Don't count it as using a term if you only destruct it (#2099)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: isovector

plugins/hls-tactics-plugin/src/Wingman/CodeGen.hs

@@ -225,7 +225,6 @@ destruct' use_field_puns f hi jdg = do
            $ disallowing AlreadyDestructed (S.singleton term) jdg
   pure $ ext
     & #syn_trace     %~ rose ("destruct " <> show term) . pure
-    & #syn_used_vals %~ S.insert term
     & #syn_val       %~ noLoc . case' (var' term)
 
 

plugins/hls-tactics-plugin/src/Wingman/Tactics.hs

@@ -63,7 +63,7 @@ assume name = rule $ \jdg -> do
         -- reasonable for a default value.
         (pure (noLoc $ var' name))
           { syn_trace = tracePrim $ "assume " <> occNameString name
-          , syn_used_vals = S.singleton name
+          , syn_used_vals = S.singleton name <> getAncestry jdg name
           }
     Nothing -> cut
 
@@ -298,7 +298,7 @@ apply (Unsaturated n) hi = tracing ("apply' " <> show (hi_name hi)) $ do
                     ) saturated_args
     pure $
       ext
-        & #syn_used_vals %~ S.insert func
+        & #syn_used_vals %~ (\x -> S.insert func x <> getAncestry jdg func)
         & #syn_val       %~ mkApply func . fmap unLoc
 
 application :: TacticsM ()

plugins/hls-tactics-plugin/test/CodeAction/AutoSpec.hs

@@ -49,6 +49,7 @@ spec = do
     autoTest  2 25 "AutoInfixInfix"
     autoTest 19 12 "AutoTypeLevel"
     autoTest 11  9 "AutoForallClassMethod"
+    autoTest  2  8 "AutoUnusedPatternMatch"
 
     failing "flaky in CI" $
       autoTest 2 11 "GoldenApplicativeThen"

plugins/hls-tactics-plugin/test/golden/AutoUnusedPatternMatch.expected.hs

@@ -0,0 +1,2 @@
+test :: Bool -> ()
+test _ = ()

plugins/hls-tactics-plugin/test/golden/AutoUnusedPatternMatch.hs

@@ -0,0 +1,2 @@
+test :: Bool -> ()
+test = _