fix(to_cpp1): define static data member with placeholder type in class

regression-tests/pure2-type-and-namespace-aliases.cpp2

@@ -33,3 +33,21 @@ main: () = {
     myfunc2 :== myfunc;
     myfunc2();
 }
+
+myclass5: type == myclass4;
+
+myclass3: @struct type = {
+    v0 :== :std::array = (0);;
+    v1 :== v0; // OK: Also uses the Cpp2 placeholder type.
+    v2: myclass3 == myclass3(); // OK: Doesn't use the Cpp2 placeholder type.
+    v3: _ == v0;
+    v4: myclass3 == v2; // OK: Doesn't use the Cpp2 placeholder type.
+    v5: myclass4 == myclass4(); // OK: Doesn't use the Cpp2 placeholder type.
+    v6: myclass5 == myclass5(); // OK: Doesn't use the Cpp2 placeholder type.
+}
+
+myclass4: @struct type = { }
+
+myclass6: @struct <T: type> type = {
+    v: <U> _ requires true == 0;
+}

regression-tests/test-results/gcc-13/pure2-bugfix-for-non-local-function-expression.cpp.output

@@ -1 +1,3 @@
 pure2-bugfix-for-non-local-function-expression.cpp2:9:7: warning: ‘t’ has a base ‘t::<lambda()>’ which has no linkage [-Wsubobject-linkage]
+    9 | t: @struct type = {
+      |       ^

regression-tests/test-results/pure2-type-and-namespace-aliases.cpp

@@ -20,6 +20,16 @@ class myclass;
 template<typename T> class myclass2;
 
 
+#line 39 "pure2-type-and-namespace-aliases.cpp2"
+class myclass3;
+
+
+#line 49 "pure2-type-and-namespace-aliases.cpp2"
+class myclass4;
+
+template<typename T> class myclass6;
+
+
 //=== Cpp2 type definitions and function declarations ===========================
 
 
@@ -60,6 +70,29 @@ template<typename T> class myclass2 {
 auto main() -> int;
 
 
+#line 37 "pure2-type-and-namespace-aliases.cpp2"
+using myclass5 = myclass4;
+
+class myclass3 {
+    public: static constexpr auto v0 = std::array{0};
+    public: static constexpr auto v1 = v0;// OK: Also uses the Cpp2 placeholder type.
+    public: static const myclass3 v2;// OK: Doesn't use the Cpp2 placeholder type.
+    public: static constexpr auto v3 = v0;
+    public: static const myclass3 v4;// OK: Doesn't use the Cpp2 placeholder type.
+    public: static const myclass4 v5;// OK: Doesn't use the Cpp2 placeholder type.
+    public: static const myclass5 v6;// OK: Doesn't use the Cpp2 placeholder type.
+};
+
+class myclass4 {};
+
+template<typename T> class myclass6 {
+    public: template<typename U> 
+CPP2_REQUIRES_ (true)
+#line 52 "pure2-type-and-namespace-aliases.cpp2"
+    static constexpr auto v = 0;
+};
+
+
 //=== Cpp2 function definitions =================================================
 
 
@@ -93,3 +126,10 @@ auto main() -> int{
     myfunc2();
 }
 
+#line 42 "pure2-type-and-namespace-aliases.cpp2"
+    inline CPP2_CONSTEXPR myclass3 myclass3::v2 = myclass3();
+
+    inline CPP2_CONSTEXPR myclass3 myclass3::v4 = v2;
+    inline CPP2_CONSTEXPR myclass4 myclass3::v5 = myclass4();
+    inline CPP2_CONSTEXPR myclass5 myclass3::v6 = myclass5();
+

source/to_cpp1.h

@@ -5080,8 +5080,18 @@ class cppfront
             auto& a = std::get<declaration_node::an_alias>(n.type);
             assert(a);
 
+            //  Helper for aliases that emit as a defining declaration.
+            auto const type_scope_object_alias_emits_in_phase_1_only = [&]() {
+                assert(
+                    n.parent_is_type()
+                    && n.is_object_alias()
+                );
+                return !a->type_id
+                       || a->type_id->is_wildcard();
+            };
+
             //  Namespace-scope aliases are emitted in phase 1,
-            //  type-scope object aliases in both phases 1 and 2, and
+            //  type-scope object aliases is emitted in phase 1 and maybe 2, and
             //  function-scope aliases in phase 2
             if (
                 (
@@ -5093,6 +5103,7 @@ class cppfront
                     n.parent_is_type()
                     && n.is_object_alias()
                     && printer.get_phase() == printer.phase2_func_defs
+                    && !type_scope_object_alias_emits_in_phase_1_only()
                     )
                 ||
                 (
@@ -5158,21 +5169,34 @@ class cppfront
                 //  Handle object aliases:
                 //      - at function scope, it's const&
                 //      - at namespace scope, it's inline constexpr
-                //      - at type scope, it's also inline constexpr but see note (*) below
+                //      - at type scope, it's also static constexpr but see note (*) below
                 else if (a->is_object_alias())
                 {
                     auto type = std::string{"auto"};
                     if (a->type_id) {
                         type = print_to_string(*a->type_id);
                     }
 
-                    //  (*) If this is at type scope, Cpp1 requires an out-of-line declaration dance
-                    //  for some cases to work - see https://stackoverflow.com/questions/11928089/
                     if (n.parent_is_type())
                     {
                         assert (n.parent_declaration->name());
 
-                        if (printer.get_phase() == printer.phase1_type_defs_func_decls) {
+                        if (type_scope_object_alias_emits_in_phase_1_only()) {
+                            if (printer.get_phase() == printer.phase1_type_defs_func_decls) {
+                                printer.print_cpp2(
+                                    "static constexpr "
+                                        + type + " "
+                                        + print_to_string(*n.identifier)
+                                        + " = "
+                                        + print_to_string( *std::get<alias_node::an_object>(a->initializer) )
+                                        + ";\n",
+                                    n.position()
+                                );
+                            }
+                        }
+                        //  At type scope, Cpp1 requires an out-of-line declaration dance
+                        //  for some cases to work - see https://stackoverflow.com/questions/11928089/
+                        else if (printer.get_phase() == printer.phase1_type_defs_func_decls) {
                             printer.print_cpp2(
                                 "static const "
                                     + type + " "