Tweak wording

src/librustc/traits/error_reporting.rs

@@ -1164,9 +1164,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                         );
                     } else {
                         err.note(&format!(
-                            "`{}` is implemented for `{:?}`",
+                            "`{}` is implemented for `{:?}`, but not for `{:?}`",
                             trait_ref,
                             trait_type,
+                            trait_ref.skip_binder().self_ty(),
                         ));
                     }
                 }

src/librustc_typeck/check/method/suggest.rs

@@ -582,7 +582,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         hir::Mutability::MutImmutable => self.tcx.mk_mut_ref(region, t_type),
                     };
                     if needs_mut {
-                        err.note(&format!("you need `{}` instead", trait_type));
+                        err.note(&format!("you need `{}` instead of `{}`", trait_type, rcvr_ty));
                     }
                 }
                 err.emit();

src/test/ui/not-panic/not-panic-safe.stderr

@@ -8,7 +8,7 @@ LL |     assert::<&mut i32>();
    |     ^^^^^^^^^^^^^^^^^^ `&mut i32` may not be safely transferred across an unwind boundary
    |
    = help: the trait `std::panic::UnwindSafe` is not implemented for `&mut i32`
-   = note: `std::panic::UnwindSafe` is implemented for `&i32`
+   = note: `std::panic::UnwindSafe` is implemented for `&i32`, but not for `&mut i32`
 
 error: aborting due to previous error
 

src/test/ui/parser/lex-bad-char-literals-6.stderr

@@ -35,7 +35,7 @@ LL |     if x == y {}
    |          ^^ no implementation for `&str == char`
    |
    = help: the trait `std::cmp::PartialEq<char>` is not implemented for `&str`
-   = note: `std::cmp::PartialEq<char>` is implemented for `&mut str`
+   = note: `std::cmp::PartialEq<char>` is implemented for `&mut str`, but not for `&str`
 
 error[E0308]: mismatched types
   --> $DIR/lex-bad-char-literals-6.rs:15:20
@@ -53,7 +53,7 @@ LL |     if x == z {}
    |          ^^ no implementation for `&str == char`
    |
    = help: the trait `std::cmp::PartialEq<char>` is not implemented for `&str`
-   = note: `std::cmp::PartialEq<char>` is implemented for `&mut str`
+   = note: `std::cmp::PartialEq<char>` is implemented for `&mut str`, but not for `&str`
 
 error: aborting due to 6 previous errors
 

src/test/ui/suggestions/imm-ref-trait-object.stderr

@@ -4,7 +4,7 @@ error: the `min` method cannot be invoked on a trait object
 LL |      t.min().unwrap()
    |        ^^^
    |
-   = note: you need `&mut dyn std::iter::Iterator<Item = &u64>` instead
+   = note: you need `&mut dyn std::iter::Iterator<Item = &u64>` instead of `&dyn std::iter::Iterator<Item = &u64>`
 
 error: aborting due to previous error
 

src/test/ui/suggestions/into-str.stderr

@@ -8,7 +8,7 @@ LL |     foo(String::new());
    |     ^^^ the trait `std::convert::From<std::string::String>` is not implemented for `&str`
    |
    = note: to coerce a `std::string::String` into a `&str`, use `&*` as a prefix
-   = note: `std::convert::From<std::string::String>` is implemented for `&mut str`
+   = note: `std::convert::From<std::string::String>` is implemented for `&mut str`, but not for `&str`
    = note: required because of the requirements on the impl of `std::convert::Into<&str>` for `std::string::String`
 
 error: aborting due to previous error

src/test/ui/suggestions/mut-borrow-needed-by-trait.stderr

@@ -4,7 +4,7 @@ error[E0277]: the trait bound `&dyn std::io::Write: std::io::Write` is not satis
 LL |     let fp = BufWriter::new(fp);
    |                             ^^ the trait `std::io::Write` is not implemented for `&dyn std::io::Write`
    |
-   = note: `std::io::Write` is implemented for `&mut dyn std::io::Write`
+   = note: `std::io::Write` is implemented for `&mut dyn std::io::Write`, but not for `&dyn std::io::Write`
    = note: required by `std::io::BufWriter::<W>::new`
 
 error[E0277]: the trait bound `&dyn std::io::Write: std::io::Write` is not satisfied
@@ -13,7 +13,7 @@ error[E0277]: the trait bound `&dyn std::io::Write: std::io::Write` is not satis
 LL |     let fp = BufWriter::new(fp);
    |              ^^^^^^^^^^^^^^ the trait `std::io::Write` is not implemented for `&dyn std::io::Write`
    |
-   = note: `std::io::Write` is implemented for `&mut dyn std::io::Write`
+   = note: `std::io::Write` is implemented for `&mut dyn std::io::Write`, but not for `&dyn std::io::Write`
    = note: required by `std::io::BufWriter`
 
 error[E0277]: the trait bound `&dyn std::io::Write: std::io::Write` is not satisfied
@@ -22,7 +22,7 @@ error[E0277]: the trait bound `&dyn std::io::Write: std::io::Write` is not satis
 LL |     let fp = BufWriter::new(fp);
    |              ^^^^^^^^^^^^^^^^^^ the trait `std::io::Write` is not implemented for `&dyn std::io::Write`
    |
-   = note: `std::io::Write` is implemented for `&mut dyn std::io::Write`
+   = note: `std::io::Write` is implemented for `&mut dyn std::io::Write`, but not for `&dyn std::io::Write`
    = note: required by `std::io::BufWriter`
 
 error[E0599]: no method named `write_fmt` found for type `std::io::BufWriter<&dyn std::io::Write>` in the current scope

src/test/ui/suggestions/suggest-remove-refs-1.stderr

@@ -8,7 +8,7 @@ LL |     for (i, n) in &v.iter().enumerate() {
    |                   help: consider removing 1 leading `&`-references
    |
    = help: the trait `std::iter::Iterator` is not implemented for `&std::iter::Enumerate<std::slice::Iter<'_, {integer}>>`
-   = note: `std::iter::Iterator` is implemented for `&mut std::iter::Enumerate<std::slice::Iter<'_, {integer}>>`
+   = note: `std::iter::Iterator` is implemented for `&mut std::iter::Enumerate<std::slice::Iter<'_, {integer}>>`, but not for `&std::iter::Enumerate<std::slice::Iter<'_, {integer}>>`
    = note: required by `std::iter::IntoIterator::into_iter`
 
 error: aborting due to previous error