Refactor GHCi UI to fix #11606, #12091, #15721, #16096

Instead of parsing and executing a statement or declaration directly we
now parse them first and then execute in a separate step. This gives us
the flexibility to inspect the parsed declaration before execution.
Using this we now inspect parsed declarations, and if it's a single
declaration of form `x = y` we execute it as `let x = y` instead, fixing
a ton of problems caused by poor declaration support in GHCi.

To avoid any users of the modules I left `execStmt` and `runDecls`
unchanged and added `execStmt'` and `runDecls'` which work on parsed
statements/declarations.

16 files changed, 246 insertions, 76 deletions

diff --git a/compiler/deSugar/Desugar.hs b/compiler/deSugar/Desugar.hs
index aa24ee0..aa9748e 100644
--- a/compiler/deSugar/Desugar.hs
+++ b/compiler/deSugar/Desugar.hs
@@ -149,8 +149,7 @@ deSugar hsc_env
           keep_alive <- readIORef keep_var
         ; let (rules_for_locals, rules_for_imps) = partition isLocalRule all_rules
               final_prs = addExportFlagsAndRules target export_set keep_alive
-                                                 mod rules_for_locals
-                                                 (fromOL all_prs)
+                                                 rules_for_locals (fromOL all_prs)
 
               final_pgm = combineEvBinds ds_ev_binds final_prs
         -- Notice that we put the whole lot in a big Rec, even the foreign binds
@@ -284,9 +283,9 @@ deSugarExpr hsc_env tc_expr = do {
 -}
 
 addExportFlagsAndRules
-    :: HscTarget -> NameSet -> NameSet -> Module -> [CoreRule]
+    :: HscTarget -> NameSet -> NameSet -> [CoreRule]
     -> [(Id, t)] -> [(Id, t)]
-addExportFlagsAndRules target exports keep_alive mod rules prs
+addExportFlagsAndRules target exports keep_alive rules prs
   = mapFst add_one prs
   where
     add_one bndr = add_rules name (add_export name bndr)
@@ -319,20 +318,10 @@ addExportFlagsAndRules target exports keep_alive mod rules prs
         -- simplification), and retain them all in the TypeEnv so they are
         -- available from the command line.
         --
-        -- Most of the time, this can be accomplished by use of
-        -- targetRetainsAllBindings, which returns True if the target is
-        -- HscInteractive. However, there are cases when one can use GHCi with
-        -- a target other than HscInteractive (e.g., with the -fobject-code
-        -- flag enabled, as in #12091). In such scenarios,
-        -- targetRetainsAllBindings can return False, so we must fall back on
-        -- isInteractiveModule to be doubly sure we export entities defined in
-        -- a GHCi session.
-        --
         -- isExternalName separates the user-defined top-level names from those
         -- introduced by the type checker.
     is_exported :: Name -> Bool
-    is_exported | targetRetainsAllBindings target
-                  || isInteractiveModule mod      = isExternalName
+    is_exported | targetRetainsAllBindings target = isExternalName
                 | otherwise                       = (`elemNameSet` exports)
 
 {-
diff --git a/compiler/main/GHC.hs b/compiler/main/GHC.hs
index 8817b41..f289cd4 100644
--- a/compiler/main/GHC.hs
+++ b/compiler/main/GHC.hs
@@ -96,11 +96,11 @@ module GHC (
         -- * Interactive evaluation
 
         -- ** Executing statements
-        execStmt, ExecOptions(..), execOptions, ExecResult(..),
+        execStmt, execStmt', ExecOptions(..), execOptions, ExecResult(..),
         resumeExec,
 
         -- ** Adding new declarations
-        runDecls, runDeclsWithLocation,
+        runDecls, runDeclsWithLocation, runParsedDecls,
 
