strengthen unused * testing (#6467)

changelog_begin
changelog_end

compiler/damlc/daml-opts/daml-opts/DA/Daml/Options.hs

@@ -284,9 +284,21 @@ xFlagsSet options =
 wOptsSet :: [ WarningFlag ]
 wOptsSet =
   [ Opt_WarnUnusedImports
+-- Can enable when we are on GHC >= 8.10 (we should, after all we
+-- upstreamed it :) ).
 --  , Opt_WarnPrepositiveQualifiedModule
   , Opt_WarnOverlappingPatterns
   , Opt_WarnIncompletePatterns
+-- Confirmed that nothing in template desugaring prevents us from
+-- enabling these.
+  -- , Opt_WarnUnusedMatches
+  -- , Opt_WarnUnusedForalls
+  -- , Opt_WarnUnusedPatternBinds
+  -- , Opt_WarnUnusedTopBinds
+  -- , Opt_WarnUnusedTypePatterns
+-- Template desugaring in the presence of local binds will currently
+-- trigger this.
+  -- , Opt_WarnUnusedLocalBinds
   ]
 
 -- | Warning options set for DAML compilation, which become errors.

compiler/damlc/daml-stdlib-src/DA/Internal/Template/Functions.daml

@@ -202,7 +202,7 @@ exerciseByKey k c = do
     exercise cid c
 
 -- | Create a contract and exercise the choice on the newly created contract.
-createAndExercise : forall t k c r. (HasCreate t, HasExercise t c r) => t -> c -> Update r
+createAndExercise : forall t c r. (HasCreate t, HasExercise t c r) => t -> c -> Update r
 createAndExercise t c = do
     cid <- create t
     exercise cid c

compiler/damlc/tests/daml-test-files/ContractKeyNotVisible.daml

@@ -78,7 +78,7 @@ divulgeeLookup = scenario do
 blindLookup = scenario do
   sig <- getParty "s" -- Signatory
   blind <- getParty "b" -- Blind
-  keyedCid <- submit sig do create Keyed with ..
+  _ <- submit sig do create Keyed with ..
   -- Blind party can't do positive lookup with maintainer authority.
   submit blind do
     mcid <- createAndExercise (Delegation sig blind) LookupKeyed

compiler/damlc/tests/daml-test-files/ExportList.daml

@@ -1,4 +1,5 @@
-
+-- Copyright (c) 2020, Digital Asset (Switzerland) GmbH and/or its
+-- affiliates. All rights reserved.
 module ExportList
     ( function1
     , Data1

compiler/damlc/tests/daml-test-files/TyConAppCoercion.daml

@@ -1,5 +1,6 @@
-
-module TyConAppCoercion () where
+-- Copyright (c) 2020, Digital Asset (Switzerland) GmbH and/or its
+-- affiliates. All rights reserved.
+module TyConAppCoercion (X(..)) where
 
 class MyClass a where
   f1 : Optional a -> a

compiler/damlc/tests/daml-test-files/UnusedMatchTests.daml

@@ -1,13 +1,20 @@
 -- Copyright (c) 2020, Digital Asset (Switzerland) GmbH and/or its
 -- affiliates. All rights reserved.
 
--- @WARN range=12:2-12:3; Defined but not used
+-- @WARN range=19:2-19:3; Defined but not used
 
 {-# OPTIONS_GHC -Wunused-matches #-}
+{-# OPTIONS_GHC -Wunused-foralls #-}
+{-# OPTIONS_GHC -Wunused-imports #-}
+{-# OPTIONS_GHC -Wunused-pattern-binds #-}
+{-# OPTIONS_GHC -Wunused-top-binds #-}
+{-# OPTIONS_GHC -Wunused-type-patterns #-}
+-- We know this will fail and why.
+--   {-# OPTIONS_GHC -Wunused-local-binds #-}
 module UnusedMatchTests where
 
--- It should be OK to enable -Wunused-matches and not get warnings
--- from template desugared code.
+-- It should be OK to enable -Wunused-* and not get warnings from
+-- template desugared code.
 
 f x = 12 -- Defined but not used 'x'; prove unsed match detection.