C# 15 (.NET 11 preview 5) encodes the closed modifier as
System.Runtime.CompilerServices.ClosedAttribute on the implicitly
abstract type plus CompilerFeatureRequired("ClosedClasses") on every
constructor; the BCL does not ship the attribute yet, so assemblies
declare their own copy or reference one from another assembly. The
decompiler now reconstructs the modifier from this encoding, gated on a
new C# 15 ClosedHierarchies setting. Exported projects state LangVersion
preview because the compiler does not accept 15.0 yet.
The pretty tests cover the definition side only: switch exhaustiveness
over a closed hierarchy is compile-time knowledge that leaves no trace
in the IL of consuming code.
Compiling "#dependency" test assemblies to a temp file left them
unresolvable while decompiling the main test assembly; they now land
next to the main output. With its dependency resolvable, Issue3684 no
longer needs the disambiguating base-class cast. The cross-assembly
fixture also exposed a latent NRE in RecordDecompiler when a record's
base type cannot be resolved.
Assisted-by: Claude:claude-fable-5:Claude Code
Record AST transform groups and mutation steps through the C# pipeline, replay selected steps with the stepper, and carry modified-node ranges through output so the Debug Steps pane can highlight the selected mutation without replacing its full step tree.
Assisted-by: CodeAlta:gpt-5.5:CodeAlta
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