         -- ** Get/set the current context
         parseImportDecl,
diff --git a/compiler/main/HscMain.hs b/compiler/main/HscMain.hs
index 2ff2ca0..9a4dd4a 100644
--- a/compiler/main/HscMain.hs
+++ b/compiler/main/HscMain.hs
@@ -63,8 +63,8 @@ module HscMain
     , hscGetModuleInterface
     , hscRnImportDecls
     , hscTcRnLookupRdrName
-    , hscStmt, hscStmtWithLocation, hscParsedStmt
-    , hscDecls, hscDeclsWithLocation
+    , hscStmt, hscParseStmtWithLocation, hscStmtWithLocation, hscParsedStmt
+    , hscDecls, hscParseDeclsWithLocation, hscDeclsWithLocation, hscParsedDecls
     , hscTcExpr, TcRnExprMode(..), hscImport, hscKcType
     , hscParseExpr
     , hscCompileCoreExpr
@@ -1602,17 +1602,27 @@ hscDecls :: HscEnv
          -> IO ([TyThing], InteractiveContext)
 hscDecls hsc_env str = hscDeclsWithLocation hsc_env str "<interactive>" 1
 
+hscParseDeclsWithLocation :: HscEnv -> String -> Int -> String -> IO [LHsDecl GhcPs]
+hscParseDeclsWithLocation hsc_env source line_num str = do
+    L _ (HsModule{ hsmodDecls = decls }) <-
+      runInteractiveHsc hsc_env $
+        hscParseThingWithLocation source line_num parseModule str
+    return decls
+
 -- | Compile a decls
 hscDeclsWithLocation :: HscEnv
                      -> String -- ^ The statement
                      -> String -- ^ The source
                      -> Int    -- ^ Starting line
                      -> IO ([TyThing], InteractiveContext)
-hscDeclsWithLocation hsc_env0 str source linenumber =
- runInteractiveHsc hsc_env0 $ do
+hscDeclsWithLocation hsc_env str source linenumber = do
     L _ (HsModule{ hsmodDecls = decls }) <-
+      runInteractiveHsc hsc_env $
         hscParseThingWithLocation source linenumber parseModule str
+    hscParsedDecls hsc_env decls
 
+hscParsedDecls :: HscEnv -> [LHsDecl GhcPs] -> IO ([TyThing], InteractiveContext)
+hscParsedDecls hsc_env decls = runInteractiveHsc hsc_env $ do
     {- Rename and typecheck it -}
     hsc_env <- getHscEnv
     tc_gblenv <- ioMsgMaybe $ tcRnDeclsi hsc_env decls
diff --git a/compiler/main/HscTypes.hs b/compiler/main/HscTypes.hs
index 456332d..d17fa5f 100644
--- a/compiler/main/HscTypes.hs
+++ b/compiler/main/HscTypes.hs
@@ -23,7 +23,7 @@ module HscTypes (
         needsTemplateHaskellOrQQ, mgBootModules,
 
         -- * Hsc monad
-        Hsc(..), runHsc, runInteractiveHsc,
+        Hsc(..), runHsc, mkInteractiveHscEnv, runInteractiveHsc,
 
         -- * Information about modules
         ModDetails(..), emptyModDetails,
@@ -253,13 +253,15 @@ runHsc hsc_env (Hsc hsc) = do
     printOrThrowWarnings (hsc_dflags hsc_env) w
     return a
 
+mkInteractiveHscEnv :: HscEnv -> HscEnv
+mkInteractiveHscEnv hsc_env = hsc_env{ hsc_dflags = interactive_dflags }
+  where
+    interactive_dflags = ic_dflags (hsc_IC hsc_env)
+
 runInteractiveHsc :: HscEnv -> Hsc a -> IO a
 -- A variant of runHsc that switches in the DynFlags from the
 -- InteractiveContext before running the Hsc computation.
-runInteractiveHsc hsc_env
-  = runHsc (hsc_env { hsc_dflags = interactive_dflags })
-  where
-    interactive_dflags = ic_dflags (hsc_IC hsc_env)
+runInteractiveHsc hsc_env = runHsc (mkInteractiveHscEnv hsc_env)
 
 -- -----------------------------------------------------------------------------
 -- Source Errors
diff --git a/compiler/main/InteractiveEval.hs b/compiler/main/InteractiveEval.hs
index cceec31..ad3c500 100644
--- a/compiler/main/InteractiveEval.hs
+++ b/compiler/main/InteractiveEval.hs
@@ -11,8 +11,8 @@
 
