Add two tests for Phantom type, fix error messages

sdk/compiler/daml-lf-tools/src/DA/Daml/LF/TypeChecker/Error.hs

@@ -696,8 +696,8 @@ instance Pretty UnwarnableError where
       pprintDep (pkgId, Just meta) = pPrint pkgId <> "(" <> pPrint (packageName meta) <> ", " <> pPrint (packageVersion meta) <> ")"
       pprintDep (pkgId, Nothing) = pPrint pkgId
     EUpgradeMultiplePackagesWithSameNameAndVersion name version ids -> "Multiple packages with name " <> pPrint name <> " and version " <> pPrint (show version) <> ": " <> hcat (L.intersperse ", " (map pPrint ids))
-    EUpgradeDifferentParamsCount origin -> "EUpgradeDifferentParamsCount " <> pPrint origin
-    EUpgradeDifferentParamsKinds origin -> "EUpgradeDifferentParamsKinds " <> pPrint origin
+    EUpgradeDifferentParamsCount origin -> "The upgraded " <> pPrint origin <> " has changed the number of type variables it has."
+    EUpgradeDifferentParamsKinds origin -> "The upgraded " <> pPrint origin <> " has changed the kind of one of its type variables."
 
 
 instance Pretty UpgradedRecordOrigin where

sdk/compiler/damlc/tests/BUILD.bazel

@@ -488,6 +488,7 @@ da_haskell_test(
         "//test-common:upgrades-RecordFieldsNewNonOptional-files",
         "//test-common:upgrades-SucceedWhenATopLevelEnumAddsAField-files",
         "//test-common:upgrades-SucceedWhenParamNameChanges-files",
+        "//test-common:upgrades-SucceedWhenPhantomParamBecomesUsed-files",
         "//test-common:upgrades-SucceedsWhenATopLevelEnumChanges-files",
         "//test-common:upgrades-SucceedsWhenATopLevelRecordAddsAnOptionalFieldAtTheEnd-files",
         "//test-common:upgrades-SucceedsWhenATopLevelRecordAddsAnOptionalFieldAtTheEnd-v1.dar",

sdk/compiler/damlc/tests/src/DA/Test/DamlcUpgrades.hs

@@ -620,14 +620,14 @@ tests damlc =
                   version1_dev
             , test
                   "FailWhenParamCountChanges"
-                  (FailWithError "\ESC\\[0;91merror type checking data type Main.MyStruct:\n  EUpgradeDifferentParamsCount")
+                  (FailWithError "\ESC\\[0;91merror type checking data type Main.MyStruct:\n  The upgraded data type MyStruct has changed the number of type variables it has.")
                   versionDefault
                   NoDependencies
                   False
                   True
             , test
                   "FailWhenParamKindChanges"
-                  (FailWithError "\ESC\\[0;91merror type checking data type Main.MyStruct:\n  EUpgradeDifferentParamsKinds")
+                  (FailWithError "\ESC\\[0;91merror type checking data type Main.MyStruct:\n  The upgraded data type MyStruct has changed the kind of one of its type variables.")
                   versionDefault
                   NoDependencies
                   False
@@ -639,6 +639,13 @@ tests damlc =
                   NoDependencies
                   False
                   True
+            , test
+                  "SucceedWhenPhantomParamBecomesUsed"
+                  Succeed
+                  versionDefault
+                  NoDependencies
+                  False
+                  True
             ]
        )
   where

sdk/test-common/BUILD.bazel

@@ -506,6 +506,7 @@ da_scala_dar_resources_library(
         ("FailWhenParamCountChanges", {}, {}),
         ("FailWhenParamKindChanges", {}, {}),
         ("SucceedWhenParamNameChanges", {}, {}),
+        ("SucceedWhenPhantomParamBecomesUsed", {}, {}),
     ]
 ]
 

sdk/test-common/src/main/daml/upgrades/SucceedWhenParamNameChanges/v1/Main.daml

@@ -3,5 +3,5 @@
 
 module Main where
 
-data MyStruct a = MyStruct { field1 : a }
-
+data MyStruct1 a = MyStruct1 { field1 : a }
+data MyStruct2 a b = MyStruct2 { field1 : a }

sdk/test-common/src/main/daml/upgrades/SucceedWhenParamNameChanges/v2/Main.daml

@@ -3,5 +3,6 @@
 
 module Main where
 
-data MyStruct b = MyStruct { field1 : b }
+data MyStruct1 b = MyStruct1 { field1 : b }
+data MyStruct2 b a = MyStruct2 { field1 : b, field2 : Optional a, field3: Optional b }
 

sdk/test-common/src/main/daml/upgrades/SucceedWhenPhantomParamBecomesUsed/v1/Main.daml

@@ -0,0 +1,8 @@
+-- Copyright (c) 2024 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+-- SPDX-License-Identifier: Apache-2.0
+
+module Main where
+
+data MyStruct a b = MyStruct { field1 : a }
+
+

sdk/test-common/src/main/daml/upgrades/SucceedWhenPhantomParamBecomesUsed/v2/Main.daml

@@ -0,0 +1,7 @@
+-- Copyright (c) 2024 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+-- SPDX-License-Identifier: Apache-2.0
+
+module Main where
+
+data MyStruct a b = MyStruct { field1 : a, field2 : Optional b }
+