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While the deriving machinery always unifies the kind of the typeclass
argument with the kind of the datatype, this proves not to be sufficient
to produce well kinded instances for some poly-kinded datatypes. For
example:

```
newtype Compose (f :: k2 -> *) (g :: k1 -> k2) (a :: k1)
  = Compose (f (g a)) deriving Functor
```

would fail because only `k1` would get unified with `*`, causing the
following
ill kinded instance to be generated:

```
instance (Functor (f :: k2 -> *), Functor (g :: * -> k2)) =>
  Functor (Compose f g) where ...
```

To prevent this, we need to take the subtypes and unify their kinds with
`* -> *`.

Fixes #10524 for good.

Test Plan: ./validate

Reviewers: simonpj, hvr, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2097

GHC Trac Issues: #10524, #10561

(cherry picked from commit aadde2b9)

  * `Identity` and `Const` now have `Num`, `Real`, `Integral`,
    `Fractional`, `Floating`, `RealFrac` and `RealFloat` instances

  * `Identity` and `Const` now have `Bits` and `FiniteBits` instances

  * `Identity` and `Const` now have `IsString` instances

Reviewers: RyanGlScott, austin, hvr, bgamari, ekmett

Reviewed By: ekmett

Subscribers: nomeata, ekmett, RyanGlScott, thomie

Differential Revision: https://phabricator.haskell.org/D2079

GHC Trac Issues: #11790

(cherry picked from commit 8b57cac5)

Previously, all kind arguments were being reified, which would cause
something like this:

```
type Id a = a
data Proxy (a :: Id k) = Proxy
```

to output

```
data Proxy (a :: Id * k) = Proxy
```

when `Proxy`'s `Info` is reified. The fix is simple: simply call
`filterOutInvisibleTypes` on the kind arguments of a kind synonym
application.

Fixes #11463.

Test Plan: ./validate

Reviewers: austin, bgamari, goldfire

Reviewed By: goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2081

GHC Trac Issues: #11463

(cherry picked from commit 02a5c580)

Now we check whether a closed type family's equation is headed with
the correct type before we kind-check the equation.

Also, instead of "expected only no parameters" we now generate the
message "expected no parameters".

Fixes #11623.

Reviewers: simonpj, austin, bgamari

Reviewed By: simonpj, bgamari

Subscribers: simonpj, goldfire, thomie

Differential Revision: https://phabricator.haskell.org/D2089

GHC Trac Issues: #11623

(cherry picked from commit 46e8f199)

(cherry picked from commit d935d209)

The Runtime Linker is currently eagerly loading all object files on all
platforms which do not use the system linker for `GHCi`.

The problem with this approach is that it requires all symbols to be
found.  Even those of functions never used/called. This makes the number
of libraries required to link things like `mingwex` quite high.

To work around this the `rts` was relying on a trick. It itself was
compiled with `MingW64-w`'s `GCC`. So it was already linked against
`mingwex`.  As such, it re-exported the symbols from itself.

While this worked it made it impossible to link against `mingwex` in
user libraries. And with this means no `C99` code could ever run in
`GHCi` on Windows without having the required symbols re-exported from
the rts.

Consequently this rules out a large number of packages on Windows.
SDL2, HMatrix etc.

After talking with @rwbarton I have taken the approach of loading entire
object files when a symbol is needed instead of doing the dependency
tracking on a per symbol basis. This is a lot less fragile and a lot
less complicated to implement.

The changes come down to the following steps:

1) modify the linker to and introduce a new state for ObjectCode:
   `Needed`.  A Needed object is one that is required for the linking to
   succeed.  The initial set consists of all Object files passed as
   arguments to the link.

2) Change `ObjectCode`'s to be indexed but not initialized or resolved.
   This means we know where we would load the symbols,
   but haven't actually done so.

3) Mark any `ObjectCode` belonging to `.o` passed as argument
   as required: ObjectState `NEEDED`.

4) During `Resolve` object calls, mark all `ObjectCode`
   containing the required symbols as `NEEDED`

5) During `lookupSymbol` lookups, (which is called from `linkExpr`
   and `linkDecl` in `GHCI.hs`) is the symbol is in a not-yet-loaded
   `ObjectCode` then load the `ObjectCode` on demand and return the
   address of the symbol. Otherwise produce an unresolved symbols error
   as expected.

6) On `unloadObj` we then change the state of the object and remove
   it's symbols from the `reqSymHash` table so it can be reloaded.

This change affects all platforms and OSes which use the runtime linker.
It seems there are no real perf tests for `GHCi`, but performance
shouldn't be impacted much. We gain a lot of time not loading all `obj`
files, and we lose some time in `lookupSymbol` when we're finding
sections that have to be loaded. The actual finding itself is O(1)
(Assuming the hashtnl is perfect)

It also consumes slighly more memory as instead of storing just the
address of a symbol I also store some other information, like if the
symbol is weak or not.

This change will break any packages relying on renamed POSIX functions
that were re-named and re-exported by the rts. Any packages following
the proper naming for functions as found on MSDN will work fine.

