Macrology.jl

module Macrology
export @declare, @with_macro_arg

using MLStyle

macro declare(expr)
  (head, val) = @match expr begin
    :($head = $val) => (head, val)
  end

  quote
    macro $(esc(head))(expr)
      @match expr begin
        Expr(:macrocall, name, line, args...) =>
          Expr(:macrocall, name, line, $val, args...)
      end
    end
  end
end

macro with_macro_arg(macrodef)
  @match macrodef begin
    Expr(:macro, Expr(:call, name, x, y), body) => begin
      internal = gensym(:internal)
      quote
        macro $(esc(name))($x, $y)
          @match $x begin
            Expr(:macrocall, name, line) =>
              Expr(:macrocall, name, line, Expr(:macrocall, $(esc(Symbol("@" * string(internal)))), line, $y))
          end
        end

        macro $(esc(internal))($x, $y)
          $body
        end
      end
    end
  end
end

@with_macro_arg macro add(x,y)
  x + y
end

@declare x 9

(@macroexpand (@add (@x) 3)) == 12

end