module My

const Here = My
macro fieldsof(Texpr)
    T = eval(Texpr)
    names_and_types = zip(fieldnames(T), fieldtypes(T))
    fields = (:($(esc(a))::$(esc(A))) for (a, A) in names_and_types)
    Expr(:block, fields...)
end
fieldsof(T) = macroexpand(Here, :(@fieldsof($T)))

abstract type AbstractPerson end
name(x::AbstractPerson) = x.name
age(x::AbstractPerson) = x.age
data(x::AbstractPerson) = x.data
struct Person{T} <: AbstractPerson
    name::String
    age::Int
    data::T
end

abstract type AbstractStudent <: AbstractPerson end
grade(x::AbstractStudent) = x.grade
struct Student{T} <: AbstractStudent
    @fieldsof Person{:T}
    grade::Int
end

end

My.fieldsof(My.Person{:T})

My.fieldsof(My.Person{:T}) |> Meta.show_sexpr

p = My.Person("Ken", 28, "魔術師")

@show My.name(p)
@show My.age(p)
@show My.data(p)
;

My.fieldsof(My.Student{:T})

s = My.Student("Taro", 14, Dict("好き"=>"カレーライス", "嫌い"=>"ピーマン"), 8)

@show My.name(s)
@show My.age(s)
@show My.data(s)
@show My.grade(s)
;