## Symptom
`[set TargetLocation (x, y)` (quoted or not) answers **"That is not properly formatted."**, and in `[props` the `>` next to `TargetLocation` does nothing when the value is null — which is its normal idle state (`BaseAI.cs:650` clears it).
This looked like a `Point3D` parsing regression from #2624/#2625, but `Point3D`/`Point2D`-typed properties (`Location`, etc.) were never affected. The only `[CommandProperty]` in the tree declared as an **interface** is `BaseCreature.TargetLocation : IPoint2D` (`BaseCreature.cs:1111`), and both code paths only knew the structs. `git log -S"IPoint"` over the parser and gump files hits nothing but the initial import — the gap is inherited from RunUO, not recent.
## Root cause
- **`[set`** — `Types.TryParse` has no branch for `IPoint2D`/`IPoint3D`. An interface has no static `Parse`, so `GetParseMethod` returns null and the value falls into `Convert.ChangeType("(x, y)", typeof(IPoint2D))`, which throws → "not properly formatted".
- **Props gump** — `PropsGump` routes on `obj?.GetType() ?? prop.PropertyType` (since #2180). With a null value the type is `IPoint2D`; `Point2D.IsAssignableFrom(IPoint2D)` is false, no branch matches, and the click is inert. It only worked when the slot already held a `Point2D`, because the runtime type is then the struct.
## Fix
- `Types.TryParse`: `IPoint3D`/`IPoint2D` targets resolve to the concrete struct — `Point3D` first, then `Point2D` for an `IPoint2D` target (a 3-tuple is a valid `IPoint2D`). `(-null-)` still clears; the existing null branch runs first.
- `PropsGump`: the interface types route to `SetPoint3DGump`/`SetPoint2DGump`. The entity branch stays ahead of them — `TargetLocation` legitimately holds a Mobile too (`ShepherdsCrook.cs:148`, herding toward the shepherd), and that case still opens `SetObjectGump`.
- `SetPoint2DGump`/`SetPoint3DGump`: seed the text entries from `value is IPoint2D/IPoint3D` rather than a hard cast, so a `Point3D` sitting in an `IPoint2D` slot cannot `InvalidCast`.
## Not covered
`[set TargetLocation 0x40001234` (assigning a mobile by serial) still reports "not properly formatted" — the entity branch keys on the *target* type being `IEntity`, which `IPoint2D` isn't. Real state, but niche; left out to keep this to the reported symptom.
## Testing
Five cases in `InterfacePointParseTests`, watched fail before the change (three returned the error string; two pin existing behaviour that must survive): tuple → `Point3D` for both interfaces, pair → `Point2D`, pair rejected for `IPoint3D`, `(-null-)` clears.
`dotnet build` 0 warnings. **1059 UOContent** and **891 Server** tests pass, 0 failures. The gump routing is a one-line branch with no automated test — needs an in-game check: `[props` a creature with a null `TargetLocation`, press `>`, expect the Point2D editor.
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