[Variant] Shredded typed_value columns must have valid variant types

[scovich]

Describe the bug

Currently, variant code is quite willing to support non-variant types such as unsigned integers -- including on the read path for shredded variants in e.g. VariantArray::value (see the typed_value_to_variant helper function).

I don't know if the shredding spec specifically rejects shredding as non-variant types, but there is a certain logic to the idea. And case 127 of parquet-testing/shredded_variant specifically verifies that the reader rejects a typed_value column of (parquet) type INTEGER(32, false).

To Reproduce

Found while making changes related to shredded struct support; case 127 stopped erroring out with the "expected message ("received empty bytes") and started succeeding.

Expected behavior

The read should fail.

[scovich]

Attn @alamb

[scovich]

Case 137 also expects the reader to reject a 4-byte fixed size binary typed_value column (16-byte for UUID being the only valid case).

[scovich]

• Fixed by Variant integration fixes #8438