This package provides a consistent interface to a subset of Template Haskell.
Currently the package provides a consistent view of the reified declaration
information about datatypes, newtypes, and data family instances. These
interfaces abstract away the differences in the normal and GADT syntax used to
define these types.
Contact Information
Please contact me via GitHub or on the #haskell IRC channel on irc.libera.chat
Changes
Revision history for th-abstraction
0.5.0.0 – 2023.02.27
Support the TypeData language extension added in GHC 9.6. The
DatatypeVariant data type now has a separate TypeData constructor to
represent type data declarations.
Add a Lift instance for th-abstraction’s compatibility shim for
Specificity when building with pre-9.0 versions of GHC.
0.4.5.0 – 2022.09.12
Fix a bug in which data family declarations with interesting return kinds
(e.g., data family F :: Type -> Type) would be reified incorrectly when
using reifyDatatype.
0.4.4.0 – 2022.07.23
Support free variable substitution and infix resolution for
PromotedInfixT and PromotedUInfixT on template-haskell-2.19.0.0 or
later.
0.4.3.0 – 2021.08.30
Make applySubstitution avoid capturing type variable binders when
substituting into foralls.
Fix a bug in which resolveTypeSynonyms would incorrectly expand type
synonyms that are not applied to enough arguments.
Allow the test suite to build with GHC 9.2.
0.4.2.0 – 2020-12-30
Explicitly mark modules as Safe (or Trustworthy for GHC versions prior to 8.4).
0.4.1.0 – 2020-12-09
Fix a bug in which normalizeDec would give incorrect kind annotations to
type variables in quoted Decs. normalizeDec now leaves the kinds of
type variable binders alone.
0.4.0.0 – 2020-09-29
Adapt to the TyVarBndr data type gaining a new flag type parameter
(in template-haskell-2.17.0.0) to represent its specificity:
Introduce a new Language.Haskell.TH.Datatype.TyVarBndr module that
defines TyVarBndr_, a backwards-compatible type synonym for TyVarBndr,
as well as backporting TyVarBndrSpec, TyVarBndrUnit, and Specificity.
This module also defines other useful functions for constructing and
manipulating TyVarBndrs.
The types in Language.Haskell.TH.Datatype now use TyVarBndr_,
TyVarBndrUnit, and TyVarBndrSpec where appropriate. Technically, this
is not a breaking change, since all three are simple type synonyms around
TyVarBndr, but it is likely that you will need to update your
th-abstraction-using code anyway if it involves a TyVarBndr-consuming
function.
0.3.2.0 – 2020-02-06
Support substituting into and extracting free variables from ForallVisTs
on template-haskell-2.16.0.0 (GHC 8.10) or later.
Fix a bug in which freeVariables could report duplicate kind variables when
they occur in the kinds of the type variable binders in a ForallT.
Fix a bug in which resolveInfixT would not resolve UInfixTs occurring in
the kinds of type variable binders in a ForallT.
Fix a bug in which the TypeSubstitution ConstructorInfo instance would not
detect free kind variables in the constructorVars.
0.3.1.0 – 2019-04-28
Fix a bug which would cause data family information to be reified incorrectly
with GHC 8.8+ in some situations.
0.3.0.0 – 2019-04-26
Breaking change: the datatypeVars field of DatatypeInfo is now of type
[TyVarBndr] instead of [Type], as it now refers to all of the bound type
variables in the data type. The old datatypeVars field has been renamed to
datatypeInstTypes to better reflect its purpose.
In addition, the type of normalizeCon now has an additional [TyVarBndr]
argument, since DatatypeInfo now requires it.
Support template-haskell-2.15.
Fix a bug in which normalizeDec would not detect existential type variables
in a GADT constructor if they were implicitly quantified.
Fix a bug in which normalizeDec would report an incorrect number of
datatypeVars for GADT declarations with explicit return kinds (such as
data Foo :: * -> * where).
0.2.11.0 – 2019-02-26
Fix a bug in which freeVariablesWellScoped would sometimes not preserve
the left-to-right ordering of Names generated with newName.
