Fix #8759 by not panicking with TH and patsyns.

We should still have pattern synonyms in TH, though.

compiler/deSugar/DsMeta.hs

@@ -1238,7 +1238,7 @@ rep_bind (L _ (VarBind { var_id = v, var_rhs = e}))
         ; return (srcLocSpan (getSrcLoc v), ans) }
 
 rep_bind (L _ (AbsBinds {}))  = panic "rep_bind: AbsBinds"
-rep_bind (L _ (PatSynBind {})) = panic "rep_bind: PatSynBind"
+rep_bind (L _ dec@(PatSynBind {})) = notHandled "pattern synonyms" (ppr dec)
 -----------------------------------------------------------------------------
 -- Since everything in a Bind is mutually recursive we need rename all
 -- all the variables simultaneously. For example:

compiler/typecheck/TcSplice.lhs

@@ -70,6 +70,7 @@ import Class
 import Inst
 import TyCon
 import CoAxiom
+import PatSyn ( patSynId )
 import ConLike
 import DataCon
 import TcEvidence( TcEvBinds(..) )
@@ -1173,6 +1174,8 @@ reifyThing (AGlobal (AConLike (RealDataCon dc)))
         ; return (TH.DataConI (reifyName name) ty
                               (reifyName (dataConOrigTyCon dc)) fix)
         }
+reifyThing (AGlobal (AConLike (PatSynCon ps)))
+  = noTH (sLit "pattern synonyms") (ppr $ patSynId ps)
 
 reifyThing (ATcId {tct_id = id})
   = do  { ty1 <- zonkTcType (idType id) -- Make use of all the info we have, even

testsuite/tests/th/T8759.hs

+{-# LANGUAGE TemplateHaskell, PatternSynonyms #-}
+
+module T8759 where
+
+import Language.Haskell.TH
+
+pattern P = ()
+
+$( do info <- reify 'P
+      reportWarning (show info)
+      return [] )

testsuite/tests/th/T8759.stderr

+
+T8759.hs:9:4:
+    Can't represent pattern synonyms in Template Haskell: P

testsuite/tests/th/T8759a.hs

+{-# LANGUAGE TemplateHaskell, PatternSynonyms #-}
+
+module T8759a where
+
+foo = [d| pattern Q = False |]

testsuite/tests/th/T8759a.stderr

+
+T8759a.hs:5:7:
+    pattern synonyms not (yet) handled by Template Haskell
+      pattern Q = False

testsuite/tests/th/all.T

@@ -317,3 +317,5 @@ test('T8577',
      ['T8577', '-v0 ' + config.ghc_th_way_flags])
 test('T8633', normal, compile_and_run, [''])
 test('T8625', normal, ghci_script, ['T8625.script'])
+test('T8759', normal, compile_fail, ['-v0'])
+test('T8759a', normal, compile_fail, ['-v0'])
\ No newline at end of file