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<h3>
Vladislav Zavialov pushed to branch wip/tycl-group
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/64f207566931469648e791df4f0f0384d45cddd0">64f20756</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-03-19T12:16:49-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Refactoring: use Platform instead of DynFlags when possible
Metric Decrease:
ManyConstructors
T12707
T13035
T1969
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/cb1785d9f839e34a3a4892f354f0c51cc6553c0e">cb1785d9</a></strong>
<div>
<span>by Ömer Sinan Ağacan</span>
<i>at 2020-03-19T12:16:54-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">FastString: fix eager reading of string ptr in hashStr
This read causes NULL dereferencing when len is 0.
Fixes #17909
In the reproducer in #17909 this bug is triggered as follows:
- SimplOpt.dealWithStringLiteral is called with a single-char string
("=" in #17909)
- tailFS gets called on the FastString of the single-char string.
- tailFS checks the length of the string, which is 1, and calls
mkFastStringByteString on the tail of the ByteString, which is an
empty ByteString as the original ByteString has only one char.
- ByteString's unsafeUseAsCStringLen returns (NULL, 0) for the empty
ByteString, which is passed to mkFastStringWith.
- mkFastStringWith gets hash of the NULL pointer via hashStr, which
fails on empty strings because of this bug.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/73a7383ebc17f495d7acd04007c8c56b46532cb6">73a7383e</a></strong>
<div>
<span>by Richard Eisenberg</span>
<i>at 2020-03-20T20:42:56-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Simplify treatment of heterogeneous equality
Previously, if we had a [W] (a :: k1) ~ (rhs :: k2), we would
spit out a [D] k1 ~ k2 and part the W as irreducible, hoping for
a unification. But we needn't do this. Instead, we now spit out
a [W] co :: k2 ~ k1 and then use co to cast the rhs of the original
Wanted. This means that we retain the connection between the
spat-out constraint and the original.
The problem with this new approach is that we cannot use the
casted equality for substitution; it's too like wanteds-rewriting-
wanteds. So, we forbid CTyEqCans that mention coercion holes.
All the details are in Note [Equalities with incompatible kinds]
in TcCanonical.
There are a few knock-on effects, documented where they occur.
While debugging an error in this patch, Simon and I ran into
infelicities in how patterns and matches are printed; we made
small improvements.
This patch includes mitigations for #17828, which causes spurious
pattern-match warnings. When #17828 is fixed, these lines should
be removed.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/faa36e5b3674a7b2cfc6b931eec27b3558fad33b">faa36e5b</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-03-20T20:43:41-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Hadrian: ignore in-tree GMP objects with ``--lint``
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9a96ff6b1c19c9d0af9c9a39fb2c086f311c7239">9a96ff6b</a></strong>
<div>
<span>by Richard Eisenberg</span>
<i>at 2020-03-20T20:44:17-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Update core spec to reflect changes to Core.
Key changes:
* Adds a new rule for forall-coercions over coercion variables, which
was implemented but conspicuously missing from the spec.
* Adds treatment for FunCo.
* Adds treatment for ForAllTy over coercion variables.
* Improves commentary (including restoring a Note lost in
03d4852658e1b7407abb4da84b1b03bfa6f6db3b) in the source.
