The .NET 10 BCL ships static [Extension] classes that contain ordinary
nested types (e.g. XDocumentExtensions.XDocumentNavigable). Decompiling
such a nested type's member in isolation resolved the enclosing
container's ExtensionInfo, and DecompileBody then dereferenced the
missing extension-member mapping. A container without any extension
blocks now reports no ExtensionInfo at all, and ResolveExtensionInfo
applies a container's info only to members that actually belong to one
of its extension blocks.
Assisted-by: Claude:claude-fable-5:Claude Code
Siegfried Pammer