sqlfluff: Parser incorrectly swaps BigQuery struct grammars when `parse_grammar` is not supplied.

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What Happened

When a STRUCT is used in conjunction with an AS alias, it’s columns are recognised as datatypes, which can trigger L063.

Expected Behaviour

STRUCT column names should not trigger L063.

Observed Behaviour

L:   3 | P:   9 | L063 | Datatypes must be upper case.
L:   4 | P:   9 | L063 | Datatypes must be upper case.

How to reproduce

Run sqlfluff lint on

SELECT
    STRUCT(
        some_field,
        some_other_field
    ) AS col,
    STRUCT(
        some_field,
        some_other_field
    )
FROM table

Dialect

bigquery

Version

0.13.1

Configuration

[sqlfluff]
templater = jinja
dialect = bigquery

[sqlfluff:rules:L063]
# Inconsistent capitalisation of datatypes
extended_capitalisation_policy = upper

Are you willing to work on and submit a PR to address the issue?

• Yes I am willing to submit a PR!

Code of Conduct

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