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the worker/wrapper creates an artificial INLINE pragma, which caused CSE
to not do its work. We now recognize such artificial pragmas by using
`NoUserInline` instead of `Inline` as the `InlineSpec`.

Differential Revision: https://phabricator.haskell.org/D3939

This is a pre-requisite for implementing the Semigroup/Monoid proposal.
The instances have been introduced in a way to minimise warnings.

We pretty-print a type by converting it to an IfaceType and
pretty-printing that.  But
 (a) that's a bit indirect, and
 (b) delibrately loses information about (e.g.) the kind
      on the /occurrences/ of a type variable

So this patch implements debugPprType, which pretty prints
the type directly, with no fancy formatting.  It's just used
for debugging.

I took the opportunity to refactor the debug-pretty-printing
machinery a little.  In particular, define these functions
and use them:

  ifPprDeubug :: SDoc -> SDOc -> SDoc
    -- Says what to do with and without -dppr-debug
  whenPprDebug :: SDoc -> SDoc
    -- Says what to do with  -dppr-debug; without is empty
  getPprDebug :: (Bool -> SDoc) -> SDoc

getPprDebug used to be called sdocPprDebugWith
whenPprDebug used to be called ifPprDebug

So a lot of files get touched in a very mechanical way

I prematurely committed the D3892 before adding a Note. Fix this.

This implements @simonpj's suggested refactoring of the abstract syntax
for type/data family instances (from
https://ghc.haskell.org/trac/ghc/ticket/14131#comment:9). This combines
the previously separate `TyFamEqn` and `DataFamInstDecl` types into a
single `FamEqn` datatype. This also factors the `HsImplicitBndrs` out of
`HsTyPats` in favor of putting them just outside of `FamEqn` (as opposed
to before, where all of the implicit binders were embedded inside of
`TyFamEqn`/`DataFamInstDecl`). Finally, along the way I noticed that
`dfid_fvs` and `tfid_fvs` were completely unused, so I removed them.

Aside from some changes in parser test output, there is no change in
behavior.

Requires a Haddock submodule commit from my fork (at
https://github.com/RyanGlScott/haddock/commit/815d2deb9c0222c916becccf84
64b740c26255fd)

Test Plan: ./validate

Reviewers: simonpj, austin, goldfire, bgamari, alanz

Reviewed By: bgamari

Subscribers: mpickering, goldfire, rwbarton, thomie, simonpj

GHC Trac Issues: #14131

Differential Revision: https://phabricator.haskell.org/D3881

Consider that we have two modules, A and B, both with hs-boot files,

  * A.hs contains a SOURCE import of B
  * B.hs-boot contains a SOURCE import of A
  * A.hs-boot declares an orphan instance
  * A.hs defines the orphan instance

In this case, B's dep_orphs will contain A due to its SOURCE import of
A.  Consequently, A will contain itself in its imp_orphs due to its
import of B.  This fact would end up being recorded in A's interface
file. This would then break the invariant asserted by calculateAvails
that a module does not itself in its dep_orphs. This was the cause
of #14128.

The solution is to remove self-references from imp_orphs when
constructing dep_orphs; we already did a similar thing for dep_mods. I
believe we should do the same for dep_finsts, although I'm treating this
as a separate bug.

Reviewers: austin

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3892

Instead of using a string argument, use HasDebugCallStack.
(Oddly, some functions were using both!)

Plus, use getRuntimeRep rather than getRuntimeRep_maybe when
if the caller panics on Nothing. Less code, and a better debug
stack.

The desugarer was using `targetRetainsAllBindings` as a litmus test for
determining if a function was defined in interactive mode (and thus
should be exported). However, there is a corner case where one can be in
interactive mode and have `targetRetainsAllBindings` return `False`: if
`-fobject-code` is enabled (since the target will no longer be
`HscInteractive`). In such a scenario, we should fall back on a
different test for determining if we are in a GHCi session. I chose to
use `isInteractiveModule`, which appears to do the trick.

Test Plan: make test TEST=T12091

Reviewers: austin, bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #12091

Differential Revision: https://phabricator.haskell.org/D3849

Summary:
In a267580e, I somewhat awkwardly
inserted a special case for `TYPE` in the `EmptyCase` coverage checker.
Instead of placing it there, @mpickering noted that `isClosedAlgType` would
be a better fit for it. I do just that in this patch.

