.NET interfaces allowing implicit casts from non-derived types

Question

I was reading the Roslyn source code when I noticed this strange section:

    // Implicit casts are not emitted. As a result verifier may operate on a different 
    // types from the types of operands when performing stack merges in coalesce/ternary.
    // Such differences are in general irrelevant since merging rules work the same way
    // for base and derived types.
    //
    // Situation becomes more complicated with delegates, arrays and interfaces since they 
    // allow implicit casts from types that do not derive from them. In such cases
    // we may need to introduce static casts in the code to prod the verifier to the 
    // right direction

I'm curious of what would be needed for this to happen. I care in particular about when does an interface allow for an implicit cast from a non-derived type. However, an explanation for arrays/delegates would be interesting as well.