fix: EXPOSED-280 Comparison operators show incorrect compiler warning with datetime columns

[bog-walk]

I came across this warning while scanning the datetime modules for PR #1983 .

A strange compiler warning is flagged for the following code in exposed-jodatime and exposed-java-time modules:

object TestTable : Table() {
    val created = date("created")
    val deleted = date("deleted")
}
TestTable
    .selectAll()
    .where { TestTable.created eq TestTable.deleted }

Type argument for a type parameter E can't be inferred because it has incompatible upper bounds: LocalDate, EntityID (multiple incompatible classes). This will become an error in Kotlin 2.0

The same warning doesn't appear in the exposed-kotlin-datetime module.
But a user has already reported that they are seeing the warning with regular (non-entity id) UUID columns, suggesting a pattern only involving objects that aren't part of the Kotlin standard library.

This occurs because this convenience overload (introduced by PR #1961 ) is being incorrectly chosen:

infix fun <T : Comparable<T>, V : T?, E : EntityID<T>?> Expression<V>.eq(
    other: ExpressionWithColumnType<in E>
): Op<Boolean> = other eq this

These overloads incorrectly make the ExpressionWithColumnType argument's type parameter contravariant, when this annotation should instead be set on the calling Expression object's type parameter.

Note: No tests have been added but there are multiple examples of the highlighted warning in JodaTimeTests/testlocalDateComparison and testLocalDateTimeComparison. Switching between branches confirms the warning is resolved by this fix.

[e5l]

lgtm