Due to #17945.

The linear arrow can be parsed as `%1 ->` or a direct single token unicode
equivalent.

Make sure that this distinction is captured in the parsed AST by using
IsUnicodeSyntax where it appears, and introduce a new API Annotation,
AnnMult to represent its location when unicode is not used.

Updated haddock submodule

Previously the Hadrian jobs used the `FLAVOUR` environment variable to
communicate which flavour `ci.sh` should build whereas `make` used
`BUILD_FLAVOUR`. This caused unnecessary confusion. Consolidate these
two.

Compile modules with `-fobject-code` enabled to byte-code when loaded with `*` prefix in ghci (#8042)

The documentation states that when using :add and :load, the `*` prefix forces a module
to be loaded as byte-code. However, this seems to be ignored when -fobject-code has been
enabled. In that case, the compiled code is always used, regardless of whether the *-form
is used.

The idea is to consult the Targets in HscEnv and check the 'targetAllowObjCode' flag. If
the flag for given module is set, then patch up DynFlags and select compilation backend
accordingly.

This would require a linear scan of course, but that shouldn't be too costly.

- Update comments: placeHolderTypeTc no longer exists
  "another level check problem" was a temporary comment from linear types
- Use Mult type synonym (reported in #18676)
- Mention multiplicity-polymorphic fields in linear types docs

This was fixed by 4291bdda.

pdocPrec was only used in GHC.Cmm.DebugBlock.pprUnwindExpr, so remove
it. OutputableP becomes a one-function class which might be better for
performance.

This patch implements two related warnings:

  -Woperator-whitespace-ext-conflict
      warns on uses of infix operators that would be parsed
      differently were a particular GHC extension enabled

  -Woperator-whitespace
      warns on prefix, suffix, and tight infix uses of infix
      operators

Updates submodules: haddock, containers.

* Bring back LANGUAGE pragmas in GHC.IO.Handle.Lock.Windows
* Exclude some modules that are wrongfully reported

To correctly perform a linking hack for Windows we need to link with the
RTS GHC is currently using. We used to query the RTS ways via the
"settings" file but it is fragile (#18651). The hack hasn't been fixed
to take into account all the ways (Tracing) and it makes linking of GHC
with another RTS more difficult (we need to link with another RTS and to
regenerate the settings file).

So this patch uses the ways reported by the RTS itself
(GHC.Platform.Ways.hostWays) instead of the "settings" file.

This diff makes sure that incall threads, when using `rts_setInCallCapability`, will be created as locked.
If the thread is not locked, the thread might end up being scheduled to a different capability.
While this is mentioned in the docs for `rts_setInCallCapability,`, it makes the method significantly less useful as there is no guarantees on the capability being used.

This commit also adds a test to make sure things stay on the correct capability.

We didn't seem to test these old tests at all, judging from their
expected output.

In #18793, we saw a compelling example which requires us to look at
non-recursive let-bindings during arity analysis and unleash their arity
types at use sites.

After the refactoring in the previous patch, the needed change is quite
simple and very local to `arityType`'s defn for non-recurisve `Let`.

Apart from that, we had to get rid of the second item of
`Note [Dealing with bottoms]`, which was entirely a safety measure and
hindered optimistic fixed-point iteration.

Fixes #18793.

The following metric increases are all caused by this commit and a
result of the fact that we just do more work now:

Metric Increase:
    T3294
    T12545
    T12707

Arity analysis used to propagate optimistic arity types during
fixed-point interation through the `ArityEnv`'s `ae_cheap_fun` field,
which is like `GHC.Core.Utils.exprIsCheap`, but also considers the
current iteration's optimistic arity, for the binder in question only.

In #18793, we have seen that this is a problematic design, because it
doesn't allow us to look through PAP bindings of that binder.

Hence this patch refactors to a more traditional form with an explicit
signature environment, in which we record the optimistic `ArityType` of
the binder in question (and at the moment is the *only* binder that is
recorded in the arity environment).

