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<h3>
Ryan Scott pushed to branch wip/T18191
at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
</h3>
<h4>
Commits:
</h4>
<ul>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/d830bbc9921bcc59164a0a18f0e0874ae4ce226e">d830bbc9</a></strong>
<div>
<span>by Adam Sandberg Ericsson</span>
<i>at 2020-05-23T13:36:20-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">docs: fix formatting and add some links
[skip ci]
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/49301ad6226d9a83d110bee8c419615dd94f5ded">49301ad6</a></strong>
<div>
<span>by Andrew Martin</span>
<i>at 2020-05-23T13:37:01-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Implement cstringLength# and FinalPtr
This function and its accompanying rule resolve issue #5218.
A future PR to the bytestring library will make the internal
Data.ByteString.Internal.unsafePackAddress compute string length
with cstringLength#. This will improve the status quo because it is
eligible for constant folding.
Additionally, introduce a new data constructor to ForeignPtrContents
named FinalPtr. This additional data constructor, when used in the
IsString instance for ByteString, leads to more Core-to-Core
optimization opportunities, fewer runtime allocations, and smaller
binaries.
Also, this commit re-exports all the functions from GHC.CString
(including cstringLength#) in GHC.Exts. It also adds a new test
driver. This test driver is used to perform substring matches on Core
that is dumped after all the simplifier passes. In this commit, it is
used to check that constant folding of cstringLength# works.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/dcd6bdcce57430d08b335014625722c487ea08e4">dcd6bdcc</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-05-23T13:37:48-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">simplCore: Ignore ticks in rule templates
This fixes #17619, where a tick snuck in to the template of a rule,
resulting in a panic during rule matching. The tick in question was
introduced via post-inlining, as discussed in `Note [Simplifying
rules]`. The solution we decided upon was to simply ignore ticks in the
rule template, as discussed in `Note [Tick annotations in RULE
matching]`.
Fixes #18162.
Fixes #17619.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/82cb8913b38d44ef20e928ff8b08f3f0770ebf80">82cb8913</a></strong>
<div>
<span>by John Ericson</span>
<i>at 2020-05-23T13:38:32-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Fix #18145 and also avoid needless work with implicit vars
- `forAllOrNothing` now is monadic, so we can trace whether we bind
an explicit `forall` or not.
- #18145 arose because the free vars calculation was needlessly
complex. It is now greatly simplified.
- Replaced some other implicit var code with `filterFreeVarsToBind`.
Co-authored-by: Ryan Scott <ryan.gl.scott@gmail.com>
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/a60dc83552c38af9bbc159bd4e092531196db9c0">a60dc835</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-05-23T13:39:12-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Bump process submodule
Fixes #17926.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/856adf54ab50fc3be66d17a0b94ba3074453b279">856adf54</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-05-23T13:40:21-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">users-guide: Clarify meaning of -haddock flag
Fixes #18206.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7ae57afd7abee9dec1050d9feace254ac04800bc">7ae57afd</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-05-23T13:41:03-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">git: Add ignored commits file
This can be used to tell git to ignore bulk renaming commits like the
recently-finished module hierarchy refactoring. Configured with,
git config blame.ignoreRevsFile .git-ignore-revs
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0d54179051725461fa5a74cb80ed1e0880fb74b1">0d541790</a></strong>
<div>
<span>by Ryan Scott</span>
<i>at 2020-05-23T13:53:52-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Make GADT constructors adhere to the forall-or-nothing rule properly
Issue #18191 revealed that the types of GADT constructors don't quite
adhere to the `forall`-or-nothing rule. This patch serves to clean up
this sad state of affairs somewhat. The main change is not in the
code itself, but in the documentation, as this patch introduces two
sections to the GHC User's Guide:
* A "Formal syntax for GADTs" section that presents a BNF-style
grammar for what is and isn't allowed in GADT constructor types.
This mostly exists to codify GHC's existing behavior, but it also
imposes a new restriction that addresses #18191: the outermost
`forall` and/or context in a GADT constructor is not allowed to be
surrounded by parentheses. Doing so would make these
`forall`s/contexts nested, and GADTs do not support nested
`forall`s/contexts at present.
* A "`forall`-or-nothing rule" section that describes exactly what
the `forall`-or-nothing rule is all about. Surprisingly, there was
no mention of this anywhere in the User's Guide up until now!
To adhere the new specification in the "Formal syntax for GADTs"
section of the User's Guide, the following code changes were made:
* `GHC.Parser.PostProcess.mkGadtDecl` no longer strips away
parentheses from the outermost `forall` and context. Instead, these
parentheses are preserved so that the renamer can check for nested
`forall`s/contexts later. See
`Note [No nested foralls or contexts in GADT constructors]` in
`GHC.Parser.PostProcess` for more details.
One nice side effect of this change is that we can get rid of the
explicit `AddAnn` tracking in `mkGadtDecl`, as we no longer need to
remember the `AddAnn`s for stripped-away parentheses.
* `GHC.Renamer.Module.rnConDecl` now checks for nested
`forall`s/contexts, rather than checking for this in the typechcker
(in `GHC.Tc.TyCl.badDataConTyCon`). For the most part, this code
was ported directly from `badDataConTyCon`, but designed to work
over `HsType`s instead of `Type`s.
One nice side effect of this change is that we are able to give a
more accurate error message for GADT constructors that use visible
dependent quantification (e.g., `MkFoo :: forall a -> a -> Foo a`),
which improves the stderr in the `T16326_Fail6` test case.
Fixes #18191.
</pre>
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