Fix counter in gcc

include/utempl/loopholes/core.hpp

@@ -1,3 +1,4 @@
+#include <type_traits>
 #pragma once
 
 namespace utempl::loopholes {
@@ -12,8 +13,18 @@ struct Injector {
 };
 
 
-template <auto I, typename...>
-concept Injected = requires{Magic(Getter<I>{});};
+template <auto, typename = void, typename... Ts>
+struct InjectedImpl {
+  static constexpr bool value = false;
+};
+template <auto V, typename... Ts>
+struct InjectedImpl<V, std::void_t<decltype(Magic(Getter<V>{}))>, Ts...> {
+  static constexpr bool value = true;
+};
+
+template <auto I, typename... Ts>
+concept Injected = InjectedImpl<I, void, Ts...>::value;
+
 
 
 

include/utempl/loopholes/counter.hpp

@@ -7,15 +7,15 @@ namespace utempl::loopholes {
 namespace impl {
 
 template <typename Tag, auto Value>
-struct TagWithTalue {};
+struct TagWithValue {};
 
-template <auto I = 0, typename Tag, typename... Ts, auto = Injector<TagWithTalue<Tag, I>{}>{}>
+template <auto I = 0, typename Tag, typename... Ts, auto = Injector<TagWithValue<Tag, I>{}>{}>
 constexpr auto Counter(...) {
   return I;
 };
 
 template <auto I = 0, typename Tag, typename... Ts>
-consteval auto Counter(std::size_t arg) requires Injected<TagWithTalue<Tag, I>{}, Ts...> {
+consteval auto Counter(std::size_t arg) requires Injected<TagWithValue<Tag, I>{}, Ts...> {
   return Counter<I + 1, Tag, Ts...>(arg);
 };
 } // namespace impl;
@@ -24,12 +24,14 @@ consteval auto Counter(std::size_t arg) requires Injected<TagWithTalue<Tag, I>{}
 template <
   typename Tag,
   typename... Ts,
-  std::size_t R = impl::Counter<0, Tag, Ts...>(std::size_t{}) - 1
+  std::size_t R = impl::Counter<0, Tag, Ts...>(std::size_t{})
+#if defined __clang__
+  - 1
+#endif
 >
 consteval auto Counter(auto...) -> std::size_t {
   return R;
 };
 
 
-
 } // namespace utempl::loopholes