Reword E0277 default error message

```
error[E0277]: the trait `Copy` is not implemented for `X`
  --> $DIR/trait-impl-bound-suggestions.rs:14:52
   |
LL |     fn return_the_constrained_type(&self, x: X) -> ConstrainedStruct<X> {
   |                                                    ^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `X`
```

Author: estebank

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

@@ -4774,21 +4774,23 @@ pub(super) fn get_explanation_based_on_obligation<'tcx>(
         } else {
             String::new()
         };
-        match ty_desc {
-            Some(desc) => format!(
-                "{}the trait `{}` is not implemented for {} `{}`{post}",
-                pre_message,
-                trait_predicate.print_modifiers_and_trait_path(),
-                desc,
-                tcx.short_ty_string(trait_ref.skip_binder().self_ty(), &mut None),
-            ),
-            None => format!(
-                "{}the trait `{}` is not implemented for `{}`{post}",
-                pre_message,
-                trait_predicate.print_modifiers_and_trait_path(),
-                tcx.short_ty_string(trait_ref.skip_binder().self_ty(), &mut None),
-            ),
-        }
+        let desc = match ty_desc {
+            Some(desc) => format!(" {desc}"),
+            None => String::new(),
+        };
+
+        let pred = tcx.erase_regions(if tcx.features().non_lifetime_binders {
+            // We can't erase the lifetime bounds on their own when this feature is enabled.
+            // `instantiate_bound_regions_with_erased` expects there to be no type bounds.
+            trait_predicate.skip_binder()
+        } else {
+            tcx.instantiate_bound_regions_with_erased(*trait_predicate)
+        });
+        format!(
+            "{pre_message}the trait `{}` is not implemented for{desc} `{}`{post}",
+            pred.print_modifiers_and_trait_path(),
+            tcx.short_ty_string(pred.self_ty(), &mut None),
+        )
     }
 }
 

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

@@ -2950,7 +2950,24 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 }
             })
             .unwrap_or_else(|| {
-                format!("the trait bound `{trait_predicate}` is not satisfied{post_message}")
+                let pred = self.tcx.erase_regions(if self.tcx.features().non_lifetime_binders {
+                    // We can't erase the lifetime bounds on their own when this feature is enabled.
+                    // `instantiate_bound_regions_with_erased` expects there to be no type bounds.
+                    trait_predicate.skip_binder()
+                } else {
+                    self.tcx.instantiate_bound_regions_with_erased(*trait_predicate)
+                });
+                if let ty::ImplPolarity::Positive = pred.polarity {
+                    format!(
+                        "the trait `{}` is not implemented for `{}`{post_message}",
+                        pred.print_modifiers_and_trait_path(),
+                        self.tcx.short_ty_string(pred.self_ty(), &mut None),
+                    )
+                } else {
+                    // "the trait bound `!Send: T` is not satisfied" reads better than "`!Send` is
+                    // not implemented for `T`".
+                    format!("the trait bound `{pred}` is not satisfied{post_message}")
+                }
             })
     }
 

tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.rs

@@ -34,7 +34,7 @@ struct Test {
     span: Span,
     /// A doc comment
     arg: NotIntoDiagnosticArg,
-    //~^ ERROR the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+    //~^ ERROR trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
 }
 
 #[derive(Subdiagnostic)]
@@ -44,5 +44,5 @@ struct SubTest {
     span: Span,
     /// A doc comment
     arg: NotIntoDiagnosticArg,
-    //~^ ERROR the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+    //~^ ERROR trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
 }

tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+error[E0277]: the trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
   --> $DIR/diagnostic-derive-doc-comment-field.rs:36:10
    |
 LL | #[derive(Diagnostic)]
@@ -12,7 +12,7 @@ note: required by a bound in `DiagnosticBuilder::<'a, G>::arg`
   --> $COMPILER_DIR/rustc_errors/src/diagnostic.rs:LL:CC
    = note: this error originates in the macro `with_fn` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+error[E0277]: the trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
   --> $DIR/diagnostic-derive-doc-comment-field.rs:46:10
    |
 LL | #[derive(Subdiagnostic)]

tests/ui-fulldeps/session-diagnostic/diagnostic-derive.rs

@@ -347,7 +347,7 @@ struct ArgFieldWithoutSkip {
     #[primary_span]
     span: Span,
     other: Hello,
-    //~^ ERROR the trait bound `Hello: IntoDiagnosticArg` is not satisfied
+    //~^ ERROR trait `IntoDiagnosticArg` is not implemented for `Hello`
 }
 
