hie-compat: Add basic support for ghc-9.0.1

A tiny step towards #297

Author: anka-213

hie-compat/hie-compat.cabal

@@ -23,11 +23,15 @@ flag ghc-lib
 library
   default-language:    Haskell2010
   build-depends:
-     base < 4.15, array, bytestring, containers, directory, filepath, transformers
+     base < 4.16, array, bytestring, containers, directory, filepath, transformers
   if flag(ghc-lib)
     build-depends: ghc-lib
   else
     build-depends: ghc, ghc-boot
+  if (impl(ghc >= 9.0) && impl(ghc < 9.1))
+    -- Used by src-reexport/...
+    build-depends: ghc-api-compat
+    ghc-options: -Wall -Wno-name-shadowing
 
   exposed-modules:
     Compat.HieAst
@@ -38,8 +42,10 @@ library
 
   if (impl(ghc > 8.5) && impl(ghc < 8.7) && !flag(ghc-lib))
     hs-source-dirs: src-ghc86
-  if (impl(ghc > 8.7) && impl(ghc < 8.10)) 
+  if (impl(ghc > 8.7) && impl(ghc < 8.10))
     hs-source-dirs: src-ghc88 src-reexport
-  if (impl(ghc > 8.9) && impl(ghc < 8.11) || flag(ghc-lib))
+  if (impl(ghc > 8.9) && impl(ghc < 8.11))
     hs-source-dirs: src-ghc810 src-reexport
+  if (impl(ghc >= 9.0) && impl(ghc < 9.1) || flag(ghc-lib))
+    hs-source-dirs: src-ghc901 src-reexport