driver: Fix recompilation for modules importing GHC.Prim

The GHC.Prim module is quite special as there is no interface file,
therefore it doesn't appear in ms_textual_imports, but the ghc-prim
package does appear in the direct package dependencies. This confused
the recompilation checking which couldn't find any modules from ghc-prim
and concluded that the package was no longer a dependency.

The fix is to keep track of whether GHC.Prim is imported separately in
the relevant places.

Fixes #20084

1 files changed, 4 insertions, 3 deletions

diff --git a/compiler/GHC/Driver/Pipeline/Execute.hs b/compiler/GHC/Driver/Pipeline/Execute.hs
index 57d491104e..022e8ce1a1 100644
--- a/compiler/GHC/Driver/Pipeline/Execute.hs
+++ b/compiler/GHC/Driver/Pipeline/Execute.hs
@@ -632,15 +632,15 @@ runHscPhase pipe_env hsc_env0 input_fn src_flavour = do
 
 
   -- gather the imports and module name
-  (hspp_buf,mod_name,imps,src_imps) <- do
+  (hspp_buf,mod_name,imps,src_imps, ghc_prim_imp) <- do
               buf <- hGetStringBuffer input_fn
               let imp_prelude = xopt LangExt.ImplicitPrelude dflags
                   popts = initParserOpts dflags
               eimps <- getImports popts imp_prelude buf input_fn (basename <.> suff)
               case eimps of
                   Left errs -> throwErrors (GhcPsMessage <$> errs)
-                  Right (src_imps,imps,L _ mod_name) -> return
-                        (Just buf, mod_name, imps, src_imps)
+                  Right (src_imps,imps, ghc_prim_imp, L _ mod_name) -> return
+                        (Just buf, mod_name, imps, src_imps, ghc_prim_imp)
 
   -- Take -o into account if present
   -- Very like -ohi, but we must *only* do this if we aren't linking
@@ -679,6 +679,7 @@ runHscPhase pipe_env hsc_env0 input_fn src_flavour = do
                                 ms_parsed_mod   = Nothing,
                                 ms_iface_date   = hi_date,
                                 ms_hie_date     = hie_date,
+                                ms_ghc_prim_import = ghc_prim_imp,
                                 ms_textual_imps = imps,
                                 ms_srcimps      = src_imps }