Ppx_deriving_tools.derivingSourceA deriver is represented by this api
method virtual name : Ppxlib.labelname of the deriver
method virtual extension : loc:Ppxlib.location ->
path:Ppxlib.label ->
Ppxlib.core_type ->
Ppxlib.expressiona deriver can be applied to as type expression as extension node.
method virtual str_type_decl : ctxt:Ppxlib.Expansion_context.Deriver.t ->
(Ppxlib.rec_flag * Ppxlib.type_declaration list) ->
Ppxlib.structureor it can be attached to a type declaration.
method virtual sig_type_decl : ctxt:Ppxlib.Expansion_context.Deriver.t ->
(Ppxlib.rec_flag * Ppxlib.type_declaration list) ->
Ppxlib.signature