No changes to running code.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7e0451c6ce78b08b5f7564aa03a9a86051b35163">7e0451c6</a></strong>
<div>
<span>by Sergej Jaskiewicz</span>
<i>at 2020-03-20T20:44:55-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Fix event message in withTiming'
This typo caused generating 'end' events without the corresponding 'begin' events.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1542a626a3649e5fc1becec1eff2715a6108d144">1542a626</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">fs.h: Add missing declarations on Windows
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/3bcf2ccdd0bdd3cf176943ddb946e4fcef2ac7c1">3bcf2ccd</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Bump process submodule
Avoids redundant case alternative warning.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/3b363ef9405c52369b63fc167ded8a533c6a5079">3b363ef9</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Normalize slashes in ghc-api annotations output
Enable `normalise_slashes` on `annotations`, `listcomps`, and
`parseTree` to fix Windows failures.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/25fc94295c68620c6928751aaadc46b11a185f0c">25fc9429</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Update expected output on Windows
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7f58ec6d94f49cf5713757710c6b80a682ee066b">7f58ec6d</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Fix TOP of T17786
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/aadcd909563d5ddf7b2fc469ee3c09c301b1a813">aadcd909</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Update expected output on Windows
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/dc1eb10dae03f3fe5f11de845c6772c229684c28">dc1eb10d</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">hadrian: Fix executable extension passed to testsuite driver
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/58f62e2caa19e13082807da1d49f94e9cf869322">58f62e2c</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">gitlab-ci: Require that Windows-hadrian job passes
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/8dd2415dd2f423688f33a8fb267857e3ff39754d">8dd2415d</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">hadrian: Eliminate redundant .exe from GHC path
Previously we were invoking:
bash -c
"c:/GitLabRunner/builds/eEQrxK4p/0/ghc/ghc/toolchain/bin/ghc.exe.exe
testsuite/mk/ghc-config.hs -o _build/test/bin/ghc-config.exe"
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/373621f61f812accdeba39c745eb7d015430ff8e">373621f6</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-22T22:37:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Bump hsc2hs submodule
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/abc02b4036c2d8efe50b720d8c8103c4f1b8899a">abc02b40</a></strong>
<div>
<span>by Hécate</span>
<i>at 2020-03-22T22:38:33-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Annotate the non-total function in Data.Foldable as such
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/19f125578247dfe8036b5793cb3f6b684474f9c7">19f12557</a></strong>
<div>
<span>by Josef Svenningsson</span>
<i>at 2020-03-23T14:05:33-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Fix ApplicativeDo regression #17835
A previous fix for #15344 made sure that monadic 'fail' is used properly
when translating ApplicativeDo. However, it didn't properly account
for when a 'fail' will be inserted which resulted in some programs
failing with a type error.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/2643ba465cd2a133b6f495f34fc59cd1a6d23525">2643ba46</a></strong>
<div>
<span>by Paavo</span>
<i>at 2020-03-24T08:31:32-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Add example and doc for Arg (Fixes #17153)
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/703221f408b023a1b3433938572e7b5c24b4af60">703221f4</a></strong>
<div>
<span>by Roland Senn</span>
<i>at 2020-03-25T14:45:04-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Use export list of Main module in function TcRnDriver.hs:check_main (Fix #16453)
- Provide the export list of the `Main` module as parameter to the
`compiler/typecheck/TcRnDriver.hs:check_main` function.
- Instead of `lookupOccRn_maybe` call the function `lookupInfoOccRn`.
It returns the list `mains_all` of all the main functions in scope.
- Select from this list `mains_all` all `main` functions that are in
the export list of the `Main` module.
- If this new list contains exactly one single `main` function, then
typechecking continues.
- Otherwise issue an appropriate error message.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/3e27205a66b06a4501d87eb31e285eadbc693eb7">3e27205a</a></strong>
<div>
<span>by Sebastian Graf</span>
<i>at 2020-03-25T14:45:40-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Remove -fkill-absence and -fkill-one-shot flags
They seem to be a benchmarking vestige of the Cardinality paper and
probably shouldn't have been merged to HEAD in the first place.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/262e42aa34c4d5705c8d011907c351497dd4e862">262e42aa</a></strong>
<div>
<span>by Peter Trommler</span>
<i>at 2020-03-25T22:41:39-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Do not panic on linker errors
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0de03cd78729dc58a846c64b645e71057ec5d24e">0de03cd7</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-03-25T22:42:02-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">DynFlags refactoring III
Use Platform instead of DynFlags when possible:
* `tARGET_MIN_INT` et al. replaced with `platformMinInt` et al.
* no more DynFlags in PreRules: added a new `RuleOpts` datatype
* don't use `wORD_SIZE` in the compiler
* make `wordAlignment` use `Platform`
* make `dOUBLE_SIZE` a constant
Metric Decrease:
T13035
T1969
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7a04920b23376b2759b5049820400ddd40f7b89e">7a04920b</a></strong>
<div>
<span>by Tristan Cacqueray</span>
<i>at 2020-03-25T22:42:06-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Base: fix a typo in liftA doc
This change removes an extra '|' that should not be rendered in
the liftA documentation.
Tracking: #17929
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1c5a15f7d257d0a2ded4850e38b6174965a7735b">1c5a15f7</a></strong>
<div>
<span>by Tristan Cacqueray</span>
<i>at 2020-03-25T22:42:06-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Base: add Control.Applicative optional example
This change adds an optional example.
