reify does not work on data structures defined in files without Language pragma of Template Haskell and without -fth or -XTemplateHaskell command line flags

reify does not work on data structures defined in files compiled without TemplateHaskell.

• Main.hs: File with the splice expression
• Fields.hs: File with the Template Haskell code that lists all the fields in particular datastructures recursively.
• DataStructure.hs: File with the datastructure being reified in TH.hs

When all the files have the TemplateHaskell Language pragma, everything works. When the command line flag -fth or -XTemplateHaskell are used, everything works. When the DataStructure.hs does not have the TemplateHaskell Language pragma, then when the data-structure is being reified in TH.hs, it generates blank lists for all the fields of TyConI (DataD ...