[Mono-bugs] [Bug 553655] New: The compiler fails to recognize fulfilled generic type constraints when another generic parameter is the argument to a nested generic interface two-deep or more

[bugzilla_noreply at novell.com]

http://bugzilla.novell.com/show_bug.cgi?id=553655


           Summary: The compiler fails to recognize fulfilled generic type
                    constraints when another generic parameter is the
                    argument to a nested generic interface two-deep or
                    more
    Classification: Mono
           Product: Mono: Compilers
           Version: SVN
          Platform: Other
        OS/Version: Other
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: C#
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: lunchtimemama at gmail.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---


If you actually understood that summary, you win the Gold Cookie. Here's what
you really need to know. csc compiles this, gmcs does not:

interface I<T>
{
}

class Foo<T1, T2> where T2 : I<I<T1>>
{
    public Foo(T2 t2)
    {
    }
}

class Bar : I<I<string>>
{
    Bar()
    {
        var foo = new Foo<string, Bar>(this);
    }
}


Expected result:
It ought to compile


Actual result:
Error CS0309: The type `Bar' must be convertible to `I<I<T1>>' in order to use
it as parameter `T2' in the generic type or method `Foo<T1,T2>'

The `I<I<T1>>' in this error message should really be `I<I<string>>' (because
that is the type we are using) to which the type `Bar' IS convertible.

NOTE: If we constrain T2 to implement I<T1> and then have Bar implement
I<string>, the code will compile. Also note: gmcs will fail if T1 is used as an
argument to ANY two-deep generic interface (not just I<I<T>>). For example: if
T2 is constrained to I<IEnumerable<T1>> and Bar implements
I<IEnumerable<string>>, the compiler will barf.

-- 
Configure bugmail: http://bugzilla.novell.com/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.
You are the assignee for the bug.