address review comments

Author: estebank

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

@@ -2682,35 +2682,27 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 .flatten()
                                 .chain(impls_of.blanket_impls().iter())
                                 .collect::<Vec<_>>();
-                            match &impls[..] {
-                                [] => {}
-                                [only] => {
-                                    err.help(with_no_trimmed_paths!(format!(
-                                        "type `{}` implements the trait",
-                                        tcx.type_of(*only).instantiate_identity(),
-                                    )));
-                                }
-                                impls => {
-                                    let mut types = impls.iter()
-                                        .map(|t| with_no_trimmed_paths!(format!(
-                                            " - {}\n",
-                                            tcx.type_of(*t).instantiate_identity(),
-                                        )))
-                                        .collect::<Vec<_>>();
-                                    let post = if types.len() > 9 {
-                                        let len = types.len();
-                                        types.truncate(8);
-                                        format!("and {} others", len - 8)
-                                    } else {
-                                        String::new()
-                                    };
-                                    err.help(format!(
-                                        "the following types implement the trait:\n{}{post}",
-                                        types.join(""),
-                                    ));
-                                }
+                            if !impls.is_empty() {
+                                let len = impls.len();
+                                let mut types = impls.iter()
+                                    .map(|t| with_no_trimmed_paths!(format!(
+                                        "  {}",
+                                        tcx.type_of(*t).instantiate_identity(),
+                                    )))
+                                    .collect::<Vec<_>>();
+                                let post = if types.len() > 9 {
+                                    types.truncate(8);
+                                    format!("\nand {} others", len - 8)
+                                } else {
+                                    String::new()
+                                };
+                                err.help(format!(
+                                    "the following type{} implement{} the trait:\n{}{post}",
+                                    pluralize!(len),
+                                    if len == 1 { "s" } else { "" },
+                                    types.join("\n"),
+                                ));
                             }
-
                         }
                     }
                 } else {

tests/ui/privacy/sealed-traits/sealed-trait-local.stderr

@@ -10,7 +10,8 @@ note: required by a bound in `a::Sealed`
 LL |     pub trait Sealed: self::b::Hidden {
    |                       ^^^^^^^^^^^^^^^ required by this bound in `Sealed`
    = note: `Sealed` is a "sealed trait", because to implement it you also need to implement `a::b::Hidden`, which is not accessible; this is usually done to force you to use one of the provided types that already implement it
-   = help: type `a::X` implements the trait
+   = help: the following type implements the trait:
+             a::X
 
 error[E0277]: the trait bound `S: d::Hidden` is not satisfied
   --> $DIR/sealed-trait-local.rs:53:20
@@ -25,9 +26,8 @@ LL |     pub trait Sealed: self::d::Hidden {
    |                       ^^^^^^^^^^^^^^^ required by this bound in `Sealed`
    = note: `Sealed` is a "sealed trait", because to implement it you also need to implement `c::d::Hidden`, which is not accessible; this is usually done to force you to use one of the provided types that already implement it
    = help: the following types implement the trait:
-            - c::X
-            - c::Y
-           
+             c::X
+             c::Y
 
 error[E0277]: the trait bound `S: f::Hidden` is not satisfied
   --> $DIR/sealed-trait-local.rs:54:20
@@ -42,9 +42,8 @@ LL |     pub trait Sealed: self::f::Hidden {
    |                       ^^^^^^^^^^^^^^^ required by this bound in `Sealed`
    = note: `Sealed` is a "sealed trait", because to implement it you also need to implement `e::f::Hidden`, which is not accessible; this is usually done to force you to use one of the provided types that already implement it
    = help: the following types implement the trait:
-            - e::X
-            - e::Y
-           
+             e::X
+             e::Y
 
 error: aborting due to 3 previous errors