Works around #17190, possible resolution for #17224. New design is is
according to accepted [GHC Propoal 320].

Instances in signatures currently unconditionally opt into associated
family defaults if no explicit instance is given. This is bad for two
reasons:

  1. It constrains possible instantiations to use the default, rather
  than possibly define the associated family differently.

  2. It breaks compilation as type families are unsupported in
  signatures.

This PR simply turns off the filling in of defaults in those cases.
Additionally, it squelches a missing definition warning for hs-boot too
that was only squelched for hsig before.

The downsides are:

  1. There is no way to opt into the default, other than copying its
  definition.

  2. If we fixed type classes in signatures, and wanted instances to
  have to explicitly *out of* rather than into the default, that would
  now be a breaking change.

The change that is most unambiguously goood is harmonizing the warning
squelching between hs-boot or hsig. Maybe they should have the warning
(opt out of default) maybe they shouldn't (opt in to default), but
surely it should be the same for both.

Add hs-boot version of a backpack test regarding class-specified
defaults in instances that appear in an hs-boot file.

The metrics increase is very slight and makes no sense --- at least no
one has figured anything out after this languishing for a while, so I'm
just going to accept it.

Metric Increase:
  T10421a

[GHC proposal 320]: https://github.com/ghc-proposals/ghc-proposals/pull/320

Silly mistake on my part.

Currently the Hadrian build appears not to package documentation correctly,
causing doc-tarball to fail due to the Windows build.

Following the model of the other printf symbols. See Note [Symbols for
MinGW's printf].

Closes #18838.

These were incorrectly removed in a recent cleanup commit.

This should have been done when the toolchain was bumped.

This widens LocalLabel to 2^16, avoiding the crash observed in #14334.

Closes #14334.

As well a ctuples and sums.

Makes it possible for GHC to optimize away intermediate Generic representation
for more types.

Metric Increase:
    T12227

This otherwise fails on newer Clangs, which warn
more aggressively on undeclared symbols.

-fPIE and -fno-PIE flags were (un)setting Opt_PIC instead of Opt_PIE.

Original commit: 3625728a

No longer neccessary - TypeRep is now indexed, there is no ambiguity.

Also fix a comment in Evidence.hs, IsLabel no longer takes a Proxy#.

There are two signficant changes here:

* Ticket #18815 showed that we were missing some opportunities for
  preInlineUnconditionally.  The one-line fix is in the code for
  GHC.Core.Opt.Simplify.Utils.preInlineUnconditionally, which now
  switches off only for INLINE pragmas.  I expanded
  Note [Stable unfoldings and preInlineUnconditionally] to explain.

* When doing this I discovered a way in which preInlineUnconditionally
  was occasionally /too/ eager.  It's all explained in
  Note [Occurrences in stable unfoldings] in GHC.Core.Opt.OccurAnal,
  and the one-line change adding markAllMany to occAnalUnfolding.

I also got confused about what NoUserInline meant, so I've renamed
it to NoUserInlinePrag, and changed its pretty-printing slightly.
That led to soem error messate wibbling, and touches quite a few
files, but there is no change in functionality.

I did a nofib run.  As expected, no significant changes.

        Program           Size    Allocs
----------------------------------------
         sphere          -0.0%     -0.4%
----------------------------------------
            Min          -0.0%     -0.4%
            Max          -0.0%     +0.0%
 Geometric Mean          -0.0%     -0.0%

I'm allowing a max-residency increase for T10370, which seems
very irreproducible. (See comments on !4241.)  There is always
sampling error for max-residency measurements; and in any case
the change shows up on some platforms but not others.

Metric Increase:
    T10370

```----------------------
Metric Decrease:
   T12425
Metric Increase:
   T17516
```

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

This fixes a regression introduced in 2b89ca5b
See the new T18151x test case.

The issue described in that section was fixed by
2b89ca5b