Cannot parse some table header references

[WillemJann]

The following formula with a reference to a table header can be parsed by XLParser:

=SUBTOTAL(103,[Column6])

However, the following formula does not parse:

=SUBTOTAL(103,[2021])

Obviously, this reference to a numeric table header is valid in Excel. XLParser should parse this formula.

[dcrasch]

Unqualified structured reference cell must be inside a table