Backpack signatures can't be compiled in one shot mode
signature Sig where
data A
data B
foo :: A -> B
[nix-shell:~/ghc-abi]$ ghc Sig.hsig -this-component-id sig -instantiated-with Sig=\<Sig\> -this-unit-id=sig -c
typecheckIfacesForMerging
Declaration for foo:
Bad interface file: Sig.hi
Sig.hi: openBinaryFile: does not exist (No such file or directory)
Cannot continue after interface file error