Not sure if bug...

...but I set it to the fsbugs e-mail anyway.

Let's start with this F# code:

	module Test.Component
	// After the Haskell type
	type public Either<'TFault, 'TSuccess> =
	| Left of 'TFault
	| Right of 'TSuccess
	with
	[<CompiledName("ForEvery")>]
	static member iter (fault : 'TFault -> unit) (fix : 'TSuccess -> unit) (value : Either<'TFault, 'TSuccess>) =
	match value with
	| Left a -> fault a
	| Right b -> fix b
	[<CompiledName("ForEach")>]
	static member iter0 =
	Either<'TFault, 'TSuccess>.iter ignore
	[<CompiledName("ToOption")>]
	static member toOption (value:Either<'TFault, 'TSuccess>) =
	match value with
	| Right y -> Some y
	| _ -> None
	end

view raw gistfile1.fs hosted with ❤ by GitHub

The last function maps to C# as

	namespace Test
	{
	[CompilationMapping(SourceConstructFlags.Module)]
	public static class Component
	{
	[DebuggerDisplay("{__DebugDisplay(),nq}"), CompilationMapping(SourceConstructFlags.SumType)]
	[Serializable]
	[StructLayout(LayoutKind.Auto, CharSet = CharSet.Auto)]
	public abstract class Either<TFault, TSuccess> : IEquatable<Component.Either<TFault, TSuccess>>, IStructuralEquatable, IComparable<Component.Either<TFault, TSuccess>>, IComparable, IStructuralComparable
	{
	...
	[CompilationSourceName("toOption")]
	public static FSharpOption<TSuccess> ToOption(Component.Either<TFault, TSuccess> value)
	{
	if (value is Component.Either<TFault, TSuccess>.Right)
	{
	Component.Either<TFault, TSuccess>.Right right = (Component.Either<TFault, TSuccess>.Right)value;
	TSuccess y = right.item;
	return FSharpOption<TSuccess>.Some(y);
	}
	return null;
	}
	...
	}
	}
	}

view raw gistfile1.cs hosted with ❤ by GitHub

Now change the initial F# line to be namespace rather than module...

File1.fs(9,18): error FS0755: The 'CompiledName' attribute cannot be used with this language element
File1.fs(15,18): error FS0755: The 'CompiledName' attribute cannot be used with this language element
File1.fs(19,18): error FS0755: The 'CompiledName' attribute cannot be used with this language element

So for comparison purposes, let's replace CompiledName with Obsolete, and see what we've built...

	namespace Test.Component
	{
	[DebuggerDisplay("{__DebugDisplay(),nq}"), CompilationMapping(SourceConstructFlags.SumType)]
	[Serializable]
	[StructLayout(LayoutKind.Auto, CharSet = CharSet.Auto)]
	public abstract class Either<TFault, TSuccess> : IEquatable<Either<TFault, TSuccess>>, IStructuralEquatable, IComparable<Either<TFault, TSuccess>>, IComparable, IStructuralComparable
	{
	...
	[Obsolete("ToOption")]
	public static FSharpOption<TSuccess> toOption(Either<TFault, TSuccess> value)
	{
	if (value is Either<TFault, TSuccess>.Right)
	{
	Either<TFault, TSuccess>.Right right = (Either<TFault, TSuccess>.Right)value;
	TSuccess y = right.item;
	return FSharpOption<TSuccess>.Some(y);
	}
	return null;
	}
	...
	}
	}
	where I can't for th

view raw gistfile1.cs hosted with ❤ by GitHub

where I can't for the life of me see the difference.

This happens when building using the latest compiler release in either VS2008 shell or VS2010 shell; or from the command line using MSBuild for either .net3.5 or 4.