Expand constants inside literals in macro calls

[jhass]

Ref #2392 #2388

The following should expand the constant:

require "json"

ID_TYPE = {type: Int32, converter: ObscureApi}
class Foo
  JSON.mapping(
    id: {{ID_TYPE}},
    other: Stuff
  )
end

class Bar
  JSON.mapping(
    id: {{ID_TYPE}},
    different: Stuff
  )
end

[HertzDevil]

I would consider this a bug. Only named arguments are not expanded:

macro foo(x0, x1, *xs, n0, n1, **ns)
  {% x0 %} # => 1
  {% x1 %} # => 2
  {% xs %} # => {3, 4}
  {% n0 %} # => {{ 5 }}
  {% n1 %} # => {{ 7 }}
  {% ns %} # => {n2: {{ 6 }}, n3: {{ 8 }}}
end

foo(
  {{ 1 }}, {{ 2 }}, {{ 3 }}, {{ 4 }},
  n0: {{ 5 }}, n2: {{ 6 }}, n1: {{ 7 }}, n3: {{ 8 }},
)