Template Haskell support for reifying non-vanilla data constructors
Apart from not supporting GADT syntax, Template Haskell also doesn't currently have support for reifying non-vanilla data constructors given with the normal syntax, even though the API is fully capable of representing all of its features.
In the case where I try to reify a data declaration of the form,
data AnyShow = forall a. Show a => AnyShow a(using !ExistentialQuantification)
I get the error: Can't reify a GADT data constructor: `!AnyShow',
Even though it can easily be represented:
DataD [] AnyShow [] [ForallC [PlainTV a] [ClassP Show [VarT a]] (NormalC AnyShow [(NotStrict,VarT a)])] []I propose to add support for reifying non-vanilla data constructors given with the normal syntax.
(Of note is that everything that can be done using GADT syntax can also be done with the normal syntax, using !ExistentialQuantification and equality constraints from !TypeFamilies.)
Patch shortly.
Trac metadata
| Trac field | Value |
|---|---|
| Version | |
| Type | FeatureRequest |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Template Haskell |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |