Compiler error with new using pattern

[tomrus88]

Version Used:
VS 16.0.0 Preview 4.0

Steps to Reproduce:

class Test
{
    public void Dispose()
    {

    }
}

using (var t = new Test()) // Error CS1674
{

}

Expected Behavior:
No compiler error?

Actual Behavior:
Compiler error: Error CS1674 'Test': type used in a using statement must be implicitly convertible to 'System.IDisposable' or implement a suitable 'Dispose' method.

Not sure what's intended behavior... If everything is working as intended, then error message is misleading...

According to dotnet/csharplang#1623

This proposal is allow any type which structurally matches IDisposable (has a public void-returning non-generic instance method taking no arguments) to be used in a using statement.

this is a bug...

[gafter]

I believe there has been a spec change not reflected in the spec or diagnostic.

[jcouv]

The diagnostic message should be updated.
Pattern-based disposal is only supported on ref structs. Otherwise, it would affect existing code (foreach where the enumerator type happens to have a Dispose() method would now start calling that method).

[jcouv]

This is a message tweak