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This reverts commit 09d05050.

Two main things here

* Previously we only warned about the "head" function of the rule,
  but actually the warning applies to any free variable on the LHS.

* We now warn not only when one of these free vars can inline, but
  also if it has an active RULE (c.f. Trac #10528)

See Note [Rules and inlining/other rules] in Desugar

This actually shows up quite a few warnings in the libraries, notably
in Control.Arrow, where it correctly points out that rules like
    "compose/arr"   forall f g .
                    (arr f) . (arr g) = arr (f . g)
might never fire, because the rule for 'arr' (dictionary selection)
might fire first.  I'm not really sure what to do here; there is some
discussion in Trac #10595.

A minor change is adding BasicTypes.pprRuleName to pretty-print RuleName.

This is the right thing to do anyway, and fixes Trac #10528

It has no special treatment in the compiler any more. The last use
was removed in 99d4e5b4 "Implement cardinality analysis".

Test Plan: validate

Reviewers: austin, bgamari, simonpj

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1099

UInfixT is like UInfixE or UInfixP but for types. Template Haskell
splices can use it to punt fixity handling to GHC when constructing
types.

UInfixT is converted in compiler/hsSyn/Convert to a right-biased tree of
HsOpTy, which is already rearranged in compiler/rename/RnTypes to match
operator fixities.

This patch consists of (1) adding UInfixT to the AST, (2) implementing
the conversion and updating relevant comments, (3) updating
pretty-printing and library support, and (4) adding tests.

Test Plan: validate

Reviewers: austin, goldfire, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1088

GHC Trac Issues: #10522

This implements the `StrictData` language extension, which lets the
programmer default to strict data fields in datatype declarations on a
per-module basis.

Specification and motivation can be found at
https://ghc.haskell.org/trac/ghc/wiki/StrictPragma

This includes a tricky parser change due to conflicts regarding `~` in
the type level syntax: all ~'s are parsed as strictness annotations (see
`strict_mark` in Parser.y) and then turned into equality constraints at
the appropriate places using `RdrHsSyn.splitTilde`.

Updates haddock submodule.

Test Plan: Validate through Harbormaster.

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

Reviewed By: simonpj, tibbe, bgamari

Subscribers: lelf, simonpj, alanz, goldfire, thomie, bgamari, mpickering

Differential Revision: https://phabricator.haskell.org/D1033

GHC Trac Issues: #8347

Summary:
I'm pretty sure that parentheses were intended here. But oddly, they
make very little difference.

The presumably intended expression
    (sizeofBigNat# bn ==# 1#) `andI#` (bigNatToWord bn `eqWord#` w#)
is 1# exactly when bn consists of a single limb equal to w#, clearly.

In the original expression
    sizeofBigNat# bn ==# 1# `andI#` (bigNatToWord bn `eqWord#` w#)
the right-hand side of ==# is always 0# or 1#. So it is 1# when bn
consists of a single limb equal to w#. It is also 1# when bn has
zero limbs and the word past the end of bn does not happen to be
equal to w#. So in practice the difference is that nullBigNat was
eqBigNatWord# to almost everything, but eqBigNatWord# is never
supposed to be called on nullBigNat anyways.

Note that even the corrected version might perform an out-of-bounds
memory access if passed nullBigNat, because `andI#` is not guaranteed
to short-circuit, though in fact GHC does convert isZeroBigNat to a
series of branches in my local build.

Test Plan: validate

Reviewers: hvr, bgamari, goldfire, austin

Reviewed By: hvr, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1095

Summary:
The form
  case na# ==# nb# of
    0# -> ...
    _  -> ...
sometimes generates convoluted assembly, see #10676.
timesInt2Integer was the most spectacular offender, especially as
it is a rather cheap function overall (no calls to gmp).

I checked a few instances and some of the old generated assembly
was fine already, but I changed them all for consistency. The new
form is also more consistent with use of these primops in general.

