Function is_try_catch_frame_call 

fn is_try_catch_frame_call(call: SEXP) -> bool

Whether call is doTryCatch(return(expr), name, parentenv, handler), the frame of R’s tryCatch(), which R_tryCatchError evaluates in. An error raised at the top of the evaluated expression (stop() called directly, not from a function) takes that frame’s call as its own; it is no call of the user’s code, so REvalError::call reports None there. Base R’s try() recognises the frame by the same doTryCatch head.