Revert "GHCi: Don't remove shadowed bindings from typechecker scope."

This reverts commit 59d7ee53 and enables
the test for #14052.

(See #14052 for the discussion)

Reviewers: bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #14052

Differential Revision: https://phabricator.haskell.org/D4478

(cherry picked from commit 98c7749c)

compiler/main/HscTypes.hs

@@ -1641,7 +1641,7 @@ extendInteractiveContext ictxt new_tythings new_cls_insts new_fam_insts defaults
   = ictxt { ic_mod_index  = ic_mod_index ictxt + 1
                             -- Always bump this; even instances should create
                             -- a new mod_index (Trac #9426)
-          , ic_tythings   = new_tythings ++ ic_tythings ictxt
+          , ic_tythings   = new_tythings ++ old_tythings
           , ic_rn_gbl_env = ic_rn_gbl_env ictxt `icExtendGblRdrEnv` new_tythings
           , ic_instances  = ( new_cls_insts ++ old_cls_insts
                             , new_fam_insts ++ fam_insts )
@@ -1651,6 +1651,8 @@ extendInteractiveContext ictxt new_tythings new_cls_insts new_fam_insts defaults
           , ic_fix_env    = fix_env  -- See Note [Fixity declarations in GHCi]
           }
   where
+    new_ids = [id | AnId id <- new_tythings]
+    old_tythings = filterOut (shadowed_by new_ids) (ic_tythings ictxt)
 
     -- Discard old instances that have been fully overridden
     -- See Note [Override identical instances in GHCi]
@@ -1662,10 +1664,17 @@ extendInteractiveContextWithIds :: InteractiveContext -> [Id] -> InteractiveCont
 extendInteractiveContextWithIds ictxt new_ids
   | null new_ids = ictxt
   | otherwise    = ictxt { ic_mod_index  = ic_mod_index ictxt + 1
-                         , ic_tythings   = new_tythings ++ ic_tythings ictxt
+                         , ic_tythings   = new_tythings ++ old_tythings
                          , ic_rn_gbl_env = ic_rn_gbl_env ictxt `icExtendGblRdrEnv` new_tythings }
   where
     new_tythings = map AnId new_ids
+    old_tythings = filterOut (shadowed_by new_ids) (ic_tythings ictxt)
+
+shadowed_by :: [Id] -> TyThing -> Bool
+shadowed_by ids = shadowed
+  where
+    shadowed id = getOccName id `elemOccSet` new_occs
+    new_occs = mkOccSet (map getOccName ids)
 
 setInteractivePackage :: HscEnv -> HscEnv
 -- Set the 'thisPackage' DynFlag to 'interactive'

testsuite/tests/ghci.debugger/scripts/break011.stdout

@@ -23,13 +23,6 @@ _exception = SomeException
                   "foo"
                   "CallStack (from HasCallStack):
   error, called at Test7.hs:2:18 in main:Main")
-Ghci1._exception :: SomeException = SomeException
-                                      (ErrorCallWithLocation
-                                         "foo"
-                                         "CallStack (from HasCallStack):
-  error, called at Test7.hs:<line>:<column> in <package-id>:Main")
-Ghci2._result :: a = _
-Ghci3._result :: IO a = _
 _result :: a = _
 _exception :: SomeException = SomeException
                                 (ErrorCallWithLocation

testsuite/tests/ghci.debugger/scripts/hist001.stdout

@@ -12,7 +12,6 @@ Logged breakpoint at Test3.hs:2:22-31
 _result :: [a]
 f :: t -> a
 xs :: [t]
-Ghci1._result :: [a] = _
 xs :: [t] = []
 f :: t -> a = _
 _result :: [a] = _
@@ -20,10 +19,7 @@ Logged breakpoint at Test3.hs:2:18-20
 _result :: a
 f :: Integer -> a
 x :: Integer
-Ghci1._result :: [a] = _
 xs :: [t] = []
-Ghci2.f :: t -> a = _
-Ghci2._result :: [a] = _
 x :: Integer = 2
 f :: Integer -> a = _
 _result :: a = _

testsuite/tests/ghci.debugger/scripts/hist002.stdout

@@ -12,7 +12,6 @@ Logged breakpoint at Test3.hs:2:22-31
 _result :: [a]
 f :: t -> a
 xs :: [t]
-Ghci1._result :: [a] = _
 xs :: [t] = []
 f :: t -> a = _
 _result :: [a] = _
@@ -20,10 +19,7 @@ Logged breakpoint at Test3.hs:2:18-20
 _result :: a
 f :: Integer -> a
 x :: Integer
-Ghci1._result :: [a] = _
 xs :: [t] = []
-Ghci2.f :: t -> a = _
-Ghci2._result :: [a] = _
 x :: Integer = 2
 f :: Integer -> a = _
 _result :: a = _

testsuite/tests/ghci/scripts/T11547.script

-foo = foo
-:t Ghci1.foo
-foo = foo
-:t Ghci2.foo
-:t Ghci1.foo
-data Foo = Foo | Bar
-data Foo = Bar
-:t Foo
-:t Ghci3.Bar

testsuite/tests/ghci/scripts/T11547.stdout

-Ghci1.foo :: t
-Ghci2.foo :: t
-Ghci1.foo :: t
-Foo :: Ghci3.Foo
-Ghci3.Bar :: Ghci3.Foo

testsuite/tests/ghci/scripts/T2976.stdout

 test :: Integer = 0
 test = 0
 test :: Integer = 0
-Ghci1.test :: Integer = 0
 test :: [Char] = _
 test = "test"
-Ghci1.test :: Integer = 0
 test :: [Char] = "test"

testsuite/tests/ghci/scripts/all.T

@@ -238,7 +238,6 @@ test('T11376', normal, ghci_script, ['T11376.script'])
 test('T12007', normal, ghci_script, ['T12007.script'])
 test('T11975', normal, ghci_script, ['T11975.script'])
 test('T10963', normal, ghci_script, ['T10963.script'])
-test('T11547', normal, ghci_script, ['T11547.script'])
 test('T11721', normal, ghci_script, ['T11721.script'])
 test('T12520', normal, ghci_script, ['T12520.script'])
 test('T12091', [extra_run_opts('-fobject-code')], ghci_script,