Let's look at a minimal code sample which reproduces the compiler error:
template foo*(sFoo: untyped) =
type A = object
str: string
sFoo
foo:
echo A(str: "hello").str
Run
Type definitions inside a template are by default invisible to code from the
instantiation scope (or gensym ed, see the manual chapter @Hlaaftana linked).
`sFoo` comes from the instantiation scope, thus the error, which can be avoided
by giving `A` an `{.inject.}` pragma.
When the definition of `A` is included instead, the `include` is apparently
resolved after template substitution: `A` is not defined in the template body,
but immediatly inside the instantiating context.
