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<h3>
Ben Gamari pushed to branch wip/T18291
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/686e06c59c3aa6b66895e8a501c7afb019b09e36">686e06c5</a></strong>
<div>
<span>by Vladislav Zavialov</span>
<i>at 2020-08-06T13:34:05-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Grammar for types and data/newtype constructors
Before this patch, we parsed types into a reversed sequence
of operators and operands. For example, (F x y + G a b * X)
would be parsed as [X, *, b, a, G, +, y, x, F],
using a simple grammar:
tyapps
: tyapp
| tyapps tyapp
tyapp
: atype
| PREFIX_AT atype
| tyop
| unpackedness
Then we used a hand-written state machine to assemble this
either into a type, using 'mergeOps',
or into a constructor, using 'mergeDataCon'.
This is due to a syntactic ambiguity:
data T1 a = MkT1 a
data T2 a = Ord a => MkT2 a
In T1, what follows after the = sign is a data/newtype constructor
declaration. However, in T2, what follows is a type (of kind
Constraint). We don't know which of the two we are parsing until we
encounter =>, and we cannot check for => without unlimited lookahead.
This poses a few issues when it comes to e.g. infix operators:
data I1 = Int :+ Bool :+ Char -- bad
data I2 = Int :+ Bool :+ Char => MkI2 -- fine
By this issue alone we are forced into parsing into an intermediate
representation and doing a separate validation pass.
However, should that intermediate representation be as low-level as a
flat sequence of operators and operands?
Before GHC Proposal #229, the answer was Yes, due to some particularly
nasty corner cases:
data T = ! A :+ ! B -- used to be fine, hard to parse
data T = ! A :+ ! B => MkT -- bad
However, now the answer is No, as this corner case is gone:
data T = ! A :+ ! B -- bad
data T = ! A :+ ! B => MkT -- bad
This means we can write a proper grammar for types, overloading it in
the DisambECP style, see Note [Ambiguous syntactic categories].
With this patch, we introduce a new class, DisambTD. Just like
DisambECP is used to disambiguate between expressions, commands, and patterns,
DisambTD is used to disambiguate between types and data/newtype constructors.
This way, we get a proper, declarative grammar for constructors and
types:
infixtype
: ftype
| ftype tyop infixtype
| unpackedness infixtype
ftype
: atype
| tyop
| ftype tyarg
| ftype PREFIX_AT tyarg
tyarg
: atype
| unpackedness atype
And having a grammar for types means we are a step closer to using a
single grammar for types and expressions.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/6770e199645b0753d2edfddc68c199861a1be980">6770e199</a></strong>
<div>
<span>by Vladislav Zavialov</span>
<i>at 2020-08-06T13:34:05-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Clean up the story around runPV/runECP_P/runECP_PV
This patch started as a small documentation change, an attempt to make
Note [Parser-Validator] and Note [Ambiguous syntactic categories]
more clear and up-to-date.
But it turned out that runECP_P/runECP_PV are weakly motivated,
and it's easier to remove them than to find a good rationale/explanation
for their existence.
As the result, there's a bit of refactoring in addition to
a documentation update.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/826d07db0e0f31fe2b2d2e0661be7f0cb3cde3c7">826d07db</a></strong>
<div>
<span>by Vladislav Zavialov</span>
<i>at 2020-08-06T13:34:06-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Fix debug_ppr_ty ForAllTy (#18522)
Before this change, GHC would
pretty-print forall k. forall a -> ()
as forall @k a. ()
which isn't even valid Haskell.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0ddb43848b9fc24f5404915f57dc504546e68292">0ddb4384</a></strong>
<div>
<span>by Vladislav Zavialov</span>
<i>at 2020-08-06T13:34:06-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Fix visible forall in ppr_ty (#18522)
Before this patch, this type:
T :: forall k -> (k ~ k) => forall j -> k -> j -> Type
was printed incorrectly as:
T :: forall k j -> (k ~ k) => k -> j -> Type
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/d2a432258fa00e22ca386ef30d0a77ff5b277db8">d2a43225</a></strong>
<div>
<span>by Richard Eisenberg</span>
<i>at 2020-08-06T13:34:06-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Fail eagerly on a lev-poly datacon arg
Close #18534.
