Cope with frozen-string-literal

When running irb 1.2.1 (2019-12-24) with frozen-string-literal enabled, it crashes in reline with `can't modify frozen String (FrozenError)` Steps to reproduce: `RUBYOPT="--enable-frozen-string-literal" irb`
ruby · Dec 4, 2020 · f438641 · f438641
1 parent 0cf0730
commit f438641
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/lib/reline/ansi.rb b/lib/reline/ansi.rb
@@ -172,7 +172,7 @@ def self.set_screen_size(rows, columns)
 
   def self.cursor_pos
     begin
-      res = ''
+      res = String.new
       m = nil
       @@input.raw do |stdin|
         @@output << "\e[6n"