0.2.10.0 – 2018-12-20
Optimization: quantifyType now collapses consecutive foralls. For
instance, calling quantifyType on forall b. a -> b -> T a now produces
forall a b. a -> b -> T a instead of forall a. forall b. a -> b -> T a.
0.2.9.0 – 2018-12-20
Fix a bug in which resolveTypeSynonyms would not look into ForallTs,
SigTs, InfixTs, or ParensTs.
Fix a bug in which quantifyType would not respect the dependency order of
type variables (e.g., Proxy (a :: k) would have erroneously been quantified
as forall a k. Proxy (a :: k)).
Fix a bug in which asEqualPred would return incorrect results with GHC 8.7.
Add a freeVariablesWellScoped function which computes the free variables of
a list of types and sorts them according to dependency order.
Add a resolveKindSynonyms function which expands all type synonyms in a
Kind. This is mostly useful for supporting old GHCs where Type and Kind
were not the same.
0.2.8.0 – 2018-06-29
GADT reification is now much more robust with respect to PolyKinds:
A bug in which universally quantified kind variables were mistakenly
flagged as existential has been fixed.
A bug in which the kinds of existentially quantified type variables
were not substituted properly has been fixed.
More kind equalities are detected than before. For example, in the
following data type:
data T (a :: k) where
MkT :: forall (a :: Bool). T a
We now catch the k ~ Bool equality.
Tweak resolveTypeSynonyms so that failing to reify a type constructor
name so longer results in an error. Among other benefits, this makes
it possible to pass data types with GADT syntax to normalizeDec.
0.2.7.0 – 2018-06-17
Fix bug in which data family instances with duplicate occurrences of type
variables in the left-hand side would have redundant equality constraints
in their contexts.
0.2.6.0 – 2017-09-04
Fix bug in which applySubstitution and freeVariables would ignore
type variables in the kinds of type variable binders.
0.2.5.0
Added pragLineDCompat, newtypeDCompat and tySynInstDCompat
0.2.4.0 – 2017-07-31
Fix bug that caused GADT equality constraints to be incorrect in some cases.
Expose Unpackedness and Strictness (which were unexported by accident).
0.2.3.0 – 2017-06-26
Add resolvePredSynonyms
Add reifyConstructor, which allows reification of ConstructorInfo from
a constructor name, and lookupByConstructorName, which allows directly
looking up a ConstructorInfo from a DatatypeInfo value for a given
constructor Name.
Augment reifyDatatype to be able to look up DatatypeInfo from the Name
of a record selector for one of its constructors. Also add reifyRecord for
reification of of ConstructorInfo from a record name, and
lookupByRecordName, which allows directly looking up a ConstructorInfo
from a DatatypeInfo value for a given record Name.
Fix bug that caused th-abstraction to fail on GHC 7.0 and 7.2 when passing
a vanilla constructor name to reifyDatatype
Make normalizeDec and normalizeCon more robust with respect to
data family instances on GHC 7.6 and 7.8
0.2.2.0 – 2017-06-10
Fix freeVariables on lists not not produce duplicates.
0.2.1.0 – 2017-06-09
Add sensible reify defaults and error messages when we
can’t backport fixes to old GHC Template Haskell output
due to hand-written Decs being processed.
0.2.0.0 – 2017-06-03
Added reifyFixityCompat
Added constructorStrictness field to ConstructorInfo
Infer more kind signatures when missing on old GHCs
Added parameter to normalizeCon
Support GHC back to 7.0.4
0.1.3.0 – 2017-05-27
Added resolveInfixT which uses reified fixity information to resolve UInfixT
Added asEqualPred and asClassPred
Fixed data-instance GADTs
0.1.2.1 – 2017-05-21
Add eta reduction fixes to GHC 7.6
0.1.2.0 – 2017-05-21
Added arrowKCompat
Added workaround for GHC 7.8 data instance eta reduction bug
Added kind signatures to datatypeVars
0.1.1.0 – 2017-05-20
Better matching of constraints generated for GADTs across GHC versions
Added dataDCompat
Support for giving value constructors to reifyDatatype. This enables
data families to be reified easily.
