driver: In oneshot mode, look for interface files in hidir

How things should work:

*  -i is the search path for source files
*  -hidir explicitly sets the search path for interface files and the output location for interface files.
*  -odir sets the search path and output location for object files.

Before in one shot mode we would look for the interface file in the
search locations given by `-i`, but then set the path to be in the
`hidir`, so in unusual situations the finder could find an interface
file in the `-i` dir but later fail because it tried to read the
interface file from the `-hidir`.

A bug identified by #20569

1 files changed, 10 insertions, 3 deletions

diff --git a/compiler/GHC/Unit/Finder.hs b/compiler/GHC/Unit/Finder.hs
index c3c517cb18..45057d13e2 100644
--- a/compiler/GHC/Unit/Finder.hs
+++ b/compiler/GHC/Unit/Finder.hs
@@ -412,6 +412,12 @@ findInstalledHomeModule fc fopts home_unit mod_name = do
      home_path = case maybe_working_dir of
                   Nothing -> finder_importPaths fopts
                   Just fp -> augmentImports fp (finder_importPaths fopts)
+     hi_dir_path =
+      case finder_hiDir fopts of
+        Just hiDir -> case maybe_working_dir of
+                        Nothing -> [hiDir]
+                        Just fp -> [fp </> hiDir]
+        Nothing -> home_path
      hisuf = finder_hiSuf fopts
      mod = mkModule home_unit mod_name
 
@@ -431,8 +437,9 @@ findInstalledHomeModule fc fopts home_unit mod_name = do
         -- In compilation manager modes, we look for source files in the home
         -- package because we can compile these automatically.  In one-shot
         -- compilation mode we look for .hi and .hi-boot files only.
-     exts | finder_lookupHomeInterfaces fopts = hi_exts
-          | otherwise                         = source_exts
+     (search_dirs, exts)
+          | finder_lookupHomeInterfaces fopts = (hi_dir_path, hi_exts)
+          | otherwise                         = (home_path, source_exts)
    in
 
    -- special case for GHC.Prim; we won't find it in the filesystem.
@@ -440,7 +447,7 @@ findInstalledHomeModule fc fopts home_unit mod_name = do
    -- is a home module).
    if mod `installedModuleEq` gHC_PRIM
          then return (InstalledFound (error "GHC.Prim ModLocation") mod)
-         else searchPathExts home_path mod exts
+         else searchPathExts search_dirs mod exts
 
 -- | Prepend the working directory to the search path.
 augmentImports :: FilePath -> [FilePath] -> [FilePath]