Precision gap: self-owned-source exemption too narrow (AssociatedObject, app-scoped instance, owned-collection element) #221

Found by: the issue #201 oracle sweep, docs/notes/oracle-sweep-2026-07-10.md; catalogued as docs/notes/field-notes-patterns.md entry 15 (plus the App-scoped-source case discussed in the sweep note under MaterialDesignInXamlToolkit).

The patterns

The shipped self-owned-source exemption (a class subscribing to something it owns is a collectable cycle, not a leak) keys off a directly constructed/assigned field. Three sibling shapes reach the same co-lifetime guarantee through a different path and aren't covered:

(a) Behavior<T>.AssociatedObject — a base-class accessor for the element the behavior is attached to (necessarily co-lifetimed; a Behavior cannot outlive being attached):

protected override void OnAttached() {
    this.attachedElement = this.AssociatedObject;
    if (this.attachedElement is Panel panel)
        panel.Loaded += (sl, el) => { ... };   // <- flagged; panel IS this.AssociatedObject
}

MahApps.Metro src/MahApps.Metro/Behaviors/TiltBehavior.cs:62-70.

(b) An Application-derived subscriber whose source is an app-scoped (not literal static) instance. The existing clsIsApp exemption gates on source == "static"; here the source is PaletteHelper().GetThemeManager() → an app-scoped IThemeManager bound to the app's own merged ResourceDictionary (PaletteHelper.cs:22-26, verified) — genuinely process-lifetime, just not a literal static field:

public partial class App : Application {
    protected override void OnStartup(StartupEventArgs e) {
        if (helper.GetThemeManager() is { } themeManager)
            themeManager.ThemeChanged += ThemeManager_ThemeChanged;   // <- flagged
    }
}

MaterialDesignInXamlToolkit src/MahMaterialDragablzMashUp/App.xaml.cs:10,22.

(c) Subscribing to an element of the class's own constructed collection:

public ListsAndGridsViewModel() {
    Items1 = CreateData();                              // own factory
    foreach (var model in Items1)
        model.PropertyChanged += (s, a) => OnPropertyChanged(...);   // <- flagged
}

MaterialDesignInXamlToolkit src/MainDemo.Wpf/Domain/ListsAndGridsViewModel.cs:16-17 (both demo app variants).

Note: (b) is deliberately narrower than the clsIsStatic broadening rejected in oracle-known-fps.md ("Rejected approaches" — a static-class subscriber exemption was reverted as unsound because it says nothing about a lambda capturing a shorter-lived local). (b) only fires when the subscriber class itself derives from Application, exactly matching the existing clsIsApp precedent — it only loosens the source check, not the subscriber check.

Suggested direction (not prescriptive)

Extend the self-owned-source classifier to recognise: this.AssociatedObject (or equivalent well-known base-class accessors) as a self-owned reference; a clsIsApp subscriber whose source resolves from Application-scoped state (not just a literal static field); and a += on a loop variable drawn from a collection field the constructor/factory itself populated.

Scope

No analyzer code changed as part of the sweep — this issue tracks the fix as its own unit of work.