I also renamed `isClosedAlgType` to `pmIsClosedType`, reflecting the fact that
`TYPE` technically isn't an algebraic type (it's a primitive one), and that its
behavior is pattern-match coverage checking-oriented. I also moved it to
`Check`, which is a better home for this function than `Type`. Luckily,
the only call sites for `isClosedAlgType` were in the pattern-match coverage
checker anyways, so this change is simple enough.

Test Plan: ./validate

Reviewers: mpickering, austin, goldfire, bgamari

Reviewed By: goldfire

Subscribers: rwbarton, thomie, mpickering

GHC Trac Issues: #14086

Differential Revision: https://phabricator.haskell.org/D3830

Summary:
`Type` (a.k.a. `TYPE LiftedRep`) can be used at the type level thanks
to `TypeInType`. However, expressions like

```lang=haskell
f :: Type -> Int
f x = case x of {}
```

were falsely claiming that the empty case on the value of type `Type` was
non-exhaustive. The reason is a bit silly: `TYPE` is technically not an empty
datatype in GHC's eyes, since it's a builtin, primitive type. To convince the
pattern coverage checker otherwise, this adds a special case for `TYPE`.

Test Plan: make test TEST=T14086

Reviewers: gkaracha, austin, bgamari, goldfire

Reviewed By: goldfire

Subscribers: goldfire, rwbarton, thomie

GHC Trac Issues: #14086

Differential Revision: https://phabricator.haskell.org/D3819

GHC 8.2.1 is out, so now GHC's support window only extends back to GHC
8.0. This means we can delete gobs of code that was only used for GHC
7.10 support. Hooray!

Test Plan: ./validate

Reviewers: hvr, bgamari, austin, goldfire, simonmar

Reviewed By: bgamari

Subscribers: Phyx, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3781

This is refactoring only... elimiante all positional uses
of the data constructor Match in favour of field names.

No change in behaviour.

See comment:22 in Trac #13594

Bizarrely, we were not rejecting
  !x = e

Fix:

* In the test in DsBinds.dsTopLHsBinds, use isBangedHsBind, not
  isBangedPatBind.  (Indeed the latter dies altogther.)

* Implement isBangedHsBind in HsUtils;
  be sure to handle AbsBinds

All this was shown up by Trac #13594

Trac #14035 showed that -XStrict was generating some TERRIBLE
desugarings, espcially for bindings with INLINE pragmas. Reason: with
-XStrict, all AbsBinds (even for non-recursive functions) went via the
general-case deguaring for AbsBinds, namely "generate a tuple and
select from it", even though in this case there was only one variable
in the tuple.  And that in turn interacts terribly badly with INLINE
pragmas.

This patch cleans things up:

* I killed off AbsBindsSig completely, in favour of a boolean flag
  abs_sig in AbsBinds.  See Note [The abs_sig field of AbsBinds]

  This allowed me to delete lots of code; and instance-method
  declarations can enjoy the benefits too.  (They could have
  before, but no one had changed them to use AbsBindsSig.)

* I refactored all the AbsBinds handling in DsBinds into a new
  function DsBinds.dsAbsBinds.  This allowed me to handle the
  strict case uniformly

* Clarify the comments around the mc_strictness field of FunRhs
* Use record field names consistently for FunRhs

Summary:
Types and kinds are now the same in GHC... well, except in the code
that involves Template Haskell, where types and kinds are given separate
treatment. This aims to unify that treatment in the `DsMeta` module.

The gist of this patch is replacing all uses of `repLKind` with `repLTy`.
This is isn't quite as simple as one might imagine, since `repLTy` returns a
`Core (Q Type)` (a monadic expression), whereas `repLKind` returns a
`Core Kind` (a pure expression). This causes many awkward impedance mismatches.

One option would be to change every combinator in `Language.Haskell.TH.Lib` to
take `KindQ` as an argument instead of `Kind`. But this would be a breaking
change of colossal proportions.