Test Plan: ./validate on all platforms which use the Runtime linker.

Reviewers: thomie, rwbarton, simonmar, erikd, bgamari, austin, hvr

Reviewed By: erikd

Subscribers: kgardas, gridaphobe, RyanGlScott, simonmar,
             rwbarton, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D1805

GHC Trac Issues: #11223

(cherry picked from commit 90538d86)

This patch brings in two improvements:
a) m32_allocator will now reuse the pages that are no longer
used by anyone else.
b) m32_allocator will preallocate the "filling" area,
so that the pages it allocates end up as a big chunk
instead of being allocated on demand in random places,
fragmenting the precious lower 2G address space.

Test Plan: testsuite - 3 tests failing with substTy asserts

Reviewers: ezyang, austin, bgamari, erikd, hsyl20, simonmar

Reviewed By: hsyl20, simonmar

Subscribers: hvr, thomie

Differential Revision: https://phabricator.haskell.org/D1976

(cherry picked from commit 82e36edc)

Windows uses wchar_t* for paths. The code committed won't compile for
Windows as the types are incorrect and the types in the branches of the
ternary operator aren't consistent.

Test Plan: ./validate --fast

Reviewers: austin, rwbarton, erikd, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1878

(cherry picked from commit 01c587c0)

Test Plan: Actually run validate. This fixes test linker_error3.

Reviewers: austin, erikd, bgamari

Reviewed By: erikd, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1874

(cherry picked from commit 73293109)

Test Plan: Used this to track down an issue I was having.

Reviewers: simonmar, austin, erikd, bgamari

Reviewed By: erikd, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1863

(cherry picked from commit 34519f08)

Fixes #11818, where haddock's documentation broke `make install` when
Sphinx is not available.

Otherwise we get a const-ness mismatch when we free the buffer, which
for some reason gcc 5.3 didn't notice.

(cherry picked from commit 378091c9)

Previously, deriving `Generic(1)` bailed out when attempting to
instantiate visible type parameters (#5939), but this instantiation
check was quite fragile and doesn't interact well with `-XTypeInType`.
It has been decided that `Generic(1)` shouldn't be subjected to this
check anyway, so it has been removed, and `gen_Generic_binds`'s
machinery has been updated to substitute the type variables in a
generated `Rep`/`Rep1` instance with the user-supplied type arguments.

In addition, this also refactors `Condition` in `TcDeriv` a bit. Namely,
since we no longer need `tc_args` to check any conditions, the `[Type]`
component of `Condition` has been removed.

Fixes #11732.

Test Plan: ./validate

Reviewers: goldfire, kosmikus, simonpj, bgamari, austin

Reviewed By: simonpj, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2061

GHC Trac Issues: #5939, #11732

(cherry picked from commit 7443e5c8)

I have no idea where "4.11" came from.

(cherry picked from commit ad532ded)

When the typechecker generates the error message for an out-of-scope
variable, it now uses the GlobalRdrEnv with respect to which the
variable is unbound, not the GlobalRdrEnv which is available at the time
the error is reported.  Doing so ensures we do not provide suggestions
which themselves are out-of-scope (because they are bound in a later
inter-splice group).

Nonetheless, we do note in the error message if an unambiguous, exact
match to the out-of-scope variable is found in a later inter-splice
group, and we specify where that match is not in scope.

Test Plan: ./validate

Reviewers: goldfire, austin, bgamari

Reviewed By: goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2000

GHC Trac Issues: #11680

(cherry picked from commit 470d4d5b)

Needed for constructing correct constraint-satisfying code
(particularly type class instances) in a Core-to-Core transformation.

Reviewers: simonpj, austin, bgamari

Reviewed By: austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2088

GHC Trac Issues: #11804

(cherry picked from commit 5a1add13)

The commit 28f951ed introduced the
`-fmax-pmcheck-iterations` flag and set the default limit to 1e7
iterations.

However, this value is still high enough that it can result GHC to
exhibit memory spikes beyond 1 GiB of RAM usage (heap profile showed
several `(:)`s, as well as `THUNK_2_0`, and `PmCon` during the memory
spikes)

A value of 2e6 seems to be a safer upper bound which still manages to
let the checker not run into the limit in most cases.

Test Plan: Validate, try building a few Hackage packages

Reviewers: austin, gkaracha, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2095

(cherry picked from commit d2e05c6b)

Record selectors of data types spliced in with Template Haskell are not
renamer-resolved correctly in GHC HEAD. The culprit is
`newRecordSelector` which violates notes `Note [Binders in Template
Haskell] in Convert.hs` and `Note [Looking up Exact RdrNames] in
RnEnv.hs`. This commit fixes `newRecordSelector` accordingly.

Test Plan: ./validate

Reviewers: thomie, mpickering, bgamari, austin, simonpj, goldfire

Reviewed By: goldfire

Differential Revision: https://phabricator.haskell.org/D2091

GHC Trac Issues: #11809

(cherry picked from commit 2f82da76)

This is another documentation addition similar to D1989, this time
comparing the type of the Kleisli composition operator (<=<) to that
of plain function composition (.).

