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Previously, GHC would not warn whenever there was a class instance that
didn't implement a class method whose name begins with an underscore.

Fixes #12959.

Test Plan: make test TEST=WarnMinimal

Reviewers: austin, bgamari, simonpj

Reviewed By: bgamari, simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2849

GHC Trac Issues: #12959

Reviewers: austin, alanz, bgamari

Reviewed By: alanz, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2836

This fixes some cases of wrong stacks being generated by the profiler.
For background and details on the fix see
`Note [Evaluating functions with profiling]` in `rts/Apply.cmm`.

This does have an impact on allocations for some programs when
profiling.  nofib results:

```
   k-nucleotide          +0.0%     +8.8%    +11.0%    +11.0%      0.0%
         puzzle          +0.0%    +12.5%     0.244     0.246      0.0%
      typecheck           0.0%     +8.7%    +16.1%    +16.2%      0.0%
------------------------------------------------------------------------
--------
            Min          -0.0%     -0.0%    -34.4%    -35.5%    -25.0%
            Max          +0.0%    +12.5%    +48.9%    +49.4%    +10.6%
 Geometric Mean          +0.0%     +0.6%     +2.0%     +1.8%     -0.3%

```

But runtimes don't seem to be affected much, and the examples I looked
at were completely legitimate.  For example, in puzzle we have this:

```
position :: ItemType -> StateType ->  BankType
position Bono = bonoPos
position Edge = edgePos
position Larry = larryPos
position Adam = adamPos
```

where the identifiers on the rhs are all record selectors.  Previously
the profiler gave a stack that looked like

```
  position
  bonoPos
  ...
```

i.e. `bonoPos` was at the same level of the call stack as `position`,
but now it looks like

```
  position
   bonoPos
   ...
```

I used the normaliser from the testsuite to diff the profiling output
from other nofib programs and they all looked better.

Test Plan:
* the broken test passes
* validate
* compiled and ran all of nofib, measured perf, diff'd several .prof
files

Reviewers: niteria, erikd, austin, scpmw, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2804

GHC Trac Issues: #5654, #10007

This deviated by 12% from the expected allocations on Windows.
Yet another case of #12758.

Previously, these functions were hardcoded so as to always `error`
whenever given an argument of 0 or 1. This restriction can be lifted
pretty easily, however.

This requires a slight tweak to `isBuiltInOcc_maybe` in `TysWiredIn` to
allow it to recognize `Unit#` (which is the hard-wired `OccName` for
unboxed 1-tuples).

Fixes #12977.

Test Plan: make test TEST=12977

Reviewers: austin, goldfire, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2847

GHC Trac Issues: #12977

Test Plan: validate

Reviewers: austin, Phyx

Reviewed By: Phyx

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2835

GHC Trac Issues: #12965

Mingw-w64 does a stupid thing. They set the FPU precision to extended
mode by default.  The reasoning is that it's for compatibility with GNU
Linux ported libraries. However the problem is this is incompatible with
the standard Windows double precision mode.  In fact, if we create a new
OS thread then Windows will reset the FPU to double precision mode.  So
we end up with a weird state where the main thread by default has a
different precision than any child threads.

Test Plan: ./validate new test T7289

Reviewers: simonmar, austin, bgamari, erikd

Reviewed By: simonmar

Subscribers: thomie, #ghc_windows_task_force

Differential Revision: https://phabricator.haskell.org/D2819

GHC Trac Issues: #7289

This patch implements the display of constraints in the error message
for typed holes.

Test Plan: validate, read docs

Reviewers: simonpj, austin, bgamari

Reviewed By: simonpj, bgamari

Subscribers: simonpj, thomie

Differential Revision: https://phabricator.haskell.org/D2767

GHC Trac Issues: #10614

Summary:
If we didn't load the orphans, we might conclude an instance
is not implemented when it is.  See test bkp42.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2841

Reviewers: austin, alanz, bgamari

Reviewed By: alanz, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2834

Test Plan: validate

Reviewers: simonpj, austin, bgamari, goldfire

Reviewed By: bgamari, goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2829

Old test used timeouts that leads to the various sporadic errors.
Tet was rewritten to not use timeouts.

Reviewers: austin, erikd, simonmar, bgamari

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2827

GHC Trac Issues: #12956

This reverts commit bc3d37da.

Summary:
Previously, we only checked to recompile if a signature we
previously depended on changed; however, if the -unit-id
settings changed, this could have resulted in more or less
signatures needing to be merged in; we weren't checking
for this case.

(Note that this logic is irrelevant for normal module imports,
which we also check using -unit-id, as we record each import
and redo it, forcing a recompile if the result changed.)
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2832

Summary:
Previously we would just let compilation proceed along until
we tried to pull up the Module for the hsig file, and get
main:A instead of <A>, and get a mysterious error.  Check
for this earlier!

Fixes #12955.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2815

GHC Trac Issues: #12955

This patch makes GHC's floating more robust, by allowing it
to float unboxed expressions of at least some common types.

See Note [Floating MFEs of unlifted type] in SetLevels.

This was all provoked by Trac #12603

Test seems to randomly fail on harbormaster. Disabling it until it can be fixed.

