Requires on NativeAOT has problems with CompilerGeneratedCode

[tlakollo]

Description

Doing some testing with the Requires attribute on CompilerGeneratedCode I realized that NativeAOT has differences with linker, it will not produce warnings for code using ldftn for example:

//[ExpectedWarning("IL2026", "--MethodWithRequires--", CompilerGeneratedCode = true)]
//[ExpectedWarning("IL3050", "--MethodWithRequires--")]
static IEnumerable<int> TestLdftn()
{
    yield return 0;
    yield return 1;
    var action = new Action(MethodWithRequires);
}
[RequiresUnreferencedCode("--MethodWithRequires--")]
[RequiresDynamicCode("--MethodWithRequires--")]
static void MethodWithRequires()
{
}

It will have problems with Lazy Delegates too

// Cannot annotate fields either with RUC nor RAF therefore the warning persists
//[ExpectedWarning("IL2026", "Message from --MethodWithRequiresAndReturns--", CompilerGeneratedCode = true)]
//[ExpectedWarning("IL3050", "Message from --MethodWithRequiresAndReturns--")]
public static Lazy<string> _default = new Lazy<string>(MethodWithRequiresAndReturns);

static IEnumerable<int> TestLazyDelegate()
{
    yield return 0;
    yield return 1;
    _ = _default.Value;
}
[RequiresUnreferencedCode("Message from --MethodWithRequiresAndReturns--")]
[RequiresDynamicCode("Message from --MethodWithRequiresAndReturns--")]
public static string MethodWithRequiresAndReturns()
{
    return "string";
}

Suppression inside CompilerGeneratedCode is also not working

Reproduction Steps

• Copy the RequiresInCompilerGeneratedCode code in dotnet/linker and paste into the NativeAOT Program.cs
• Comment the ExpectedWarning attributes since there is no support for the attribute in NativeAOT
• Execute the program.cs following the instructions in https://github.com/dotnet/runtime/blob/main/docs/workflow/building/coreclr/nativeaot.md#running-tests
• Review the warnings generated vs the ExpectedWarnings manually

Expected behavior

The warnings generated by dotnet/linker and nativeAOT should be the same

Actual behavior

NativeAOT sometimes misses generating some of the warnings and some other times it generates extra warnings

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[sbomer]

Another problem is that nativeaot doesn't always treat RUC on method as applying to local functions within:

			[RequiresUnreferencedCode ("")]
			static void TestLocalFunctionInMethodWithRequires ()
			{
				LocalFunction ();

				void LocalFunction () => MethodWithRequires ();
			}

			static void TestAll ()
			{
				typeof (LocalFunctionsReferencedViaReflection).RequiresAll ();
			}

The TestAll method should produce two warnings for RUC - once for TestLocalFunctionInMethodWithRequires and once for MethodWithRequires , but it doesn't produce the latter.

[sbomer]

NativeAot is also missing warnings for reflection access to compiler-generated code (IL2118).

[sbomer]

The problems with ldftn and lazy delegates are being addressed in #77457.

[vitek-karas]

The remaining bits are fixed in #84770