The pre-condition on `mkTopTCvSubst` turned out to be wrong and
not satisfied by any of the callers. I've fixed it, so that it
constructs the in_scope set from the range of the substitution.
`mkTopTCvSubst` was also unnecessarily general it is never called
with `CoVars`, so I changed the type signature and added an assertion.

Test Plan: ./validate --slow

Reviewers: goldfire, simonpj, bgamari, austin

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1801

GHC Trac Issues: #11371

Summary:
Previously, `-Wunused-matches` would fire whenever it detected unused type
variables in a type family or data family instance. This can be annoying for
users who wish to use type variable names as documentation, as being
`-Wall`-compliant would mean that they'd have to prefix many of their type
variable names with underscores, making the documentation harder to read.

To avoid this, a new warning `-Wunused-type-variables` was created that only
encompasses unused variables in family instances. `-Wunused-matches` reverts
back to its role of only warning on unused term-level pattern names. Unlike
`-Wunused-matches`, `-Wunused-type-variables` is not implied by `-Wall`.

Fixes #11451.

Test Plan: ./validate

Reviewers: goldfire, ekmett, austin, hvr, simonpj, bgamari

Reviewed By: simonpj, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1825

GHC Trac Issues: #11451

There are two ways to do retainer profiling. Quoting from the user's guide:
  1. `+RTS -hr` "Breaks down the graph by retainer set"
  2. `+RTS -hr<cc> -h<x>`, where `-h<x>` is one of normal heap profiling
     break-down options (e.g. `-hc`), and `-hr<cc> means "Restrict the
     profile to closures with retainer sets containing cost-centre
     stacks with one of the specified cost centres at the top."

Retainer profiling writes to a .hp file, like the other heap profiling
options, but also to a .prof file. Therefore, when the .prof file is not
writeable for whatever reason, retainer profiling should be turned off
completely.

This worked ok when running the program with `+RTS -hr` (option 1), but a
segfault would occur when using `+RTS -hr<cc> -h<x>`, with `x!=r` (option 2).

This commit fixes that.

Reviewed by: bgamari

Differential Revision: https://phabricator.haskell.org/D1849

GHC Trac Issues: #11489

Before:
 * without -rtsopts: Most RTS options are disabled. Link with -rtsopts to enable them.
 * with -rtsopts: invalid heap profile option: -hc
After:
 * the flag -hc requires the program to be built with -prof

Copy `Note [OPTION_SAFE vs OPTION_UNSAFE]` from commit 8c7ad0bd.

Reviewed by: bgamari

Differential Revision: https://phabricator.haskell.org/D1845

This is the fix proposed in #11371:
```
In other cases, we already have the in-scope set in hand. Example: in
CoreLint.lintTyApp we find a call to substTyWith. But Lint carries an
in-scope set, so it would be easy to pass it to substTyWith.
```

Test Plan: ./validate --slow (only pre-existing problems)

Reviewers: simonpj, goldfire, austin, nomeata, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1820

GHC Trac Issues: #11371

See comment:16 in Trac #10712. The tests were wrong, not GHC!

Most notably, this pulls in a feature needed for #11100 (remote ghci)
windows-support

This shouldn't have any noticeable API changes for GHC

Follow-up to 132c2089

[skip ci]

Crikey!  Not just one but two bugs in type variable cloning,
both dating from the days before PolyKinds.  Both were shown up
by Trac #11330.

1. In SetLevels, when floating a case expression we must clone its
   binders, *and* do so in a telescope-aware way, because the
   constructor may bind a kind variable that appears in the kind
   of a type variable.

   Instead of doing this (wrongly) by steam, call CoreSubst.cloneBndrs.

   I added Notes and did other refactoring at the same time.

2. It turned out that CoreSubst.cloneBndrs calls TyCoRep.cloneTyVarBndr,
   and that too was bogus!  It didn't substitute in the kind of the
   TyVar being cloned.  There was even a comment to say "variables can't
   appear in kinds".  Thta hasn't been true for a long time now.

Easily fixed.

Interestingly, I then found that test
   dependent/should_compile/KindEqualities
was emitting a new inexhaustive-pattern-match warning.  Sure enough
it was valid!  So the lack of cloning in cloneTyVarBndr really was
causing an observable bug; just one that we had not observed.

As Bartosz has discovered, the invariants for substitutions were
wrong, and in particular the "mkTop...Subst" and "zipTop..Subst"
functions were building substitutions that didn't obey even the
old invariants.

This patch kills of the bogus zipTopTCvSubst in favour of the
more robust zipOpenTCvSubst.

I tripped over this because my upcoming patch (concerning SetLevels,
Trac #11330) triggered an ASSERT failure in the substitution
well-formedness assertion in TyCoRep.

This code deliberately builds a subtle negative-occurrence-of-data-type
example, described in the paper, so with -O it'll give "simplifier
ticks exhausted".

This patch just adds a comment to explain.

With -dppr-debug the output for the (ofen-large) InScope set
was overwhelming.  This makes it smaller.

Only affects debugging.

