[Agda] Library not compiling for me

[Samuel Bronson]

I just tried to change something in Data.Product, and now
Relation.Binary.Consequences won't rebuild. As far as *I* can see,
there is nothing wrong with the code -- the compilers complaint looks
false...

I think probably it's a compiler bug that wasn't caught because nobody
did anything that resulted in that module being rebuilt since the bug
was introduced. (Yes, I *did* try building with all my changes
reverted.)