Let's say I have the following Jakt code:

/// Expect:
/// - output: ""
struct SecretHolder<T> {
    private secret: T
    function create(secret: T) -> SecretHolder<T> => SecretHolder(secret)
}

function main() {
    let holder = SecretHolder::create(42i32)
}

It will typecheck and generate:

#include <lib.h>
namespace Jakt {
template <typename T>struct SecretHolder;
template <typename T>struct SecretHolder {
  public:
T secret;static SecretHolder<T> create(const T secret) {
{
return (SecretHolder());
}
}
SecretHolder(T a_secret) :secret(a_secret){}

ErrorOr<String> debug_description() const { auto builder = MUST(StringBuilder::create());TRY(builder.append("SecretHolder("));JaktInternal::_pretty_print_level++;
TRY(JaktInternal::_output_pretty_indent(builder));TRY(builder.append("secret: "));TRY(builder.appendff("{}", secret));
JaktInternal::_pretty_print_level--;
TRY(builder.append(")"));return builder.to_string(); }};ErrorOr<int> main(Array<String>) {
{
const SecretHolder<i32> holder = SecretHolder::create(static_cast<i32>(42));
}
return 0;
}

template<typename T>struct Formatter<SecretHolder<T>
> : Formatter<StringView>{
ErrorOr<void> format(FormatBuilder& builder, SecretHolder<T>
 const& value)
{ if (m_alternative_form) { JaktInternal::_pretty_print_enabled = true; }return Formatter<StringView>::format(builder, MUST(value.debug_description())); }};
} // namespace Jakt

Here, the typechecking is correct. It inferred correctly that I have created a SecretHolder<i32>, and that SecretHolder::create does not throw. The problem is that codegen did not add the template arguments in SecretHolder<T>::create, and this confuses clang++:

❯ clang++ -w -I. -I<path/to/runtime> test.cpp -std=c++20
test.cpp:18:34: error: 'SecretHolder' is not a class, namespace, or enumeration
const SecretHolder<i32> holder = SecretHolder::create(static_cast<i32>(42));
                                 ^
test.cpp:4:29: note: 'SecretHolder' declared here
template <typename T>struct SecretHolder {
                            ^
1 error generated.

Clang fails at recognizing SecretHolder as a struct, since it's really a template.

The correct behavior should use SecretHolder<i32>::create(static_cast<i32>), i.e instantiating the template explicitly.

EDIT: simplified sample snippet to contain just Jakt code.