Uses of Binary decode should have a proper error message
In #8144 I changed the interface file format.
That can happen without you noticing because it just uses the Binary instance.
To deserialize it, we also use Binary. When that fails, the error message is
The error message should at least also mention:
Reading the interface file failed
This is not a specific problem with interface files (it is actually a minor problem there since ghc will refrain from reading .hi files created by an older version), but it is in development, and independent from that, all uses of Binary decode should be guarded as it is a very partial function.