Comments only
Test #7484 in th/T7484
Fix #7484, checking for good binder names in Convert.

This commit also refactors a bunch of lexeme-oriented code into
a new module Lexeme, and includes a submodule update for haddock.
Test #1476 in th/T1476
Test that nested pattern splices don't scope (#1476).

Test case: th/T1476b.
Fix #1476 by making splice patterns work.

Unfortunately, splice patterns in brackets still do not work
because we don't run splices in brackets. Without running a pattern
splice, we can't know what variables it binds, so we're stuck.

This is still a substantial improvement, and it may be the best
we can do. Still must document new behavior.
Release notes for #1476, #7484.
Test #9824 in th/T9824
Fix #9824 by not warning about unused matches in pattern quotes.
Update manual for pattern splices (#1476)
AST changes to prepare for API annotations, for #9628

Summary:
AST changes to prepare for API annotations

Add locations to parts of the AST so that API annotations can
then be added.

The outline of the whole process is captured here
https://ghc.haskell.org/trac/ghc/wiki/GhcAstAnnotations

This change updates the haddock submodule.

Test Plan: sh ./validate

Reviewers: austin, simonpj, Mikolaj

Reviewed By: simonpj, Mikolaj

Subscribers: thomie, goldfire, carter

Differential Revision: https://phabricator.haskell.org/D426

GHC Trac Issues: #9628
Add API Annotations

Summary:
The final design and discussion is captured at
https://ghc.haskell.org/trac/ghc/wiki/GhcAstAnnotations

This is a proof of concept implementation of a completely
separate annotation structure, populated in the parser,and tied to the
AST by means of a virtual "node-key" comprising the surrounding
SrcSpan and a value derived from the specific constructor used for the
node.

The key parts of the design are the following.

== The Annotations ==

In `hsSyn/ApiAnnotation.hs`

```lang=haskell
type ApiAnns = (Map.Map ApiAnnKey SrcSpan, Map.Map SrcSpan [Located Token])

type ApiAnnKey = (SrcSpan,AnnKeywordId)

-- ---------------------------------------------------------------------

-- | Retrieve an annotation based on the @SrcSpan@ of the annotated AST
-- element, and the known type of the annotation.
getAnnotation :: ApiAnns -> SrcSpan -> AnnKeywordId -> Maybe SrcSpan
getAnnotation (anns,_) span ann = Map.lookup (span,ann) anns

-- |Retrieve the comments allocated to the current @SrcSpan@
getAnnotationComments :: ApiAnns -> SrcSpan -> [Located Token]
getAnnotationComments (_,anns) span =
  case Map.lookup span anns of
    Just cs -> cs
    Nothing -> []

-- | Note: in general the names of these are taken from the
-- corresponding token, unless otherwise noted
data AnnKeywordId
         = AnnAs
         | AnnBang
         | AnnClass
         | AnnClose -- ^ } or ] or ) or #) etc
         | AnnComma
         | AnnDarrow
         | AnnData
         | AnnDcolon
         ....
```

== Capturing in the lexer/parser ==

The annotations are captured in the lexer / parser by extending PState to include a field

In `parser/Lexer.x`

```lang=haskell
data PState = PState {
        ....
        annotations :: [(ApiAnnKey,SrcSpan)]
        -- Annotations giving the locations of 'noise' tokens in the
        -- source, so that users of the GHC API can do source to
        -- source conversions.
     }
```

The lexer exposes a helper function to add an annotation

```lang=haskell
addAnnotation :: SrcSpan -> Ann -> SrcSpan -> P ()
addAnnotation l a v = P $ \s -> POk s {
  annotations = ((AK l a), v) : annotations s
  } ()

```

The parser also has some helper functions of the form

```lang=haskell
type MaybeAnn = Maybe (SrcSpan -> P ())

gl = getLoc
gj x = Just (gl x)

ams :: Located a -> [MaybeAnn] -> P (Located a)
ams a@(L l _) bs = (mapM_ (\a -> a l) $ catMaybes bs) >> return a
```

