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Before, the type of an expression, and the type of a variable
binding that expression used to be different in GHCi. The
reason being that types of bound variables were already normalised.
Now, both are normalised.

This implements the suggestions as given in Trac #10321
Also adds an expected output for test T10321

Reviewed By: goldfire, simonpj

Differential Revision: https://phabricator.haskell.org/D870

GHC Trac Issues: #10321

Clarify that repeated checkCrossStageLifting in RnSplice/TcExpr
check untyped/typed brackets, respectively.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

This was supposed to be part of commit 63a10bbc

 but I pushed
from the wrong machine. This fixes cross compiling to arm.
Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>

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

Test Plan: validate

Reviewers: simonpj, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D850

Previously, if we got a package key in our splice, we'd give
a very unhelpful error message saying we couldn't find
a package 'base-4.7.0.1', despite there being a package with
that source package ID.  Really, we couldn't find a package with
that *key*, so clarify, and also tell the user what the real
package key is.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test was failing (could not execute: pgmlc) for arm (which uses
the llvm backend) due to the `-pgmlc pgmlc` in OPTIONS_GHC. It
was also failing on amd64 in the same way when `-fllvm` was
added to the command line. Its safe to remove because the
compiler should already know which llvm tool to use.

Test Plan: validate

Reviewers: dterei, austin

Subscribers: bgamari, thomie

Differential Revision: https://phabricator.haskell.org/D874

Test `T703` was found to be failing on arm/linux. The solution
was to add a linker flag to explicitly set the stack to
non-executable.
Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>

Test Plan: validate on x86_64 and arm linux

Reviewers: ezyang, rwbarton, austin

Subscribers: bgamari, thomie

Differential Revision: https://phabricator.haskell.org/D875

GHC Trac Issues: #10369

Fixes #9840 and #10306, and includes an alternative resolution to #8028.
This permits empty closed type families, and documents them in the user
guide. It updates the Haddock submodule to support the API change.

Test Plan: Added `indexed-types/should_compile/T9840` and updated
`indexed-types/should_fail/ClosedFam4` and `th/T8028`.

Reviewers: austin, simonpj, goldfire

Reviewed By: goldfire

Subscribers: bgamari, jstolarek, thomie, goldfire

Differential Revision: https://phabricator.haskell.org/D841

GHC Trac Issues: #9840, #10306

This motivation is to declare class IP much earlier (in ghc-prim),
so that implicit parameters (which depend on IP) is available
to library code, notably the 'error' function.

* Move class IP from base:GHC.IP
                to ghc-prim:GHC.Classes
* Delete module GHC.IP from base

* Move types Symbol and Nat
      from base:GHC.TypeLits
      to ghc-prim:GHC.Types

There was a name clash in GHC.RTS.Flags, where I renamed
the local type Nat to RtsNat.

We were trying to load the type for Integer to do defaulting
in ghc-prim, but it's simply not available at that time.

See Note [Deriveds do rewrite Deriveds].  The important point
is that we want to maintain the Note [Can-rewrite relation]
property, lest we risk loops.

This makes TupleTyCon into an ordinary AlgTyCon, distinguished
by its AlgTyConRhs, rather than a separate constructor of TyCon.

It is preparatory work for making constraint tuples into classes,
for which the ConstraintTuple tuples will have a TyConParent
of a ClassTyCon.  Tuples didn't have this possiblity before.

The patch affects other modules because I eliminated the
unsatisfactory partial functions tupleTyConBoxity and tupleTyConSort.
And tupleTyConArity which is just tyConArity.

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

Previously (Trac #10351) we could get

    Non type-variable argument in the constraint: C [t]
    (Use FlexibleContexts to permit this)
    When checking that `f' has the inferred type
      f :: forall t. C [t] => t -> ()

which is a bit stupid: we have *inferred* a type that we
immediately *reject*.  This patch arranges that that the
generalisation mechanism (TcSimplify.decideQuantification)
doesn't pick a predicate that will be rejected by the
subsequent validity check.

This forced some minor refactoring, as usual.

Fixed by the patch for #10009

This regrettably-big patch substantially improves the way in which
"improvement" happens in the constraint solver.  It was triggered by
trying to crack Trac #10009, but it turned out to solve #10340 as
well.

The big picture, with several of the trickiest examples, is described
in Note [The improvement story] in TcInteract.

The major change is this:

* After solving we explicitly try "improvement", by
     - making the unsolved Wanteds into Deriveds
     - allowing Deriveds to rewrite Deriveds
  This more aggressive rewriting "unlocks" some extra
  guess-free unifications.

* The main loop is in TcInteract.solveSimpleWanteds, but I also ended
  up refactoring TcSimplify.simpl_loop, and its surrounding code.

  Notably, any insolubles from the Givens are pulled out
  and treated separately, rather than staying in the inert set
  during the solveSimpleWanteds loop.

There are a lot of follow-on changes

* Do not emit generate Derived improvements from Wanteds.
  This saves work in the common case where they aren't needed.

* For improvement we should really do type-class reduction on Derived
  constraints in doTopReactDict.  That entailed changing the GenInst
  constructor a bit; a local and minor change

* Some annoying faffing about with dropping derived constraints;
  see dropDerivedWC, dropDerivedSimples, dropDerivedInsols,
  and their Notes.

* Some substantial refactoring in TcErrors.reportWanteds.
  This work wasn't strictly forced, but I got sucked into it.
  All the changes are in TcErrors.

* Use TcS.unifyTyVar consistently, rather than setWantedTyBind,
  so that unifications are properly tracked.

* Refactoring around solveWantedsTcM, solveWantedsAndDrop.
  They previously guaranteed a zonked result, but it's more
  straightforward for clients to zonk.

Because when flattening a Derived constraint, the evidence doesn't exist
(it's an error thunk)

I had 'ev' where I should have had 'new_ev'.  It's quite hard to make
this bug cause a failure, but I did eventually get a Lint error
somewhere.  Anyway, it's just a typo, I think.

Seed SpecConstr based on *local* calls as well as *RHS* calls.
See Note [Seeding top-level recursive groups].  The change here
is mentioned here:

   NB: before Apr 15 we used (a) only, but Dimitrios had an example
       where (b) was  crucial, so I added that.

This is a pretty small change, requested by Dimitrios, that adds
SpecConstr call patterns from the rest of the module, as well as ones
from the RHS.

Still to come: #10346.

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>

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

Ben Gamari authored Apr 25, 2015 and Herbert Valerio Riedel committed Apr 25, 2015

This was an unfortunate oversight in the original event manager rework
patch. Fixes #10308

Differential Revision: https://phabricator.haskell.org/D845

See also #9049

This is needed because GHC 7.10.2 requires a minor version bump to base-4.8.1.0

Several test outputs needed base-4.8.1.0 replaced by base-4.8.2.0

Includes lots of shaping examples, and a shaping algorithm description.
Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test case: roles/should_compile/T9204b

This adapts the work of Christiaan Baaij to present a sensible
operational semantics for FC with mutual recursion.

During this commit, I tested to make sure that CoreLint actually
catches the Core error if the typechecker doesn't.

Test case: typecheck/should_fail/T10285

Fix #10263.

by eta-expanding its definition so that GHC optmizes the foldl here.
Also make sure that other uses of last go via foldl as well, to allow
list fusion (tested in T9339). Fixes #10260.

(Next time, when fixing someone else’s mistake, I really shouldn’t do
the precise same thing.)