fix Issue 24026 - ImportC: ICE on nested C initializer 2 (#15375)

compiler/test/runnable/test23786.c

@@ -0,0 +1,66 @@
+// https://issues.dlang.org/show_bug.cgi?id=23768
+
+typedef struct {
+  union {
+    struct {
+      int o;
+    } f;
+  };
+} T;
+
+void f(void) {
+    T data = (T) {
+      {.f = {.o = 0}}
+    };
+}
+
+/***************/
+
+typedef struct {
+  union {
+    struct {
+      struct { double o; } f;
+    };
+  };
+} S;
+
+_Static_assert(sizeof(S) == 8, "1");
+
+void test23768()
+{
+    S data = (S) {
+      {{.f = {.o = 3}}}
+    };
+    __check(data.f.o == 3);
+    S s;
+    s.f.o = 4;
+    __check(s.f.o == 4);
+}
+
+/**************************/
+// https://issues.dlang.org/show_bug.cgi?id=24026
+
+struct A
+{
+    int type;
+};
+
+struct E
+{
+    struct A action;
+};
+
+void test24026()
+{
+    struct E entry = {{ .type = 1 }};
+    __check(entry.action.type == 1);
+}
+
+/**************************/
+
+int main()
+{
+    test23768();
+    test24026();
+    return 0;
+}