Avoid incomplete-uni-patterns in `GHC.Types.Literal`.

We do so by introducing `mkLitNumberWrap'` whose ultimate codomain is `Integer` rather than `Literal`, and then use that rather than `mkLitNumberWrap` where we just need the number rather than the `Literal`.

compiler/GHC/Types/Literal.hs

@@ -9,8 +9,6 @@
 {-# LANGUAGE MagicHash #-}
 {-# LANGUAGE AllowAmbiguousTypes #-}
 
-{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-
 -- | Core literals
 module GHC.Types.Literal
         (
@@ -328,7 +326,12 @@ Int/Word range.
 -- | Make a literal number using wrapping semantics if the value is out of
 -- bound.
 mkLitNumberWrap :: Platform -> LitNumType -> Integer -> Literal
-mkLitNumberWrap platform nt i = case nt of
+mkLitNumberWrap platform nt i = LitNumber nt $ mkLitNumberWrap' platform nt i
+
+-- | Make a literal number using wrapping semantics if the value is out of
+-- bound.
+mkLitNumberWrap' :: Platform -> LitNumType -> Integer -> Integer
+mkLitNumberWrap' platform nt i = case nt of
   LitNumInt -> case platformWordSize platform of
     PW4 -> wrap @Int32
     PW8 -> wrap @Int64
@@ -345,10 +348,10 @@ mkLitNumberWrap platform nt i = case nt of
   LitNumWord64  -> wrap @Word64
   LitNumBigNat
     | i < 0     -> panic "mkLitNumberWrap: trying to create a negative BigNat"
-    | otherwise -> LitNumber nt i
+    | otherwise -> i
   where
-    wrap :: forall a. (Integral a, Num a) => Literal
-    wrap = LitNumber nt (toInteger (fromIntegral i :: a))
+    wrap :: forall a. (Integral a, Num a) => Integer
+    wrap = toInteger (fromIntegral i :: a)
 
 -- | Wrap a literal number according to its type using wrapping semantics.
 litNumWrap :: Platform -> Literal -> Literal
@@ -364,9 +367,7 @@ litNumCoerce _  _        l                 = pprPanic "litNumWrapCoerce: not a n
 -- converting it back to its original type.
 litNumNarrow :: LitNumType -> Platform -> Literal -> Literal
 litNumNarrow pt platform (LitNumber nt i)
-   = case mkLitNumberWrap platform pt i of
-      LitNumber _ j -> mkLitNumberWrap platform nt j
-      l             -> pprPanic "litNumNarrow: got invalid literal" (ppr l)
+   = mkLitNumberWrap platform nt . mkLitNumberWrap' platform pt $ i
 litNumNarrow _ _ l = pprPanic "litNumNarrow: invalid literal" (ppr l)
 
 
@@ -429,9 +430,9 @@ mkLitIntUnchecked i = LitNumber LitNumInt i
 --   the argument is wrapped and the overflow flag will be set.
 --   See Note [Word/Int underflow/overflow]
 mkLitIntWrapC :: Platform -> Integer -> (Literal, Bool)
-mkLitIntWrapC platform i = (n, i /= i')
+mkLitIntWrapC platform i = (LitNumber LitNumInt i', i /= i')
   where
-    n@(LitNumber _ i') = mkLitIntWrap platform i
+    i' = mkLitNumberWrap' platform LitNumInt i
 
 -- | Creates a 'Literal' of type @Word#@
 mkLitWord :: Platform -> Integer -> Literal
@@ -453,9 +454,9 @@ mkLitWordUnchecked i = LitNumber LitNumWord i
 --   the argument is wrapped and the carry flag will be set.
 --   See Note [Word/Int underflow/overflow]
 mkLitWordWrapC :: Platform -> Integer -> (Literal, Bool)
-mkLitWordWrapC platform i = (n, i /= i')
+mkLitWordWrapC platform i = (LitNumber LitNumWord i', i /= i')
   where
-    n@(LitNumber _ i') = mkLitWordWrap platform i
+    i' = mkLitNumberWrap' platform LitNumWord i
 
 -- | Creates a 'Literal' of type @Int8#@
 mkLitInt8 :: Integer -> Literal