Metaprogramming first steps

[Mason]

@andrey2185

# what am I doing wrong ?
# why i get var"#30#Foo" or #31#a instead of Foo or :a ?
# where is my function Foo(builder::Main.FooBuilder) ?

This is about macro hygiene. e.g. here is a simple example:

julia> macro foo(ex)
           ex
       end
@foo (macro with 1 method)

julia> @macroexpand @foo x = 1
:(var"#64#x" = 1)

julia> macro foo(ex)
           esc(ex)
       end
@foo (macro with 1 method)

julia> @macroexpand @foo x = 1
:(x = 1)

Here is the relevant docs section on Hygiene: Metaprogramming · The Julia Language