 module InteractiveEval (
         Resume(..), History(..),
-        execStmt, ExecOptions(..), execOptions, ExecResult(..), resumeExec,
-        runDecls, runDeclsWithLocation,
+        execStmt, execStmt', ExecOptions(..), execOptions, ExecResult(..), resumeExec,
+        runDecls, runDeclsWithLocation, runParsedDecls,
         isStmt, hasImport, isImport, isDecl,
         parseImportDecl, SingleStep(..),
         abandon, abandonAll,
@@ -165,23 +165,40 @@ execStmt
   => String             -- ^ a statement (bind or expression)
   -> ExecOptions
   -> m ExecResult
-execStmt stmt ExecOptions{..} = do
+execStmt input exec_opts@ExecOptions{..} = do
+    hsc_env <- getSession
+
+    mb_stmt <-
+      liftIO $
+      runInteractiveHsc hsc_env $
+      hscParseStmtWithLocation execSourceFile execLineNumber input
+
+    case mb_stmt of
+      -- empty statement / comment
+      Nothing -> return (ExecComplete (Right []) 0)
+      Just stmt -> execStmt' stmt input exec_opts
+
+-- | Like `execStmt`, but takes a parsed statement as argument. Useful when
+-- doing preprocessing on the AST before execution, e.g. in GHCi (see
+-- GHCi.UI.runStmt).
+execStmt' :: GhcMonad m => GhciLStmt GhcPs -> String -> ExecOptions -> m ExecResult
+execStmt' stmt stmt_text ExecOptions{..} = do
     hsc_env <- getSession
 
     -- Turn off -fwarn-unused-local-binds when running a statement, to hide
     -- warnings about the implicit bindings we introduce.
+    -- (This is basically `mkInteractiveHscEnv hsc_env`, except we unset
+    -- -wwarn-unused-local-binds)
     let ic       = hsc_IC hsc_env -- use the interactive dflags
         idflags' = ic_dflags ic `wopt_unset` Opt_WarnUnusedLocalBinds
-        hsc_env' = hsc_env{ hsc_IC = ic{ ic_dflags = idflags' } }
+        hsc_env' = mkInteractiveHscEnv (hsc_env{ hsc_IC = ic{ ic_dflags = idflags' } })
 
-    -- compile to value (IO [HValue]), don't run
-    r <- liftIO $ hscStmtWithLocation hsc_env' stmt
-                    execSourceFile execLineNumber
+    r <- liftIO $ hscParsedStmt hsc_env' stmt
 
     case r of
-      -- empty statement / comment
-      Nothing -> return (ExecComplete (Right []) 0)
-
+      Nothing ->
+        -- empty statement / comment
+        return (ExecComplete (Right []) 0)
       Just (ids, hval, fix_env) -> do
         updateFixityEnv fix_env
 
@@ -195,20 +212,27 @@ execStmt stmt ExecOptions{..} = do
 
             size = ghciHistSize idflags'
 
-        handleRunStatus execSingleStep stmt bindings ids
+        handleRunStatus execSingleStep stmt_text bindings ids
                         status (emptyHistory size)
 
-
 runDecls :: GhcMonad m => String -> m [Name]
 runDecls = runDeclsWithLocation "<interactive>" 1
 
 -- | Run some declarations and return any user-visible names that were brought
 -- into scope.
 runDeclsWithLocation :: GhcMonad m => String -> Int -> String -> m [Name]
-runDeclsWithLocation source linenumber expr =
-  do
+runDeclsWithLocation source line_num input = do
+    hsc_env <- getSession
+    decls <- liftIO (hscParseDeclsWithLocation hsc_env source line_num input)
+    runParsedDecls decls
+
+-- | Like `runDeclsWithLocation`, but takes parsed declarations as argument.
+-- Useful when doing preprocessing on the AST before execution, e.g. in GHCi
+-- (see GHCi.UI.runStmt).
+runParsedDecls :: GhcMonad m => [LHsDecl GhcPs] -> m [Name]
+runParsedDecls decls = do
     hsc_env <- getSession
-    (tyThings, ic) <- liftIO $ hscDeclsWithLocation hsc_env expr source linenumber
+    (tyThings, ic) <- liftIO (hscParsedDecls hsc_env decls)
 
     setSession $ hsc_env { hsc_IC = ic }
     hsc_env <- getSession
diff --git a/ghc/GHCi/UI.hs b/ghc/GHCi/UI.hs
index 2cc055a..d6d86fc 100644
--- a/ghc/GHCi/UI.hs
+++ b/ghc/GHCi/UI.hs
@@ -31,8 +31,8 @@ module GHCi.UI (
 #include "HsVersions.h"
 