Test Plan: validate

Reviewers: hvr, bgamari, goldfire, austin

Reviewed By: hvr

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1094

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

Noticed today that deprecation warnings are
slightly broken in -HEAD:

  mtl-2.2.1/Control/Monad/Error/Class.hs:46:1: warning:
    Module ‘Control.Monad.Trans.Error’ is deprecated:
      ([", U, s, e,  , C, o, n, t, r, o, l, ., M, o, n, a, d, ., T, r, a,
        n, s, ., E, x, c, e, p, t,  , i, n, s, t, e, a, d, "],
       Use Control.Monad.Trans.Except instead)

Commit e6191d1c
slightly changed WarningTxt declaration:

-data WarningTxt = WarningTxt (Located SourceText) [Located FastString]
-                | DeprecatedTxt (Located SourceText) [Located FastString]
+data WarningTxt = WarningTxt (Located SourceText)
+                             [Located (SourceText,FastString)]
+                | DeprecatedTxt (Located SourceText)
+                                [Located (SourceText,FastString)]

But 'moduleWarn' function was not updated to do the stripping.
Signed-off-by: Sergei Trofimovich <siarheit@google.com>

Reviewers: austin, bgamari, hvr, goldfire, rwbarton, alanz

Reviewed By: rwbarton, alanz

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1096

GHC Trac Issues: #10313

When staring at instanceCantMatch I realised that it
was returning False (safe but inefficient) when it could
validly return True, on arguments like
   [Nothing,   Just Int]
   [Just Bool, Just Bool]

This patch makes it a bit cleverer.

This refactoring was triggered by Trac #10675.

We were using 'improveClsFD' (previously called 'checkClsFD') for
both
  * Improvement: improving a constraint against top-level instances
  * Consistency: checking when two top-level instances are
    consistent

Using the same code for both seemed attractive at the time, but
it's just too complicated.  So I've split it:
 * Improvement: improveClsFD
 * Consistency: checkFunDeps

Much clearer now!

In "Improve strictness analysis for exceptions"
   commit 7c0fff41
   Author: Simon Peyton Jones <simonpj@microsoft.com>
   Date:   Tue Jul 21 12:28:42 2015 +0100

I made catch# strict in its first argument.  But today I found
a very old comment suggesting the opposite.  I disagree with the
old comment, but I've elaborated the Note, which I reproduce here:

    {- Note [Strictness for mask/unmask/catch]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Consider this example, which comes from GHC.IO.Handle.Internals:
       wantReadableHandle3 f ma b st
         = case ... of
             DEFAULT -> case ma of MVar a -> ...
             0#      -> maskAsynchExceptions#
                           (\st -> case ma of MVar a -> ...)
    The outer case just decides whether to mask exceptions, but we
    don't want thereby to hide the strictness in 'ma'!  Hence the use
    of strictApply1Dmd.

    For catch, we know that the first branch will be evaluated, but
    not necessarily the second.  Hence strictApply1Dmd and
    lazyApply1Dmd

    Howver, consider
        catch# (\st -> case x of ...) (..handler..) st
    We'll see that the entire thing is strict in 'x', so 'x' may be
    evaluated before the catch#.  So fi evaluting 'x' causes a
    divide-by-zero exception, it won't be caught.  This seems
    acceptable:
      - x might be evaluated somewhere else outside the catch# anyway
      - It's an imprecise eception anyway.  Synchronous exceptions (in
        the IO monad) will never move in this way.
    There was originally a comment
      "Catch is actually strict in its first argument
       but we don't want to tell the strictness
       analyser about that, so that exceptions stay inside it."
    but tracing it back through the commit logs did not give any
    rationale.  And making catch# lazy has performance costs for
    everyone.

A library name is a package name, package version, and hash of the
version names of all textual dependencies (i.e. packages which were included.) A library
name is a coarse approximation of installed package IDs, which are suitable for
inclusion in package keys (you don't want to put an IPID in a package key, since
it means the key will change any time the source changes.)

    - We define ShPackageKey, which is the semantic object which
      is hashed into a PackageKey.  You can use 'newPackageKey'
      to hash a ShPackageKey to a PackageKey

    - Given a PackageKey, we can lookup its ShPackageKey with
      'lookupPackageKey'.  The way we can do this is by consulting
      the 'pkgKeyCache', which records a reverse mapping from
      every hash to the ShPackageKey.  This means that if you
      load in PackageKeys from external sources (e.g. interface
      files), you also need to load in a mapping of PackageKeys
      to their ShPackageKeys so we can populate the cache.

    - We define a 'LibraryName' which encapsulates the full
      depenency resolution that Cabal may have selected; this
      is opaque to GHC but can be used to distinguish different
      versions of a package.

    - Definite packages don't have an interesting PackageKey,
      so we rely on Cabal to pass them to us.

    - We can pretty-print package keys while displaying the
      instantiation, but it's not wired up to anything (e.g.
      the Outputable instance of PackageKey).
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: austin, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1056

GHC Trac Issues: #10566

Declaring a custom fixity for an infix data constructor should work:

    Prelude> data Infix a b = a :@: b; infixl 4 :@:

This is a followup to #2947, which handled fixity declarations in ghci
statements (e.g. let add = (+); infixl 6 `add`).

