internal: Migrate remove_mut assist to SyntaxEditor

Author: Giga-Bowser

src/tools/rust-analyzer/crates/ide-assists/src/handlers/remove_mut.rs

@@ -1,4 +1,4 @@
-use syntax::{SyntaxKind, TextRange, T};
+use syntax::{SyntaxKind, T};
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
 
@@ -19,19 +19,20 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 // ```
 pub(crate) fn remove_mut(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
     let mut_token = ctx.find_token_syntax_at_offset(T![mut])?;
-    let delete_from = mut_token.text_range().start();
-    let delete_to = match mut_token.next_token() {
-        Some(it) if it.kind() == SyntaxKind::WHITESPACE => it.text_range().end(),
-        _ => mut_token.text_range().end(),
-    };
 
     let target = mut_token.text_range();
     acc.add(
         AssistId("remove_mut", AssistKind::Refactor),
         "Remove `mut` keyword",
         target,
         |builder| {
-            builder.delete(TextRange::new(delete_from, delete_to));
+            let mut editor = builder.make_editor(&mut_token.parent().unwrap());
+            match mut_token.next_token() {
+                Some(it) if it.kind() == SyntaxKind::WHITESPACE => editor.delete(it),
+                _ => (),
+            }
+            editor.delete(mut_token);
+            builder.add_file_edits(ctx.file_id(), editor);
         },
     )
 }