 -- GHCi
-import qualified GHCi.UI.Monad as GhciMonad ( args, runStmt, runDecls )
-import GHCi.UI.Monad hiding ( args, runStmt, runDecls )
+import qualified GHCi.UI.Monad as GhciMonad ( args, runStmt, runDecls' )
+import GHCi.UI.Monad hiding ( args, runStmt )
 import GHCi.UI.Tags
 import GHCi.UI.Info
 import Debugger
@@ -50,10 +50,11 @@ import GHC ( LoadHowMuch(..), Target(..),  TargetId(..), InteractiveImport(..),
              TyThing(..), Phase, BreakIndex, Resume, SingleStep, Ghc,
              GetDocsFailure(..),
              getModuleGraph, handleSourceError )
+import HscMain (hscParseDeclsWithLocation, hscParseStmtWithLocation)
 import HsImpExp
 import HsSyn
 import HscTypes ( tyThingParent_maybe, handleFlagWarnings, getSafeMode, hsc_IC,
-                  setInteractivePrintName, hsc_dflags, msObjFilePath )
+                  setInteractivePrintName, hsc_dflags, msObjFilePath, runInteractiveHsc )
 import Module
 import Name
 import Packages ( trusted, getPackageDetails, getInstalledPackageDetails,
@@ -82,6 +83,7 @@ import NameSet
 import Panic hiding ( showException )
 import Util
 import qualified GHC.LanguageExtensions as LangExt
+import Bag (unitBag)
 
 -- Haskell Libraries
 import System.Console.Haskeline as Haskeline
@@ -1088,51 +1090,94 @@ enqueueCommands cmds = do
 -- | Entry point to execute some haskell code from user.
 -- The return value True indicates success, as in `runOneCommand`.
 runStmt :: String -> SingleStep -> GHCi (Maybe GHC.ExecResult)
-runStmt stmt step = do
+runStmt input step = do
   dflags <- GHC.getInteractiveDynFlags
   -- In GHCi, we disable `-fdefer-type-errors`, as well as `-fdefer-type-holes`
   -- and `-fdefer-out-of-scope-variables` for **naked expressions**. The
   -- declarations and statements are not affected.
   -- See Note [Deferred type errors in GHCi] in typecheck/TcRnDriver.hs
-  if | GHC.isStmt dflags stmt    -> run_stmt
-     | GHC.isImport dflags stmt  -> run_import
+  st <- getGHCiState
+  let source = progname st
+  let line = line_number st
+
+  if | GHC.isStmt dflags input -> do
+         hsc_env <- GHC.getSession
+         mb_stmt <- liftIO (runInteractiveHsc hsc_env (hscParseStmtWithLocation source line input))
+         case mb_stmt of
+           Nothing ->
+             -- empty statement / comment
+             return (Just exec_complete)
+           Just stmt ->
+             run_stmt stmt
+
+     | GHC.isImport dflags input -> run_import
+
      -- Every import declaration should be handled by `run_import`. As GHCi
      -- in general only accepts one command at a time, we simply throw an
      -- exception when the input contains multiple commands of which at least
      -- one is an import command (see #10663).
-     | GHC.hasImport dflags stmt -> throwGhcException
+     | GHC.hasImport dflags input -> throwGhcException
        (CmdLineError "error: expecting a single import declaration")
+
+     -- Otherwise assume a declaration (or a list of declarations)
      -- Note: `GHC.isDecl` returns False on input like
      -- `data Infix a b = a :@: b; infixl 4 :@:`
      -- and should therefore not be used here.
-     | otherwise                 -> run_decl
-
+     | otherwise -> do
+         hsc_env <- GHC.getSession
+         decls <- liftIO (hscParseDeclsWithLocation hsc_env source line input)
+         run_decls decls
   where
+    exec_complete = GHC.ExecComplete (Right []) 0
+
     run_import = do
-      addImportToContext stmt
-      return (Just (GHC.ExecComplete (Right []) 0))
+      addImportToContext input
+      return (Just exec_complete)
 
