fix regression of comparison of key_hash and add a test for it

src/bin/expect_tests/contract_tests.ml

@@ -1130,3 +1130,10 @@ let%expect_test _ =
   run_ligo_good [ "compile-storage" ; contract "big_map.ligo" ; "main" ; "(big_map1,unit)" ] ;
   [%expect {|
     (Pair { Elt 23 0 ; Elt 42 0 } Unit) |}]
+
+let%expect_test _ =
+  run_ligo_good [ "compile-contract" ; contract "key_hash_comparable.ligo" ; "main" ] ;
+  [%expect {|
+    { parameter int ;
+      storage (pair (map %one key_hash nat) (big_map %two key_hash bool)) ;
+      code { DUP ; CDR ; NIL operation ; PAIR ; DIP { DROP } } } |}]

src/passes/8-compiler/compiler_type.ml

@@ -16,7 +16,7 @@ module Ty = struct
   let tez_k = Mutez_key None
   let int_k = Int_key None
   let string_k = String_key None
-  let _key_hash_k = Key_hash_key None
+  let key_hash_k = Key_hash_key None
   let address_k = Address_key None
   let timestamp_k = Timestamp_key None
   let bytes_k = Bytes_key None
@@ -74,7 +74,7 @@ module Ty = struct
     | TC_operation -> fail (not_comparable "operation")
     | TC_signature -> fail (not_comparable "signature")
     | TC_key -> fail (not_comparable "key")
-    | TC_key_hash -> fail (not_comparable "key_hash")
+    | TC_key_hash -> return key_hash_k
     | TC_chain_id -> fail (not_comparable "chain_id")
 
   let comparable_type : type_value -> ex_comparable_ty result = fun tv ->

src/test/contracts/key_hash_comparable.ligo

@@ -0,0 +1,8 @@
+type storage is record
+  one: map(key_hash, nat);
+  two: big_map(key_hash, bool);
+end
+
+type return is list (operation) * storage
+
+function main (const a : int; const store : storage) : return is ((nil: list(operation)), store)