There are several data-types used within **`Language.Haskell.Syntax.Decls`** which are from **`GHC.Types.ForeignCall`** and *do not* require extensibility via the *"Trees that Grow"* (TTG) methodology. The following data-types will be migrated from **`GHC.Types.ForeignCall`** to **`Language.Haskell.Syntax.Decls`**: * `Saftey` * `Header` * `CExportSpec` The fact that these data-types do not require TTG change makes this issue more tractable that removing all data-types imported from **`GHC.Types.ForeignCall`**. Specifically, the follow data-types will be handled in a subsequent issue and MR. Changes for another issue: * `CType`: the data-type construction is very stringy, need to separate things out for pretty printing. * `CCallTarget`: TTG extension with `Maybe Unit`