-    run_decl =
-        do _ <- liftIO $ tryIO $ hFlushAll stdin
-           m_result <- GhciMonad.runDecls stmt
-           case m_result of
-               Nothing     -> return Nothing
-               Just result ->
-                 Just <$> afterRunStmt (const True)
-                            (GHC.ExecComplete (Right result) 0)
-
-    run_stmt =
-        do -- In the new IO library, read handles buffer data even if the Handle
-           -- is set to NoBuffering.  This causes problems for GHCi where there
-           -- are really two stdin Handles.  So we flush any bufferred data in
-           -- GHCi's stdin Handle here (only relevant if stdin is attached to
-           -- a file, otherwise the read buffer can't be flushed).
-           _ <- liftIO $ tryIO $ hFlushAll stdin
-           m_result <- GhciMonad.runStmt stmt step
+    run_stmt :: GhciLStmt GhcPs -> GHCi (Maybe GHC.ExecResult)
+    run_stmt stmt = do
+           m_result <- GhciMonad.runStmt stmt input step
            case m_result of
                Nothing     -> return Nothing
                Just result -> Just <$> afterRunStmt (const True) result
 
+    -- `x = y` (a declaration) should be treated as `let x = y` (a statement).
+    -- The reason is because GHCi wasn't designed to support `x = y`, but then
+    -- b98ff3 (#7253) added support for it, except it did not do a good job and
+    -- caused problems like:
+    --
+    --  - not adding the binders defined this way in the necessary places caused
+    --    `x = y` to not work in some cases (#12091).
+    --  - some GHCi command crashed after `x = y` (#15721)
+    --  - warning generation did not work for `x = y` (#11606)
+    --  - because `x = y` is a declaration (instead of a statement) differences
+    --    in generated code caused confusion (#16089)
+    --
+    -- Instead of dealing with all these problems individually here we fix this
+    -- mess by just treating `x = y` as `let x = y`.
+    run_decls :: [LHsDecl GhcPs] -> GHCi (Maybe GHC.ExecResult)
+    -- Only turn `FunBind` and `VarBind` into statements, other bindings
+    -- (e.g. `PatBind`) need to stay as decls.
+    run_decls [L l (ValD _ bind@FunBind{})] = run_stmt (mk_stmt l bind)
+    run_decls [L l (ValD _ bind@VarBind{})] = run_stmt (mk_stmt l bind)
+    -- Note that any `x = y` declarations below will be run as declarations
+    -- instead of statements (e.g. `...; x = y; ...`)
+    run_decls decls = do
+      -- In the new IO library, read handles buffer data even if the Handle
+      -- is set to NoBuffering.  This causes problems for GHCi where there
+      -- are really two stdin Handles.  So we flush any bufferred data in
+      -- GHCi's stdin Handle here (only relevant if stdin is attached to
+      -- a file, otherwise the read buffer can't be flushed).
+      _ <- liftIO $ tryIO $ hFlushAll stdin
+      m_result <- GhciMonad.runDecls' decls
+      forM m_result $ \result ->
+        afterRunStmt (const True) (GHC.ExecComplete (Right result) 0)
+
+    mk_stmt :: SrcSpan -> HsBind GhcPs -> GhciLStmt GhcPs
+    mk_stmt loc bind =
+      let l = L loc
+      in l (LetStmt noExt (l (HsValBinds noExt (ValBinds noExt (unitBag (l bind)) []))))
+
 -- | Clean up the GHCi environment after a statement has run
 afterRunStmt :: (SrcSpan -> Bool) -> GHC.ExecResult -> GHCi GHC.ExecResult
 afterRunStmt step_here run_result = do
diff --git a/ghc/GHCi/UI/Monad.hs b/ghc/GHCi/UI/Monad.hs
index 969111b..cbf527e 100644
--- a/ghc/GHCi/UI/Monad.hs
+++ b/ghc/GHCi/UI/Monad.hs
@@ -20,7 +20,7 @@ module GHCi.UI.Monad (
         TickArray,
         getDynFlags,
 
-        runStmt, runDecls, resume, timeIt, recordBreak, revertCAFs,
+        runStmt, runDecls, runDecls', resume, timeIt, recordBreak, revertCAFs,
 
         printForUserNeverQualify, printForUserModInfo,
         printForUser, printForUserPartWay, prettyLocations,
@@ -46,7 +46,7 @@ import SrcLoc
 import Module
 import GHCi
 import GHCi.RemoteTypes
-import HsSyn (ImportDecl, GhcPs)
+import HsSyn (ImportDecl, GhcPs, GhciLStmt, LHsDecl)
 import Util
 
 import Exception
@@ -338,8 +338,8 @@ printForUserPartWay doc = do
   liftIO $ Outputable.printForUserPartWay dflags stdout (pprUserLength dflags) unqual doc
 
