If both the LHS and the RHS are nil,
then ErrorIs should treat them as equal.
For example: c.Assert(nil, qt.ErrorIs, nil) should succeed.
If the LHS is non-nil, and the RHS is nil,
then ErrorIs should treat the RHS as an error.
For example: c.Assert(io.EOF, qt.ErrorIs, nil) should fail
due to io.EOF not being part of the error chain of nil,
rather than nil not being a valid error value.
If both the LHS and the RHS are nil, then ErrorIs should treat them as equal.
For example:
c.Assert(nil, qt.ErrorIs, nil)
should succeed.If the LHS is non-nil, and the RHS is nil, then ErrorIs should treat the RHS as an error.
For example:
c.Assert(io.EOF, qt.ErrorIs, nil)
should fail due toio.EOF
not being part of the error chain of nil, rather than nil not being a valid error value.