Related, but not entirely a duplicate: #4901.

Same for:

 contract C {
        uint[] a;
        uint[] b;
        function f() public view {
            uint[] storage c = a;
            uint[] memory d = b;
            d = uint[](c);
        }
}

#4901 is fixed in PR 4904. I do not know why Chriseth stoped respond on the PR for more than 5 days.

This issue looks interesting. The conversion looks valid since the base type is exactly the same.

The type analysis for type conversion actually will always convert array pointer to array ref since array inherits from ReferenceType. Therefore, the target type will be a reference, instead of a pointer which makes the assertion to be violated.
@chriseth suggested me to add a branch to only allow bytes and string array conversion. I have added tests in the PR4904, this issue is fixed by adding the restriction. All code and the test are added to the PR.

Something here is very wrong. In T(x) for a type T, the check whether conversion is possible should check whether a conversion to a pointer can be done. After the conversion has happened, the result should again be a reference, I think. But perhaps we should rather fully re-architect this and add the copyof operator.

@chriseth Actually, the array pointer is modified to reference before checking if it is possible to convert.