* In GHC 8.4.1, the operator <> has become a method of the Semigroup class
and is exported from the Prelude. This is unfortunate, since <> is also
exported from the standard library module Text.PrettyPrint, so in any
module that defines a pretty printer, there is likely to be an ambiguity.
This affects ~18 modules in GF. Solution:
import Prelude hiding (<>)
This works also in older versions of GHC, since GHC does't complain if
you hide something that doesn't exists.
* In GHC 8.4.1, Semigroup has become a superclass of Monoid. This means
that anywhere you define an instance of the Monoid class you also have to
define an instance in the Semigroup class.
This affects Data.Binary.Builder in GF. Solution: conditionally define
a Semigroup instance if compiling with base>=4.11 (ghc>=8.4.1)
This is implemented as a simple post-processing step after partial evaluation
to try compute pre{...} tokens in token sequences. Nothing is done to deal
with intervening free variants.
This was done in response to a query from René T on the gf-dev mailing list.
Becacuse of the new special tokens added to the Symbol type, .gfo and .pgf
files produced with the current version of GF can not always be used with
older versions of GF and the PGF run-time system.
The PGF version number was increased from (2,0) to (2,1). GF can still
read version (2,0) and (1,0), so old PGF files continue to work.
The GFO version was increased from "GF03" to "GF04".
For further separation of pretty printing concerns from conversion concerns,
the Haskell AST and pretty printer has been moved to its own module,
GF.Haskell, also allowing it to be reused in other places where Haskell
code is generated.
If the enumaration of table parameter values fails during the static
traversal phase, try again in the dynamic computation phase, when the values
of bound variables are known.
This is necessary to properly deal with generic table construction in opers,
like the ones found in prelude/Coordination.gf, e.g.
consTable : (P : PType) -> ... = \P ... -> {s1 = table P {...} ; ... }
GF.Compile.Optimize.mkLinReference can fail and cause this error because
the helper function inside it applies msum to a list that might be empty
(if there is a record type that does not contain a field of type Str).
This means that it can return mzero::Err, i.e.
Bad "error (no reason given)"
which can slip through the top level test that only catches Bad "no string".
2 modules: Name clashes caused by Applicative-Monad change in Prelude
2 modules: Ambiguities caused by Foldable/Traversable in Prelude
2 modules: Backwards incompatible changes in time-1.5 for defaultTimeLocale
9 modules: {-# LANGUAGE FlexibleContexts #-} (because GHC checks inferred types
now, in addition to explicitly given type signatures)
Also silenced warnings about tab characters in source files.
+ Some additional simplifying rewrites.
+ Use an intermediate representation for Haskell types, for separation of
concerns and cleaner code.
+ Pretty printer layout tuning
+ Code cleanup.
Introduced an intermediate representation for the generated Haskell expressions.
This allows pretty printing concerns to be separated from conversion concerns,
and makes it easy to apply some simplifying rewrites to the generated
expressions, e.g.
[x] ++ [y] ==> [x,y]
pure f <*> x ==> f <$> x
f <$> pure x ==> pure (f x)
join (pure x) ==> x
