The following are reserved keywords in Rhai:

Active keywordsReserved keywordsUsageInactive under feature
true, falseconstants
let, const, globalvar, staticvariables
begin, endblock scopes
is_sharedshared valuesno_closure
if, elsethen, unless, goto, exitcontrol flow
switchmatch, caseswitching and matching
do, while, loop, until, for, in, continue, breakeachlooping
fn, privatepublic, protected, newfunctionsno_function
returnreturn values
throw, try, catchthrow/catch exceptions
import, export, asuse, with, module, package, supermodulesno_module
Fn, call, curryfunction pointers
spawn, thread, go, sync, async, await, yieldthreading/async
type_of, print, debug, evalspecial functions
default, void, null, nilspecial values

Keywords cannot become the name of a function or variable, even when they are disabled.