Prefer Array.new(n) {} to n.times.map {}

* It is quite a bit faster:
  ruby -rbenchmark/ips -e 'Benchmark.ips { |x| x.report("times.map") { 1000.times.map {} }; x.report("Array.new") { Array.new(1000) {} }; x.compare! }'
  ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-linux]
  Warming up --------------------------------------
         times.map   976.000 i/100ms
         Array.new     1.641k i/100ms
  Calculating -------------------------------------
         times.map      9.808k (± 0.3%) i/s -     49.776k in   5.075013s
         Array.new     16.601k (± 1.0%) i/s -     83.691k in   5.041970s

  Comparison:
         Array.new:    16600.8 i/s
         times.map:     9808.2 i/s - 1.69x  slower

templates/lib/prism/serialize.rb.erb

@@ -83,11 +83,11 @@ module Prism
       end
 
       def load_line_offsets
-        source.instance_variable_set :@offsets, load_varuint.times.map { load_varuint }
+        source.instance_variable_set :@offsets, Array.new(load_varuint) { load_varuint }
       end
 
       def load_comments
-        load_varuint.times.map do
+        Array.new(load_varuint) do
           case load_varuint
           when 0 then InlineComment.new(load_location)
           when 1 then EmbDocComment.new(load_location)
@@ -98,10 +98,10 @@ module Prism
 
       def load_metadata
         comments = load_comments
-        magic_comments = load_varuint.times.map { MagicComment.new(load_location, load_location) }
+        magic_comments = Array.new(load_varuint) { MagicComment.new(load_location, load_location) }
         data_loc = load_optional_location
-        errors = load_varuint.times.map { ParseError.new(load_embedded_string, load_location, load_error_level) }
-        warnings = load_varuint.times.map { ParseWarning.new(load_embedded_string, load_location, load_warning_level) }
+        errors = Array.new(load_varuint) { ParseError.new(load_embedded_string, load_location, load_error_level) }
+        warnings = Array.new(load_varuint) { ParseWarning.new(load_embedded_string, load_location, load_warning_level) }
         [comments, magic_comments, data_loc, errors, warnings]
       end