Why does Eclipse complain about this use of C++ templates?

Question

In Eclipse, I’m looking at code which is essentially the same as the example posted in the codereview.SX question “C++17: Boost.Hana based compile-time plugin registration”, just condensed into one file and with the Boost stuff stripped out:

#include <iostream>
#include <type_traits>

template<class>
struct sfinae_true;

template<unsigned int>
struct registry_hook;

namespace registry {
  template<class Dummy, unsigned int testN>
  constexpr sfinae_true<decltype(registry_hook<testN>{})> test(int);
  template<class Dummy, unsigned int testN>
  constexpr std::false_type test(long);

  template<class Dummy, unsigned int testN = 0>
  constexpr unsigned int get_free_N() {
    if constexpr (std::is_same<decltype(test<Dummy, testN>(0)), std::false_type>::value) {
        return testN;
    } else {
        return get_free_N<Dummy, testN + 1>();
    }
  }
}

struct Dummy1;
template<>
struct registry_hook<registry::get_free_N<Dummy1>()> {
    constexpr static unsigned int my_N = registry::get_free_N<Dummy1>();
};

struct Dummy2;
template<>
struct registry_hook<registry::get_free_N<Dummy2>()> {
    constexpr static unsigned int my_N = registry::get_free_N<Dummy2>();
};


int main() {
    constexpr unsigned int max_N = registry::get_free_N<void>() - 1;
    std::cout << max_N << std::endl;
}

This compiles and works fine with both GCC and clang:

$ g++     -std=c++17 -Wall -Wextra -pedantic main.cc && ./a.out
1
$ clang++ -std=c++17 -Wall -Wextra -pedantic main.cc && ./a.out
1

However, Eclipse complains about the lines with explicit template specializations, giving the error “Invalid template argument”. The parser log file shows the same, without any more context:

Project:               test
File:                  file:[…]/main.cc
Language:              GNU C++
Index Version:         220.0
Build Configuration:   Default
Context:               file:[…]/main.cc
   C++, {}
Versions in Index:     1
   C++: {}; 0 macros, 2 includes, 47 names;

Include Search Path (option -I):
   /usr/include/c++/11
   /usr/include/x86_64-linux-gnu/c++/11
   /usr/include/c++/11/backward
   /usr/lib/gcc/x86_64-linux-gnu/11/include
   /usr/local/include
   /usr/include/x86_64-linux-gnu
   /usr/include

Macro definitions (option -D):
   […]

Unresolved names:
   A template id provides illegal arguments for the instantiation: registry_hook in file […]/main.cc:28
   A template id provides illegal arguments for the instantiation: registry_hook in file […]/main.cc:34

Written on Tue Dec 05 23:01:27 EST 2023

I don’t see what the problem is supposed to be. Is this just a bug in Eclipse/CDT?