -128,6 +133,11 @@ LL |     check(m2::S{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -142,6 +152,11 @@ LL |     check(m2::S);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -156,6 +171,11 @@ LL |     check(xm1::S{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -170,6 +190,11 @@ LL |     check(xm2::S{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -184,6 +209,11 @@ LL |     check(xm2::S);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -198,6 +228,11 @@ LL |     check(m3::TS{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -212,6 +247,11 @@ LL |     check(m3::TS);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -226,6 +266,11 @@ LL |     check(m4::TS{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -240,6 +285,11 @@ LL |     check(m4::TS);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -254,6 +304,11 @@ LL |     check(xm3::TS{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -268,6 +323,11 @@ LL |     check(xm3::TS);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -282,6 +342,11 @@ LL |     check(xm4::TS{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -296,6 +361,11 @@ LL |     check(xm4::TS);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -310,6 +380,11 @@ LL |     check(m5::US{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -324,6 +399,11 @@ LL |     check(m5::US);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -338,6 +418,11 @@ LL |     check(m6::US{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -352,6 +437,11 @@ LL |     check(m6::US);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -366,6 +456,11 @@ LL |     check(xm5::US{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -380,6 +475,11 @@ LL |     check(xm5::US);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -394,6 +494,11 @@ LL |     check(xm6::US{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -408,6 +513,11 @@ LL |     check(xm6::US);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -422,6 +532,11 @@ LL |     check(m7::V{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -436,6 +551,11 @@ LL |     check(m8::V{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -450,6 +570,11 @@ LL |     check(m8::V);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -464,6 +589,11 @@ LL |     check(xm7::V{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -478,6 +608,11 @@ LL |     check(xm8::V{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -492,6 +627,11 @@ LL |     check(xm8::V);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -506,6 +646,11 @@ LL |     check(m9::TV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -520,6 +665,11 @@ LL |     check(m9::TV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -534,6 +684,11 @@ LL |     check(mA::TV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -548,6 +703,11 @@ LL |     check(mA::TV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -562,6 +722,11 @@ LL |     check(xm9::TV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -576,6 +741,11 @@ LL |     check(xm9::TV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -590,6 +760,11 @@ LL |     check(xmA::TV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -604,6 +779,11 @@ LL |     check(xmA::TV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -618,6 +798,11 @@ LL |     check(mB::UV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -632,6 +817,11 @@ LL |     check(mB::UV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -646,6 +836,11 @@ LL |     check(mC::UV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -660,6 +855,11 @@ LL |     check(mC::UV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -674,6 +874,11 @@ LL |     check(xmB::UV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -688,6 +893,11 @@ LL |     check(xmB::UV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -702,6 +912,11 @@ LL |     check(xmC::UV{});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |
@@ -716,6 +931,11 @@ LL |     check(xmC::UV);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/namespace-mix.rs:20:1
+   |
+LL | trait Impossible {}
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `check`
   --> $DIR/namespace-mix.rs:21:13
    |

tests/ui/never_type/feature-gate-never_type_fallback.stderr

@@ -8,6 +8,11 @@ LL |     foo(panic!())
    |     |   this tail expression is of type `()`
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/feature-gate-never_type_fallback.rs:7:1
+   |
+LL | trait T {}
+   | ^^^^^^^
 note: required by a bound in `foo`
   --> $DIR/feature-gate-never_type_fallback.rs:13:16
    |

tests/ui/never_type/impl_trait_fallback3.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `(): T` is not satisfied
    |
 LL | fn a() -> Foo {
    |           ^^^ the trait `T` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/impl_trait_fallback3.rs:5:1
+   |
+LL | trait T {
+   | ^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/never_type/impl_trait_fallback4.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `(): T` is not satisfied
    |
 LL | fn foo() -> impl T {
    |             ^^^^^^ the trait `T` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/impl_trait_fallback4.rs:3:1
+   |
+LL | trait T {
+   | ^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/on-unimplemented/on-trait.stderr

