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During parsing, GHC collects lexical information about AST nodes and
stores it in a map. It is needed to faithfully restore original source
code, e.g. compare these expressions:

	a =  b
	a  = b

The position of the equality sign is not recorded in the AST, so it must
be stored elsewhere.

This system is described in Note [Api annotations].

Before this patch, the mapping was represented by:

	Map (SrcSpan, AnnKeywordId) SrcSpan

After this patch, the mapping is represented by:

	Map (RealSrcSpan, AnnKeywordId) RealSrcSpan

The motivation behind this change is to avoid using the Ord SrcSpan
instance (required by Map here), as it interferes with #17632 (see the
discussion there).

SrcSpan is isomorphic to  Either String RealSrcSpan,  but we shouldn't
use those strings as Map keys. Those strings are intended as hints to
the user, e.g. "<interactive>" or "<compiler-generated code>", so they
are not a valid way to identify nodes in the source code.

For an API annotation to be useful, it must not occur before the span
it is enclosed in.

So, for check-api-annotation output, a line such as

((Test16212.hs:3:22-36,AnnOpenP), [Test16212.hs:3:21]),

should be flagged as an error, as the AnnOpenP location of 3:21
precedes its enclosing span of 3:22-26.

This patch does this.

Closes #16217

This implements the `DerivingVia` proposal put forth in
https://github.com/ghc-proposals/ghc-proposals/pull/120.

This introduces the `DerivingVia` deriving strategy. This is a
generalization of `GeneralizedNewtypeDeriving` that permits the user
to specify the type to `coerce` from.

The major change in this patch is the introduction of the
`ViaStrategy` constructor to `DerivStrategy`, which takes a type
as a field. As a result, `DerivStrategy` is no longer a simple
enumeration type, but rather something that must be renamed and
typechecked. The process by which this is done is explained more
thoroughly in section 3 of this paper
( https://www.kosmikus.org/DerivingVia/deriving-via-paper.pdf ),
although I have inlined the relevant parts into Notes where possible.

There are some knock-on changes as well. I took the opportunity to
do some refactoring of code in `TcDeriv`, especially the
`mkNewTypeEqn` function, since it was bundling all of the logic for
(1) deriving instances for newtypes and
(2) `GeneralizedNewtypeDeriving`
into one huge broth. `DerivingVia` reuses much of part (2), so that
was factored out as much as possible.

Bumps the Haddock submodule.

Test Plan: ./validate

Reviewers: simonpj, bgamari, goldfire, alanz

Subscribers: alanz, goldfire, rwbarton, thomie, mpickering, carter

GHC Trac Issues: #15178

Differential Revision: https://phabricator.haskell.org/D4684

This adds support for adding Haddocks on individual non-record fields
of regular (and GADT) constructors. The following now parses just fine
with `-haddock` enabled:

data Foo
  = Baz             -- ^ doc on the `Baz` constructor
      Int           -- ^ doc on the `Int` field of `Baz`
      String        -- ^ doc on the `String` field of `Baz`

  | Int             -- ^ doc on the `Int` field of the `:*` constructor
      :*            -- ^ doc on the `:*` constructor
    String          -- ^ doc on the `String` field of the `:*`
constructor

  | Boa             -- ^ doc on the `Boa` record constructor
      { y :: () }

The change is backwards compatible: if there is only one doc and it
occurs
on the last field, it is lifted to apply to the whole constructor (as
before).

Reviewers: bgamari, alanz

Subscribers: rwbarton, thomie, mpickering, carter

Differential Revision: https://phabricator.haskell.org/D4292

Summary:
This also changes the backpack Renaming type to use a Maybe for the
renameTo field, to more accurately reflect the parsed source.

Updates haddock submodule to match AST changes

Test Plan: ./validate

Reviewers: ezyang, bgamari, austin

Reviewed By: bgamari

Subscribers: thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D2670

This implements the ideas originally put forward in
"System FC with Explicit Kind Equality" (ICFP'13).

There are several noteworthy changes with this patch:
 * We now have casts in types. These change the kind
   of a type. See new constructor `CastTy`.

 * All types and all constructors can be promoted.
   This includes GADT constructors. GADT pattern matches
   take place in type family equations. In Core,
   types can now be applied to coercions via the
   `CoercionTy` constructor.

