With every optional slot nullable, the null-object pattern is dead. Generated
non-nullable getters return the backing field directly, which surfaced a last
tier of slots the decompiler legitimately leaves empty (omitted range operands,
an implicitly-typed array creation, unnamed parameters, an unbound generic
argument, and others) and flips them to nullable too. The machinery is then
removed entirely: the per-node null classes, the .Null statics and
VisitNullNode, AstNode.IsNull, the role null object, and Identifier.Null.
AcceptVisitor becomes unconditionally generated, and consumers move from
.IsNull to is null and from unconditional visits to ?.AcceptVisitor.
Assisted-by: Claude:claude-opus-4-8:Claude Code
Ports the WPF assemblyList_CollectionChanged history-prune from
ILSpy/AssemblyTree/AssemblyTreeModel.cs to the Avalonia
DockWorkspace.OnAssemblyListChanged handler. NavigationHistory<T>
already exposed the RemoveAll(Predicate<T>) primitive; the caller
wiring was the missing piece. Without it, a tree-row click after
removing an assembly walked through NavigationEntry.DisplayText
on a stale TreeNodeEntry, which hit MemberReferenceTreeNode.Signature
-> Language.EntityToString -> ILAmbience.ConvertSymbol and NRE'd on
a now-null ParentModule.
Assisted-by: Claude:claude-opus-4-7:Claude Code