Undocumented feature. Using number as structure element.

[TheCoolerSuptelov]

I tried to create an expression where one of the keys is number, but tokenizer recognizes as NUMBER_LITERAL, not VARIABLE_OR_CONSTANT.
But I found a way around this limitation which is not described in the documentation, should I open an issue or is this a known issue?

Code samples I wrote in TokenizerStructureTest for reproduction

Workaroung with "_" prefix:

  @Test
  void testStructureRightIsNumber()throws ParseException{
    assertAllTokensParsedCorrectly(
            "a._101",
            new Token(1, "a", TokenType.VARIABLE_OR_CONSTANT),
            new Token(2, ".", TokenType.STRUCTURE_SEPARATOR),
            new Token(3, "_101", TokenType.VARIABLE_OR_CONSTANT));
  }

Test without prefix "_" in number key:
will be failed with:
[Token(startPosition=2, value=.101, type=NUMBER_LITERAL)]

  @Test
  void testStructureRightIsNumber()throws ParseException{
    assertAllTokensParsedCorrectly(
            "a.101",
            new Token(1, "a", TokenType.VARIABLE_OR_CONSTANT),
            new Token(2, ".", TokenType.STRUCTURE_SEPARATOR),
            new Token(3, "101", TokenType.VARIABLE_OR_CONSTANT));
  }

[uklimaschewski]

I never had the idea that structure elements could also be numbers, always thought that they must be a name (variable).
Unsure about if it makes sense to support numbers as names for structure elements.

[TheCoolerSuptelov]

Can I do a pull request with the first tests and propose changes to the documentation, to commit the contract ?
The test I'm talking about

@Test
  void testStructureRightIsNumber()throws ParseException{
    assertAllTokensParsedCorrectly(
            "a._101",
            new Token(1, "a", TokenType.VARIABLE_OR_CONSTANT),
            new Token(2, ".", TokenType.STRUCTURE_SEPARATOR),
            new Token(3, "_101", TokenType.VARIABLE_OR_CONSTANT));
  }