Instead, this patch takes a somewhat different approach. This migrates the
existing `Language.Haskell.TH.Lib` module to
`Language.Haskell.TH.Lib.Internal`, and changes all `Kind`-related combinators
in `Language.Haskell.TH.Lib.Internal` to live in `Q`. The new
`Language.Haskell.TH.Lib` module then re-exports most of
`Language.Haskell.TH.Lib.Internal` with the exception of the `Kind`-related
combinators, for which it redefines them to be their current definitions (which
don't live in `Q`). This allows us to retain backwards compatibility with
previous `template-haskell` releases, but more importantly, it allows GHC to
make as many changes to the `Internal` code as it wants for its purposes
without fear of disrupting the public API.

This solves half of #11785 (the other half being `TcSplice`).

Test Plan: ./validate

Reviewers: goldfire, austin, bgamari

Reviewed By: goldfire

Subscribers: rwbarton, thomie

GHC Trac Issues: #11785

Differential Revision: https://phabricator.haskell.org/D3751

In Check.hs (pattern match ovelap checking) we to figure out the
instantiation of a pattern synonym from the type of the pattern. We
were doing this utterly wrongly.  Trac #13768 demonstrated this
bogosity.

The fix is easy; and is described in PatSyn.hs
  Note [Pattern synonym result type]

Reviewers: RyanGlScott, austin, goldfire, bgamari

Reviewed By: RyanGlScott, goldfire, bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3715

This is another attempt at resolving #13594 by treating strict variable
binds as FunBinds instead of PatBinds (as suggested in comment:1).

Test Plan: Validate

Reviewers: austin, alanz

Subscribers: rwbarton, thomie, mpickering

GHC Trac Issues: #13594

Differential Revision: https://phabricator.haskell.org/D3670

`repNonArrowKind` was missing a case for `HsKindSig`, which this
commit adds. Fixes #13781.

Test Plan: make test TEST=T13781

Reviewers: goldfire, austin, bgamari

Reviewed By: goldfire

Subscribers: rwbarton, thomie

GHC Trac Issues: #13781

Differential Revision: https://phabricator.haskell.org/D3627

The problem was that the generated label included
a freshly assigned Unique value.

Test Plan:
Added a new test and looked at the generated stub:

```
 #include "HsFFI.h"
 #ifdef __cplusplus
 extern "C" {
 #endif
 extern HsInt zdmainzdAzdAzuzzlzzgzzg(StgStablePtr the_stableptr);
 extern HsInt zdmainzdAzdAzumkStringWriter(StgStablePtr the_stableptr);
 #ifdef __cplusplus
 }
 #endif
```

./validate

Reviewers: simonmar, austin, bgamari

Reviewed By: simonmar

Subscribers: rwbarton, thomie

GHC Trac Issues: #13807

Differential Revision: https://phabricator.haskell.org/D3633

Summary:
See https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow

This commit prepares the ground for a full extensible AST, by replacing the type
parameter for the hsSyn data types with a set of indices into type families,

    data GhcPs -- ^ Index for GHC parser output
    data GhcRn -- ^ Index for GHC renamer output
    data GhcTc -- ^ Index for GHC typechecker output

These are now used instead of `RdrName`, `Name` and `Id`/`TcId`/`Var`

Where the original name type is required in a polymorphic context, this is
accessible via the IdP type family, defined as

    type family IdP p
    type instance IdP GhcPs = RdrName
    type instance IdP GhcRn = Name
    type instance IdP GhcTc = Id

These types are declared in the new 'hsSyn/HsExtension.hs' module.

To gain a better understanding of the extension mechanism, it has been applied
to `HsLit` only, also replacing the `SourceText` fields in them with extension
types.

To preserve extension generality, a type class is introduced to capture the
`SourceText` interface, which must be honoured by all of the extension points
which originally had a `SourceText`.  The class is defined as

    class HasSourceText a where
      -- Provide setters to mimic existing constructors
      noSourceText  :: a
      sourceText    :: String -> a

      setSourceText :: SourceText -> a
      getSourceText :: a -> SourceText

And the constraint is captured in `SourceTextX`, which is a constraint type
listing all the extension points that make use of the class.

Updating Haddock submodule to match.

