| Copyright | (c) 2017 Commonwealth Scientific and Industrial Research Organisation |
|---|---|
| License | BSD3 |
| Maintainer | jack.kelly@data61.csiro.au |
| Stability | experimental |
| Portability | Non-Portable |
| Safe Haskell | None |
| Language | Haskell2010 |
Language.Haskell.Instance.Ban
Description
Synopsis
- banInstance :: TypeQ -> String -> DecsQ
Documentation
Arguments
| :: TypeQ | The instance you want to ban.
Most easily written with a type-quote: |
| -> String | The reason that this instance is banned. |
| -> DecsQ |
Ban an instance of a typeclass; code which tries to use the banned instance will fail at compile time. This works by generating an instance that depends on a custom type error:
instance TypeError (..) => ToJSON Foo where ...
Use it like this:
$(banInstance [t|ToJSON Foo|] "why ToJSON Foo should never be defined")