@@ -5,6 +5,11 @@ LL |     let y: Option<Vec<u8>> = collect(x.iter()); // this should give approxi
    |                              ^^^^^^^ a collection of type `Option<Vec<u8>>` cannot be built from an iterator over elements of type `&u8`
    |
    = help: the trait `MyFromIterator<&u8>` is not implemented for `Option<Vec<u8>>`
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-trait.rs:17:1
+   |
+LL | trait MyFromIterator<A> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^
 note: required by a bound in `collect`
   --> $DIR/on-trait.rs:22:39
    |
@@ -18,6 +23,11 @@ LL |     let x: String = foobar();
    |                     ^^^^^^ test error `String` with `u8` `_` `u32` in `Foo`
    |
    = help: the trait `Foo<u8, _, u32>` is not implemented for `String`
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-trait.rs:7:3
+   |
+LL |   pub trait Foo<Bar, Baz, Quux> {}
+   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 note: required by a bound in `foobar`
   --> $DIR/on-trait.rs:12:24
    |

tests/ui/on-unimplemented/parent-label.stderr

@@ -8,6 +8,11 @@ LL |         f(Foo {});
    |         |
    |         required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/parent-label.rs:6:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `f`
   --> $DIR/parent-label.rs:10:9
    |
@@ -24,6 +29,11 @@ LL |             f(Foo {});
    |             |
    |             required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/parent-label.rs:6:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `f`
   --> $DIR/parent-label.rs:10:9
    |
@@ -41,6 +51,11 @@ LL |             f(Foo {});
    |             |
    |             required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/parent-label.rs:6:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `f`
   --> $DIR/parent-label.rs:10:9
    |
@@ -58,6 +73,11 @@ LL |     f(Foo {});
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/parent-label.rs:6:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `f`
   --> $DIR/parent-label.rs:10:9
    |

tests/ui/proc-macro/bad-projection.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `(): Project` is not satisfied
    |
 LL | pub fn uwu() -> <() as Project>::Assoc {}
    |                 ^^^^^^^^^^^^^^^^^^^^^^ the trait `Project` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/bad-projection.rs:9:1
+   |
+LL | trait Project {
+   | ^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/span/issue-29595.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `u8: Tr` is not satisfied
    |
 LL |     let a: u8 = Tr::C;
    |                 ^^^^^ the trait `Tr` is not implemented for `u8`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-29595.rs:1:1
+   |
+LL | trait Tr {
+   | ^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/specialization/issue-38091.stderr

@@ -14,6 +14,11 @@ error[E0277]: the trait bound `(): Valid` is not satisfied
 LL |     default type Ty = ();
    |                       ^^ the trait `Valid` is not implemented for `()`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-38091.rs:20:1
+   |
+LL | trait Valid {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Iterate::Ty`
   --> $DIR/issue-38091.rs:5:14
    |

tests/ui/suggestions/issue-89333.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `for<'a> &'a _: Trait` is not satisfied
 LL |     test(&|| 0);
    |     ^^^^ the trait `for<'a> Trait` is not implemented for `&'a _`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-89333.rs:9:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `test`
   --> $DIR/issue-89333.rs:11:55
    |

tests/ui/trait-bounds/issue-82038.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `bool: Foo` is not satisfied
    |
 LL |     <bool as Foo>::my_method();
    |      ^^^^ the trait `Foo` is not implemented for `bool`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-82038.rs:3:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/traits/bound/on-structs-and-enums-in-fns.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `u32: Trait` is not satisfied
 LL | fn explode(x: Foo<u32>) {}
    |               ^^^^^^^^ the trait `Trait` is not implemented for `u32`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums-in-fns.rs:1:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Foo`
   --> $DIR/on-structs-and-enums-in-fns.rs:3:14
    |
@@ -16,6 +21,11 @@ error[E0277]: the trait bound `f32: Trait` is not satisfied
 LL | fn kaboom(y: Bar<f32>) {}
    |              ^^^^^^^^ the trait `Trait` is not implemented for `f32`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums-in-fns.rs:1:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Bar`
   --> $DIR/on-structs-and-enums-in-fns.rs:7:12
    |

tests/ui/traits/bound/on-structs-and-enums-in-impls.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `u16: Trait` is not satisfied
 LL | impl PolyTrait<Foo<u16>> for Struct {
    |      ^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `u16`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums-in-impls.rs:1:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Foo`
   --> $DIR/on-structs-and-enums-in-impls.rs:3:14
    |

tests/ui/traits/bound/on-structs-and-enums-locals.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `usize: Trait` is not satisfied
 LL |     let baz: Foo<usize> = loop { };
    |              ^^^^^^^^^^ the trait `Trait` is not implemented for `usize`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums-locals.rs:1:1
+   |
+LL | trait Trait {
+   | ^^^^^^^^^^^
 note: required by a bound in `Foo`
   --> $DIR/on-structs-and-enums-locals.rs:5:14
    |
@@ -16,6 +21,11 @@ error[E0277]: the trait bound `{integer}: Trait` is not satisfied
 LL |         x: 3
    |            ^ the trait `Trait` is not implemented for `{integer}`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums-locals.rs:1:1
+   |
+LL | trait Trait {
+   | ^^^^^^^^^^^
 note: required by a bound in `Foo`
   --> $DIR/on-structs-and-enums-locals.rs:5:14
    |