Test Plan: ./validate

Reviewers: simonpj, shayan-najd, goldfire, austin, bgamari

Subscribers: rwbarton, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D3609

While investigating #12545, I discovered several places in the code
that performed length-checks like so:

```
length ts == 4
```

This is not ideal, since the length of `ts` could be much longer than 4,
and we'd be doing way more work than necessary! There are already a slew
of helper functions in `Util` such as `lengthIs` that are designed to do
this efficiently, so I found every place where they ought to be used and
did just that. I also defined a couple more utility functions for list
length that were common patterns (e.g., `ltLength`).

Test Plan: ./validate

Reviewers: austin, hvr, goldfire, bgamari, simonmar

Reviewed By: bgamari, simonmar

Subscribers: goldfire, rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3622

This reverts commit 7fea7121.
It turns out that on a newly added MultiLayerModules test
case it gets very expensive to union the transitive module
sets while preserving determinism.

Fortunately, we can just sort to restore determinism
when converting imp_dep_mods to a list.

Test Plan: ./validate

Reviewers: simonmar, austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3577

This reverts commit e527fc2e.

I merged more than I intended in e527fc2e, I will merge
D3575 and D3577 separately.

I'm optimizing a case that is well approximated by
multiple layers of modules where every module in a layer
imports all the modules in the layer below.

It turns out I regressed performance on such cases in 7fea7121.
I'm adding a test case to track improvements and prevent
future regressions.

Test Plan: ./validate

Reviewers: simonmar, austin, bgamari

Reviewed By: simonmar

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3575

This partially reverts commit 37299536 as it
doesn't actually fix #13594. Namely it does not revert the mkPrefixFunRhs
refactoring since this is rather independent from the functional changes.

Going to try again with a whole working patch

Instead of excluding `isAnyInlinePragma`, just exclude
`isInlinePragma`. This makes GHC behave as documented;
the user's guide only indicates that GHC does not automatically
add SCCs to `INLINE` bindings.

Fixes #12962.

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: DemiMarie, osa1, Mikolaj, simonpj, rwbarton, thomie

GHC Trac Issues: #12962

Differential Revision: https://phabricator.haskell.org/D3550

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3565

Doug Wilson astutely noticed that the pattern match checker was spending
a significant amount of time in mkPmId. It turns out that it was
producing Ids with OccNames that were generated from a Unique, which are
non-trivial to render. Since Var is strict in Name, Name in OccName, and
OccName in its FastString all of this encoding work was being done
despite the fact that it was (as far as I can tell) never actually
needed.

Test Plan: Validate, note allocations of `T11195`

Reviewers: austin, gkaracha

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3568

This reworks the HsSyn representation to make banged variable patterns
(e.g. !x = e) be represented as FunBinds instead of PatBinds, adding a flag to
FunRhs to record the bang.

Fixes #13594.

Reviewers: austin, goldfire, alanz, simonpj

Reviewed By: simonpj

Subscribers: simonpj, rwbarton, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D3525

Reviewers: austin, goldfire, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie, mpickering

GHC Trac Issues: #13211

Differential Revision: https://phabricator.haskell.org/D3543

Gracious me.  Ever since this patch

  commit 37445780
  Author: Jan Stolarek <jan.stolarek@p.lodz.pl>
  Date:   Fri Jul 11 13:54:45 2014 +0200

      Injective type families

TcRnMonad.askNoErrs has been wrong. It looked like this

   askNoErrs :: TcRn a -> TcRn (a, Bool)
   askNoErrs m
    = do { errs_var <- newTcRef emptyMessages
         ; res  <- setErrsVar errs_var m
         ; (warns, errs) <- readTcRef errs_var
         ; addMessages (warns, errs)
         ; return (res, isEmptyBag errs) }

The trouble comes if 'm' throws an exception in the TcRn monad.
Then 'errs_var is never read, so any errors are simply lost.

This mistake was then propgated into DsMonad.dsWhenNoErrs, where
it gave rise to Trac #13642.

Thank to Ryan for narrowing it down so sharply.

I did some refactoring, as usual.

The implementation plan is all in Note [Detecting forced eta expansion]
in DsExpr.

Test Plan: ./validate, codeGen/should_fail/T13233

Reviewers: simonpj, austin, bgamari

Subscribers: rwbarton, thomie

GHC Trac Issues: #13233

Differential Revision: https://phabricator.haskell.org/D3490