Add roles declarations to allow safe coercions (#175)

Author: kl0tl

src/React.purs

@@ -93,6 +93,8 @@ foreign import data ReactComponent :: Type
 -- | A reference to a component, essentially React's `this`.
 foreign import data ReactThis :: Type -> Type -> Type
 
+type role ReactThis representational representational
+
 foreign import data ReactUnusedSnapshot :: Type
 
 type SyntheticEventHandler event = EffectFn1 event Unit
@@ -251,6 +253,8 @@ foreign import statelessComponent :: forall props.
 -- | React class for components.
 foreign import data ReactClass :: Type -> Type
 
+type role ReactClass representational
+
 foreign import fragment :: ReactClass { children :: Children }
 
 -- | Read the component props.

src/React/Ref.purs

@@ -27,8 +27,12 @@ foreign import data NativeNode :: Type
 
 foreign import data Ref :: Type -> Type
 
+type role Ref representational
+
 foreign import data RefHandler :: Type -> Type
 
+type role RefHandler representational
+
 
 foreign import createRef :: forall a. Effect (Ref a)
 

src/React/SyntheticEvent.purs

@@ -136,6 +136,8 @@ type SyntheticWheelEvent
 
 foreign import data SyntheticEvent_ :: Row Type -> Type
 
+type role SyntheticEvent_ representational
+
 foreign import data NativeEventTarget :: Type
 
 foreign import data NativeEvent :: Type