rust-lang · rust-bors · Mar 23, 2026 · Mar 21, 2026
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -2299,6 +2299,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             // FIXME: this could use a better heuristic, like just checking
             // that args[1..] is the same.
             let all_traits_equal = traits.len() == 1;
+            let mut types: Vec<_> =
+                candidates.iter().map(|(c, _)| c.self_ty().to_string()).collect();
+            types.sort();
+            types.dedup();
+            let all_types_equal = types.len() == 1;
 
             let end = if candidates.len() <= 9 || self.tcx.sess.opts.verbose {
                 candidates.len()
@@ -2312,6 +2317,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 for (c, def_id) in &candidates {
                     let msg = if all_traits_equal {
                         format!("`{}`", self.tcx.short_string(c.self_ty(), err.long_ty_path()))
+                    } else if all_types_equal {
+                        format!(
+                            "`{}`",
+                            self.tcx.short_string(c.print_only_trait_path(), err.long_ty_path())
+                        )
                     } else {
                         format!(
                             "`{}` implements `{}`",
@@ -2321,13 +2331,19 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     };
                     span.push_span_label(self.tcx.def_span(*def_id), msg);
                 }
-                err.span_help(
-                    span,
+                let msg = if all_types_equal {
+                    format!(
+                        "`{}` implements trait `{}`",
+                        self.tcx.short_string(candidates[0].0.self_ty(), err.long_ty_path()),
+                        self.tcx.short_string(trait_ref.print_trait_sugared(), err.long_ty_path()),
+                    )
+                } else {
                     format!(
                         "the following {other}types implement trait `{}`",
-                        trait_ref.print_trait_sugared(),
-                    ),
-                );
+                        self.tcx.short_string(trait_ref.print_trait_sugared(), err.long_ty_path()),
+                    )
+                };
+                err.span_help(span, msg);
             } else {
                 let candidate_names: Vec<String> = candidates
                     .iter()
@@ -2337,6 +2353,12 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                                 "\n  {}",
                                 self.tcx.short_string(c.self_ty(), err.long_ty_path())
                             )
+                        } else if all_types_equal {
+                            format!(
+                                "\n  {}",
+                                self.tcx
+                                    .short_string(c.print_only_trait_path(), err.long_ty_path())
+                            )
                         } else {
                             format!(
                                 "\n  `{}` implements `{}`",
@@ -2347,9 +2369,21 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         }
                     })
                     .collect();
+                let msg = if all_types_equal {
+                    format!(
+                        "`{}` implements trait `{}`",
+                        self.tcx.short_string(candidates[0].0.self_ty(), err.long_ty_path()),
+                        self.tcx.short_string(trait_ref.print_trait_sugared(), err.long_ty_path()),
+                    )
+                } else {
+                    format!(
+                        "the following {other}types implement trait `{}`",
+                        self.tcx.short_string(trait_ref.print_trait_sugared(), err.long_ty_path()),
+                    )
+                };
+
                 err.help(format!(
-                    "the following {other}types implement trait `{}`:{}{}",
-                    trait_ref.print_trait_sugared(),
+                    "{msg}:{}{}",
                     candidate_names[..end].join(""),
                     if candidates.len() > 9 && !self.tcx.sess.opts.verbose {
                         format!("\nand {} others", candidates.len() - 8)

diff --git a/tests/run-make/crate-loading/multiple-dep-versions.stderr b/tests/run-make/crate-loading/multiple-dep-versions.stderr
@@ -177,14 +177,14 @@ LL |     Err(Error2)?;
    |     this can't be annotated with `?` because it has type `Result<_, Error2>`
    |
    = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
-help: the following other types implement trait `From<T>`
+help: `dependency::OtherError` implements trait `From<T>`
   --> replaced
    |
 LL | impl From<()> for OtherError {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dependency::OtherError` implements `From<()>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `From<()>`
 ...
 LL | impl From<i32> for OtherError {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dependency::OtherError` implements `From<i32>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `From<i32>`
    = note: there are multiple different versions of crate `dependency` in the dependency graph
    = help: you can use `cargo tree` to explore your dependency tree
 

