Erase regions in default main E0277 message

Author: estebank

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

@@ -2941,17 +2941,23 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 }
             })
             .unwrap_or_else(|| {
-                if let ty::ImplPolarity::Positive = trait_predicate.polarity() {
+                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}",
-                        trait_predicate.print_modifiers_and_trait_path(),
-                        self.tcx
-                            .short_ty_string(trait_predicate.skip_binder().self_ty(), &mut None),
+                        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 `{trait_predicate}` is not satisfied{post_message}")
+                    format!("the trait bound `{pred}` is not satisfied{post_message}")
                 }
             })
     }

tests/ui/associated-types/hr-associated-type-bound-object.rs

@@ -5,10 +5,10 @@ where
     type U: ?Sized;
 }
 fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) {
-    //~^ ERROR trait `for<'b> Clone` is not implemented for `<T as X<'b>>::U`
+    //~^ ERROR trait `Clone` is not implemented for `<T as X<'_>>::U`
     <<T as X<'_>>::U>::clone(x);
-    //~^ ERROR trait `for<'b> Clone` is not implemented for `<T as X<'b>>::U`
-    //~| ERROR trait `for<'b> Clone` is not implemented for `<T as X<'b>>::U`
+    //~^ ERROR trait `Clone` is not implemented for `<T as X<'_>>::U`
+    //~| ERROR trait `Clone` is not implemented for `<T as X<'_>>::U`
     //~| ERROR trait `Clone` is not implemented for `<T as X<'_>>::U`
 }
 

tests/ui/associated-types/hr-associated-type-bound-object.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait `for<'b> Clone` is not implemented for `<T as X<'b>>::U`
+error[E0277]: the trait `Clone` is not implemented for `<T as X<'_>>::U`
   --> $DIR/hr-associated-type-bound-object.rs:7:13
    |
 LL | fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) {
@@ -17,7 +17,7 @@ help: consider further restricting the associated type
 LL | fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) where for<'b> <T as X<'b>>::U: Clone {
    |                                                  ++++++++++++++++++++++++++++++++++++
 
-error[E0277]: the trait `for<'b> Clone` is not implemented for `<T as X<'b>>::U`
+error[E0277]: the trait `Clone` is not implemented for `<T as X<'_>>::U`
   --> $DIR/hr-associated-type-bound-object.rs:9:7
    |
 LL |     <<T as X<'_>>::U>::clone(x);
@@ -47,7 +47,7 @@ help: consider further restricting the associated type
 LL | fn f<'a, T: X<'a> + ?Sized>(x: &<T as X<'a>>::U) where <T as X<'_>>::U: Clone {
    |                                                  ++++++++++++++++++++++++++++
 
-error[E0277]: the trait `for<'b> Clone` is not implemented for `<T as X<'b>>::U`
+error[E0277]: the trait `Clone` is not implemented for `<T as X<'_>>::U`
   --> $DIR/hr-associated-type-bound-object.rs:9:5
    |
 LL |     <<T as X<'_>>::U>::clone(x);

tests/ui/associated-types/hr-associated-type-bound-param-6.rs

@@ -10,12 +10,12 @@ where
 }
 
 impl<S, T> X<'_, T> for (S,) {
-    //~^ ERROR trait `for<'b> X<'b, T>` is not implemented for `T`
+    //~^ ERROR trait `X<'_, T>` is not implemented for `T`
     type U = str;
 }
 
 pub fn main() {
     <(i32,) as X<i32>>::f("abc");
     //~^ ERROR trait `X<'_, i32>` is not implemented for `i32`
-    //~| ERROR trait `for<'b> X<'b, i32>` is not implemented for `i32`
+    //~| ERROR trait `X<'_, i32>` is not implemented for `i32`
 }

tests/ui/associated-types/hr-associated-type-bound-param-6.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait `for<'b> X<'b, T>` is not implemented for `T`
+error[E0277]: the trait `X<'_, T>` is not implemented for `T`
   --> $DIR/hr-associated-type-bound-param-6.rs:12:12
    |
 LL | impl<S, T> X<'_, T> for (S,) {
@@ -9,7 +9,7 @@ help: consider restricting type parameter `T`
 LL | impl<S, T: for<'b> X<'b, T>> X<'_, T> for (S,) {
    |          ++++++++++++++++++
 
-error[E0277]: the trait `for<'b> X<'b, i32>` is not implemented for `i32`
+error[E0277]: the trait `X<'_, i32>` is not implemented for `i32`
   --> $DIR/hr-associated-type-bound-param-6.rs:18:5
    |
 LL |     <(i32,) as X<i32>>::f("abc");

tests/ui/associated-types/issue-43924.rs

@@ -5,7 +5,7 @@
 
 trait Foo<T: Default + ToString> {
     type Out: Default + ToString + ?Sized = dyn ToString;
-    //~^ ERROR the trait `Default` is not implemented for `(dyn ToString + 'static)`
+    //~^ ERROR the trait `Default` is not implemented for `dyn ToString`
 }
 
 impl Foo<u32> for () {}

tests/ui/associated-types/issue-43924.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait `Default` is not implemented for `(dyn ToString + 'static)`
+error[E0277]: the trait `Default` is not implemented for `dyn ToString`
   --> $DIR/issue-43924.rs:7:45
    |
 LL |     type Out: Default + ToString + ?Sized = dyn ToString;

tests/ui/for/issue-20605.next.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the trait `IntoIterator` is not implemented for `dyn Iterator<Item = &'a mut u8>`
+error[E0277]: the trait `IntoIterator` is not implemented for `dyn Iterator<Item = &mut u8>`
   --> $DIR/issue-20605.rs:5:17
    |
 LL |     for item in *things { *item = 0 }

tests/ui/for/issue-20605.rs

@@ -4,7 +4,7 @@
 fn changer<'a>(mut things: Box<dyn Iterator<Item=&'a mut u8>>) {
     for item in *things { *item = 0 }
     //[current]~^ ERROR the size for values of type
-    //[next]~^^ ERROR the trait `IntoIterator` is not implemented for `dyn Iterator<Item = &'a mut u8>`
+    //[next]~^^ ERROR the trait `IntoIterator` is not implemented for `dyn Iterator<Item = &mut u8>`
     //[next]~| ERROR the type `<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter` is not well-formed
     //[next]~| ERROR the type `&mut <dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter` is not well-formed
     //[next]~| ERROR the type `Option<<<dyn Iterator<Item = &'a mut u8> as IntoIterator>::IntoIter as Iterator>::Item>` is not well-formed

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

@@ -29,7 +29,7 @@ trait Foo<T> {}
 
 fn map_test() {
     (&mut EmptyIter).consume(());
-    //~^ ERROR trait `for<'a> Foo<&'a mut ()>` is not implemented for `&'a mut ()`
+    //~^ ERROR trait `Foo<&mut ()>` is not implemented for `&mut ()`
 }
 
 fn main() {}