51:12 A computed property name in a class property declaration must refer to an
expression whose type is a literal type or a 'unique symbol' type.
    49 | })
    50 | export default class Main extends Vue {
  > 51 |   readonly [PROPS.VALUE]: string
Expected behavior
There was no error.
          
Hi @iliyaZelenko! This repository is for TSLint, a program that uses TypeScript APIs to provide additional analysis on TypeScript code. The error you're receiving is from TypeScript itself. Those issues should be filed on https://github.com/Microsoft/TypeScript.
Note: the reason why TypeScript is complaining is because PROPS.VALUE is itself not a literal type or 'unique symbol' type. It would be valid for someone to do this:
const PROPS = {
  VALUE: 'value'
PROPS.VALUE = 'aha!';
export default class Main extends Vue {
  readonly [PROPS.VALUE]: string
Once TypeScript 3.4 is released (very soon!), you'll want to use a const assertion. Until then you can typecast VALUE to be as 'value':
const PROPS = {
  VALUE: 'value' as 'value'
Without an as const or as 'value', the type of PROPS.VALUE is general string.
          
@JoshuaKGoldberg, thank you so much for the answer. Sorry for creating the question in the wrong place.
Thanks to you, now I understand what the "literal type" is.
Thanks for telling me what they will add const assertion in version TypeScript 3.4. Since my project is new, I installed version ^3.4-rc and the error disappeared (with as const).
@JoshuaKGoldberg, really thank you!
      Type error causing build failure in the destination package: A computed property name in an interface must refer to an expression whose type is a literal type or a 'unique symbol' type.
      adobe/react-spectrum-charts#272