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Among doing other things, Phab:D201 (bc2289e1)
tried to improve the error messages thrown by the parser. For example a missing
else clause now prints "parse error in if statement: else clause empty" instead
of "parse error (possibly incorrect indentation or mismatched brackets)".

Some error messages got much worse however (see tests), and the result seems to
be a net negative. Although not entirely satisfactory, this commits therefore
reverts those parser changes.

Reviewed By: austin

Differential Revision: https://phabricator.haskell.org/D1309

GHC Trac Issues: #10498

For example

```
pattern head `Cons` tail = head : tail
```

Reviewed By: goldfire, austin

Differential Revision: https://phabricator.haskell.org/D1295

GHC Trac Issues: #10747

Improved error messages are only printed when the old message would be
"No instance for...", since they're not as helpful for "Could not deduce..."

No special test case as error messages are tested by other tests already.
Signed-off-by: David Kraeutmann <kane@kane.cx>

Reviewed By: austin, goldfire

Differential Revision: https://phabricator.haskell.org/D1182

GHC Trac Issues: #10733

A missing 'closeOverKinds' triggered Trac #10934.
Happily the fix is simple.

Merge to 7.10.3

Summary:
We had a duplicate copy of the code for --make and for -c
which was a pain.  The call graph looked something like this:

    compileOne -> genericHscCompileGetFrontendResult -> genericHscFrontend
                                   hscCompileOneShot ---^

with genericHscCompileGetFrontendResult and hscCompileOneShot
duplicating logic for deciding whether or not recompilation
was needed.

This patchset fixes it, so now everything goes through this call-chain:

    compileOne (--make entry point)
        Calls hscIncrementCompile, invokes the pipeline to do codegen
        and sets up linkables.
    hscIncrementalCompile (-c entry point)
        Calls hscIncrementalFrontend, and then simplifying,
        desugaring, and writing out the interface.
    hscIncrementalFrontend
        Performs recompilation avoidance, if recompilation needed,
        does parses typechecking.

I also cleaned up some of the MergeBoot nonsense by introducing
a FrontendResult type.

NB: this BREAKS #8101 again, because I can't unconditionally desugar
due to Haddock barfing on lint, see #10600
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, bgamari, simonmar, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1302

The Windows Linker has 3 main parts that this patch changes.

1) Identification and classification of sections
2) Adding of symbols to the symbols tables
3) Reallocation of sections

1.
Previously section identification used to be done on a whitelisted
basis. It was also exclusively being done based on the names of the
sections. This meant that there was a bit of a cat and mouse game
between `GCC` and `GHC`. Every time `GCC` added new sections there was a
good chance `GHC` would break. Luckily this hasn't happened much in the
past because the `GCC` versions `GHC` used were largely unchanged.

The new code instead treats all new section as `CODE` or `DATA`
sections, and changes the classifications based on the `Characteristics`
flag in the PE header. By doing so we no longer have the fragility of
changing section names. The one exception to this is the `.ctors`
section, which has no differentiating flag in the PE header, but we know
we need to treat it as initialization data.

The check to see if the sections are aligned by `4` has been removed.
The reason is that debug sections often time are `1 aligned` but do have
relocation symbols. In order to support relocations of `.debug` sections
this check needs to be gone. Crucially this assumption doesn't seem to
be in the rest of the code. We only check if there are at least 4 bytes
to realign further down the road.

2.
The second loop is iterating of all the symbols in the file and trying
to add them to the symbols table. Because the classification of the
sections we did previously are (currently) not available in this phase
we still have to exclude the sections by hand. If they don't we will
load in symbols from sections we've explicitly ignored the in # 1. This
whole part should rewritten to avoid this. But didn't want to do it in
this commit.

3.
Finally the sections are relocated. But for some reason the PE files
contain a Linux relocation constant in them `0x0011` This constant as
far as I can tell does not come from GHC (or I couldn't find where it's
being set). I believe this is probably a bug in GAS. But because the
constant is in the output we have to handle it. I am thus mapping it to
the constant I think it should be `0x0003`.