Reviewers: hvr, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2100

(cherry picked from commit 90d66ded)

In my testing, the worker/wrapper transformation applied here
significantly decreases the number of allocations performed when using
replicateM_. Additionally, this version of the function behaves
correctly for negative numbers (namely, it will behave the same as
replicateM_ 0, which is what previous versions of base have done).

Reviewers: bgamari, simonpj, hvr, austin

Reviewed By: bgamari, simonpj, austin

Subscribers: nomeata, simonpj, mpickering, thomie

Differential Revision: https://phabricator.haskell.org/D2086

GHC Trac Issues: #11795

(cherry picked from commit c4a7520e)

69822f0c broke this as it held on to a
reference into the `arg` string, which is later freed. Humbug.

Test Plan: Try using filtering

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2090

GHC Trac Issues: #11810

(cherry picked from commit 535896e5)

Previously the `_static` and `_sources` directories were installed in
the wrong parents. See #11803

(cherry picked from commit 6b6bebaf)

This just adds the Prox stuff from the Description in Trac #11376
to the test case,

The class stuff seems weird becuase the type is ambiguous

(cherry picked from commit b3ecd047)

It's been quite a while since this has happened for some of our tests.

Shifts by amounts greater-than-or-equal-to the word size are undefined.

(cherry picked from commit 49c55e68)

See Trac #11376 and
 Note [Deeply instantiate in :type] in TcRnDriver

Sadly this showed up one new problem (Trac #11786) and one opportunity
(Trac #11787), so test T11549 is now marked expect-broken on these two.

(cherry picked from commit f2a2b79f)

This fixes a bug where warnings actually controlled by

- `Opt_WarnUnusedMatches`
- `Opt_WarnUnusedTypePatterns`
- `Opt_WarnUnusedTopBinds`

were incorrectly reported as being controlled by
`Opt_WarnUnusedLocalBinds` as well

This bug was introduced in bb5afd3c
while implementing #10752

Test Plan: ./validate still running -- testsuite output wiggles expected

Reviewers: barrucadu, quchen, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2077

(cherry picked from commit 003e0802fdc2b38b2c3e96cdd387619d33c44967)

Stable pointers can now be safely dereferenced while the stable pointer
table is simultaneously being enlarged.

Test Plan: ./validate

Reviewers: ezyang, austin, bgamari, simonmar

Subscribers: carter, thomie

Differential Revision: https://phabricator.haskell.org/D2031

GHC Trac Issues: #10296

(cherry picked from commit 90d7d608)

We originally wanted CallStacks to be opt-in, but dealing with let
binders complicated things, forcing us to infer CallStacks. It turns
out that the inference is actually unnecessary though, we can let the
wanted CallStacks bubble up to the outer context by refusing to
quantify over them. Eventually they'll be solved from a given CallStack
or defaulted to the empty CallStack if they reach the top.

So this patch prevents GHC from quantifying over CallStacks, getting us
back to the original plan. There's a small ugliness to do with
PartialTypeSignatures, if the partial theta contains a CallStack
constraint, we *do* want to quantify over the CallStack; the user asked
us to!

Note that this means that

  foo :: _ => CallStack
  foo = getCallStack callStack

will be an *empty* CallStack, since we won't infer a CallStack for the
hole in the theta. I think this is the right move though, since we want
CallStacks to be opt-in. One can always write

  foo :: (HasCallStack, _) => CallStack
  foo = getCallStack callStack

to get the CallStack and still have GHC infer the rest of the theta.

Test Plan: ./validate

Reviewers: goldfire, simonpj, austin, hvr, bgamari

Reviewed By: simonpj, bgamari

Subscribers: bitemyapp, thomie

Projects: #ghc

Differential Revision: https://phabricator.haskell.org/D1912

GHC Trac Issues: #11573

(cherry picked from commit 7407a66d)

(cherry picked from commit 9b6820cd)

Add the function `pprPatSynType :: PatSyn -> SDoc` for printing pattern
synonym types, and remove the ambiguous `patSynType` function. Also,
the types in a `PatSyn` are now tidy.

Haddock submodule updated to reflect the removal of `patSynType` by
mpickering.

Fixes: #11213.

Reviewers: goldfire, simonpj, austin, mpickering, bgamari

Reviewed By: simonpj, mpickering

Subscribers: bollmann, simonpj, thomie

Differential Revision: https://phabricator.haskell.org/D1896

GHC Trac Issues: #11213

(cherry picked from commit 72bd7f7b)

`ghc` fails without `-dep-suffix ''`.

Test Plan: visual inspection

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: thomie, simonmar

Differential Revision: https://phabricator.haskell.org/D2075

(cherry picked from commit 38068913)

Richard accidetally introduced this change in his big kind-equality
patch.  The code is wrong, and potentially could cause binders to
be re-ordered.

Worth merging to 8.0.

(cherry picked from commit da260a5b)

See Note [Eta-reduction in -O0] in DynFlags.

Bottom line: doing eta reduction unconditionally is benign, and
removes an ASSERT failure (Trac #11562).

(cherry picked from commit 85008555)