fix: allow full specialization with metafunction

Author: JohelEGP

regression-tests/pure2-template-specialization.cpp2

@@ -4,11 +4,15 @@ t: @struct <T: type> type = {
 t: @struct <T: type> type < T> type requires std::is_void_v < T> = {
   b: i32 = 2;
 }
+t: @struct type < i64> type = {
+  c: i32 = 3;
+}
 v: <T> i32 = 1; // clang-format off
 v: <> type<void> i32 = 2; // clang-format on
 main: ()   = {
   [[assert Testing: t<i32>().a == 1]]
   [[assert Testing: t<void>().b == 2]]
+  [[assert Testing: t<i64>().c == 3]]
   [[assert Testing: (v<i32>) == 1]]
   [[assert Testing: (v<void>) == 2]]
 }

regression-tests/test-results/pure2-template-specialization.cpp

@@ -19,6 +19,9 @@ template<typename T> class t {
 template<typename T> requires( std::is_void_v<T> )
   class t<T> {public: cpp2::i32 b {2}; 
 };
+template<> class t<cpp2::i64> {
+  public: cpp2::i32 c {3}; 
+};
 template<typename T> extern cpp2::i32 v;// clang-format off
                           // clang-format on
 auto main() -> int;
@@ -27,12 +30,13 @@ auto main() -> int;
 //=== Cpp2 function definitions =================================================
 
 
-#line 7 "pure2-template-specialization.cpp2"
+#line 10 "pure2-template-specialization.cpp2"
 template<typename T> cpp2::i32 v {1}; 
 template<> cpp2::i32 v<void> {2}; 
 auto main() -> int{
   cpp2::Testing.expects(t<cpp2::i32>().a==1, "");
   cpp2::Testing.expects(t<void>().b==2, "");
+  cpp2::Testing.expects(t<cpp2::i64>().c==3, "");
   cpp2::Testing.expects((v<cpp2::i32>)==1, "");
   cpp2::Testing.expects((v<void>)==2, "");
 }

source/cppfront.cpp

@@ -5153,7 +5153,7 @@ class cppfront
 
         //  Now, emit our own template parameters
         if (
-            n.template_parameters
+            (n.template_parameters || n.is_specialization())
             && (
                 printer.get_phase() <  printer.phase2_func_defs
                 || n.is_object()
@@ -5171,7 +5171,12 @@ class cppfront
             )
         {
             printer.print_cpp2("template", n.position());
-            emit(*n.template_parameters, false, true);
+            if (n.template_parameters) {
+                emit(*n.template_parameters, false, true);
+            } else {
+                assert(n.is_specialization());
+                printer.print_cpp2("<>", n.position());
+            }
             printer.print_cpp2(" ", n.position());
         }