fix rename to replace only the referenced identifier in paths

When renaming Bar in Foo::Bar, the entire path was being replaced
with just the new name instead of producing Foo::Baz.

Added PathView::last_segment_span() to get only the identifier span
of the last segment. Added ReferenceView::rename_span() that delegates
to last_segment_span for paths while returning normal spans for other
reference types. Updated rename handler to use rename_span() instead
of span() for text edits.

This preserves goto-definition behavior (which needs full path spans
to detect intermediate segment clicks) while fixing rename to only
replace the actual referenced item.

Author: micahscopes

crates/language-server/src/functionality/rename.rs

@@ -71,7 +71,7 @@ pub async fn handle_rename(
                 }
                 let mod_ = map_file_to_mod(&backend.db, file);
                 for ref_view in mod_.references_to_target(&backend.db, target.clone()) {
-                    if let Some(span) = ref_view.span().resolve(&backend.db)
+                    if let Some(span) = ref_view.rename_span(&backend.db).resolve(&backend.db)
                         && let Ok(range) = to_lsp_range_from_span(span, &backend.db)
                     {
                         changes.entry(file_url.clone()).or_default().push(TextEdit {
@@ -97,7 +97,7 @@ pub async fn handle_rename(
         Target::Local { span, .. } => {
             // For local bindings, search within the function body
             for ref_view in top_mod.references_to_target(&backend.db, target.clone()) {
-                if let Some(resolved) = ref_view.span().resolve(&backend.db)
+                if let Some(resolved) = ref_view.rename_span(&backend.db).resolve(&backend.db)
                     && let Some(ref_url) = resolved.file.url(&backend.db)
                     && let Ok(range) = to_lsp_range_from_span(resolved, &backend.db)
                 {