diff --git a/tests/ui/const-generics/exhaustive-value.stderr b/tests/ui/const-generics/exhaustive-value.stderr
@@ -4,15 +4,15 @@ error[E0277]: the trait bound `(): Foo<N>` is not satisfied
 LL |     <() as Foo<N>>::test()
    |      ^^ the trait `Foo<N>` is not implemented for `()`
    |
-   = help: the following other types implement trait `Foo<N>`:
-             `()` implements `Foo<0>`
-             `()` implements `Foo<100>`
-             `()` implements `Foo<101>`
-             `()` implements `Foo<102>`
-             `()` implements `Foo<103>`
-             `()` implements `Foo<104>`
-             `()` implements `Foo<105>`
-             `()` implements `Foo<106>`
+   = help: `()` implements trait `Foo<N>`:
+             Foo<0>
+             Foo<100>
+             Foo<101>
+             Foo<102>
+             Foo<103>
+             Foo<104>
+             Foo<105>
+             Foo<106>
            and 248 others
 
 error: aborting due to 1 previous error

diff --git a/tests/ui/did_you_mean/issue-21659-show-relevant-trait-impls-1.stderr b/tests/ui/did_you_mean/issue-21659-show-relevant-trait-impls-1.stderr
@@ -11,14 +11,14 @@ help: the trait `Foo<usize>` is not implemented for `Bar`
    |
 LL | struct Bar;
    | ^^^^^^^^^^
-help: the following other types implement trait `Foo<A>`
+help: `Bar` implements trait `Foo<A>`
   --> $DIR/issue-21659-show-relevant-trait-impls-1.rs:15:1
    |
 LL | impl Foo<i32> for Bar {}
-   | ^^^^^^^^^^^^^^^^^^^^^ `Bar` implements `Foo<i32>`
+   | ^^^^^^^^^^^^^^^^^^^^^ `Foo<i32>`
 LL |
 LL | impl Foo<u8> for Bar {}
-   | ^^^^^^^^^^^^^^^^^^^^ `Bar` implements `Foo<u8>`
+   | ^^^^^^^^^^^^^^^^^^^^ `Foo<u8>`
 
 error: aborting due to 1 previous error
 

diff --git a/tests/ui/did_you_mean/issue-21659-show-relevant-trait-impls-2.stderr b/tests/ui/did_you_mean/issue-21659-show-relevant-trait-impls-2.stderr
@@ -11,13 +11,13 @@ help: the trait `Foo<usize>` is not implemented for `Bar`
    |
 LL | struct Bar;
    | ^^^^^^^^^^
-   = help: the following other types implement trait `Foo<A>`:
-             `Bar` implements `Foo<i16>`
-             `Bar` implements `Foo<i32>`
-             `Bar` implements `Foo<i8>`
-             `Bar` implements `Foo<u16>`
-             `Bar` implements `Foo<u32>`
-             `Bar` implements `Foo<u8>`
+   = help: `Bar` implements trait `Foo<A>`:
+             Foo<i16>
+             Foo<i32>
+             Foo<i8>
+             Foo<u16>
+             Foo<u32>
+             Foo<u8>
 
 error: aborting due to 1 previous error
 

diff --git a/tests/ui/did_you_mean/issue-39802-show-5-trait-impls.stderr b/tests/ui/did_you_mean/issue-39802-show-5-trait-impls.stderr
@@ -6,12 +6,12 @@ LL |     Foo::<i32>::bar(&1i8);
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the following other types implement trait `Foo<B>`:
-             `i8` implements `Foo<bool>`
-             `i8` implements `Foo<u16>`
-             `i8` implements `Foo<u32>`
-             `i8` implements `Foo<u64>`
-             `i8` implements `Foo<u8>`
+   = help: `i8` implements trait `Foo<B>`:
+             Foo<bool>
+             Foo<u16>
+             Foo<u32>
+             Foo<u64>
+             Foo<u8>
 
 error[E0277]: the trait bound `u8: Foo<i32>` is not satisfied
   --> $DIR/issue-39802-show-5-trait-impls.rs:25:21
@@ -21,17 +21,17 @@ LL |     Foo::<i32>::bar(&1u8);
    |     |
    |     required by a bound introduced by this call
    |
-help: the following other types implement trait `Foo<B>`
+help: `u8` implements trait `Foo<B>`
   --> $DIR/issue-39802-show-5-trait-impls.rs:11:1
    |
 LL | impl Foo<u16> for u8 {}
-   | ^^^^^^^^^^^^^^^^^^^^ `u8` implements `Foo<u16>`
+   | ^^^^^^^^^^^^^^^^^^^^ `Foo<u16>`
 LL | impl Foo<u32> for u8 {}
-   | ^^^^^^^^^^^^^^^^^^^^ `u8` implements `Foo<u32>`
+   | ^^^^^^^^^^^^^^^^^^^^ `Foo<u32>`
 LL | impl Foo<u64> for u8 {}
-   | ^^^^^^^^^^^^^^^^^^^^ `u8` implements `Foo<u64>`
+   | ^^^^^^^^^^^^^^^^^^^^ `Foo<u64>`
 LL | impl Foo<bool> for u8 {}
-   | ^^^^^^^^^^^^^^^^^^^^^ `u8` implements `Foo<bool>`
+   | ^^^^^^^^^^^^^^^^^^^^^ `Foo<bool>`
 
