Use UnsafeAccessorType in System.Private.CoreLib and the BCL

[jkoritzinsky]

Use the new UnsafeAccessorTypeAttribute to provide a more strongly-typed and straightforward mechanism to solve our layering issues in the product than the traditional Reflection API surface.

[Copilot]

Pull Request Overview

This PR replaces legacy reflection‐based access with the new UnsafeAccessorTypeAttribute mechanism to provide strongly-typed, direct calls for improved performance and maintainability across core libraries. Key changes include:

• Replacing reflection calls with extern methods annotated with UnsafeAccessor attributes in libraries like System.Security.Cryptography, System.Private.CoreLib, and System.Net.Requests.
• Removing intermediate reflection caching and delegate creation in favor of direct unsafe access to type members.
• Updating several helper and interop classes to use these new patterns for cleaner API interactions.

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/XmlKeyHelper.cs	Replaces reflection-based XML element access with unsafe accessor extern methods.
src/libraries/System.Private.CoreLib/src/System/Resources/ResourceReader.Core.cs	Eliminates reflection for BinaryFormatter-related instantiation in favor of unsafe accessors.
src/libraries/System.Private.CoreLib/src/System/ComponentModel/DefaultValueAttribute.cs	Switches from ad hoc reflection delegates to a direct unsafe accessor call for conversion.
src/libraries/System.Private.CoreLib/src/System/AppDomain.cs	Substitutes reflection-based principal retrieval with unsafe accessor methods.
src/libraries/System.Net.Requests/src/System/Net/HttpWebRequest.cs	Uses unsafe accessor extern methods to directly get/set private fields instead of reflection.
src/libraries/System.Linq.Expressions/src/System/Dynamic/Utils/DelegateHelpers.cs	Utilizes an unsafe accessor method to create object array delegates.
src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/TypeDescriptor.cs	Implements an unsafe accessor call to perform type conversion reliably under trimming.
src/coreclr/System.Private.CoreLib/src/System/Diagnostics/StackFrameHelper.cs	Replaces dynamic delegate creation with unsafe accessor caching for source line info.
src/coreclr/System.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivator.cs	Refactors licensing interop to use static unsafe accessor methods for COM activation.

Comments suppressed due to low confidence (4)

src/coreclr/System.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivator.cs:893

• Confirm that switching to the UnsafeAccessor-based SetSavedLicenseKey call maintains the required initialization order and COM activation assumptions without side effects.

SetSavedLicenseKey(_licContext, _targetRcwType, key);

src/libraries/System.Net.Requests/src/System/Net/HttpWebRequest.cs:1696

• Ensure that the ref-return usage from GetImpersonationLevel supports inline assignment on all targeted platforms and behaves equivalently to the previous reflection-based implementation.

GetImpersonationLevel(GetSettings(handler)) = request.ImpersonationLevel;

src/libraries/System.Linq.Expressions/src/System/Dynamic/Utils/DelegateHelpers.cs:32

• Verify that passing null as the first parameter to CreateObjectArrayDelegate is safe and does not lead to unexpected behavior in scenarios where an instance value might be required.

return CreateObjectArrayDelegate(null, delegateType, invoker);

src/libraries/System.Private.CoreLib/src/System/Resources/ResourceReader.Core.cs:116

• Review the removal of the fallback logic for s_binaryFormatterType and s_deserializeMethod to ensure that the new unsafe accessor approach does not introduce regressions in environments with differing binary formatter support.

return true;

[teo-tsirpanis]

There's also this:

runtime/src/libraries/System.Private.CoreLib/src/System/Reflection/AssemblyName.cs

Lines 168 to 193 in c7c961a

	private static Func<string, AssemblyName>? s_getAssemblyName;
	private static Func<string, AssemblyName> InitGetAssemblyName()
	{
	Type readerType = Type.GetType(
	"System.Reflection.Metadata.MetadataReader, System.Reflection.Metadata",
	throwOnError: true)!;
	MethodInfo? getAssemblyNameMethod = readerType.GetMethod(
	"GetAssemblyName",
	BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static,
	null,
	[typeof(string)],
	null) ??
	throw new MissingMethodException(readerType.FullName, "GetAssemblyName");
	return s_getAssemblyName = getAssemblyNameMethod.CreateDelegate<Func<string, AssemblyName>>();
	}
	/*
	* Get the AssemblyName for a given file. This will only work
	* if the file contains an assembly manifest. This method causes
	* the file to be opened and closed.
	*/
	public static AssemblyName GetAssemblyName(string assemblyFile)
	{
	return (s_getAssemblyName ?? InitGetAssemblyName())(assemblyFile);
	}

[jkotas]

A few style nits. LGTM otherwise. Thank you!

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[jkoritzinsky]

/ba-g ios failure unrelated

[kotlarmilos]

I think this commit caused a runtime initialization error in iOS library mode: #116558. I tested against the latest main branch without this change, and it worked correctly. I assume it is calling into UnsafeAccessor methods that have no actual implementation in the Mono runtime.

@jkoritzinsky Do you have an idea what could be the cause? If not, I’ll disable the test to avoid polluting the CI.

[jkoritzinsky]

I don't know which type might not be on Mono (99% of these types are in the shared BCL).

If this could have been caused by an invalid UnsafeAccessor, I did just fix one around HttpClient. If this test is still broken in main then I'm not sure.