Partial Type
src/Compilers/Core/Portable/InternalUtilities/SpecializedCollections.ReadOnly.Collection.cs
src/Compilers/Core/Portable/InternalUtilities/SpecializedCollections.ReadOnly.Enumerable`1.cs
src/Compilers/Core/Portable/InternalUtilities/SpecializedCollections.ReadOnly.Enumerable`2.cs
src/Compilers/Core/Portable/InternalUtilities/SpecializedCollections.ReadOnly.Set.cs