 * Coercions can now be heterogeneous, relating types
   of different kinds. A coercion proving `t1 :: k1 ~ t2 :: k2`
   proves both that `t1` and `t2` are the same and also that
   `k1` and `k2` are the same.

 * The `Coercion` type has been significantly enhanced.
   The documentation in `docs/core-spec/core-spec.pdf` reflects
   the new reality.

 * The type of `*` is now `*`. No more `BOX`.

 * Users can write explicit kind variables in their code,
   anywhere they can write type variables. For backward compatibility,
   automatic inference of kind-variable binding is still permitted.

 * The new extension `TypeInType` turns on the new user-facing
   features.

 * Type families and synonyms are now promoted to kinds. This causes
   trouble with parsing `*`, leading to the somewhat awkward new
   `HsAppsTy` constructor for `HsType`. This is dispatched with in
   the renamer, where the kind `*` can be told apart from a
   type-level multiplication operator. Without `-XTypeInType` the
   old behavior persists. With `-XTypeInType`, you need to import
   `Data.Kind` to get `*`, also known as `Type`.

 * The kind-checking algorithms in TcHsType have been significantly
   rewritten to allow for enhanced kinds.

 * The new features are still quite experimental and may be in flux.

 * TODO: Several open tickets: #11195, #11196, #11197, #11198, #11203.

 * TODO: Update user manual.

Tickets addressed: #9017, #9173, #7961, #10524, #8566, #11142.
Updates Haddock submodule.

Summary:
At the moment there is no way to tell if a given token used its unicode
variant or its normal one, except to look at the length of the token.

This fails for the unicode '*'.

Expose the original source text for unicode variants so that API
Annotations can capture them specifically.

Test Plan: ./validate

Reviewers: mpickering, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1473

GHC Trac Issues: #11018

A utility to check API Annotations was provided in
https://git.haskell.org/ghc.git/commitdiff/43751b2436f370d956d8021b3cdd3
eb77801470b

This commit had poor documentation.

This patch improves the output generated by the utility as well as
supplying better documentation

Test Plan: ./validate

Reviewers: simonpj, austin, bgamari

Reviewed By: austin, bgamari

Subscribers: thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D1397

GHC Trac Issues: #10917

Summary:
At the moment the API Annotations tests have a driver that has been
copy/pasted multiple times.

Compile it once, and run it for each test case.

Test Plan: ./validate

Reviewers: hvr, austin

Reviewed By: austin

Subscribers: bgamari, thomie

Differential Revision: https://phabricator.haskell.org/D913

GHC Trac Issues: #10452

Summary:
When mkGadtDecl is presented wih a HsFunTy it discards the SrcSpan, thus
disconnecting any annotations on the HsFunTy.

```
mkGadtDecl names (L ls (HsForAllTy imp Nothing qvars cxt tau))
  = return $ mk_gadt_con names
  where
    (details, res_ty)           -- See Note [Sorting out the result type]
      = case tau of
          L _ (HsFunTy (L l (HsRecTy flds)) res_ty)
                                            -> (RecCon (L l flds), res_ty)
          _other                                    -> (PrefixCon [], tau)
...
```

This can be triggered by the following

```
{-# LANGUAGE GADTs #-}
module GADTRecords2 (H1(..)) where

-- | h1
data H1 a b where
  C3 :: (Num a) => { field :: a -- ^ hello docs
                   } -> H1 Int Int
```

Test Plan: ./validate

Reviewers: hvr, austin

Reviewed By: austin

Subscribers: bgamari, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D848

GHC Trac Issues: #10309

Summary:
The parser production for squals has

    : squals ',' transformqual
             {% addAnnotation (gl $ last $ unLoc $1) AnnComma (gl $2) >>
                ams (sLL $1 $> ()) (fst $ unLoc $3) >>
                return (sLL $1 $> [sLL $1 $> ((snd $ unLoc $3) (reverse (unLoc $1)))]) }

This attaches the comma to the wrong part of the squals, as it is
generated in reverse order.

Test Plan: ./validate

Reviewers: hvr, austin

Reviewed By: austin

Subscribers: bgamari, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D846

GHC Trac Issues: #10312