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<h3 style="margin-top: 20px; margin-bottom: 10px;">
John Ericson pushed to branch wip/wither-eq1-and-friends
at <a href="https://gitlab.haskell.org/ghc/ghc" style="color: #1068bf; text-decoration: none;">Glasgow Haskell Compiler / GHC</a>
</h3>
<h4 style="margin-top: 10px; margin-bottom: 10px;">
Commits:
</h4>
<ul>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/ff67c79ee742024ca0ef41a9a7e540e1662d46bd" style="color: #1068bf; text-decoration: none;">ff67c79e</a></strong>
<div>
<span>by Alan Zimmerman</span>
<i>at 2022-08-11T16:19:57-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>EPA: DotFieldOcc does not have exact print annotations
For the code
{-# LANGUAGE OverloadedRecordUpdate #-}
operatorUpdate f = f{(+) = 1}
There are no exact print annotations for the parens around the +
symbol, nor does normal ppr print them.
This MR fixes that.
Closes #21805
Updates haddock submodule
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/dca43a04fb36e0ae0ed61455f215660eed2856a9" style="color: #1068bf; text-decoration: none;">dca43a04</a></strong>
<div>
<span>by Matthew Pickering</span>
<i>at 2022-08-11T16:20:33-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Revert "gitlab-ci: Add release job for aarch64/debian 11"
This reverts commit 5765e13370634979eb6a0d9f67aa9afa797bee46.
The job was not tested before being merged and fails CI
(https://gitlab.haskell.org/ghc/ghc/-/jobs/1139392)
Ticket #22005
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/a3a23ca525956b08a893a099c94cbab53c480ef5" style="color: #1068bf; text-decoration: none;">a3a23ca5</a></strong>
<div>
<span>by John Ericson</span>
<i>at 2022-08-13T09:08:17-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Add `Eq` and `Ord` instances for `Generically1`
These are needed so the subsequent commit overhauling the `*1` classes
type-checks.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/a6e183622920c8f32d5bd8e86f324e65432c55f1" style="color: #1068bf; text-decoration: none;">a6e18362</a></strong>
<div>
<span>by John Ericson</span>
<i>at 2022-08-13T09:09:07-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Relax instances for Functor combinators; put superclass on Class1 to make non-breaking
The first change makes the `Eq`, `Ord`, `Show`, and `Read` instances for
`Sum`, `Product`, and `Compose` match those for `:+:`, `:*:`, and `:.:`.
These have the proper flexible contexts that are exactly what the
instance needs:
For example, instead of
```haskell
instance (Eq1 f, Eq1 g, Eq a) => Eq (Compose f g a) where
(==) = eq1
```
we do
```haskell
deriving instance Eq (f (g a)) => Eq (Compose f g a)
```
But, that change alone is rather breaking, because until now `Eq (f a)`
and `Eq1 f` (and respectively the other classes and their `*1`
equivalents too) are *incomparable* constraints. This has always been an
annoyance of working with the `*1` classes, and now it would rear it's
head one last time as an pesky migration.
Instead, we give the `*1` classes superclasses, like so:
```haskell
(forall a. Eq a => Eq (f a)) => Eq1 f
```
along with some laws that canonicity is preserved, like:
```haskell
liftEq (==) = (==)
```
and likewise for `*2` classes:
```haskell
(forall a. Eq a => Eq1 (f a)) => Eq2 f
```
and laws:
```haskell
liftEq2 (==) = liftEq1
```
The `*1` classes also have default methods using the `*2` classes where
possible.
What this means, as explained in the docs, is that `*1` classes really
are generations of the regular classes, indicating that the methods can
be split into a canonical lifting combined with a canonical inner, with
the super class "witnessing" the laws[1] in a fashion.
Circling back to the pragmatics of migrating, note that the superclass
means evidence for the old `Sum`, `Product`, and `Compose` instances is
(more than) sufficient, so breakage is less likely --- as long no
instances are "missing", existing polymorphic code will continue to
work.
Breakage can occur when a datatype implements the `*1` class but not the
corresponding regular class, but this is almost certainly an oversight.
For example, containers made that mistake for `Tree` and `Ord`, which I
fixed in https://github.com/haskell/containers/pull/761, but fixing the
issue by adding `Ord1` was extremely *un*controversial.
`Generically1` was also missing `Eq`, `Ord`, `Read,` and `Show`
instances. It is unlikely this would have been caught without
implementing this change.
-----
[1]: In fact, someday, when the laws are part of the language and not
only documentation, we might be able to drop the superclass field of the
dictionary by using the laws to recover the superclass in an
instance-agnostic manner, e.g. with a *non*-overloaded function with
type:
```haskell
DictEq1 f -> DictEq a -> DictEq (f a)
```
But I don't wish to get into optomizations now, just demonstrate the
close relationship between the law and the superclass.
Bump haddock submodule because of test output changing.
</pre>
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<a href="#a6883fe5ffe69ebc49b16c7e553faba405221f57" style="color: #1068bf; text-decoration: none;">
.gitlab/gen_ci.hs
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<a href="#4f7fc727dfc06c2591e6043f44b9602eddfc3673" style="color: #1068bf; text-decoration: none;">
.gitlab/jobs.yaml
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compiler/GHC/Core/PatSyn.hs
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compiler/GHC/Core/TyCon.hs
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compiler/GHC/Hs/Expr.hs
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compiler/GHC/HsToCore/Quote.hs
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compiler/GHC/Iface/Syntax.hs
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compiler/GHC/Parser/PostProcess.hs
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compiler/GHC/Rename/Expr.hs
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compiler/GHC/Rename/Pat.hs
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compiler/GHC/Tc/Deriv/Generate.hs
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compiler/GHC/Tc/Deriv/Generics.hs
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