Property patterns and dynamic

Version Used: SharpLab for branch features/recursive-patterns from 24 Jul 2018 (commit b364cfc)

Steps to Reproduce:

Try to compile the following code:

class C
{
    void M(dynamic o)
    {
        _ = o is { Foo: 42 };
    }
}

Expected Behavior:

Since code like o is { Foo: 42 } normally compiles to the equivalent of o != null && o.Foo == 42 and since that code is valid for o of type dynamic, I would expect the above method to compile.

Actual Behavior:

error CS0117: 'dynamic' does not contain a definition for 'Foo'

I think the error message is somewhat confusing, because the whole point of dynamic is that it's not checked at compile time whether a member exists.

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As usual with work-in-progress features, it's not clear to me if this is by design, not implemented yet, just a confusing error message or an actual bug, so feel free to handle this issue accordingly.