Merge pull request #2227 from ucsd-progsys/fd/test-case-desugaring

Add a GHC API test for case desugaring
ucsd-progsys · Sep 27, 2023 · c55c331 · c55c331
2 parents 79b339c + fbf68a6
commit c55c331
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Showing 2 changed files with 84 additions and 5 deletions.
diff --git a/liquidhaskell-boot/ghc-api-tests/GhcApiTests.hs b/liquidhaskell-boot/ghc-api-tests/GhcApiTests.hs
@@ -1,29 +1,45 @@
 
 import           Control.Monad
+import           Data.List (find)
+import           Data.Time (getCurrentTime)
 import           Liquid.GHC.API
     ( ApiComment(ApiBlockComment)
+    , Expr(..)
+    , Alt(..)
+    , AltCon(..)
     , apiCommentsParsedSource
+    , occNameString
+    , pAT_ERROR_ID
+    , showPprQualified
     )
 import           Test.Tasty
 import           Test.Tasty.HUnit
 import           Test.Tasty.Runners.AntXML
 
+import qualified GHC as GHC
+import qualified GHC.Core as GHC
 import qualified GHC.Data.EnumSet as EnumSet
 import qualified GHC.Data.FastString as GHC
 import qualified GHC.Data.StringBuffer as GHC
-import qualified GHC.Parser as GHC
+import qualified GHC.Parser as Parser
 import qualified GHC.Parser.Lexer as GHC
+import qualified GHC.Types.Name.Occurrence as GHC
 import qualified GHC.Types.SrcLoc as GHC
+import qualified GHC.Unit.Module.ModGuts as GHC
+
+import GHC.Paths (libdir)
+
 
 main :: IO ()
 main =
   defaultMainWithIngredients (antXMLRunner:defaultIngredients) testTree
 
 testTree :: TestTree
 testTree =
-    testGroup "GHC API" [
-      testCase "apiComments" testApiComments
-    ]
+    testGroup "GHC API"
+      [ testCase "apiComments" testApiComments
+      , testCase "caseDesugaring" testCaseDesugaring
+      ]
 
 -- Tests that Liquid.GHC.API.Extra.apiComments can retrieve the comments in
 -- the right order from an AST
@@ -64,6 +80,67 @@ testApiComments = do
           buffer = GHC.stringToStringBuffer str
           popts = GHC.mkParserOpts EnumSet.empty EnumSet.empty False True True True
           parseState = GHC.initParserState popts buffer location
-      case GHC.unP GHC.parseModule parseState of
+      case GHC.unP Parser.parseModule parseState of
         GHC.POk _ result -> return result
         _ -> fail "Unexpected parser error"
+
+
+-- | Tests that case expressions desugar as Liquid Haskell expects.
+testCaseDesugaring :: IO ()
+testCaseDesugaring = do
+    let inputSource = unlines
+          [ "module CaseDesugaring where"
+          , "f :: Bool -> ()"
+          , "f x = case x of"
+          , "        True -> ()"
+          ]
+
+        fBind (GHC.NonRec b _e) =
+          occNameString (GHC.occName b) == "f"
+        fBind _ = False
+
+        -- Expected desugaring:
+        --
+        -- CaseDesugaring.f
+        --      = \ (x :: GHC.Types.Bool) ->
+        --          case x of {
+        --            __DEFAULT ->
+        --              case Control.Exception.Base.patError ...
+        --              of {
+        --              };
+        --            GHC.Types.True -> GHC.Tuple.()
+        --          }
+        --
+        isExpectedDesugaring p = case find fBind p of
+          Just (GHC.NonRec _ e0)
+            | Lam x (Case (Var x') _ _ [alt0, _alt1]) <- e0
+            , x == x'
+            , Alt DEFAULT [] e1 <- alt0
+            , Case e2 _ _ [] <- e1
+            , (Var e3,_) <- GHC.collectArgs e2
+            -> e3 == pAT_ERROR_ID
+          _ -> False
+
+    coreProgram <- compileToCore inputSource
+    unless (isExpectedDesugaring coreProgram) $
+      fail $ unlines $
+        "Unexpected desugaring:" : map showPprQualified coreProgram
+  where
+    compileToCore inputSource = do
+      now <- getCurrentTime
+      GHC.runGhc (Just libdir) $ do
+        df1 <- GHC.getSessionDynFlags
+        GHC.setSessionDynFlags df1
+        let target = GHC.Target {
+                     GHC.targetId           = GHC.TargetFile "CaseDesugaring.hs" Nothing
+                   , GHC.targetAllowObjCode = False
+                   , GHC.targetContents     = Just (GHC.stringToStringBuffer inputSource, now)
+                   }
+        GHC.setTargets [target]
+        void $ GHC.load GHC.LoadAllTargets
+
+        dsMod <- GHC.getModSummary (GHC.mkModuleName "CaseDesugaring")
+               >>= GHC.parseModule
+               >>= GHC.typecheckModule
+               >>= GHC.desugarModule
+        return $ GHC.mg_binds $ GHC.dm_core_module dsMod
diff --git a/liquidhaskell-boot/liquidhaskell-boot.cabal b/liquidhaskell-boot/liquidhaskell-boot.cabal
@@ -173,10 +173,12 @@ test-suite ghc-api-tests
   hs-source-dirs:   ghc-api-tests
   build-depends:    base
                   , ghc
+                  , ghc-paths
                   , liquidhaskell-boot
                   , tasty
                   , tasty-ant-xml
                   , tasty-hunit
+                  , time
   default-language: Haskell2010
   ghc-options:      -W