Fix #11287.

Happily, the fix is simply deleting some old code. I love it when
that happens.

compiler/coreSyn/CoreUtils.hs

@@ -616,7 +616,7 @@ refineDefaultAlt us tycon tys imposs_deflt_cons all_alts
         -- Check for no data constructors
         -- This can legitimately happen for abstract types and type families,
         -- so don't report that
-  = pprTrace "prepareDefault" (ppr tycon) (False, all_alts)
+  = (False, all_alts)
 
   | otherwise      -- The common case
   = (False, all_alts)

compiler/typecheck/TcMatches.hs

@@ -117,13 +117,6 @@ tcMatchesCase :: (Outputable (body Name)) =>
                  -- wrapper goes from MatchGroup's ty to expected ty
 
 tcMatchesCase ctxt scrut_ty matches res_ty
-  | isEmptyMatchGroup matches   -- Allow empty case expressions
-  = return (MG { mg_alts = noLoc []
-               , mg_arg_tys = [scrut_ty]
-               , mg_res_ty = res_ty
-               , mg_origin = mg_origin matches })
-
-  | otherwise
   = do { res_ty <- tauifyMultipleMatches matches res_ty
        ; tcMatches ctxt [scrut_ty] res_ty matches }
 
@@ -220,8 +213,7 @@ data TcMatchCtxt body   -- c.f. TcStmtCtxt, also in this module
 
 tcMatches ctxt pat_tys rhs_ty (MG { mg_alts = L l matches
                                   , mg_origin = origin })
-  = ASSERT( not (null matches) )        -- Ensure that rhs_ty is filled in
-    do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
+  = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
        ; return (MG { mg_alts = L l matches'
                     , mg_arg_tys = pat_tys
                     , mg_res_ty = rhs_ty

testsuite/tests/th/all.T

@@ -272,7 +272,7 @@ test('T7532',
      ['T7532', '-v0 ' + config.ghc_th_way_flags])
 test('T2222', normal, compile, ['-v0'])
 test('T1849', normal, ghci_script, ['T1849.script'])
-test('T7681', when(compiler_debugged(), expect_broken(11287)), compile, ['-v0'])
+test('T7681', normal, compile, ['-v0'])
 test('T7910', normal, compile_and_run, ['-v0'])
 
 test('ClosedFam1TH', normal, compile, ['-dsuppress-uniques -v0'])