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This commit exposes GHC's internal compiler pipeline through a `Hooks`
module in the GHC API. It currently allows you to hook:

 * Foreign import/exports declarations
 * The frontend up to type checking
 * The one shot compilation mode
 * Core compilation, and the module iface
 * Linking and the phases in DriverPhases.hs
 * Quasiquotation
Authored-by: Luite Stegeman <stegeman@gmail.com>
Authored-by: Edsko de Vries <edsko@well-typed.com>
Signed-off-by: Austin Seipp <austin@well-typed.com>

Also a small formatting change in GHCi :help

Thanks to Krzysztof Gogolewski (monoidal) for the first draft of this patch

The trace was being over-eager, which disturbs the typecheckers
careful knot-tying

There was a bit of clutter (tryTc stuff) caused by the
fact that tcLookupImported didn't return a MaybeErr.
Now it does.  That finishes up Trac #8004.

This fixes Trac #8333

Thanks to 'klao', who identified the cause and provided the patch

wordTyCon was treated as wired-in, but
  * It didn't have a WiredInName
  * It didn't appear in the list of wiredInTyCons

I'm not sure how anything worked!

In 6579a6c7 we removed existing comparison primops and introduced new ones
returning Int# instead of Bool. This commit (and associated commits in
array, base, dph, ghc-prim, integer-gmp, integer-simple, primitive, testsuite and
template-haskell) restores old names of primops. This allows us to keep
our API cleaner at the price of not having backwards compatibility.

This patch also temporalily disables fix for #8317 (optimization of
tagToEnum# at Core level). We need to fix #8326 first, otherwise
our primops code will be very slow.

It's much easier (and more efficient) to pattern match on
the HsOverLit than on the desugared version!

See Note [Optimising tagToEnum#] in Simplify

If we have
   class (F a ~ b) => C a b
then we can produce *derived* CFunEqCans.  These were not being
treated properly in two places:

a) in TcMType.zonkFlats (Trac #8134)
b) in TcSMonad.prepareInertsForImplications (Trac #8129)

This patch fixes both.

* Make isCFunEqCan_maybe return Maybe (TyCon, [Type])
* Add insertTM, deleteTM to TrieMap

It is off by default, which is meant to be a workaround for #8275.
Once #8275 is fixed we will enable this option by default.

If someone also feels that credits should better go into the
release announcement, just nuke the last line of that paragraph.

This commit adds a `{-# MINIMAL #-}` pragma, which defines the possible
minimal complete definitions for a class. The body of the pragma is a
boolean formula of names.

The old warning for missing methods is replaced with this new one.

Note: The interface file format is changed to store the minimal complete
definition.
Authored-by: Twan van Laarhoven <twanvl@gmail.com>
Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

This is temporary until new bool primops have been pushed.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

This fixes bugs #8185, #8234, and #8246. The new syntax is explained
in the comments to #8185, appears in the "Roles" subsection of the
manual, and on the [wiki:Roles] wiki page.

This change also removes the ability for a role annotation on type
synonyms, as noted in #8234.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

now brought to you by Gabor Greif... ;-)