Resolving one assembly resolves its whole reference closure, and every
reference in it asked the same framework directories the same questions.
The worst of it was the scan for the closest version folder of a shared
framework: a directory listing plus a recursive file search, repeated per
reference and per runtime pack - 42 scans for two distinct answers when
decompiling ICSharpCode.ILSpyX.dll.
The scan result is only safe to keep for a bounded time: a runtime can be
installed or removed while ILSpy runs, and reloading an assembly list has
to see that. So it is kept for the length of an explicitly opened scope,
which the type system opens around the closure it resolves and closes
again afterwards; outside a scope the file system is read as before. The
scope owns what was read, so two of them on one resolver do not stack -
the first to end takes it, and the other reads the file system again.
BeginSnapshot is on IAssemblyResolver rather than an interface of its
own: it is core functionality of a resolver, and one implementation is
not an abstraction. This breaks the interface for implementors outside
this repository, who opt out by returning null - which is what the three
resolvers here that hold nothing do.
The remaining probes cost nothing to fix: the preferred runtime pack was
listed among the defaults it already belongs to, so its directory was
scanned twice for every reference that is not in it, and one package
folder was probed once per assembly the package contains.
Measured over 27 references with a fresh resolver each time: 3.3 ms per
assembly before, 3.1 ms without a scope, 1.1 ms with one.
Assisted-by: Claude:claude-opus-5:Claude Code
* ExtensionDeclaration.SymbolKind (CA1065) — was throwing
NotImplementedException; return SymbolKind.TypeDefinition to match
TypeDeclaration / DelegateDeclaration, since `extension` declarations
are type-level.
* CustomAttribute.DecodeValue (CA2002) — replace `lock(this)` on the
sealed-but-internal class with a private syncRoot field.
* PlainTextOutput (CA1001) — implement IDisposable; track an
ownsWriter flag so we only dispose the underlying TextWriter when
the parameterless constructor created its own StringWriter.
* DotNetCorePathFinder (CA1060) — move the libc realpath / free
PInvokes into a private nested NativeMethods class.
* ILSpy.ReadyToRun (CA1016) — add [assembly: AssemblyVersion("1.0.0.0")]
in Properties/AssemblyInfo.cs to match the BamlDecompiler plugin.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>