 #[derive(Diagnostic)]

tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr

@@ -618,7 +618,7 @@ LL | #[derive(Diagnostic)]
    |
    = note: this error originates in the derive macro `Diagnostic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: the trait bound `Hello: IntoDiagnosticArg` is not satisfied
+error[E0277]: the trait `IntoDiagnosticArg` is not implemented for `Hello`
   --> $DIR/diagnostic-derive.rs:349:12
    |
 LL | #[derive(Diagnostic)]

tests/ui/allocator/not-an-allocator.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
+error[E0277]: the trait `GlobalAlloc` is not implemented for `usize`
   --> $DIR/not-an-allocator.rs:2:11
    |
 LL | #[global_allocator]
@@ -9,7 +9,7 @@ LL | static A: usize = 0;
    = help: the trait `GlobalAlloc` is implemented for `System`
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
+error[E0277]: the trait `GlobalAlloc` is not implemented for `usize`
   --> $DIR/not-an-allocator.rs:2:11
    |
 LL | #[global_allocator]
@@ -21,7 +21,7 @@ LL | static A: usize = 0;
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
+error[E0277]: the trait `GlobalAlloc` is not implemented for `usize`
   --> $DIR/not-an-allocator.rs:2:11
    |
 LL | #[global_allocator]
@@ -33,7 +33,7 @@ LL | static A: usize = 0;
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
+error[E0277]: the trait `GlobalAlloc` is not implemented for `usize`
   --> $DIR/not-an-allocator.rs:2:11
    |
 LL | #[global_allocator]

tests/ui/array-slice-vec/repeat_empty_ok.rs

@@ -6,10 +6,10 @@ pub struct Header<'a> {
 
 pub fn test() {
     let headers = [Header{value: &[]}; 128];
-    //~^ ERROR the trait bound
+    //~^ ERROR the trait
 }
 
 pub fn test2() {
     let headers = [Header{value: &[0]}; 128];
-    //~^ ERROR the trait bound
+    //~^ ERROR the trait
 }

tests/ui/array-slice-vec/repeat_empty_ok.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `Header<'_>: Copy` is not satisfied
+error[E0277]: the trait `Copy` is not implemented for `Header<'_>`
   --> $DIR/repeat_empty_ok.rs:8:20
    |
 LL |     let headers = [Header{value: &[]}; 128];
@@ -13,7 +13,7 @@ LL + #[derive(Copy)]
 LL | pub struct Header<'a> {
    |
 
-error[E0277]: the trait bound `Header<'_>: Copy` is not satisfied
+error[E0277]: the trait `Copy` is not implemented for `Header<'_>`
   --> $DIR/repeat_empty_ok.rs:13:20
    |
 LL |     let headers = [Header{value: &[0]}; 128];

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

@@ -3,7 +3,7 @@ trait Foo {
 }
 
 const X: [i32; <i32 as Foo>::ID] = [0, 1, 2];
-//~^ ERROR the trait bound `i32: Foo` is not satisfied
+//~^ ERROR trait `Foo` is not implemented for `i32`
 
 fn main() {
     assert_eq!(1, X);

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

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `i32: Foo` is not satisfied
+error[E0277]: the trait `Foo` is not implemented for `i32`
   --> $DIR/associated-const-array-len.rs:5:17
    |
 LL | const X: [i32; <i32 as Foo>::ID] = [0, 1, 2];

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

@@ -10,7 +10,7 @@ impl TraitWAssocConst for impl Demo { //~ ERROR E0404
 
 fn foo<A: TraitWAssocConst<A=32>>() { //~ ERROR E0658
     foo::<Demo>()();
-    //~^ ERROR is not satisfied
+    //~^ ERROR is not implemented
     //~| ERROR type mismatch
     //~| ERROR expected function, found `()`
 }
@@ -20,5 +20,5 @@ fn main<A: TraitWAssocConst<A=32>>() {
     //~| ERROR E0131
     foo::<Demo>();
     //~^ ERROR type mismatch
-    //~| ERROR is not satisfied
+    //~| ERROR is not implemented
 }

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

@@ -49,7 +49,7 @@ error[E0131]: `main` function is not allowed to have generic parameters
 LL | fn main<A: TraitWAssocConst<A=32>>() {
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ `main` cannot have generic parameters
 
-error[E0277]: the trait bound `Demo: TraitWAssocConst` is not satisfied
+error[E0277]: the trait `TraitWAssocConst` is not implemented for `Demo`
   --> $DIR/issue-105330.rs:12:11
    |
 LL |     foo::<Demo>()();
@@ -86,7 +86,7 @@ LL |     foo::<Demo>()();
    |     |
    |     call expression requires function
 
