[mono] Full support for System.Reflection.Emit

[alexischr]

Mono's support for System.Reflection.Emit must be brought to the same level as CoreCLR's. From the top down, this requires:

• Filling in remaining non-implemented System.Reflection.Emit API as documented in Epic: .NET 5 APIs mono/mono#14788
• Developing Mono to pass the remaining System.Reflection.Emit library tests (tracked in [mono] Tests failed: System.Reflection.Emit.Tests #2389 & [mono] Tests failed: System.Reflection.Emit.ILGeneration.Tests #2383) for:
  • MethodBuilder
  • ConstructorBuilder
  • EnumBuilder
  • FieldBuilder
  • GenericTypeParameterBuilder
  • ModuleBuilder
  • PropertyBuilder
  • TypeBuilder
  • ILGenerator
  • SignatureHelper
• Exploring all opportunities to share code with CoreCLR

Known Issues

• No lexical scope support for MethodBuilder/ILGenerator: Our implementation does not support using namespaces for resolving locals, and BeginScope()/EndScope() are no-ops currently.
• The following methods do not have tests/meaningful usage within dotnet/runtime:
  • ModuleBuilder.GetFieldToken
  • ModuleBuilder.GetSignatureToken(byte[], int)
  • ILGenerator.UsingNamespace
  • ILGenerator.EndScope

Known issues with sharing code

• interface ISymbolWriter is both tied heavily with coreclr (see CreateISymWriterForDynamicModule) and ILGenerator/MethodBuilder.
• Mono's ModuleBuilder must match memory layouts with the Mono internal struct MonoModule.

Discussion

We can share progress/ask questions in the comments.

[steveharter]

Changing area to interop-Mono. Please add a "reflection.emit-Mono" area if desired.