Use a more precise span in placeholder_type_error_diag

Closes: https://github.com/rust-lang/rust/issues/123861

1 files changed, 4 insertions, 3 deletions

diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index 96d2714252a..0bbf6aa5116 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -201,12 +201,13 @@ pub(crate) fn placeholder_type_error_diag<'cx, 'tcx>(
         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 
     if let Some(generics) = generics {
-        if let Some(arg) = params.iter().find(|arg| {
-            matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. }))
+        if let Some(span) = params.iter().find_map(|arg| match arg.name {
+            hir::ParamName::Plain(Ident { name: kw::Underscore, span }) => Some(span),
+            _ => None,
         }) {
             // Account for `_` already present in cases like `struct S<_>(_);` and suggest
             // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
-            sugg.push((arg.span, (*type_name).to_string()));
+            sugg.push((span, (*type_name).to_string()));
         } else if let Some(span) = generics.span_for_param_suggestion() {
             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
             sugg.push((span, format!(", {type_name}")));