Test Plan: make test TEST=T12903

Reviewers: austin, bgamari, simonmar, mpickering

Reviewed By: mpickering

Subscribers: mpickering, thomie, qnikst

Differential Revision: https://phabricator.haskell.org/D2821

GHC Trac Issues: #12903

I'd forgotten to turn [W] + [D] constraints back into [WD]
in dropDerivedSimples; and that led to Trac #12936.

Fortunately the fix is simple.

Summary:
The use of globals is quite painful when multiple rts are loaded, e.g.
when plugins are loaded, which bring in a second rts. The sharedCAF
appraoch was employed for the FastStringTable; I've taken the libery
to extend this to the other globals I could find.

This is a reboot of D2575, that should hopefully not exhibit the same
windows build issues.

Reviewers: Phyx, simonmar, goldfire, bgamari, austin, hvr, erikd

Reviewed By: Phyx, simonmar, bgamari

Subscribers: mpickering, thomie

Differential Revision: https://phabricator.haskell.org/D2773

Yet another reason why no change to too small to validate. Arg.

Due to #11317.

After talking to Richard, he and I concluded that choosing the rather
common name `Newtype` to represent the corresponding deriving strategy
in Template Haskell was a poor choice of name. I've opted to rename it
to something less common (`NewtypeStrategy`) while we still have time. I
also renamed the corrsponding datatype in the GHC internals so as to
match it.

Reviewers: austin, goldfire, hvr, bgamari

Reviewed By: bgamari

Subscribers: thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D2814

GHC Trac Issues: #10598

This is so that global test flags that control the error formatting are
propagated correctly.  This patch is kind of related to: D2718

The stderr for API annotations is ignored entirely now per @alanz's
suggestion.

Test Plan: validate

Reviewers: thomie, alanz, austin, bgamari

Reviewed By: bgamari

Subscribers: alanz

Differential Revision: https://phabricator.haskell.org/D2808

Something has recently broken it. See #12956.

This patch introduces new rules to perform constant folding through
case-expressions.

E.g.,
```
case t -# 10# of _ {  ===> case t of _ {
         5#      -> e1              15#     -> e1
         8#      -> e2              18#     -> e2
         DEFAULT -> e               DEFAULT -> e
```

The initial motivation is that it allows "Merge Nested Cases"
optimization to kick in and to further simplify the code
(see Trac #12877).

Currently we recognize the following operations for Word# and Int#: Add,
Sub, Xor, Not and Negate (for Int# only).

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Reviewed By: simonpj, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2762

GHC Trac Issues: #12877

Summary:
A continuation of #8953. This fixes an oversight in which the
left-hand sides of closed type families, when reified in Template Haskell,
would not be given kind annotations, even when they are necessary for
disambiguation purposes in the presence of `PolyKinds`.

Fixes #8953 and #12646.

Test Plan: ./validate

Reviewers: hvr, bgamari, austin, goldfire

Reviewed By: goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2795

GHC Trac Issues: #8953, #12646

Test Plan: Validate

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2794

GHC Trac Issues: #10249

Summary:
Previously, we always qualified names, even if they were defined
in the modules we were matching.  Adding the exports of the implementing
module into the RdrEnv greatly reduces the amount of qualification
(although we still can't qualify things that the signature *imported*.)
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2803

Summary:
Previously, we updated tcg_imports after doing all of the
actual matching, which was fine for outputting the interface,
but not good enough for checking if all type classes were
implemented; we weren't treating orphans as visible (when
they needed to be.)

Fixes #12945.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2802

GHC Trac Issues: #12945

It was doing a dump to stdout, which is not repeatable across platforms.

Summary:
Add prettyprinter tests, which take a file, parse it, pretty print it,
re-parse the pretty printed version and then compare the original and
new ASTs (ignoring locations)

Updates haddock submodule to match the AST changes.

There are three issues outstanding

1. Extra parens around a context are not reproduced. This will require an
   AST change and will be done in a separate patch.

2. Currently if an `HsTickPragma` is found, this is not pretty-printed,
   to prevent noise in the output.

   I am not sure what the desired behaviour in this case is, so have left
   it as before. Test Ppr047 is marked as expected fail for this.

3. Apart from in a context, the ParsedSource AST keeps all the parens from
   the original source.  Something is happening in the renamer to remove the
   parens around visible type application, causing T12530 to fail, as the
   dumped splice decl is after the renamer.

   This needs to be fixed by keeping the parens, but I do not know where they
   are being removed.  I have amended the test to pass, by removing the parens
   in the expected output.

Test Plan: ./validate

Reviewers: goldfire, mpickering, simonpj, bgamari, austin

Reviewed By: simonpj, bgamari

Subscribers: simonpj, goldfire, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D2752

GHC Trac Issues: #3384

I failed at the last attempt.

Test Plan: make test TEST=T12919

Reviewers: bgamari, austin

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2788

GHC Trac Issues: #12919

Removed the alignment for strings and mark then as cstring sections in
the generated asm so the linker can merge duplicate sections.

Reviewers: rwbarton, trofi, austin, trommler, simonmar, hvr, bgamari

Reviewed By: hvr, bgamari

Subscribers: simonpj, hvr, thomie

Differential Revision: https://phabricator.haskell.org/D1290

GHC Trac Issues: #9577

This reverts commit 19ae1423.