[TTG: Handling Source Locations] Foundation and Pat

This patch removes the ping-pong style from HsPat (only, for now),
using the plan laid out at
https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow/HandlingSourceLocations (solution
A).

- the class `HasSrcSpan`, and its functions (e.g., `cL` and `dL`), are introduced
- some instances of `HasSrcSpan` are introduced
- some constructors `L` are replaced with `cL`
- some patterns `L` are replaced with `dL->L` view pattern
- some type annotation are necessarily updated (e.g., `Pat p` --> `Pat (GhcPass p)`)

Phab diff: D5036
Trac Issues #15495

Updates haddock submodule

1 files changed, 8 insertions, 2 deletions

diff --git a/compiler/main/GHC.hs b/compiler/main/GHC.hs
index da5ef8ba2d..8817b41c8a 100644
--- a/compiler/main/GHC.hs
+++ b/compiler/main/GHC.hs
@@ -1,5 +1,7 @@
 {-# LANGUAGE CPP, NondecreasingIndentation, ScopedTypeVariables #-}
 {-# LANGUAGE TupleSections, NamedFieldPuns #-}
+{-# LANGUAGE ViewPatterns #-}
+{-# LANGUAGE TypeFamilies #-}
 
 -- -----------------------------------------------------------------------------
 --
@@ -250,6 +252,10 @@ module GHC (
 
         -- *** Deconstructing Located
         getLoc, unLoc,
+        getRealSrcSpan, unRealSrcSpan,
+
+        -- ** HasSrcSpan
+        HasSrcSpan(..), SrcSpanLess, dL, cL,
 
         -- *** Combining and comparing Located values
         eqLocated, cmpLocated, combineLocs, addCLoc,
@@ -1380,7 +1386,7 @@ getRichTokenStream mod = do
 addSourceToTokens :: RealSrcLoc -> StringBuffer -> [Located Token]
                   -> [(Located Token, String)]
 addSourceToTokens _ _ [] = []
-addSourceToTokens loc buf (t@(L span _) : ts)
+addSourceToTokens loc buf (t@(dL->L span _) : ts)
     = case span of
       UnhelpfulSpan _ -> (t,"") : addSourceToTokens loc buf ts
       RealSrcSpan s   -> (t,str) : addSourceToTokens newLoc newBuf ts
@@ -1406,7 +1412,7 @@ showRichTokenStream ts = go startLoc ts ""
           getFile (RealSrcSpan s : _) = srcSpanFile s
           startLoc = mkRealSrcLoc sourceFile 1 1
           go _ [] = id
-          go loc ((L span _, str):ts)
+          go loc ((dL->L span _, str):ts)
               = case span of
                 UnhelpfulSpan _ -> go loc ts
                 RealSrcSpan s