Ben Gamari authored Jan 25, 2016 and Ben Gamari committed Jan 25, 2016

We are unable to produce load/store barriers for pre-ARMv7 targets.
Phab:D894 added dummy cases to SMP.h for these barriers to prevent the
build from failing under the assumption that there are no SMP-capable
devices of this vintage. However, #10433 points out that it is more
correct to simply set NOSMP for such targets.

Tested By: rwbarton

Test Plan: Validate

Reviewers: erikd, rwbarton, austin

Reviewed By: rwbarton

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1704

GHC Trac Issues: #10433

Ben Gamari authored Jan 25, 2016 and Ben Gamari committed Jan 25, 2016

This allows the user to avoid warnings for warning flags that GHC
doesn't recognise. See #11429 for details..

Test Plan: Validate with T11429[abc] tests

Reviewers: austin, hvr

Reviewed By: hvr

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1830

GHC Trac Issues: #11429

Ben Gamari authored Jan 25, 2016 and Ben Gamari committed Jan 25, 2016

This supplements the description previously added in
6400c768. See #10560 for details.

Test Plan: read it

Reviewers: austin

Subscribers: thomie, hvr

Differential Revision: https://phabricator.haskell.org/D1831

GHC Trac Issues: #10560

Ben Gamari authored Jan 25, 2016 and Ben Gamari committed Jan 25, 2016

Test Plan: Read it

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1829

Herbert Valerio Riedel authored Jan 25, 2016 and Ben Gamari committed Jan 25, 2016

This warning flag was recently introduced as part of #10751. However,
it was missed during code-review that almost all existing warning
flags use a plural-form, so for consistency this commit renames
that warning flag to `-Wmissing-monadfail-instances`.

Test Plan: local validate (still running)

Reviewers: quchen, goldfire, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1842

GHC Trac Issues: #10751

Summary:
These are the names used by arm-linux-androideabi-objdump, so
it's helpful to have them here next to the Stg register mapping.

Reviewers: austin, erikd, bgamari

Reviewed By: erikd, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1840

Summary: This is already the behavior on Elf_Rela platforms, and is helpful.

Reviewers: simonmar, austin, bgamari, erikd

Reviewed By: erikd

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1841

Blimey!  CoreUtils.exprIsHNFlike had not one but two bugs.

 * is_hnf_like treated coercion args like type args
   (result: exprIsHNF might wrongly say True)

 * app_is_value treated type args like value args
   (result: exprIsHNF might wrongly say False)

Bizarre.  This goes back to at least 2012. It's amazing that it
hasn't caused more trouble.

It was discovered by a Lint error when compiling Trac #11248 with -O.

In fixing Trac #11480 I had omitted to deal with FunDeps.oclose,
which was making recursive use of immSuperClasses, and hence
going into a loop in the recursive case.

Solution: use transSuperClasses, which takes care not to.

I found that there was some code duplication going on,
so I've put more into the shared function checkValidFamPats.

I did some refactoring in checkConsistentFamInst too,
preparatory to #11450; the error messages change a little
but no change in behaviour.

This issue came up in Trac #11480, and is documented in
Note [When superclasses help] in TcRnTypes.

We were getting a spurious warning
  T11480.hs:1:1: warning:
     solveWanteds: too many iterations (limit = 4)

The fix is easy.  A bit of refactoring along the way.

The original bug report in Trac #11480 appears to work
fine in HEAD and the 8.0 branch but I added a regression
test in this commit as well.

The MonadFail proposal implemented so far via #10751 only warns about
missing `MonadFail` instances based on existence of failible pattern
matches in `do`-blocks.

However, based on the noncanonical Monad warnings implemented via #11150
we can provide a different mechanism for detecting missing `MonadFail`
instances quite cheaply. That is, by checking for canonical `fail` definitions.

In the case of `Monad`/`MonadFail`, we define the canonical implementation of
`fail` to be such that the soft-deprecated method shall (iff overridden) be
defined in terms of the non-deprecated method. Consequently, in case of
`MonadFail`, the `Monad(fail)` method shall be defined as alias of
the `MonadFail(fail)` method.

This allows us at some distant point in the future to remove `fail` from
the `Monad` class, while having GHC ignore/tolerate such literal canonical
method definitions.

Reviewed By: bgamari, RyanGlScott

Differential Revision: https://phabricator.haskell.org/D1838

Fixes validate on Travis.

Reviewed by: bgamari

Differential Revision: https://phabricator.haskell.org/D1834

Refactoring only. It's shorter, and brings
`HasDynFlags/ContainsDynFLags` in line with `HasModule/ContainsModule`.
Introduce `updTopEnv`.

Reviewed by: bgamari

Differential Revision: https://phabricator.haskell.org/D1832

This information is mostly useless, since hierarchical modules are valid
Haskell2010 and everybody knows how to use them.

Reviewed by: bgamari

Differential Revision: https://phabricator.haskell.org/D1835

See #5641.

Test Plan: validate --slow

Reviewers: austin, bgamari, goldfire

Reviewed By: goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1824

It is impossible to write warning-free code under the three-release
policy with this flag enabled by default. See #11370 for details.