 -- | Run a single Haskell expression
-runStmt :: String -> GHC.SingleStep -> GHCi (Maybe GHC.ExecResult)
-runStmt expr step = do
+runStmt :: GhciLStmt GhcPs -> String -> GHC.SingleStep -> GHCi (Maybe GHC.ExecResult)
+runStmt stmt stmt_text step = do
   st <- getGHCiState
   GHC.handleSourceError (\e -> do GHC.printException e; return Nothing) $ do
     let opts = GHC.execOptions
@@ -348,7 +348,7 @@ runStmt expr step = do
                   , GHC.execSingleStep = step
                   , GHC.execWrap = \fhv -> EvalApp (EvalThis (evalWrapper st))
                                                    (EvalThis fhv) }
-    Just <$> GHC.execStmt expr opts
+    Just <$> GHC.execStmt' stmt stmt_text opts
 
 runDecls :: String -> GHCi (Maybe [GHC.Name])
 runDecls decls = do
@@ -362,6 +362,18 @@ runDecls decls = do
           r <- GHC.runDeclsWithLocation (progname st) (line_number st) decls
           return (Just r)
 
+runDecls' :: [LHsDecl GhcPs] -> GHCi (Maybe [GHC.Name])
+runDecls' decls = do
+  st <- getGHCiState
+  reifyGHCi $ \x ->
+    withProgName (progname st) $
+    withArgs (args st) $
+    reflectGHCi x $
+      GHC.handleSourceError
+        (\e -> do GHC.printException e;
+                  return Nothing)
+        (Just <$> GHC.runParsedDecls decls)
+
 resume :: (SrcSpan -> Bool) -> GHC.SingleStep -> GHCi GHC.ExecResult
 resume canLogSpan step = do
   st <- getGHCiState
diff --git a/testsuite/tests/ghci/scripts/T11606.script b/testsuite/tests/ghci/scripts/T11606.script
new file mode 100644
index 0000000..0fb5fff
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T11606.script
@@ -0,0 +1,5 @@
+:set -Wall
+x = 1 :: Int
+x = 1 :: Int
+x <- return (1 :: Int)
+let x = 1 :: Int
diff --git a/testsuite/tests/ghci/scripts/T11606.stderr b/testsuite/tests/ghci/scripts/T11606.stderr
new file mode 100644
index 0000000..bbfb740
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T11606.stderr
@@ -0,0 +1,12 @@
+
+<interactive>:3:1: warning: [-Wname-shadowing (in -Wall)]
+    This binding for ‘x’ shadows the existing binding
+      defined at <interactive>:2:1
+
+<interactive>:4:1: warning: [-Wname-shadowing (in -Wall)]
+    This binding for ‘x’ shadows the existing binding
+      defined at <interactive>:3:1
+
+<interactive>:5:5: warning: [-Wname-shadowing (in -Wall)]
+    This binding for ‘x’ shadows the existing binding
+      defined at <interactive>:4:1
diff --git a/testsuite/tests/ghci/scripts/T16089.script b/testsuite/tests/ghci/scripts/T16089.script
new file mode 100644
index 0000000..d4e6676
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T16089.script
@@ -0,0 +1,4 @@
+x = [0 .. 100000] :: [Int]
+:sprint x
+x `seq` True
+:sprint x
diff --git a/testsuite/tests/ghci/scripts/T16089.stdout b/testsuite/tests/ghci/scripts/T16089.stdout
new file mode 100644
index 0000000..7d5cc0b
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/T16089.stdout
@@ -0,0 +1,3 @@
+x = _
+True
+x = 0 : _
diff --git a/testsuite/tests/ghci/scripts/all.T b/testsuite/tests/ghci/scripts/all.T
index ad4a24f..2567db4 100755
--- a/testsuite/tests/ghci/scripts/all.T
+++ b/testsuite/tests/ghci/scripts/all.T
@@ -262,7 +262,7 @@ test('T12091', [extra_run_opts('-fobject-code')], ghci_script,
      ['T12091.script'])
 test('T12523', normal, ghci_script, ['T12523.script'])
