class Opal::Nodes::HashNode

def compile_merge

Hash k/v pairs override previously defined kwsplat values
Each kwsplat overrides previosly defined keys
{ nested: 1}.merge(a: 1).merge(nested: 2)
should be compiled to
hash like { **{ nested: 1 }, a: 1, **{ nested: 2} }
Compiles hashes containing kwsplats inside. 
def compile_merge
  result, seq = [], []
  children.each do |child|
    if child.type == :kwsplat
      unless seq.empty?
        result << expr(s(:hash, *seq))
      end
      result << expr(child)
      seq = []
    else
      seq << child
    end
  end
  unless seq.empty?
    result << expr(s(:hash, *seq))
  end
  result.each_with_index do |fragment, idx|
    if idx == 0
      push fragment
    else
      push '.$merge(', fragment, ')'
    end
  end
end