See commentary in the patch.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/63348155404c64334fa864454132630f9d2a4d7f">63348155</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-08-06T13:34:08-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Use a type alias for Ways
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9570c21295a2b4a1d1e40939869124f0b9b9bf91">9570c212</a></strong>
<div>
<span>by Takenobu Tani</span>
<i>at 2020-08-06T19:46:46-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">users-guide: Rename 8.12 to 9.0
GHC 8.12.1 has been renamed to GHC 9.0.1.
See also:
https://mail.haskell.org/pipermail/ghc-devs/2020-July/019083.html
[skip ci]
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/3907ee01e68b383fa30386d163decf203acedb19">3907ee01</a></strong>
<div>
<span>by Cale Gibbard</span>
<i>at 2020-08-07T08:34:46-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">A fix to an error message in monad comprehensions, and a move of dsHandleMonadicFailure
as suggested by comments on !2330.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/fa9bb70a3fefef681cb0e80cc78977386c1dcf0a">fa9bb70a</a></strong>
<div>
<span>by Cale Gibbard</span>
<i>at 2020-08-07T08:34:46-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Add some tests for fail messages in do-expressions and monad-comprehensions.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/5f03606319f745b10e9918c76a47426b293f0bf9">5f036063</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-07T08:35:21-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">cmm: Clean up Notes a bit
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/6402c1240d5bd768b8fe8b4368413932bedbe107">6402c124</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-07T08:35:21-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">CmmLint: Check foreign call argument register invariant
As mentioned in Note [Register parameter passing] the arguments of
foreign calls cannot refer to caller-saved registers.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/15b36de030ecdd60897bc7a6a02bdeabd0825be4">15b36de0</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-07T08:35:21-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">nativeGen: One approach to fix #18527
Previously the code generator could produce corrupt C call sequences due
to register overlap between MachOp lowerings and the platform's calling
convention. We fix this using a hack described in Note [Evaluate C-call
arguments before placing in destination registers].
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/3847ae0ccf67bddf73304a39f5320c3ba285aa48">3847ae0c</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-07T08:35:21-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Add test for #18527
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/dd51d53be42114c105b5ab15fcbdb387526b1c17">dd51d53b</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-07T08:35:21-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Fix prog001
Previously it failed as the `ghc` package was not visible.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e4f1b73ad9f292a6bbeb21fee44b0ba1a7f3c33b">e4f1b73a</a></strong>
<div>
<span>by Alan Zimmerman</span>
<i>at 2020-08-07T23:58:10-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">ApiAnnotations; tweaks for ghc-exactprint update
Remove unused ApiAnns, add one for linear arrow.
Include API Annotations for trailing comma in export list.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/8a665db6174eaedbbae925c0ccb4c22b3f29bcaf">8a665db6</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-07T23:58:45-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">configure: Fix double-negation in ld merge-objects check
We want to only run the check if ld is gold.
Fixes the fix to #17962.</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/3d496ac47e265321a90db1889c09ecead17334c5">3d496ac4</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-10T13:26:36-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Allow unsaturated runRW# applications
Previously we had a very aggressive Core Lint check which caught
unsaturated applications of runRW#. However, there is nothing
wrong with such applications and they may naturally arise in desugared
Core. For instance, the desugared Core of Data.Primitive.Array.runArray#
from the `primitive` package contains:
case ($) (runRW# @_ @_) (\s -> ...) of ...
In this case it's almost certain that ($) will be inlined, turning the
application into a saturated application. However, even if this weren't
the case there isn't a problem: CorePrep (after deleting an unnecessary
case) can simply generate code in its usual way, resulting in a call to
the Haskell definition of runRW#.
Fixes #18291.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/db7b78d8fab415ee657dc31b5daa9939655b156a">db7b78d8</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-08-10T13:26:36-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Add test for #18291
</pre>
</li>
</ul>
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aclocal.m4
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compiler/GHC.hs
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compiler/GHC/Cmm/Lint.hs
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compiler/GHC/Cmm/MachOp.hs
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compiler/GHC/Unit/State.hs
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docs/users_guide/8.12.1-notes.rst
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docs/users_guide/9.0.1-notes.rst
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