code: function checkInterpolation(i) {
    const start = i;
    let l;
  
    if (i >= tokensLength) return 0;
  
    if (tokens[i].type !== TokenType.NumberSign ||
        !tokens[i + 1] ||
        tokens[i + 1].type !== TokenType.LeftCurlyBracket) return 0;
  
    i += 2;
  
    while (tokens[i].type !== TokenType.RightCurlyBracket) {
      if (l = checkArgument(i)) i += l;
      else return 0;
    }
  
    return tokens[i].type === TokenType.RightCurlyBracket ? i - start + 1 : 0;
  }
docs: Check if token is part of an interpolated variable (e.g. `#{$nani}`).
  @param {number} i Token's index number
  @return {number}