tests/ui/traits/bound/on-structs-and-enums-static.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `usize: Trait` is not satisfied
 LL | static X: Foo<usize> = Foo {
    |           ^^^^^^^^^^ the trait `Trait` is not implemented for `usize`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums-static.rs:1:1
+   |
+LL | trait Trait {
+   | ^^^^^^^^^^^
 note: required by a bound in `Foo`
   --> $DIR/on-structs-and-enums-static.rs:5:14
    |

tests/ui/traits/bound/on-structs-and-enums.stderr

@@ -20,6 +20,11 @@ error[E0277]: the trait bound `isize: Trait` is not satisfied
 LL |     a: Foo<isize>,
    |        ^^^^^^^^^^ the trait `Trait` is not implemented for `isize`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums.rs:1:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Foo`
   --> $DIR/on-structs-and-enums.rs:3:14
    |
@@ -32,6 +37,11 @@ error[E0277]: the trait bound `usize: Trait` is not satisfied
 LL |     Quux(Bar<usize>),
    |          ^^^^^^^^^^ the trait `Trait` is not implemented for `usize`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums.rs:1:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Bar`
   --> $DIR/on-structs-and-enums.rs:7:12
    |
@@ -76,6 +86,11 @@ error[E0277]: the trait bound `i32: Trait` is not satisfied
 LL |     Foo<i32>,
    |     ^^^^^^^^ the trait `Trait` is not implemented for `i32`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums.rs:1:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Foo`
   --> $DIR/on-structs-and-enums.rs:3:14
    |
@@ -88,6 +103,11 @@ error[E0277]: the trait bound `u8: Trait` is not satisfied
 LL |     DictionaryLike { field: Bar<u8> },
    |                             ^^^^^^^ the trait `Trait` is not implemented for `u8`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums.rs:1:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `Bar`
   --> $DIR/on-structs-and-enums.rs:7:12
    |

tests/ui/traits/deny-builtin-object-impl.current.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `dyn NotObject: NotObject` is not satisfied
 LL |     test_not_object::<dyn NotObject>();
    |                       ^^^^^^^^^^^^^ the trait `NotObject` is not implemented for `dyn NotObject`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/deny-builtin-object-impl.rs:10:1
+   |
+LL | trait NotObject {}
+   | ^^^^^^^^^^^^^^^
 note: required by a bound in `test_not_object`
   --> $DIR/deny-builtin-object-impl.rs:14:23
    |

tests/ui/traits/deny-builtin-object-impl.next.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `dyn NotObject: NotObject` is not satisfied
 LL |     test_not_object::<dyn NotObject>();
    |                       ^^^^^^^^^^^^^ the trait `NotObject` is not implemented for `dyn NotObject`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/deny-builtin-object-impl.rs:10:1
+   |
+LL | trait NotObject {}
+   | ^^^^^^^^^^^^^^^
 note: required by a bound in `test_not_object`
   --> $DIR/deny-builtin-object-impl.rs:14:23
    |

tests/ui/traits/dont-autoderef-ty-with-escaping-var.stderr

@@ -10,6 +10,11 @@ error[E0277]: the trait bound `for<'a> &'a mut Vec<&'a u32>: Foo<'static, i32>`
 LL |     <i32 as RefFoo<i32>>::ref_foo(unknown);
    |      ^^^ the trait `for<'a> Foo<'static, i32>` is not implemented for `&'a mut Vec<&'a u32>`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/dont-autoderef-ty-with-escaping-var.rs:3:1
+   |
+LL | trait Foo<'x, T> {}
+   | ^^^^^^^^^^^^^^^^
 note: required for `i32` to implement `RefFoo<i32>`
   --> $DIR/dont-autoderef-ty-with-escaping-var.rs:9:9
    |

tests/ui/traits/impl-bounds-checking.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `isize: Clone2` is not satisfied
 LL | impl Getter<isize> for isize {
    |                        ^^^^^ the trait `Clone2` is not implemented for `isize`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/impl-bounds-checking.rs:1:1
+   |
+LL | pub trait Clone2 {
+   | ^^^^^^^^^^^^^^^^
 note: required by a bound in `Getter`
   --> $DIR/impl-bounds-checking.rs:6:17
    |

tests/ui/traits/new-solver/projection-discr-kind.stderr

@@ -6,6 +6,11 @@ LL |     needs_bar(std::mem::discriminant(&x));
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/projection-discr-kind.rs:10:1
+   |
+LL | trait Bar {}
+   | ^^^^^^^^^
 note: required by a bound in `needs_bar`
   --> $DIR/projection-discr-kind.rs:11:22
    |