Support for declarations (data, type, newtype, class, instance,
deriving, and foreign) was added to GHCi in #4929.

Reviewers: simonpj, austin, thomie

Subscribers: thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D1028

GHC Trac Issues: #10018

Add CoreSyn.chooseOrphanAnchor, and use it

C99 does not allow unnamed parameters in definition argument lists [1].

[1] http://stackoverflow.com/questions/8776810/parameter-name-omitted-c-vs-c

When a constructor was mistakenly imported directly instead of as a
constructor of a data type, a hint will be shown on how to correctly
import
it. Just like the constructor, the data type should be surrounded in
parentheses if it is an operator (TypeOperator in this case).

Instead of:

    error:
        In module ‘Data.Type.Equality’:
          ‘Refl’ is a data constructor of ‘:~:’
        To import it use
          ‘import’ Data.Type.Equality( :~:( Refl ) )
        or
          ‘import’ Data.Type.Equality( :~:(..) )

Print:

    error:
        In module ‘Data.Type.Equality’:
          ‘Refl’ is a data constructor of ‘(:~:)’
        To import it use
          ‘import’ Data.Type.Equality( (:~:)( Refl ) )
        or
          ‘import’ Data.Type.Equality( (:~:)(..) )

Test Plan: pass new test

Reviewers: austin, bgamari, simonpj

Reviewed By: simonpj

Subscribers: simonpj, thomie

Differential Revision: https://phabricator.haskell.org/D1093

GHC Trac Issues: #10668

GHC has used surrogate code points for roundtripping since 7.4.
See Note [Roundtripping].

Also, improve the wording of that Note slightly.

Test Plan: validate still passes

Reviewers: austin, hvr, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1087

Accept next docstrings (`-- | Docstring`) on GADT constructors.

I have confirmed that this adds no shift/reduce conflicts.

Test Plan: haddockA034

Reviewers: austin, simonpj, simonmar

Reviewed By: simonmar

Subscribers: Fuuzetsu, simonmar, thomie, mpickering, edsko

Differential Revision: https://phabricator.haskell.org/D1086

With -dynamic-too, .dyn_o files were not being generated for .hsig
files.  Normally, this is handled in the pipeline; however, the branch
for .hsig files called compileEmptyStub directly instead of going
through runPipeline.  When compiling a Cabal package that included .hsig
files, this triggered a linker error later on, as it expected a .dyn_o
file to have been generated for each .hsig.

The fix is to use runPipeline for .hsig files, just as with .hs files.
Alternately, one could duplicate the logic for handling -dynamic-too in
the .hsig branch, but simply calling runPipeline ends up being much
cleaner.

Test Plan: validate

Reviewers: austin, ezyang, bgamari, thomie

Reviewed By: ezyang, thomie

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1084

GHC Trac Issues: #10660

Reviewers: austin, bgamari, Fuuzetsu

Reviewed By: bgamari

Subscribers: thomie, bgamari

Differential Revision: https://phabricator.haskell.org/D1025

GHC Trac Issues: #10398

In dataConCannotMatch we were using a GADT data con without
properly instantiating the existential type variables.
The fix is easy, and the code is tighter.

Summary:
It's shorter!  And then when Backpack overrides lookupIfaceTop
everyone will see the right information.
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/D1090

Summary:
These are going to be used by Backpack, but someone else
might find them useful.  They do the "obvious thing".
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: goldfire, bgamari, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1089

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

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

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

Note: ModIface format change is BC, no need to recompile.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

It's failing at the moment with "The log length has exceeded the limit
of 4 Megabytes".

We don't seem to have periods of >10 minutes without output after all,
which was the initial reason of not using `--quiet`.

Summary:
The current OS memory allocator conflates the concepts of allocating
address space and allocating memory, which makes the HEAP_ALLOCED()
implementation excessively complicated (as the only thing it cares
about is address space layout) and slow. Instead, what we want
is to allocate a single insanely large contiguous block of address
space (to make HEAP_ALLOCED() checks fast), and then commit subportions
of that in 1MB blocks as we did before.
This is currently behind a flag, USE_LARGE_ADDRESS_SPACE, that is only enabled for
certain OSes.

Test Plan: validate

Reviewers: simonmar, ezyang, austin

Subscribers: thomie, carter

Differential Revision: https://phabricator.haskell.org/D524

GHC Trac Issues: #9706