I independently came up with a similar hack in TXR Lisp. When a variable is named by a gensym, unused warnings are suppressed. Gensyms are almost always symbols

I independently came up with a similar hack in TXR Lisp. When a variable is named by a gensym, unused warnings are suppressed. Gensyms are almost always symbols generated by macros. Machine generated code often has cases where variables are unused. This design decision is a trade off. Any situation in which a variable is unused is potentially a bug, even if the variable is in code written by a macro and named by a generated symbol. But it is a burden on macro writers to ensure that all possible cases of general code are free of unused variable warnings.