Inconsistent output of values with union type

[philrz]

Repro is with a99b4f9.

This inconsistency was noted by @mccanne.

$ echo '[1]([(int64,string)])' | zq 'yield this[0]+1' -
2

$ echo '1((int64,string))' | zq 'yield this+1' -
error("incompatible types")

[philrz]

Verified in Zed commit b58a6d7.

The second repro example above now returns the expected result rather than an error.

$ zq -version
Version: v1.12.0-36-gb58a6d7a

$ echo '1((int64,string))' | zq 'yield this+1' -
2

Thanks @mattnibs!