GitLab

Remove null where

Wibble; fixes tcTyVarDetails breakage

Add assert

Don't use PK_Word64 and ASSIGN_Word64 on 64-bit machines;
they just make the .hc files harder to read without adding any benefit.

Allow trailing semicolon in GADT constructor list

------------------------
          GADTs and unification
  	------------------------

1. Adjustment to typechecking of pattern matching the call to
   gadtRefineTys in TcPat.  Now wobbly types are treated as wild
   cards in the unification process.

2. Add the WildCard possibility to the BindFlag in types/Unify.lhs

3. Some related refactoring of tcMatchTys etc.

recent non-GHCs can use System.Cmd.rawSystem

`rawSystem` is only available in GHC.

Use rawSystem where appropriate.

------------------
          Fix an mdo bug
  	------------------

Embarassingly, this bug makes GHC either panic (for some programs) or
go into a loop (on others) in a recursive mdo that involves a
polymorphic function.  Urk!

The fix is twofold:
  a) add a missing bindInstsOfLocalFuns to tcStmtAndThen (RecStmt case)
  b) bind the correct set of variables in dsRecStmt

I added some explanatory comments about RecStmt in HsExpr too.

The tests is mdo/should_compile/mdo006

ghc/mk/config.mk was never being included in ordinary Makefiles.  It
was only included in the top-level fptools/Makefile for the purposes
of obtaining binary distribution settings.

This fixes that problem, and now as a side-effect $(GhcHasReadline)
will start working again.

Import trimming

Remove redundant Subst hi-boot files

Fix to the pre-Xmas simplifier changes, which should make 
everything work again.  I'd forgotten to attend to this
corner.  Still not properly tested I fear.

Also remove dead code from SimplEnv, and simplify the remainder (hooray).

Wibble

import wibble

---------------------------
          Refactor the simplifier
  	---------------------------

Driven by a GADT bug, I have refactored the simpifier, and the way GHC
treats substitutions.  I hope I have gotten it right.  Be cautious about updating.

* coreSyn/Subst.lhs has gone

* coreSyn/CoreSubst replaces it, except that it's quite a bit simpler

* simplCore/SimplEnv is added, and contains the simplifier-specific substitution
  stuff

Previously Subst was trying to be all things to all men, and that was making
it Too Complicated.

There may be a little more code now, but it's much easier to understand.

Reset the export flag for the new bindings in LiberateCase

Further wibbles to the scoped-tyvar story.

This commit tidies up the ATyVar in TcTyThing, making it
	ATyVar Name Type
instead of the previous misleading
	ATyVar TyVar Type

But the main thing is that we must take care with definitions
like this:

	type T a = forall b. b -> (a,b)

	f :: forall c. T c
	f = ...

Here, we want only 'c' to scope over the RHS of f.  The renamer ensures
that... but we must also take care that we freshly instantiate the 
expanded type signature (forall c b. b -> (c,b)) before checking f's RHS,
so that we don't get false sharing between uses of T.

Simplifications, dead code elimination

minor nomenclature wibble

Enable scoped type variables only where there is an explicit forall

---------------------------------
          Template Haskell: names again
  	---------------------------------

On 2 Dec 04 I made this commit (1.58 in Convert.lhs)

    Fix a Template Haskell bug that meant that top-level names created
    with newName were not made properly unique.

But that just introduced a new bug!  THe trouble is that names created by
newName are NameUs; but I was *also* using NameU for names of free varaibles,
such as the 'x' in the quoted code here
	f x = $( g [| \y -> (x,y) |])

But when converting to HsSyn, the x and y must be treated diffferently.
The 'x' must convert to an Exact RdrName, so that it binds to the 'x' that's
in the type environment; but the 'y' must generate a nice unique RdrName.

So this commit adds NameL for the lexically-scoped bindings like 'x'.

----------------------------------------
	     Add more scoped type variables
	----------------------------------------

Now the top-level forall'd variables of a type signature scope
over the right hand side of that function.

	f :: a -> a
	f x = ....

The type variable 'a' is in scope in the RHS, and in f's patterns.

It's implied by -fglasgow-exts, but can also be switched off independently
using -fscoped-type-variables (and the -fno variant)

----------------------------------------
     New Core invariant: keep case alternatives in sorted order
	----------------------------------------

We now keep the alternatives of a Case in the Core language in sorted
order.  Sorted, that is,
	by constructor tag	for DataAlt
	by literal		for LitAlt

The main reason is that it makes matching and equality testing more robust.
But in fact some lines of code vanished from SimplUtils.mkAlts.


WARNING: no change to interface file formats, but you'll need to recompile
your libraries so that they generate interface files that respect the
invariant.

--------------------------
	Add -fwarn-orphans flag
	--------------------------

This gives a decent report for modules that contain 'orphan' instance and
rule declarations.  These are to be avoided, because GHC has to proactively
read the interface file every single time, just in case the instance/rule is
needed.

The flag just gives a convenient way of identifying the culprits.

---------------------------------
     Template Haskell: dynamically scoped qualified names
	---------------------------------

This commit adds a constructor to TH.Name, so that

	nameBase (mkName "Foo.baz")    == "baz"
	nameModule (MkName "Foo.baz") == "Foo"

We always did parse the module name off the front, but it used to
be done in hsSyn/Convert, but now it's done in TH.Syntax, which is
a better place.

Fix buglet in CSE

An old commit about paths on windows

---------------------------------
     Improve handling of lexically scoped type variables
	---------------------------------

If we have

	f :: T a -> a
	f (x :: T b) = ...

then the lexically scoped variable 'b' should refer to the rigid
type variable 'a', without any intervening wobbliness.  Previously
the in-scope type variables were always mutable TyVars, which were
instantatiated to point to the type they were bound to; but since
the advent of GADTs the intervening mutable type variable is a bad
thing.

Hence
  * In the type environment, ATyVar now carries a type
  * The call to refineTyVars in tc_pat on SigPatIn
    finds the types by matching
  * Then tcExtendTyVarEnv3 extends the type envt appropriately

Rater a lot of huff and puff, but it's quite natural for ATyVar
to contain a type.

Various other small nomenclature changes along the way.

Comments

Remove debug output

Comments

Add missing NoteTy cases to unify_

Comments only

Fix bogon in type comparison

Comment only

Another wibble to the Panic change; this time on Windows

--------------------------------
	Deal properly with dual-renaming
	--------------------------------

When comparing types and terms, and during matching, we are faced
with 
	\x.e1	~   \y.e2

There are many pitfalls here, and GHC has never done the job properly.
Now, at last it does, using a new abstraction VarEnv.RnEnv2.  See
comments there for how it works.

There are lots of consequential changes to use the new stuff, especially
in 
	types/Type (type comparison), 
	types/Unify (matching on types)
	coreSyn/CoreUtils (equality on expressions), 
	specialise/Rules (matching).

I'm not 100% certain of that I've covered all the bases, so let me
know if something unexpected happens after you update.  Maybe wait until
a nightly build has worked ok first!

The documentation breakage continues... >:-( Fixed DocBook. Again: "make html"
(or the faster "make validate" in the case of DocBook XML) is your friend! >:-(