Expand description
Expression-evaluation contract types shared between the engine, the planner, and the catalog.
TargetColumn is the central value: a column-targeting expression (insert, update, default-value resolution) either
knows the fully-resolved column it is writing to (TargetColumn::Resolved) or describes the partial information
available before resolution (TargetColumn::Partial). Number-out-of-range descriptor construction lives here too so
range-violation diagnostics are assembled identically by every evaluator.