Refactor: simplify lexing of the dot

Before this patch, the lexer did a truly roundabout thing with the dot:

1. look up the varsym in reservedSymsFM and turn it into ITdot
2. under OverloadedRecordDot, turn it into ITvarsym
3. in varsym_(prefix|suffix|...) turn it into ITvarsym, ITdot, or
   ITproj, depending on extensions and whitespace

Turns out, the last step is sufficient to handle the dot correctly.
This patch removes the first two steps.

compiler/GHC/Parser/Lexer.x

@@ -1057,9 +1057,6 @@ reservedSymsFM = listToUFM $
 
        ,("*",   ITstar NormalSyntax,        NormalSyntax,  xbit StarIsTypeBit)
 
-        -- For 'forall a . t'
-       ,(".",   ITdot,                      NormalSyntax,  0 )
-
        ,("-<",  ITlarrowtail NormalSyntax,  NormalSyntax,  xbit ArrowsBit)
        ,(">-",  ITrarrowtail NormalSyntax,  NormalSyntax,  xbit ArrowsBit)
        ,("-<<", ITLarrowtail NormalSyntax,  NormalSyntax,  xbit ArrowsBit)
@@ -1726,13 +1723,8 @@ consym = sym (\_span _exts s -> return $ ITconsym s)
 sym :: (PsSpan -> ExtsBitmap -> FastString -> P Token) -> Action
 sym con span buf len =
   case lookupUFM reservedSymsFM fs of
-    Just (keyword, NormalSyntax, 0) -> do
-      exts <- getExts
-      if fs == fsLit "." &&
-         exts .&. (xbit OverloadedRecordDotBit) /= 0 &&
-         xtest OverloadedRecordDotBit exts
-      then L span <$!> con span exts fs  -- Process by varsym_*.
-      else return $ L span keyword
+    Just (keyword, NormalSyntax, 0) ->
+      return $ L span keyword
     Just (keyword, NormalSyntax, i) -> do
       exts <- getExts
       if exts .&. i /= 0

testsuite/tests/typecheck/should_compile/abstract_refinement_hole_fits.stderr

@@ -35,7 +35,7 @@ abstract_refinement_hole_fits.hs:4:5: warning: [-Wtyped-holes (in -Wdefault)]
           where const :: forall a b. a -> b -> a
         curry (_ :: (t0, [Integer]) -> Integer) (_ :: t0)
           where curry :: forall a b c. ((a, b) -> c) -> a -> b -> c
-        (.) (_ :: b1 -> Integer) (_ :: [Integer] -> b1)
+        (.) (_ :: b3 -> Integer) (_ :: [Integer] -> b3)
           where (.) :: forall b c a. (b -> c) -> (a -> b) -> a -> c
         flip (_ :: [Integer] -> t0 -> Integer) (_ :: t0)
           where flip :: forall a b c. (a -> b -> c) -> b -> a -> c
@@ -89,7 +89,7 @@ abstract_refinement_hole_fits.hs:4:5: warning: [-Wtyped-holes (in -Wdefault)]
           where head :: forall a. GHC.Stack.Types.HasCallStack => [a] -> a
         last (_ :: [t0 -> [Integer] -> Integer]) (_ :: t0)
           where last :: forall a. GHC.Stack.Types.HasCallStack => [a] -> a
-        fst (_ :: (t0 -> [Integer] -> Integer, b2)) (_ :: t0)
+        fst (_ :: (t0 -> [Integer] -> Integer, b1)) (_ :: t0)
           where fst :: forall a b. (a, b) -> a
         snd (_ :: (a2, t0 -> [Integer] -> Integer)) (_ :: t0)
           where snd :: forall a b. (a, b) -> b
@@ -111,7 +111,7 @@ abstract_refinement_hole_fits.hs:4:5: warning: [-Wtyped-holes (in -Wdefault)]
           where snd :: forall a b. (a, b) -> b
         const (_ :: [Integer] -> Integer) (_ :: t0)
           where const :: forall a b. a -> b -> a
-        uncurry (_ :: a3 -> b3 -> [Integer] -> Integer) (_ :: (a3, b3))
+        uncurry (_ :: a3 -> b2 -> [Integer] -> Integer) (_ :: (a3, b2))
           where uncurry :: forall a b c. (a -> b -> c) -> (a, b) -> c
         seq (_ :: t2) (_ :: [Integer] -> Integer)
           where seq :: forall a b. a -> b -> b
@@ -152,7 +152,7 @@ abstract_refinement_hole_fits.hs:7:5: warning: [-Wtyped-holes (in -Wdefault)]
           where const :: forall a b. a -> b -> a
         curry (_ :: (t0, Integer) -> [Integer] -> Integer) (_ :: t0)
           where curry :: forall a b c. ((a, b) -> c) -> a -> b -> c
-        (.) (_ :: b1 -> [Integer] -> Integer) (_ :: Integer -> b1)
+        (.) (_ :: b3 -> [Integer] -> Integer) (_ :: Integer -> b3)
           where (.) :: forall b c a. (b -> c) -> (a -> b) -> a -> c
         flip (_ :: Integer -> t0 -> [Integer] -> Integer) (_ :: t0)
           where flip :: forall a b c. (a -> b -> c) -> b -> a -> c
@@ -209,7 +209,7 @@ abstract_refinement_hole_fits.hs:7:5: warning: [-Wtyped-holes (in -Wdefault)]
           where head :: forall a. GHC.Stack.Types.HasCallStack => [a] -> a
         last (_ :: [t0 -> Integer -> [Integer] -> Integer]) (_ :: t0)
           where last :: forall a. GHC.Stack.Types.HasCallStack => [a] -> a
-        fst (_ :: (t0 -> Integer -> [Integer] -> Integer, b2)) (_ :: t0)
+        fst (_ :: (t0 -> Integer -> [Integer] -> Integer, b1)) (_ :: t0)
           where fst :: forall a b. (a, b) -> a
         snd (_ :: (a2, t0 -> Integer -> [Integer] -> Integer)) (_ :: t0)
           where snd :: forall a b. (a, b) -> b
@@ -232,8 +232,8 @@ abstract_refinement_hole_fits.hs:7:5: warning: [-Wtyped-holes (in -Wdefault)]
           where snd :: forall a b. (a, b) -> b
         const (_ :: Integer -> [Integer] -> Integer) (_ :: t0)
           where const :: forall a b. a -> b -> a
-        uncurry (_ :: a3 -> b3 -> Integer -> [Integer] -> Integer)
-                (_ :: (a3, b3))
+        uncurry (_ :: a3 -> b2 -> Integer -> [Integer] -> Integer)
+                (_ :: (a3, b2))
           where uncurry :: forall a b c. (a -> b -> c) -> (a, b) -> c
         seq (_ :: t2) (_ :: Integer -> [Integer] -> Integer)
           where seq :: forall a b. a -> b -> b