Tracking: #17929
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/6d172e63f3dd3590b0a57371efb8f924f1fcdf05">6d172e63</a></strong>
<div>
<span>by Tristan Cacqueray</span>
<i>at 2020-03-25T22:42:06-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Base: add markup around Except
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/eb2162c81964b3a1057c21c73574cc2b542d863a">eb2162c8</a></strong>
<div>
<span>by John Ericson</span>
<i>at 2020-03-26T12:37:08-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Remove unused `ghciTablesNextToCode` from compiler proper
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/f51efc4bf5f20d1df3d11a2bb4c147f416367ae4">f51efc4b</a></strong>
<div>
<span>by Joachim Breitner</span>
<i>at 2020-03-26T12:37:09-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Prepare to use run-time tablesNextToCode in compiler exclusively
Factor out CPP as much as possible to prepare for runtime
determinattion.
Progress towards #15548
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1c446220250dcada51d4bb33a0cc7d8ce572e8b6">1c446220</a></strong>
<div>
<span>by Joachim Breitner</span>
<i>at 2020-03-26T12:37:09-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Use run-time tablesNextToCode in compiler exclusively (#15548)
Summary:
- There is no more use of the TABLES_NEXT_TO_CODE CPP macro in
`compiler/`. GHCI_TABLES_NEXT_TO_CODE is also removed entirely.
The field within `PlatformMisc` within `DynFlags` is used instead.
- The field is still not exposed as a CLI flag. We might consider some
way to ensure the right RTS / libraries are used before doing that.
Original reviewers:
Original subscribers: TerrorJack, rwbarton, carter
Original Differential Revision: https://phabricator.haskell.org/D5082
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1941ef4f050c0dfcb68229641fcbbde3a10f1072">1941ef4f</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-03-29T17:28:51-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Modules: Types (#13009)
Update Haddock submodule
Metric Increase:
haddock.compiler
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1c7c6f1afc8e7f7ba5d256780bc9d5bb5f3e7601">1c7c6f1a</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-03-29T17:28:51-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Remove GHC.Types.Unique.Map module
This module isn't used anywhere in GHC.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/f1a6c73d01912b389e012a0af81a5c2002e82636">f1a6c73d</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-03-29T17:28:51-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Merge GHC.Types.CostCentre.Init into GHC.Driver.CodeOutput
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/54250f2d8de910b094070c1b48f086030df634b1">54250f2d</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2020-03-29T17:29:30-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Demand analysis: simplify the demand for a RHS
Ticket #17932 showed that we were using a stupid demand for the RHS
of a let-binding, when the result is a product. This was the result
of a "fix" in 2013, which (happily) turns out to no longer be
necessary.
So I just deleted the code, which simplifies the demand analyser,
and fixes #17932. That in turn uncovered that the anticipation
of worker/wrapper in CPR analysis was inaccurate, hence the logic
that decides whether to unbox an argument in WW was extracted into
a function `wantToUnbox`, now consulted by CPR analysis.
I tried nofib, and got 0.0% perf changes.
All this came up when messing about with !2873 (ticket #17917),
but is idependent of it.
Unfortunately, this patch regresses #4267 and realised that it is now
blocked on #16335.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/03060b2f963436dd22582f3a1c218b7a74d302ec">03060b2f</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-29T17:30:05-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Fix T17786 on Windows
Fixes line ending normalization issue.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1f7995baaaf4dcba9b3abaddcd571ac66675ab19">1f7995ba</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-29T17:30:05-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Fix T17786
Fix missing quoting and expected exit code.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/ef9c608eba417c59fe45c9edd6a946c59f50b5d2">ef9c608e</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-29T17:30:05-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Mark T12971 as broken on Windows
Due to #17945.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e54500c12de051cb9695728d27c812e5160593ee">e54500c1</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-03-29T17:30:47-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Store ComponentId details
As far as GHC is concerned, installed package components ("units") are
identified by an opaque ComponentId string provided by Cabal. But we
don't want to display it to users (as it contains a hash) so GHC queries
the database to retrieve some infos about the original source package
(name, version, component name).
This patch caches these infos in the ComponentId itself so that we don't
need to provide DynFlags (which contains installed package informations)
to print a ComponentId.
In the future we want GHC to support several independent package states
(e.g. for plugins and for target code), hence we need to avoid
implicitly querying a single global package state.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7e7cb714173652165b8372c3450f4ccd6a377497">7e7cb714</a></strong>
<div>
<span>by Marius Bakke</span>
<i>at 2020-03-29T17:31:27-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Remove test that dlopens a PIE object.
glibc 2.30 disallowed dlopening PIE objects, so just remove the test.
Fixes #17952.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/6c8f80d8876965539571d37d3c7f0fee43c300d2">6c8f80d8</a></strong>
<div>
<span>by Andreas Klebinger</span>
<i>at 2020-03-29T17:32:04-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Correct haddocks for testBit in Data.Bits
It conflated the nth bit with the bit at offset n.
