Bug 30973 - Incorrect CS0425 when generic base class implements non-generic interface method
Summary: Incorrect CS0425 when generic base class implements non-generic interface method
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: 4.0.0
Hardware: PC Linux
: --- normal
Target Milestone: ---
Assignee: Marek Safar
Depends on:
Reported: 2015-06-10 09:41 UTC by peter
Modified: 2015-10-28 16:34 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

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Description peter 2015-06-10 09:41:11 UTC
Compiling the following:
	public class BaseClass<TSource> {
		public void DoStuff<TInput>( TInput stuff )
			where TInput: TSource {

	public class MyClass: BaseClass<TInterface>, MyInterface {


	public interface TInterface {


	public interface MyInterface {
		void DoStuff<TInput>( TInput stuff )
			where TInput: TInterface;

Results in the following when compiled as "Mono/.NET 4.5" with Mono 4.0.1 in monodevelop 5.9.4 on Ubuntu 15.04.

error CS0425: The constraints for type parameter `TInput' of method `MonoTypeConstraintBug.BaseClass<MonoTypeConstraintBug.TInterface>.DoStuff<TInput>(TInput)' must match the constraints for type parameter `TInput' of interface method `MonoTypeConstraintBug.MyInterface.DoStuff<TInput>(TInput)'. Consider using an explicit interface implementation instead.

It compiles fine with VS2012/.NET 4.5.

I can see that several similar bug reports exists against earlier versions that are marked as "fixed in master" (for example https://bugzilla.xamarin.com/show_bug.cgi?id=22131 ), but at least it still seems to be a problem in 4.0.1.
Comment 1 Marek Safar 2015-06-16 11:57:21 UTC
Fixed in master
Comment 2 Victor 2015-10-28 16:34:45 UTC
This is NOT fixed in master (using Xamarin Studio 5.9.7 and Xamarin iOS 9.0.1)