First step to declare a variable with specified data type.

include/ph7int.h

@@ -1618,6 +1618,8 @@ enum ph7_expr_id {
 #define PH7_KEYWORD_CALLBACK     0x80000  /* callback: MUST BE A POWER OF TWO */
 #define PH7_KEYWORD_RESOURCE     0x100000 /* resource: MUST BE A POWER OF TWO */
 #define PH7_KEYWORD_MIXED        0x200000 /* mixed: MUST BE A POWER OF TWO */
+
+#define PH7_KEYWORD_TYPEDEF (PH7_KEYWORD_VOID|PH7_KEYWORD_CHAR|PH7_KEYWORD_BOOL|PH7_KEYWORD_INT|PH7_KEYWORD_FLOAT|PH7_KEYWORD_STRING|PH7_KEYWORD_OBJECT|PH7_KEYWORD_CALLBACK|PH7_KEYWORD_RESOURCE|PH7_KEYWORD_MIXED)
 /* JSON encoding/decoding related definition */
 enum json_err_code {
 	JSON_ERROR_NONE = 0,  /* No error has occurred. */