feat: allow renaming of elided lifetimes (Fixes #19260)

Author: Amit5601

crates/ide/src/rename.rs

@@ -16,7 +16,7 @@ use std::fmt::Write;
 use stdx::{always, format_to, never};
 use syntax::{
     AstNode, SyntaxKind, SyntaxNode, TextRange, TextSize,
-    ast::{self, HasArgList, prec::ExprPrecedence},
+    ast::{self, AnyHasGenericParams, HasArgList, HasGenericParams, HasName, prec::ExprPrecedence},
 };
 
 use ide_db::text_edit::TextEdit;
@@ -79,7 +79,10 @@ pub(crate) fn prepare_rename(
     let sema = Semantics::new(db);
     let source_file = sema.parse_guess_edition(position.file_id);
     let syntax = source_file.syntax();
-
+    if let Some(lifetime_token) = syntax.token_at_offset(position.offset).find(|t| t.text() == "'_")
+    {
+        return Ok(RangeInfo::new(lifetime_token.text_range(), ()));
+    }
     let res = find_definitions(&sema, syntax, position, &Name::new_symbol_root(sym::underscore))?
         .filter(|(_, _, def, _, _)| def.range_for_rename(&sema).is_some())
         .map(|(frange, kind, _, _, _)| {
@@ -133,6 +136,13 @@ pub(crate) fn rename(
 
     let edition = file_id.edition(db);
     let (new_name, kind) = IdentifierKind::classify(edition, new_name)?;
+    if kind == IdentifierKind::Lifetime
+        && let Some(lifetime_token) =
+            syntax.token_at_offset(position.offset).find(|t| t.text() == "'_")
+    {
+        let new_name_str = new_name.display(db, edition).to_string();
+        return rename_elided_lifetime(position, lifetime_token, &new_name_str);
+    }
 
     let defs = find_definitions(&sema, syntax, position, &new_name)?;
     let alias_fallback =
@@ -797,6 +807,49 @@ fn text_edit_from_self_param(self_param: &ast::SelfParam, new_name: String) -> O
     Some(TextEdit::replace(self_param.syntax().text_range(), replacement_text))
 }
 
+fn rename_elided_lifetime(
+    position: FilePosition,
+    lifetime_token: syntax::SyntaxToken,
+    new_name: &str,
+) -> RenameResult<SourceChange> {
+    let mut edit = ide_db::text_edit::TextEdit::builder();
+
+    // 1. Replace the `'_` with the new lifetime name
+    edit.replace(lifetime_token.text_range(), new_name.to_owned());
+
+    // 2. Find the parent fn or impl using AnyHasGenericParams
+    let parent = lifetime_token.parent().unwrap();
+    if let Some(has_generic_params) = parent.ancestors().find_map(AnyHasGenericParams::cast) {
+        if let Some(generic_list) = has_generic_params.generic_param_list() {
+            // Generics list < > already exists, insert inside it
+            if let Some(l_angle) = generic_list.l_angle_token() {
+                let insert_text = if generic_list.generic_params().count() == 0 {
+                    new_name.to_owned()
+                } else {
+                    format!("{}, ", new_name)
+                };
+                edit.insert(l_angle.text_range().end(), insert_text);
+            }
+       } else {
+            // No generics exist yet, we must create the < >
+            let syntax = has_generic_params.syntax();
+            if let Some(fn_def) = ast::Fn::cast(syntax.clone())
+                && let Some(name) = fn_def.name()
+            {
+                edit.insert(name.syntax().text_range().end(), format!("<{}>", new_name));
+            } else if let Some(impl_def) = ast::Impl::cast(syntax.clone())
+                && let Some(impl_kw) = impl_def.impl_token()
+            {
+                edit.insert(impl_kw.text_range().end(), format!("<{}>", new_name));
+            }
+        }
+    }
+
+    let mut source_change = SourceChange::default();
+    source_change.insert_source_edit(position.file_id, edit.finish());
+    Ok(source_change)
+}
+
 #[cfg(test)]
 mod tests {
     use expect_test::{Expect, expect};