Finally, static linking *should* work, but won't. At least not if you
want to statically link `libgcc` with exceptions support. Doing so would
require you to link `libgcc` and `libstd++` but also `libmingwex`. The
problem is that `libmingwex` also defines a lot of symbols that the RTS
automatically injects into the symbol table. Presumably because they're
symbols that it needs. like `coshf`. The these symbols are not in a
section that is declared with weak symbols support. So if we ever want
to get this working, we should either a) Ask mingw to declare the
section as such, or b) treat all a imported symbols as being weak.
Though this doesn't seem like it's a good idea..

Test Plan:
Running ./validate for both x86 and x86_64

Also running the specific test case for #10672

make TESTS="T10672_x86 T10672_x64"

Reviewed By: ezyang, thomie, austin

Differential Revision: https://phabricator.haskell.org/D1244

GHC Trac Issues: #9907, #10672, #10563

This started intermittently failing as a result of D1239.
I suspect this was just the straw that broke the camel's back however.

Summary:
Unlike `-XDefaultSignatures`, `-XDeriveAnyClass` would not fill in
associated type family defaults when deriving a class which contained
them.

In order to fix this properly, `tcATDefault` needed to be used from
`TcGenDeriv`. To avoid a module import cycle, `tcATDefault` was moved
from `TcInstDcls` to `TcClsDcl`.

Fixes #10361.

Test Plan: ./validate

Reviewers: kosmikus, dreixel, bgamari, austin, simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1283

GHC Trac Issues: #10361

This warning was implemented via
abb3a9fa for addressing #7881. The
bounded H2010 integral types were handled, but the `Integer` type was
missed for the enumeration warning.

Fixes #10929

Test Plan: reused T7881 testcase

Reviewers: thomie, bgamari, austin

Reviewed By: thomie, bgamari, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1305

GHC Trac Issues: #10929

This adds a data family (`URec`) and six data family instances (`UAddr`,
`UChar`, `UDouble`, `UFloat`, `UInt`, and `UWord`) which a `deriving
Generic(1)` clause will generate if it sees `Addr#`, `Char#`, `Double#`,
`Float#`, `Int#`, or `Word#`, respectively. The programmer can then
provide instances for these data family instances to provide custom
implementations for unboxed types, similar to how derived `Eq`, `Ord`,
and `Show` instances currently special-case unboxed types.

Fixes #10868.

Test Plan: ./validate

Reviewers: goldfire, dreixel, bgamari, austin, hvr, kosmikus

Reviewed By: dreixel, kosmikus

Subscribers: simonpj, thomie

Differential Revision: https://phabricator.haskell.org/D1239

GHC Trac Issues: #10868

Test Plan: ./validate

Reviewers: thomie, austin, bgamari

Reviewed By: bgamari

Subscribers: #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D1304

The Windows preprocessor code calls `runInteractiveProcess` but does
not check if an exception is thrown.
`runInteractiveProcess` calls `CreateProcess` which when given a format
the system loader does not know about
will throw an exception. This is what makes #9399 fail.

Ultimately we should not use any `CreateProcess` based calls but
instead `ShellExecuteEx` as  this would allow
us to run applications that the shell knows about instead of just the
loader. More details on #365.

This patch removes `PhaseFailed` and throws `ProgramError` instead.
`PhaseFailed` was largely unneeded since it never gave
very useful information aside from the `errorcode` which was almost
always `1`. `IOErrors` have also been eliminated and `GhcExceptions`
thrown in their place wherever possible.

Updates haddock submodule.

Test Plan:
`./validate` to make sure anything didn't break and
`make TESTS="T365"` to test that an error is now properly thrown

Reviewers: austin, thomie, bgamari

Reviewed By: thomie, bgamari

Subscribers: #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D1256

GHC Trac Issues: #365

Here we fix a few mis-optimizations that could occur in code with
floating point comparisons with -0.0. These issues arose from our
insistence on rewriting equalities into case analyses and the
simplifier's ignorance of floating-point semantics.

