[C++] Support nested FieldRefs

[asfimport]

While it seems technically possible to construct nested FieldRefs, it doesn't seem that you can use them in practice. And it would also be nice to be able to get a nested FieldRef on an Expression. One solution could be to not handle this within FieldRefs at all and just handle it in Expressions: have a function like Expression GetField(Expression, name).

Reporter: Neal Richardson / @nealrichardson
Assignee: David Li / @lidavidm

Related issues:

• [R] Create a field ref to a field in a struct (blocks)
• [Python] Allow to create field reference to nested field (blocks)
• [C++] Support nested field refs into unions (relates to)
• [C++] Directly support nested field refs in exec plan (is related to)
• [C++] Add basic support for nested field refs in scanning (is related to)

PRs and other links:

• GitHub Pull Request #11466

_{Note: This issue was originally created as ARROW-13987. Please see the migration documentation for further details.}

[asfimport]

David Li / @lidavidm:
Issue resolved by pull request 11466
#11466