Typing does not work when creating a map in Kotlin through spring boot @RequestParam

Question

I am using spring boot and have made the following controller where I explicitly specify key and value types.

@PostMapping("DAC/set")
    fun setDac(@RequestParam map: HashMap<Int, Float>): ResponseEntity<JSONObject> {
        println(map)
        return dac()
    }

When I send a request like this:

http://localhost:9090/adam6024/DAC/set?a=abc,b=d,d=v

I am getting this output in console:

{a=abc,b=d,d=v}

Why am I not getting an error? Moreover, I cannot add string values to the map, my IDE does not allow me.