For instance, in Trac #10215 (and the similar issue Trac #9238) we
turned `ds == 0.0` into a case analysis,

```
case ds of
    __DEFAULT -> ...
    0.0 -> ...
```

Where the second alternative matches where `ds` is +0.0 and *also* -0.0.
However, the simplifier doesn't realize this and will introduce a local
inlining of `ds = -- +0.0` as it believes this is the only
value that matches this pattern.

Instead of teaching the simplifier about floating-point semantics
we simply prohibit case analysis on floating-point scrutinees and keep
this logic in the comparison primops, where it belongs.

We do several things here,

 - Add test cases from relevant tickets
 - Clean up a bit of documentation
 - Desugar literal matches against floats into applications of the
   appropriate equality primitive instead of case analysis
 - Add a CoreLint to ensure we don't pattern match on floats in Core

Test Plan: validate with included testcases

Reviewers: goldfire, simonpj, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1061

GHC Trac Issues: #10215, #9238

As reported in Trac #10891, Template Haskell's `reify` was not
generating Decls for associated types. This patch fixes that.

Note that even though `reifyTyCon` function used in this patch returns
some type instances, I'm ignoring that.

Here's an example of how associated types are encoded with this patch:

(Simplified representation)

    class C a where
      type F a :: *

    -->

    OpenTypeFamilyD "F" ["a"]

With default type instances:

    class C a where
      type F a :: *
      type F a = a

    -->

    OpenTypeFamilyD "F" ["a"]
    TySynInstD "F" (TySynEqn [VarT "a"] "a")

Test Plan:
This patch was already reviewed and even merged. The patch is later
reverted because apparently it broke the build some time between the
validation of this patch and merge. Creating this new ticket to fix the
validation.

Reviewers: goldfire, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1277

GHC Trac Issues: #10891

and not the system locale, which might be something else. This fixes
bug #10907. A test is added, but less useful than it could be until
task #10909 is done.

Differential Revision: D1274

Summary:
DeriveGeneric generates some data types (for data type constructors and for
selectors of those constructors) and instances for those types. This patch
changes name generation for these new types to make it working with data types
with same names imported from different modules and with data types with same
names imported from same modules(using module imports).

Bonus content:

- Some refactoring in `TcGenGenerics.metaTyConsToDerivStuff` to remove some
  redundant partial function applications and to remove a duplicated function.
- Remove some unused names from `OccName`. (those were used for an old
  implementation of `DeriveGeneric`)

Reviewers: kosmikus, simonpj, dreixel, ezyang, bgamari, austin

Reviewed By: bgamari, austin

Subscribers: ezyang, thomie

Differential Revision: https://phabricator.haskell.org/D1081

GHC Trac Issues: #10487

Summary: See Note [MallocPtr finalizers]

Test Plan: validate; new test T10904

Reviewers: ezyang, bgamari, austin, hvr, rwbarton

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1275

This caused the build to fail, due to some type checking errors. Whoops.

This reverts commit 5c115236.

As reported in Trac #10891, Template Haskell's `reify` was not generating Decls
for associated types. This patch fixes that.

Note that even though `reifyTyCon` function used in this patch returns some
type instances, I'm ignoring that.

Here's an example of how associated types are encoded with this patch:

(Simplified representation)

    class C a where
      type F a :: *

    -->

    OpenTypeFamilyD "F" ["a"]

With default type instances:

    class C a where
      type F a :: *
      type F a = a

    -->

    OpenTypeFamilyD "F" ["a"]
    TySynInstD "F" (TySynEqn [VarT "a"] "a")

Reviewed By: goldfire

Differential Revision: https://phabricator.haskell.org/D1254

GHC Trac Issues: #10891

This should (1) fix the ./validate build, which I accidentally broke in D1168,
and (2) update the Cabal submodule so that it recognizes `DeriveLift` as a GHC
extension.

Reviewed By: adamse, austin

Differential Revision: https://phabricator.haskell.org/D1269

GHC Trac Issues: #1830

This adds a constant-folding rule for `Integer`'s implementation of `bit` and
fixes the `T8832` testcase. Fixes #8832.