-error[E0277]: the trait bound `Demo: TraitWAssocConst` is not satisfied
+error[E0277]: the trait `TraitWAssocConst` is not implemented for `Demo`
   --> $DIR/issue-105330.rs:21:11
    |
 LL |     foo::<Demo>();

tests/ui/associated-inherent-types/generic-associated-types-bad.item.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `String: Copy` is not satisfied
+error[E0277]: the trait `Copy` is not implemented for `String`
   --> $DIR/generic-associated-types-bad.rs:16:10
    |
 LL | const _: Ty::Pr<String> = String::new();
@@ -10,7 +10,7 @@ note: required by a bound in `Ty::Pr`
 LL |     type Pr<T: Copy> = T;
    |                ^^^^ required by this bound in `Ty::Pr`
 
-error[E0277]: the trait bound `String: Copy` is not satisfied
+error[E0277]: the trait `Copy` is not implemented for `String`
   --> $DIR/generic-associated-types-bad.rs:16:27
    |
 LL | const _: Ty::Pr<String> = String::new();

tests/ui/associated-inherent-types/generic-associated-types-bad.local.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `Vec<()>: Copy` is not satisfied
+error[E0277]: the trait `Copy` is not implemented for `Vec<()>`
   --> $DIR/generic-associated-types-bad.rs:21:12
    |
 LL |     let _: Ty::Pr<Vec<()>>;

tests/ui/associated-inherent-types/generic-associated-types-bad.rs

@@ -13,12 +13,12 @@ impl Ty {
 }
 
 #[cfg(item)]
-const _: Ty::Pr<String> = String::new(); //[item]~ the trait bound `String: Copy` is not satisfied
-//[item]~^ the trait bound `String: Copy` is not satisfied
+const _: Ty::Pr<String> = String::new(); //[item]~ ERROR trait `Copy` is not implemented for `String`
+//[item]~^ ERROR trait `Copy` is not implemented for `String`
 
 fn main() {
     #[cfg(local)]
-    let _: Ty::Pr<Vec<()>>; //[local]~ ERROR the trait bound `Vec<()>: Copy` is not satisfied
+    let _: Ty::Pr<Vec<()>>; //[local]~ ERROR trait `Copy` is not implemented for `Vec<()>`
 }
 
 fn user<'a>() {

tests/ui/associated-inherent-types/unsatisfied-bounds-inferred-type.rs

@@ -8,5 +8,5 @@ impl<T: Copy> S<T> {
 }
 
 fn main() {
-    let _: S<_>::T = String::new(); //~ ERROR the trait bound `String: Copy` is not satisfied
+    let _: S<_>::T = String::new(); //~ ERROR trait `Copy` is not implemented for `String`
 }

tests/ui/associated-inherent-types/unsatisfied-bounds-inferred-type.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `String: Copy` is not satisfied
+error[E0277]: the trait `Copy` is not implemented for `String`
   --> $DIR/unsatisfied-bounds-inferred-type.rs:11:12
    |
 LL |     let _: S<_>::T = String::new();

tests/ui/associated-inherent-types/unsatisfied-bounds-where-clause-on-assoc-ty.rs

@@ -10,5 +10,5 @@ impl<T> S<T> {
 }
 
 fn main() {
-    let _: S::<String>::X; //~ ERROR the trait bound `String: Copy` is not satisfied
+    let _: S::<String>::X; //~ ERROR trait `Copy` is not implemented for `String`
 }

tests/ui/associated-inherent-types/unsatisfied-bounds-where-clause-on-assoc-ty.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `String: Copy` is not satisfied
+error[E0277]: the trait `Copy` is not implemented for `String`
   --> $DIR/unsatisfied-bounds-where-clause-on-assoc-ty.rs:13:12
    |
 LL |     let _: S::<String>::X;

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

@@ -21,5 +21,5 @@ trait Add<RHS=Self> {
 fn ice<A>(a: A) {
     let r = loop {};
     r = r + a;
-    //~^ ERROR the trait bound `(): Add<A>` is not satisfied
+    //~^ ERROR trait `Add<A>` is not implemented for `()`
 }

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

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `(): Add<A>` is not satisfied
+error[E0277]: the trait `Add<A>` is not implemented for `()`
   --> $DIR/associated-types-ICE-when-projecting-out-of-err.rs:23:11
    |
 LL |     r = r + a;

tests/ui/associated-types/associated-types-bound-failure.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `<G as GetToInt>::R: ToInt` is not satisfied
+error[E0277]: the trait `ToInt` is not implemented for `<G as GetToInt>::R`
   --> $DIR/associated-types-bound-failure.rs:19:19
    |
 LL |     ToInt::to_int(&g.get())

