> there is no reason to believe that the way to build it would be found before, say, the sun runs out of hydrogen.

A lot of computational power can be thrown at the problem in this time. So, the problem should admits no shortcuts, no decomposition into simpler problems, no alternative ways to get similar functionality that allow shotrcuts or decomposition. The result should look like a jumble of atoms that somehow produces the required functionality.

I wonder which problems can admit only this kind of a solution.