This introduces a TypeData constructor for DatatypeVariant that characterizes type data declarations (introduced in GHC 9.6). Because type data data constructors only exist at the type level, not the value level, it doesn't make sense to define ToJSON or FromJSON instances for a type data declaration. As a result, this patch makes it an error to use aeson's TH machinery in conjunction with a type data declaration.
This introduces a
TypeDataconstructor forDatatypeVariantthat characterizestype datadeclarations (introduced in GHC 9.6). Becausetype datadata constructors only exist at the type level, not the value level, it doesn't make sense to defineToJSONorFromJSONinstances for atype datadeclaration. As a result, this patch makes it an error to useaeson's TH machinery in conjunction with atype datadeclaration.