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The way that newtype declarations were printed in External Core files was
incomplete, since there was no declaration for the coercion introduced by a
newtype.

For example, the Haskell source:

newtype T a = MkT (a -> a)

foo (MkT x) = x

got printed out in External Core as (roughly):

  %newtype T a = a -> a;

  foo :: %forall t . T t -> t -> t =
    %cast (\ @ t -> a1 @ t)
    (%forall t . T t -> ZCCoT t);

There is no declaration anywhere in the External Core program for :CoT, so
that's bad.

I changed the newtype decl syntax so as to include the declaration for the
coercion axiom introduced by the newtype. Now, it looks like:

  %newtype T a ^ (ZCCoT :: ((T a) :=: (a -> a))) = a -> a;

And an external typechecker could conceivably typecheck code that uses this.

The major changes are to MkExternalCore and PprExternalCore (as well as
ExternalCore, to change the External Core AST.) I also corrected some typos in
comments in other files.

Documentation and external tool changes to follow.

For some reason this causes build failures for me in my 32-bit chroot,

 My earlier changes broke printing of function types in .hcr files.
  In other words: the z-encoding must die.

My earlier changes broke printing of function types in .hcr files.
In other words: the z-encoding must die.

Integer, Bool and Unit/Inl/Inr are now in new packages integer
and ghc-prim.

I updated the parser to handle hierarchical module names (with package names)
the way GHC is currently printing them out in External Core.

Beware kludgy use of z-encoding and gratutious copy-pasta from GHC.

You can now use the stand-alone Core parser to parse a very simple
GHC-generated .hcr file (progress!) but not to typecheck or interpret it
(the typechecker/interpreter don't snarf in the right libraries yet, among
other things.) And, the parser is still incomplete in that it doesn't handle
programs with newtypes/GADTs/etc. whose syntax has changed since 2003. In
other words: probably don't try to use this yet.

It's easier for the External Core parser if MkExternalCore prints
module names like:
   base:GHCziBase
rather than like:
   base:GHC.Base
(which it was doing before.)

So now we z-encode the hierarchical module-name part of a module
name, but don't z-encode the ':'.

I also removed some old comments that don't seem relevant anymore.

There was a (suppressed) warning about an incomplete pattern match in make_alt. This was because the DEFAULT alt never has variable bindings. I thought it would be better to check that case and panic if it happens than to have an incomplete pattern. It's still not great, but at least now we don't have to suppress any warnings in this file.

Very little parameter passing is needed without it, so there was no real
benefit to it.

This fixes part of trac #856

Otherwise "$(A) $(B)" will not be equal to "" even if A and B are empty.
Trac #856.

We were doing lots of cons'ing and tail'ing without forcing the tails,
so were building up lots of thunks.

Fixes trac #1893, based on a patch from Daniel Franke.

This optimisation actually make things a bit slower on average, as
measured by nofib. The example in #1136 in particular suffers from high
memory usage. Therefore we no longer do the optimisation.