tests/ui/associated-types/associated-types-for-unimpl-trait.fixed

@@ -9,8 +9,8 @@ trait Get {
 
 trait Other {
     fn uhoh<U: Get>(&self, foo: U, bar: <Self as Get>::Value) where Self: Sized, Self: Get, Self: Get {}
-    //~^ ERROR the trait bound `Self: Get` is not satisfied
-    //~| ERROR the trait bound `Self: Get` is not satisfied
+    //~^ ERROR trait `Get` is not implemented for `Self`
+    //~| ERROR trait `Get` is not implemented for `Self`
 }
 
 fn main() {}

tests/ui/associated-types/associated-types-for-unimpl-trait.rs

@@ -9,8 +9,8 @@ trait Get {
 
 trait Other {
     fn uhoh<U: Get>(&self, foo: U, bar: <Self as Get>::Value) where Self: Sized {}
-    //~^ ERROR the trait bound `Self: Get` is not satisfied
-    //~| ERROR the trait bound `Self: Get` is not satisfied
+    //~^ ERROR trait `Get` is not implemented for `Self`
+    //~| ERROR trait `Get` is not implemented for `Self`
 }
 
 fn main() {}

tests/ui/associated-types/associated-types-for-unimpl-trait.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `Self: Get` is not satisfied
+error[E0277]: the trait `Get` is not implemented for `Self`
   --> $DIR/associated-types-for-unimpl-trait.rs:11:41
    |
 LL |     fn uhoh<U: Get>(&self, foo: U, bar: <Self as Get>::Value) where Self: Sized {}
@@ -9,7 +9,7 @@ help: consider further restricting `Self`
 LL |     fn uhoh<U: Get>(&self, foo: U, bar: <Self as Get>::Value) where Self: Sized, Self: Get {}
    |                                                                                +++++++++++
 
-error[E0277]: the trait bound `Self: Get` is not satisfied
+error[E0277]: the trait `Get` is not implemented for `Self`
   --> $DIR/associated-types-for-unimpl-trait.rs:11:81
    |
 LL |     fn uhoh<U: Get>(&self, foo: U, bar: <Self as Get>::Value) where Self: Sized {}

tests/ui/associated-types/associated-types-invalid-trait-ref-issue-18865.rs

@@ -8,7 +8,7 @@ trait Foo<T> {
 
 fn f<T:Foo<isize>>(t: &T) {
     let u: <T as Foo<usize>>::Bar = t.get_bar();
-    //~^ ERROR the trait bound `T: Foo<usize>` is not satisfied
+    //~^ ERROR trait `Foo<usize>` is not implemented for `T`
 }
 
 fn main() { }

tests/ui/associated-types/associated-types-invalid-trait-ref-issue-18865.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `T: Foo<usize>` is not satisfied
+error[E0277]: the trait `Foo<usize>` is not implemented for `T`
   --> $DIR/associated-types-invalid-trait-ref-issue-18865.rs:10:13
    |
 LL |     let u: <T as Foo<usize>>::Bar = t.get_bar();

tests/ui/associated-types/associated-types-no-suitable-bound.rs

@@ -9,8 +9,8 @@ struct Struct {
 
 impl Struct {
     fn uhoh<T>(foo: <T as Get>::Value) {}
-    //~^ ERROR the trait bound `T: Get` is not satisfied
-    //~| ERROR the trait bound `T: Get` is not satisfied
+    //~^ ERROR trait `Get` is not implemented for `T`
+    //~| ERROR trait `Get` is not implemented for `T`
 }
 
 fn main() {}

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

@@ -1,4 +1,4 @@
-error[E0277]: the trait bound `T: Get` is not satisfied
+error[E0277]: the trait `Get` is not implemented for `T`
   --> $DIR/associated-types-no-suitable-bound.rs:11:21
    |
 LL |     fn uhoh<T>(foo: <T as Get>::Value) {}
@@ -9,7 +9,7 @@ help: consider restricting type parameter `T`
 LL |     fn uhoh<T: Get>(foo: <T as Get>::Value) {}
    |              +++++
 
-error[E0277]: the trait bound `T: Get` is not satisfied
+error[E0277]: the trait `Get` is not implemented for `T`
   --> $DIR/associated-types-no-suitable-bound.rs:11:40
    |
 LL |     fn uhoh<T>(foo: <T as Get>::Value) {}

tests/ui/associated-types/associated-types-no-suitable-supertrait-2.rs

@@ -15,8 +15,8 @@ trait Get {
 
 trait Other {
     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) {}
-    //~^ ERROR the trait bound `Self: Get` is not satisfied
-    //~| ERROR the trait bound `Self: Get` is not satisfied
+    //~^ ERROR trait `Get` is not implemented for `Self`
+    //~| ERROR trait `Get` is not implemented for `Self`
 }
 
 fn main() { }