Places where runtime bugs interfere with compiler or language evolution

[gafter]

This is a collection of issues where limitations or bugs in the current runtime have been impediments to compiler or language evolution. This list will evolve over time as new cases are identified or fixed.

• CLR bug with static variable in struct could be warned by the compiler roslyn#10126 Loader bug incorrectly reports struct cycle for static field (Static fields should not contribute to cyclic struct layout  runtime#5479)
• Loader bug incorrectly reports struct cycle for unused type parameter (Unused generic type parameter should not cause loader failure runtime#6924)
• Loader bug incorrectly reports struct cycle for array of type parameter (Arrays should not contribute to cyclic struct layout runtime#12024)
• Overload Console.Write and Console.WriteLine to take ConsoleColor as a parameter #3711 Delegate combine fails at runtime (Combine of covarince/contravariance delegates runtime#4556)
• Missing type parameters should be a warning. #1029 Bug in Activator.CreateInstance prevents default struct ctors (Activator.CreateInstance fails to call constructor for value types runtime#6536)
• Expression interpreter - Bug when passing Type.Missing to Invoke calls runtime#15553 No API to pass Type.Missing argument through reflection calls. Completely blocks some "dynamic" scenarios involving optional parameters when platform requires interpreting. (C# binder uses Type.Missing to designate omitted arguments and it is a problem that they do not survive calls via reflection)
• Champion "Allow Generic Attributes" #124 Support generic attributes (Enable generic attributes coreclr#9189 runtime throws an exception when reflecting on an attribute type that is generic)
• Reference assemblies need to include private struct fields runtime#16402 Reference assembly for Nullable<T> needs to contain a private field of type T runtime#24136 Reference assemblies are incorrect (omit needed private fields of structs)