The generated GetChildNodes materialized a List<AstNode> (plus a boxed
List.Enumerator at every foreach) for each node, so AstNode.Children and
the visitor's per-node child walk allocated three objects per traversal.
Decompiling System.Private.CoreLib that came to ~1.7 GB of extra garbage,
roughly +7% over the linked-list model the slot tree replaced. A yield
iterator removes the List but trades it for an equally costly per-node
state machine, so it is not enough on its own.
Enumerate children through a by-value struct enumerator over the existing
FirstChild/NextSibling primitives, capturing each child's successor before
it is yielded so a transform may still remove or replace the current child
mid-traversal. AstNodeCollection<T> gets the same struct treatment for a
direct foreach. Child enumeration now allocates nothing, bringing total
allocations back to the linked-list baseline at byte-identical output
(full Pretty suite green with CheckInvariant active).
Assisted-by: Claude:claude-opus-4-8:Claude Code
The slot kind is now the canonical typed CSharpSlotInfo<T> in Slots, matched by
object identity (the IL SlotInfo model), instead of a parallel SlotKind enum.
CSharpSlotInfo.Kind points at the canonical shared slot; a Slots constant is its
own kind (null Kind, never read -- only per-node slots are asked for their kind),
so there is no self-reference. Child access (GetChild/GetChildren/SetChild,
GetCollectionByKind, AddChild/InsertChild) and the polymorphic
node.Slot.Kind == Slots.X comparisons key on the canonical reference; the
generated SlotKind enum is removed. No behavior change.
Assisted-by: Claude:claude-opus-4-8:Claude Code
Turn on #nullable enable across the AST consumer layer: the output visitor, the
IL-to-C# builders (statement, call and expression builders, CSharpDecompiler,
TypeSystemAstBuilder), the translation-result wrappers, the sequence-point and
required-namespace collectors, and the annotation helpers. Optional inputs,
fields and returns are typed nullable, detector out-parameters use
[NotNullWhen(true)], and structurally-guaranteed dereferences use the
null-forgiving operator. A few public parameters that already tolerate null are
widened to match their downstream callers. The annotations emit no IL, so the
Pretty suite stays byte-identical.
Assisted-by: Claude:claude-opus-4-8:Claude Code
Slot identity already lived in node.Slot/CSharpSlotInfo/SlotKind after
the storage flip, so the parallel Role/Role<T> child model was redundant.
The Role-keyed mutation/query API is reexpressed over SlotKind, and the
role-index packing on AstNode flags is gone.
Because a node's Slot is now derived from its index in its parent rather
than stored on the child, the located-AST reattach in
InsertMissingTokensDecorator must capture the child's slot kind before
Remove() detaches it.
Assisted-by: Claude:claude-opus-4-8:Claude Code
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
Turn on #nullable enable across the AST transform pipeline, ahead of
annotating the slot properties themselves. TransformContext now exposes the
nullable CurrentMember/CurrentTypeDefinition/CurrentModule contract already
declared by ITypeResolveContext, and the generated pattern-to-node conversion
returns a non-null node so patterns can be used in collection initializers
without warnings. No IL changes.
Assisted-by: Claude:claude-opus-4-8:Claude Code
The pattern matcher walked collections through INode.Role/FirstChild/
NextSibling, skipping siblings of a different role. Now that each
AstNodeCollection<T> is already the per-role child list, the engine matches two
collections by list index, and INode sheds Role/FirstChild/NextSibling
entirely. A collection exposes its IReadOnlyList<INode> view through a cached
adapter rather than implementing the interface directly, so a typed collection
does not become ambiguous for LINQ. Characterization tests pin the matcher's
behavior first.
Assisted-by: Claude:claude-opus-4-8:Claude Code
Children were kept in a per-node doubly-linked list with the slot accessors
layered over it as a view. Storage now is the slot model: each node stores its
children in generated backing fields, AstNodeCollection<T> is backed by a
List<T>, and the flattened child-index space is owned by generated
GetChildCount/GetChild/SetChild/GetChildSlot members, with sibling navigation,
the role API and Clone re-expressed over them and indices renumbered lazily. A
DEBUG CheckInvariant runs after each transform, the analog of the IL
pipeline's per-transform check, so a transform that corrupts the tree fails at
that transform. Output is unchanged.
Assisted-by: Claude:claude-opus-4-8:Claude Code
Siegfried Pammer
Peter Crabtree
dotnet format
Daniel Grunwald
Christoph Wille