Resolve ILLink warnings in System.Text.RegularExpressions

[eerhardt]

• Add DynamicallyAccessedMembers All to TypeBuilder and EnumBuilder CreateType methods.

Contributes to #45623

[Dotnet-GitSync-Bot]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[stephentoub]

Unrelated, are all of the patterns employed below recognized by the linker? i.e. it's able to see it must preserve the IsBoundary method, the runtrack field, the char.IsDigit method, etc?

[eerhardt]

The ILLinker isn't warning for these methods:

        private static FieldInfo RegexRunnerField(string fieldname) => typeof(RegexRunner).GetField(fieldname, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static)!;

        private static MethodInfo RegexRunnerMethod(string methname) => typeof(RegexRunner).GetMethod(methname, BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static)!;

My understanding is because it sees the specified typeof(RegexRunner) and thinks "I must preserve all Methods and Fields on the RegexRunner Type, since these methods try getting fields and methods on this Type".

But @vitek-karas and @MichalStrehovsky would know for sure if the above reasoning is correct.

[vitek-karas]

I can validate by debugging the linker if needed, but @eerhardt is right - the call to GetField will fallback to basically mark all fields which fulfill the binding flags, if it can't figure out the name of the field statically (like in this case). Same goes for GetMethod.

[stephentoub]

Thanks for the info.

[vitek-karas]

I can validate by debugging the linker if needed, but @eerhardt is right - the call to GetField will fallback to basically mark all fields which fulfill the binding flags, if it can't figure out the name of the field statically (like in this case). Same goes for GetMethod.

[eerhardt]

Failures are #32030. Merging.