The **`Language.Haskell.Syntax.Decls`** module depends on `GHC.Unit.Module.Warnings` to import the `WarningTxt` data-type which is used by the `WarnDecl` data-type defined therein. The dependence on `WarningTxt` is core to the Haskell AST, so care must be taken to transfer the most parsimonious definitions into the **`Language.Haskell`** "namespace" and leave all other decoupled definitions in **`GHC.Unit.Module.Warnings`**. **The plan to decouple by altering the `WarnDecl` dependency on `WarningTxt`:** 1. Move `WarningTxt` to **`Language.Haskell.Syntax.Decls`** 2. Add extension points to both constructors of `WarningTxt` and an extension point for additional constructors 3. Move the occurrences of `SourceText` in both constructors of `WarningTxt` to the `XWarningTxt` and `XDeprecatedTxt` extension points 4. Substitute `[LocatedE (WithHsDocIdentifiers StringLiteral pass)]` in both by `[XRec pass (WithHsDocIdentifiers StringLiteral pass)]` - This will add another coupling edge to **`GHC.Hs.Doc`**. That's fine, as all edges to **`GHC.Hs.Doc`** will be tackled simultanteously at a later date. - Communication with `XRec` somehow that the location annotation for `WithHsDocIdentifiers StringLiteral pass` here is `LocatedE = GenLocated EpaLocation`. To do this, `type instance Anno (WithHsDocIdentifiers StringLiteral pass) = EpaLocation` is needed. See `Note [XRec and Anno in the AST]` and `Note [XRec and SrcSpans in the AST]` 5. Finally, move the `InWarningCategory` field to the **`Language.Haskell.Syntax.Decls`** as well (because `InWarningCategory` records a property of the AST). - Add a `pass` type arg and add extension points to `InWarningCategory` - The `EpToken` and `SourceText` are for exact print. Move them to the extension point. - Get rid of the `LocatedE WarningCategory` using `XRec pass WarningCategory`, see above - Move `WarningCategory` to **`Language.Haskell.Syntax.Decls`** as well - This will add another coupling edge to **`GHC.Utils.FastString`**, which is fine. That will be decoupled later. Some deviation from the plan above may be necessary, but generally the decoupling endeavor should be straight forward.