tests/ui/traits/non_lifetime_binders/fail.stderr

@@ -13,6 +13,11 @@ error[E0277]: the trait bound `T: Trait` is not satisfied
 LL |     fail();
    |     ^^^^ the trait `Trait` is not implemented for `T`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/fail.rs:6:1
+   |
+LL | trait Trait {}
+   | ^^^^^^^^^^^
 note: required by a bound in `fail`
   --> $DIR/fail.rs:10:15
    |

tests/ui/traits/object-does-not-impl-trait.stderr

@@ -6,6 +6,11 @@ LL | fn take_object(f: Box<dyn Foo>) { take_foo(f); }
    |                                   |
    |                                   required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/object-does-not-impl-trait.rs:4:1
+   |
+LL | trait Foo {}
+   | ^^^^^^^^^
 note: required by a bound in `take_foo`
   --> $DIR/object-does-not-impl-trait.rs:5:15
    |

tests/ui/traits/vtable-res-trait-param.stderr

@@ -6,6 +6,11 @@ LL |     b.gimme_an_a(y)
    |       |
    |       required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/vtable-res-trait-param.rs:1:1
+   |
+LL | trait TraitA {
+   | ^^^^^^^^^^^^
 note: required by a bound in `TraitB::gimme_an_a`
   --> $DIR/vtable-res-trait-param.rs:6:21
    |

tests/ui/trivial-bounds/trivial-bounds-leak.stderr

@@ -27,6 +27,12 @@ LL |     Foo::test(&4i32);
    |     --------- ^^^^^ the trait `Foo` is not implemented for `i32`
    |     |
    |     required by a bound introduced by this call
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/trivial-bounds-leak.rs:4:1
+   |
+LL | pub trait Foo {
+   | ^^^^^^^^^^^^^
 
 error[E0277]: the trait bound `i32: Foo` is not satisfied
   --> $DIR/trivial-bounds-leak.rs:26:22
@@ -36,6 +42,11 @@ LL |     generic_function(5i32);
    |     |
    |     required by a bound introduced by this call
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/trivial-bounds-leak.rs:4:1
+   |
+LL | pub trait Foo {
+   | ^^^^^^^^^^^^^
 note: required by a bound in `generic_function`
   --> $DIR/trivial-bounds-leak.rs:29:24
    |

tests/ui/union/projection-as-union-type-error-2.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `u8: NotImplemented` is not satisfied
 LL |     a: <Foo as Identity>::Identity,
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `NotImplemented` is not implemented for `u8`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/projection-as-union-type-error-2.rs:9:1
+   |
+LL | trait NotImplemented {}
+   | ^^^^^^^^^^^^^^^^^^^^
 note: required for `u8` to implement `Identity`
   --> $DIR/projection-as-union-type-error-2.rs:11:25
    |

tests/ui/union/projection-as-union-type-error.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `u8: Identity` is not satisfied
    |
 LL |     a:  <Foo as Identity>::Identity,
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Identity` is not implemented for `u8`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/projection-as-union-type-error.rs:6:1
+   |
+LL | pub trait Identity {
+   | ^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/unsized/issue-75707.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `MyCall: Callback` is not satisfied
 LL |     f::<dyn Processing<Call = MyCall>>();
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Callback` is not implemented for `MyCall`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-75707.rs:1:1
+   |
+LL | pub trait Callback {
+   | ^^^^^^^^^^^^^^^^^^
 note: required by a bound in `f`
   --> $DIR/issue-75707.rs:9:9
    |

tests/ui/wf/hir-wf-canonicalized.stderr

@@ -3,12 +3,24 @@ error[E0277]: the trait bound `Bar<'a, T>: Foo` is not satisfied
    |
 LL |     callback: Box<dyn Callback<dyn Callback<Bar<'a, T>>>>,
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `Bar<'a, T>`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/hir-wf-canonicalized.rs:3:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 
 error[E0277]: the trait bound `(dyn Callback<Bar<'a, T>, for<'b, 'c, 'd> Output = ()> + 'static): Foo` is not satisfied
   --> $DIR/hir-wf-canonicalized.rs:10:15
    |
 LL |     callback: Box<dyn Callback<dyn Callback<Bar<'a, T>>>>,
    |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `(dyn Callback<Bar<'a, T>, for<'b, 'c, 'd> Output = ()> + 'static)`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/hir-wf-canonicalized.rs:3:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 
 error[E0277]: the size for values of type `(dyn Callback<Bar<'a, T>, for<'b, 'c, 'd> Output = ()> + 'static)` cannot be known at compilation time
   --> $DIR/hir-wf-canonicalized.rs:10:15

