There is simple version to show the problem.
import typetraits
type Foo[T] = ref object
x: T
proc `@@`*[T](a: T): Foo[T] = new(result); result.x = a
proc `$`*[T](f: Foo[T]): string = "Foo[" & $f.x & "]"
type Bar[T] = Foo[Foo[T]]
# OOPS
# Change the Bar[T] to Foo[Foo[T]] will make compiler happy
proc core[T](vv: Bar[T]): Foo[T] =
static: echo "In core type of vv is ", name(type(vv))
# OOPS
# Should be "int" rather than "Foo[system.int]"
static: echo "In core type of T is ", name(T)
new(result)
result.x = vv.x.x
when isMainModule:
let vv = @@(@@5)
static: echo "In main type of vv is ", name(type(vv))
# OOPS
# change to "let x = core[int](vv)" will make compiler happy
let x = core(vv)
echo x