Now we instead give the definition in terms of `bit and `.&.`
on top of clearer phrasing.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c916f190b455d9c43459f81c7ee06d06ab3db957">c916f190</a></strong>
<div>
<span>by Andreas Klebinger</span>
<i>at 2020-03-29T17:32:04-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Apply suggestion to libraries/base/Data/Bits.hs</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/64bf7f51064dad9c63728ac8bccdb9cf00bdb420">64bf7f51</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-03-29T17:32:41-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">gitlab-ci: Add FreeBSD release job
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/a0d8e92e9c9b67426aa139d6bc46363d8940f992">a0d8e92e</a></strong>
<div>
<span>by Ryan Scott</span>
<i>at 2020-03-29T17:33:20-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Run checkNewDataCon before constraint-solving newtype constructors
Within `checkValidDataCon`, we used to run `checkValidType` on the
argument types of a newtype constructor before running
`checkNewDataCon`, which ensures that the user does not attempt
non-sensical things such as newtypes with multiple arguments or
constraints. This works out in most situations, but this falls over
on a corner case revealed in #17955:
```hs
newtype T = Coercible () T => T ()
```
`checkValidType`, among other things, peforms an ambiguity check on
the context of a data constructor, and that it turn invokes the
constraint solver. It turns out that there is a special case in the
constraint solver for representational equalities (read: `Coercible`
constraints) that causes newtypes to be unwrapped (see
`Note [Unwrap newtypes first]` in `TcCanonical`). This special case
does not know how to cope with an ill formed newtype like `T`, so
it ends up panicking.
The solution is surprisingly simple: just invoke `checkNewDataCon`
before `checkValidType` to ensure that the illicit newtype
constructor context is detected before the constraint solver can
run amok with it.
Fixes #17955.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/45eb9d8cad254440eaea25676d6788ca13baa2fb">45eb9d8c</a></strong>
<div>
<span>by Krzysztof Gogolewski</span>
<i>at 2020-03-29T17:33:59-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Minor cleanup
- Simplify mkBuildExpr, the function newTyVars was called
only on a one-element list.
- TTG: use noExtCon in more places. This is more future-proof.
- In zonkExpr, panic instead of printing a warning.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/4fc76474432aa891de56cdcdeddff1ddfeda0025">4fc76474</a></strong>
<div>
<span>by Vladislav Zavialov</span>
<i>at 2020-03-30T19:41:03+03:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Handle sigs in separate TyClGroups
Fixing #12088 implies that we put declarations and definitions in
separate TyClGroups.
Consider this example:
{-# LANGUAGE StandaloneKindSignatures #-}
import Data.Kind (Type)
type X :: Type
data X
If the renamer puts type X :: Type
and data X
into separate TyClGroups, then the type checker must be prepared to
handle it.
Before this patch, the type checker always assumed that signatures were
put into the same TyClGroup as the definition.
After this patch, no such assumption is made.
</pre>
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<a href="#587d266bb27a4dc3022bbed44dfa19849df3044c">
.gitlab-ci.yml
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<a href="#412267f7d5ed866deae5ac2ca598ff8092b826b6">
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compiler/GHC.hs
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compiler/GHC/ByteCode/Asm.hs
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compiler/GHC/ByteCode/InfoTable.hs
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compiler/GHC/ByteCode/Instr.hs
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compiler/GHC/ByteCode/Linker.hs
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compiler/GHC/ByteCode/Types.hs
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compiler/GHC/Cmm.hs
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compiler/GHC/Cmm/BlockId.hs
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compiler/GHC/Cmm/BlockId.hs-boot
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compiler/GHC/Cmm/CallConv.hs
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compiler/GHC/Cmm/Graph.hs
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compiler/GHC/Cmm/Info.hs
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compiler/GHC/Cmm/Info/Build.hs
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compiler/GHC/Cmm/LayoutStack.hs
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compiler/GHC/Cmm/Lexer.x
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compiler/GHC/Cmm/Lint.hs
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compiler/GHC/Cmm/MachOp.hs
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compiler/GHC/Cmm/Node.hs
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compiler/GHC/Cmm/Opt.hs
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compiler/GHC/Cmm/Parser.y
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compiler/GHC/Cmm/Pipeline.hs
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<a href="#bbf4b351b327473b112c1d212f720f929c5ce247">
compiler/GHC/Cmm/Ppr.hs
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