+Signature equality is used when checking for duplicate signatures
+
+\begin{code}
+eqHsSig :: Sig Name -> Sig Name -> Bool
+eqHsSig (FixSig (FixitySig n1 _ _)) (FixSig (FixitySig n2 _ _)) = n1 == n2
+eqHsSig (Sig n1 _ _) (Sig n2 _ _) = n1 == n2
+eqHsSig (InlineSig b1 n1 _ _) (InlineSig b2 n2 _ _) = b1 == b2 && n1 == n2
+ -- For specialisations, we don't have equality over
+ -- HsType, so it's not convenient to spot duplicate
+ -- specialisations here. Check for this later, when we're in Type land
+eqHsSig _other1 _other2 = False
+\end{code}
+