Reviewed By: simonpj, austin

Differential Revision: https://phabricator.haskell.org/D1255

GHC Trac Issues: #8832

A few tests had the same name which is a big no-no, so I reorganized them a
little. The naming is somewhat haphazard, though...
Signed-off-by: Austin Seipp <austin@well-typed.com>

Summary:
This implements -XDeriveLift, which allows for automatic derivation
of the Lift class from template-haskell. The implementation is based
off of Ian Lynagh's th-lift library
(http://hackage.haskell.org/package/th-lift).

Test Plan: ./validate

Reviewers: hvr, simonpj, bgamari, goldfire, austin

Reviewed By: goldfire, austin

Subscribers: osa1, thomie

Differential Revision: https://phabricator.haskell.org/D1168

GHC Trac Issues: #1830

The default top-level exception handler now uses the `Show` instance for
`ErrorCall` when printing exceptions, so it will actually print the out-of-band
data (e.g. `CallStack`s) in compiled binaries, instead of just printing the
error message.

This also updates the hpc submodule to fix the test output.

Reviewed By: austin, thomie

Differential Revision: https://phabricator.haskell.org/D1217

This patch drops the file level distinction between hs-boot and hsig;
we figure out which one we are compiling based on whether or not there
is a corresponding hs file lying around.

To make the "import A" syntax continue to work for bare hs-boot
files, we also introduce hs-boot merging, which takes an A.hi-boot
and converts it to an A.hi when there is no A.hs file in scope.
This will be generalized in Backpack to merge multiple A.hi files together;
which means we can jettison the "load multiple interface files" functionality.

This works automatically for --make, but for one-shot compilation
we need a new mode: ghc --merge-requirements A will generate an A.hi/A.o
from a local A.hi-boot file; Backpack will extend this mechanism further.

Has Haddock submodule update to deal with change in msHsFilePath behavior.

    - This commit drops support for the hsig extension. Can
      we support it?  It's annoying because the finder code is
      written with the assumption that where there's an hs-boot
      file, there's always an hs file too.  To support hsig, you'd
      have to probe two locations.  Easier to just not support it.

    - #10333 affects us, modifying an hs-boot still doesn't trigger
      recomp.

    - See compiler/main/Finder.hs: this diff is very skeevy, but
      it seems to work.

    - This code cunningly doesn't drop hs-boot files from the
      "drop hs-boot files" module graph, if they don't have a
      corresponding hs file.  I have no idea if this actually is useful.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari, spinda

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1098

This reverts commit 214596de.

This fixes #10896. In the indexed-types/should_fail/BadSock test,
there is a bad type definition. This gets type-checked, an error
gets reported, but then **GHC keeps going**. Later, when
running the simplifier to do an ambiguity check, the bad type
environment causes GHC to fall over. My solution: only run the
simplifier in a clean, error-free type environment.

A downside of this is that fewer error messages are reported.
This makes me a bit sad, but I'm not sure how to avoid the problem.
Suggestions welcome.

This fixes #10817 and #10899. A knock-on effect is that we must
now remember locations of associated type defaults for error
messages during validity checking. This isn't too bad, but it
increases the size of the diff somewhat.

Test cases: indexed-types/should_fail/T108{17,99}

This makes two real changes:
 - Equalities like (a ~R [a]) really *are* insoluble. Previously,
   GHC refused to give up when an occurs check bit on a representational
   equality. But for datatypes, it really should bail.

 - Now, GHC will sometimes report an occurs check error (in cases above)
   for representational equalities. Previously, it never did.

This "fixes" #10715, where by "fix", I mean clarifies the error message.
It's unclear how to do more to fix that ticket.

Test cases: typecheck/should_fail/T10715{,b}

Thanks to Gabor Greif for spotting the mistake.

This fixes #10810 by cleaning up pretty-printing of constructor
declarations. This change also removes a (in my opinion) deeply
bogus orphan instance OutputableBndr [Located name], making
HsDecls now a non-orphan module. Yay all around.

Test case: th/T10810

The previous message was wrong, as pointed out by Jan Stolarek.

This fixes #10811.