This allows annotations to be captured in the parser by means of

```
ctypedoc :: { LHsType RdrName }
        : 'forall' tv_bndrs '.' ctypedoc {% hintExplicitForall (getLoc $1) >>
                                            ams (LL $ mkExplicitHsForAllTy $2 (noLoc []) $4)
                                                [mj AnnForall $1,mj AnnDot $3] }
        | context '=>' ctypedoc         {% ams (LL $ mkQualifiedHsForAllTy   $1 $3)
                                               [mj AnnDarrow $2] }
        | ipvar '::' type               {% ams (LL (HsIParamTy (unLoc $1) $3))
                                               [mj AnnDcolon $2] }
        | typedoc                       { $1 }
```

== Parse result ==

```lang-haskell
data HsParsedModule = HsParsedModule {
    hpm_module    :: Located (HsModule RdrName),
    hpm_src_files :: [FilePath],
       -- ^ extra source files (e.g. from #includes).  The lexer collects
       -- these from '# <file> <line>' pragmas, which the C preprocessor
       -- leaves behind.  These files and their timestamps are stored in
       -- the .hi file, so that we can force recompilation if any of
       -- them change (#3589)
    hpm_annotations :: ApiAnns
  }

-- | The result of successful parsing.
data ParsedModule =
  ParsedModule { pm_mod_summary   :: ModSummary
               , pm_parsed_source :: ParsedSource
               , pm_extra_src_files :: [FilePath]
               , pm_annotations :: ApiAnns }
```

This diff depends on D426

Test Plan: sh ./validate

Reviewers: austin, simonpj, Mikolaj

Reviewed By: simonpj, Mikolaj

Subscribers: Mikolaj, goldfire, thomie, carter

Differential Revision: https://phabricator.haskell.org/D438

GHC Trac Issues: #9628
Fixes ghci :unset -X<ext> so that it doesn't fail to reverse option. (fixes trac #9293)

Summary: ghci unset could not reverse language extensions.

Reviewers: hvr, thomie, austin

Reviewed By: hvr, thomie, austin

Subscribers: goldfire, hvr, thomie, carter

Differential Revision: https://phabricator.haskell.org/D516

GHC Trac Issues: #9293
Export more Packages functions

Summary:
This patch exports functions for finding the active package
databases and their locations from the Packages module. This
allows GHC API clients to use other tools, like Cabal, to gather
package information that's not directly available from the
binary package db.

Reviewers: duncan, austin

Reviewed By: austin

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D514
Add Data.Void to base (re #9814)

This adds the module `Data.Void` (formerly provided by Edward Kmett's `void`
package) to `base`.

The original Haskell98 compatible implementation has been modified to use
modern GHC features (among others this makes use of `EmptyCase` as
motivated by #2431), and `vacuousM` was dropped since it's redundant now
with the AMP in place.  Instances for classes not part of `base` had to be
dropped as well.

TODO: Documentation could be improved

Reviewed By: ekmett, austin

Differential Revision: https://phabricator.haskell.org/D506
Capture original source for literals

Summary:
Make HsLit and OverLitVal have original source strings, for source to
source conversions using the GHC API

This is part of the ongoing AST Annotations work, as captured in
https://ghc.haskell.org/trac/ghc/wiki/GhcAstAnnotations and
https://ghc.haskell.org/trac/ghc/ticket/9628#comment:28

The motivations for the literals is as follows

```lang=haskell
x,y :: Int
x = 0003
y = 0x04

s :: String
s = "\x20"

c :: Char
c = '\x20'

d :: Double
d = 0.00

blah = x
  where
    charH = '\x41'#
    intH = 0004#
    wordH = 005##
    floatH = 3.20#
    doubleH = 04.16##
    x = 1
```

Test Plan: ./sh validate

Reviewers: simonpj, austin

Reviewed By: simonpj, austin

Subscribers: thomie, goldfire, carter, simonmar

Differential Revision: https://phabricator.haskell.org/D412

GHC Trac Issues: #9628
Add 'fillBytes' to Foreign.Marshal.Utils.

fillBytes uses 'memset' to fill a memory area with a given byte value.

Reviewed By: austin, hvr

Differential Revision: https://phabricator.haskell.org/D465