 error[E0277]: the trait bound `bool: Foo<i32>` is not satisfied
   --> $DIR/issue-39802-show-5-trait-impls.rs:26:21
@@ -41,13 +41,13 @@ LL |     Foo::<i32>::bar(&true);
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the following other types implement trait `Foo<B>`:
-             `bool` implements `Foo<bool>`
-             `bool` implements `Foo<i8>`
-             `bool` implements `Foo<u16>`
-             `bool` implements `Foo<u32>`
-             `bool` implements `Foo<u64>`
-             `bool` implements `Foo<u8>`
+   = help: `bool` implements trait `Foo<B>`:
+             Foo<bool>
+             Foo<i8>
+             Foo<u16>
+             Foo<u32>
+             Foo<u64>
+             Foo<u8>
 
 error: aborting due to 3 previous errors
 

diff --git a/tests/ui/indexing/index-help.stderr b/tests/ui/indexing/index-help.stderr
@@ -5,13 +5,13 @@ LL |     x[0i32];
    |       ^^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[{integer}]>` is not implemented for `i32`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `Vec<{integer}>` to implement `Index<i32>`
 
 error: aborting due to 1 previous error

diff --git a/tests/ui/indexing/indexing-integral-types.stderr b/tests/ui/indexing/indexing-integral-types.stderr
@@ -5,13 +5,13 @@ LL |     v[3u8];
    |       ^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[isize]>` is not implemented for `u8`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `Vec<isize>` to implement `Index<u8>`
 
 error[E0277]: the type `[isize]` cannot be indexed by `i8`
@@ -21,13 +21,13 @@ LL |     v[3i8];
    |       ^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[isize]>` is not implemented for `i8`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `Vec<isize>` to implement `Index<i8>`
 
 error[E0277]: the type `[isize]` cannot be indexed by `u32`
@@ -37,13 +37,13 @@ LL |     v[3u32];
    |       ^^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[isize]>` is not implemented for `u32`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `Vec<isize>` to implement `Index<u32>`
 
 error[E0277]: the type `[isize]` cannot be indexed by `i32`
@@ -53,13 +53,13 @@ LL |     v[3i32];
    |       ^^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[isize]>` is not implemented for `i32`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `Vec<isize>` to implement `Index<i32>`
 
 error[E0277]: the type `[u8]` cannot be indexed by `u8`
@@ -69,13 +69,13 @@ LL |     s.as_bytes()[3u8];
    |                  ^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[u8]>` is not implemented for `u8`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `[u8]` to implement `Index<u8>`
 
 error[E0277]: the type `[u8]` cannot be indexed by `i8`
@@ -85,13 +85,13 @@ LL |     s.as_bytes()[3i8];
    |                  ^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[u8]>` is not implemented for `i8`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `[u8]` to implement `Index<i8>`
 
 error[E0277]: the type `[u8]` cannot be indexed by `u32`
@@ -101,13 +101,13 @@ LL |     s.as_bytes()[3u32];
    |                  ^^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[u8]>` is not implemented for `u32`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `[u8]` to implement `Index<u32>`
 
 error[E0277]: the type `[u8]` cannot be indexed by `i32`
@@ -117,13 +117,13 @@ LL |     s.as_bytes()[3i32];
    |                  ^^^^ slice indices are of type `usize` or ranges of `usize`
    |
    = help: the trait `SliceIndex<[u8]>` is not implemented for `i32`
-help: the following other types implement trait `SliceIndex<T>`
+help: `usize` implements trait `SliceIndex<T>`
   --> $SRC_DIR/core/src/slice/index.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<[T]>`
+   = note: `SliceIndex<[T]>`
   --> $SRC_DIR/core/src/bstr/traits.rs:LL:COL
    |
-   = note: `usize` implements `SliceIndex<ByteStr>`
+   = note: `SliceIndex<ByteStr>`
    = note: required for `[u8]` to implement `Index<i32>`
 
 error: aborting due to 8 previous errors