How to disable all warnings for one file only?

Questions
1

I’d like to keep both warnings in a project, and some code source raising false warnings. So I’d like to disable all warnings for individual files.
The example for which I’d appreciate a solution is here: Exception where clause produces warning "Defined but not used: ‘this’" · Issue #11004 · digital-asset/daml · GitHub
I already tried these:

{-# OPTIONS_GHC -fno-warn-unused-top-binds #-}
{-# OPTIONS_GHC -fno-warn-unused-binds #-}
{-# OPTIONS_GHC -Wno-unused-top-binds #-}
{-# OPTIONS_GHC -Wno-unused-binds #-}
{-# OPTIONS_GHC -Wno-error #-}

{-# OPTIONS -fno-warn-unused-top-binds #-}
{-# OPTIONS -fno-warn-unused-binds #-}
{-# OPTIONS -Wno-unused-top-binds #-}
{-# OPTIONS -Wno-unused-binds #-}
{-# OPTIONS -Wno-error #-}
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2

To disable just this warning you need the following:

{-# OPTIONS -Wno-unused-matches #-}

To find the right warning your best bet is probably to look at 5.2. Warnings and sanity-checking — Glasgow Haskell Compiler 9.0.1 User's Guide or my short reference (which isn’t exhaustive) at Making the most out of DAML Compiler warnings.

Alternatively, if you just want to undo your -Wall there is -Wno-all. If you want to undo -Werror and go back to warnings instead there is -Wwarn.

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