Restrict cast types

include/elna/boot/driver.h

@@ -47,4 +47,5 @@ namespace elna::boot
     constexpr char escape_invalid_char = '\xff';
 
     char escape_char(char escape);
+    std::optional<std::string> escape_string(const char *escape);
 }

include/elna/gcc/elna-tree.h

@@ -36,6 +36,7 @@ namespace elna::gcc
     bool is_pointer_type(tree type);
     bool is_integral_type(tree type);
     bool is_numeric_type(tree type);
+    bool is_primitive_type(tree type);
     bool is_array_type(tree type);
     bool is_void_type(tree type);