(what_it_is, loc) = sig_doc sig
sig_doc (Sig _ _ loc) = (SLIT("type signature"),loc)
-sig_doc (ClassOpSig _ _ _ loc) = (SLIT("class-method type signature"), loc)
+sig_doc (ClassOpSig _ _ _ _ loc) = (SLIT("class-method type signature"), loc)
sig_doc (SpecSig _ _ loc) = (SLIT("SPECIALISE pragma"),loc)
sig_doc (InlineSig _ _ loc) = (SLIT("INLINE pragma"),loc)
sig_doc (NoInlineSig _ _ loc) = (SLIT("NOINLINE pragma"),loc)