tests/ui/wf/issue-95665.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `u8: Trait` is not satisfied
 LL |     static VAR: Struct<u8>;
    |                 ^^^^^^^^^^ the trait `Trait` is not implemented for `u8`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/issue-95665.rs:4:1
+   |
+LL | pub trait Trait: {}
+   | ^^^^^^^^^^^^^^^
 note: required by a bound in `Struct`
   --> $DIR/issue-95665.rs:6:22
    |

tests/ui/wf/wf-complex-assoc-type.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `bool: MyTrait` is not satisfied
 LL |     type MyItem = Option<((AssertMyTrait<bool>, u8))>;
    |                            ^^^^^^^^^^^^^^^^^^^ the trait `MyTrait` is not implemented for `bool`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/wf-complex-assoc-type.rs:1:1
+   |
+LL | trait MyTrait {}
+   | ^^^^^^^^^^^^^
 note: required by a bound in `AssertMyTrait`
   --> $DIR/wf-complex-assoc-type.rs:2:25
    |

tests/ui/wf/wf-foreign-fn-decl-ret.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `(): Foo` is not satisfied
    |
 LL |     pub fn lint_me() -> <() as Foo>::Assoc;
    |                         ^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/wf-foreign-fn-decl-ret.rs:6:1
+   |
+LL | pub trait Foo {
+   | ^^^^^^^^^^^^^
 
 error[E0277]: the trait bound `u32: Unsatisfied` is not satisfied
   --> $DIR/wf-foreign-fn-decl-ret.rs:14:32
@@ -10,6 +16,11 @@ error[E0277]: the trait bound `u32: Unsatisfied` is not satisfied
 LL |     pub fn lint_me_aswell() -> Bar<u32>;
    |                                ^^^^^^^^ the trait `Unsatisfied` is not implemented for `u32`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/wf-foreign-fn-decl-ret.rs:1:1
+   |
+LL | pub trait Unsatisfied {}
+   | ^^^^^^^^^^^^^^^^^^^^^
 note: required by a bound in `Bar`
   --> $DIR/wf-foreign-fn-decl-ret.rs:4:19
    |

tests/ui/wf/wf-packed-on-proj-of-type-as-unimpl-trait.stderr

@@ -3,6 +3,12 @@ error[E0277]: the trait bound `DefaultAllocator: Allocator` is not satisfied
    |
 LL | struct Foo(Matrix<<DefaultAllocator as Allocator>::Buffer>);
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Allocator` is not implemented for `DefaultAllocator`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/wf-packed-on-proj-of-type-as-unimpl-trait.rs:23:1
+   |
+LL | pub trait Allocator { type Buffer; }
+   | ^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

tests/ui/where-clauses/higher-ranked-fn-type.quiet.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `for<'b> fn(&'b ()): Foo` is not satisfied
 LL |     called()
    |     ^^^^^^ the trait `for<'b> Foo` is not implemented for `fn(&'b ())`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/higher-ranked-fn-type.rs:6:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 note: required by a bound in `called`
   --> $DIR/higher-ranked-fn-type.rs:12:25
    |

tests/ui/where-clauses/higher-ranked-fn-type.verbose.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `for<Region(BrNamed(DefId(0:6 ~ higher_ranked_fn_t
 LL |     called()
    |     ^^^^^^ the trait `for<Region(BrNamed(DefId(0:6 ~ higher_ranked_fn_type[9e51]::called::'b), 'b))> Foo` is not implemented for `fn(&ReLateBound(DebruijnIndex(1), BoundRegion { var: 0, kind: BrNamed(DefId(0:6 ~ higher_ranked_fn_type[9e51]::called::'b), 'b) }) ())`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/higher-ranked-fn-type.rs:6:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
 note: required by a bound in `called`
   --> $DIR/higher-ranked-fn-type.rs:12:25
    |

tests/ui/where-clauses/where-clause-method-substituion.stderr

@@ -4,6 +4,11 @@ error[E0277]: the trait bound `X: Foo<X>` is not satisfied
 LL |     1.method::<X>();
    |                ^ the trait `Foo<X>` is not implemented for `X`
    |
+help: this trait has no implementations, consider adding one
+  --> $DIR/where-clause-method-substituion.rs:1:1
+   |
+LL | trait Foo<T> {
+   | ^^^^^^^^^^^^
 note: required by a bound in `Bar::method`
   --> $DIR/where-clause-method-substituion.rs:6:34
    |