 test('T12024', normal, ghci_script, ['T12024.script'])
-test('T12158', expect_broken(12158), ghci_script, ['T12158.script'])
+test('T12158', normal, ghci_script, ['T12158.script'])
 test('T12447', normal, ghci_script, ['T12447.script'])
 test('T10249', normal, ghci_script, ['T10249.script'])
 test('T12550', normal, ghci_script, ['T12550.script'])
@@ -293,3 +293,5 @@ test('T15827', normal, ghci_script, ['T15827.script'])
 test('T15898', normal, ghci_script, ['T15898.script'])
 test('T15941', normal, ghci_script, ['T15941.script'])
 test('T16030', normal, ghci_script, ['T16030.script'])
+test('T11606', normal, ghci_script, ['T11606.script'])
+test('T16089', normal, ghci_script, ['T16089.script'])
diff --git a/testsuite/tests/ghci/should_run/T12525.stdout b/testsuite/tests/ghci/should_run/T12525.stdout
index 31049e1..652a5cd 100644
--- a/testsuite/tests/ghci/should_run/T12525.stdout
+++ b/testsuite/tests/ghci/should_run/T12525.stdout
@@ -1,3 +1,3 @@
-x :: () = _
+x :: () = ()
 y :: () = ()
 class Foo a
diff --git a/testsuite/tests/ghci/should_run/T16096.script b/testsuite/tests/ghci/should_run/T16096.script
new file mode 100644
index 0000000..8fb9453
--- /dev/null
+++ b/testsuite/tests/ghci/should_run/T16096.script
@@ -0,0 +1,4 @@
+:set -ddump-ds -dsuppress-uniques
+-- These two should desugar to same Core
+let x = [1..] :: [Int]
+x = [1..] :: [Int]
diff --git a/testsuite/tests/ghci/should_run/T16096.stdout b/testsuite/tests/ghci/should_run/T16096.stdout
new file mode 100644
index 0000000..8b87b7d
--- /dev/null
+++ b/testsuite/tests/ghci/should_run/T16096.stdout
@@ -0,0 +1,56 @@
+
+==================== Desugared ====================
+letrec {
+  x :: [GHC.Types.Int]
+  [LclId]
+  x = let {
+        $dEnum :: GHC.Enum.Enum GHC.Types.Int
+        [LclId]
+        $dEnum = GHC.Enum.$fEnumInt } in
+      letrec {
+        x :: [GHC.Types.Int]
+        [LclId]
+        x = GHC.Enum.enumFrom
+              @ GHC.Types.Int $dEnum (GHC.Types.I# 1#); } in
+      x; } in
+GHC.Base.returnIO
+  @ [()]
+  (GHC.Types.:
+     @ ()
+     (GHC.Prim.unsafeCoerce#
+        @ 'GHC.Types.LiftedRep
+        @ 'GHC.Types.LiftedRep
+        @ [GHC.Types.Int]
+        @ ()
+        x)
+     (GHC.Types.[] @ ()))
+
+
+
+==================== Desugared ====================
+letrec {
+  x :: [GHC.Types.Int]
+  [LclId]
+  x = let {
+        $dEnum :: GHC.Enum.Enum GHC.Types.Int
+        [LclId]
+        $dEnum = GHC.Enum.$fEnumInt } in
+      letrec {
+        x :: [GHC.Types.Int]
+        [LclId]
+        x = GHC.Enum.enumFrom
+              @ GHC.Types.Int $dEnum (GHC.Types.I# 1#); } in
+      x; } in
+GHC.Base.returnIO
+  @ [()]
+  (GHC.Types.:
+     @ ()
+     (GHC.Prim.unsafeCoerce#
+        @ 'GHC.Types.LiftedRep
+        @ 'GHC.Types.LiftedRep
+        @ [GHC.Types.Int]
+        @ ()
+        x)
+     (GHC.Types.[] @ ()))
+
+
diff --git a/testsuite/tests/ghci/should_run/all.T b/testsuite/tests/ghci/should_run/all.T
index ea734e7..004794b 100644
--- a/testsuite/tests/ghci/should_run/all.T
+++ b/testsuite/tests/ghci/should_run/all.T
@@ -56,3 +56,5 @@ test('T15633b',
       extra_hc_opts("-package-db tc-plugin-ghci/pkg.plugins01/local.package.conf")
       ],
      ghci_script, ['T15633b.script'])
+
+test('T16096', just_ghci, ghci_script, ['T16096.script'])