slim-static.rb

#!/usr/bin/env ruby
require 'benchmark/ips'
require 'slim'

t1 = 1000.times.map do |i|
  "span*{foo: #{i}}"
end.join("\n")

t2 = 1000.times.map do |i|
  "span foo=#{i}"
end.join("\n")

t3 = 1000.times.map do |i|
  "span foo='#{i}'"
end.join("\n")

obj = Object.new
obj.instance_eval("def t1; #{Slim::Engine.new.call(t1)}; end")
obj.instance_eval("def t2; #{Slim::Engine.new.call(t2)}; end")
obj.instance_eval("def t3; #{Slim::Engine.new.call(t3)}; end")

puts "Slim::VERSION #{Slim::VERSION}"
Benchmark.ips do |x|
  x.report('t1') { obj.t1 }
  x.report('t2') { obj.t2 }
  x.report('t3') { obj.t3 }
  x.compare!
end

__END__

Slim::VERSION 3.0.1
Calculating -------------------------------------
                  t1    10.000  i/100ms
                  t2    69.000  i/100ms
                  t3    12.232k i/100ms
-------------------------------------------------
                  t1    100.026  (± 2.0%) i/s -    500.000 
                  t2    691.137  (± 3.2%) i/s -      3.519k
                  t3    155.544k (± 9.7%) i/s -    782.848k

Comparison:
                  t3:   155543.8 i/s
                  t2:      691.1 i/s - 225.05x slower
                  t1:      100.0 i/s - 1555.04x slower