Teach GHC how to build indefinite libraries

These are libraries which don't have any code (uses 'whenHasCode'
combinator).  In principle this could also be extended to support
building anything with no code.

Also update 'ghcOptThisUnitId' and 'ghcOptInstantiatedWith' to
have correct values.

Cabal/Distribution/Simple/GHC.hs

@@ -66,6 +66,7 @@ import qualified Distribution.InstalledPackageInfo as InstalledPackageInfo
 import Distribution.Simple.PackageIndex (InstalledPackageIndex)
 import qualified Distribution.Simple.PackageIndex as PackageIndex
 import Distribution.Simple.LocalBuildInfo
+import Distribution.Types.ComponentLocalBuildInfo
 import qualified Distribution.Simple.Hpc as Hpc
 import Distribution.Simple.BuildPaths
 import Distribution.Simple.Utils
@@ -492,6 +493,7 @@ buildOrReplLib forRepl verbosity numJobs pkg_descr lbi lib clbi = do
       ghcVersion = compilerVersion comp
       implInfo  = getImplInfo comp
       platform@(Platform _hostArch hostOS) = hostPlatform lbi
+      has_code = not (componentIsIndefinite clbi)
 
   (ghcProg, _) <- requireProgram verbosity ghcProgram (withPrograms lbi)
   let runGhcProg = runGHC verbosity ghcProg comp platform
@@ -587,7 +589,10 @@ buildOrReplLib forRepl verbosity numJobs pkg_descr lbi lib clbi = do
                        (forceVanillaLib || withVanillaLib lbi) &&
                        (forceSharedLib  || withSharedLib  lbi) &&
                        null (hcSharedOptions GHC libBi)
-       if useDynToo
+       if not has_code
+        then vanilla
+        else
+         if useDynToo
           then do
               runGhcProg vanillaSharedOpts
               case (hpcdir Hpc.Dyn, hpcdir Hpc.Vanilla) of
@@ -603,10 +608,10 @@ buildOrReplLib forRepl verbosity numJobs pkg_descr lbi lib clbi = do
           else if isGhcDynamic
             then do shared;  vanilla
             else do vanilla; shared
-       whenProfLib (runGhcProg profOpts)
+       when has_code $ whenProfLib (runGhcProg profOpts)
 
   -- build any C sources
-  unless (null (cSources libBi)) $ do
+  unless (not has_code || null (cSources libBi)) $ do
     info verbosity "Building C Sources..."
     sequence_
       [ do let baseCcOpts    = Internal.componentCcGhcOptions verbosity implInfo
@@ -640,12 +645,12 @@ buildOrReplLib forRepl verbosity numJobs pkg_descr lbi lib clbi = do
   -- with ghci, but .c files can depend on .h files generated by ghc by ffi
   -- exports.
 
-  ifReplLib $ do
+  when has_code . ifReplLib $ do
     when (null (allLibModules lib clbi)) $ warn verbosity "No exposed modules"
     ifReplLib (runGhcProg replOpts)
 
   -- link:
-  unless forRepl $ do
+  when has_code . unless forRepl $ do
     info verbosity "Linking..."
     let cProfObjs   = map (`replaceExtension` ("p_" ++ objExtension))
                       (cSources libBi)
@@ -727,6 +732,14 @@ buildOrReplLib forRepl verbosity numJobs pkg_descr lbi lib clbi = do
                                             else mempty,
                 ghcOptNoAutoLinkPackages = toFlag True,
                 ghcOptPackageDBs         = withPackageDB lbi,
+                ghcOptThisUnitId = case clbi of
+                    LibComponentLocalBuildInfo { componentCompatPackageKey = pk }
+                      -> toFlag pk
+                    _ -> mempty,
+                ghcOptInstantiatedWith = case clbi of
+                    LibComponentLocalBuildInfo { componentInstantiatedWith = insts }
+                      -> insts
+                    _ -> [],
                 ghcOptPackages           = toNubListR $
                                            Internal.mkGhcOptPackages clbi ,
                 ghcOptLinkLibs           = toNubListR $ extraLibs libBi,
@@ -1145,10 +1158,11 @@ installLib verbosity lbi targetDir dynlibTargetDir _builtDir _pkg lib clbi = do
   whenShared  $ copyModuleFiles "dyn_hi"
 
   -- copy the built library files over:
-  whenVanilla $ installOrdinary builtDir targetDir       vanillaLibName
-  whenProf    $ installOrdinary builtDir targetDir       profileLibName
-  whenGHCi    $ installOrdinary builtDir targetDir       ghciLibName
-  whenShared  $ installShared   builtDir dynlibTargetDir sharedLibName
+  whenHasCode $ do
+    whenVanilla $ installOrdinary builtDir targetDir       vanillaLibName
+    whenProf    $ installOrdinary builtDir targetDir       profileLibName
+    whenGHCi    $ installOrdinary builtDir targetDir       ghciLibName
+    whenShared  $ installShared   builtDir dynlibTargetDir sharedLibName
 
   where
     builtDir = componentBuildDir lbi clbi
@@ -1181,10 +1195,12 @@ installLib verbosity lbi targetDir dynlibTargetDir _builtDir _pkg lib clbi = do
 
     hasLib    = not $ null (allLibModules lib clbi)
                    && null (cSources (libBuildInfo lib))
+    has_code = not (componentIsIndefinite clbi)
+    whenHasCode = when has_code
     whenVanilla = when (hasLib && withVanillaLib lbi)
-    whenProf    = when (hasLib && withProfLib    lbi)
-    whenGHCi    = when (hasLib && withGHCiLib    lbi)
-    whenShared  = when (hasLib && withSharedLib  lbi)
+    whenProf    = when (hasLib && withProfLib    lbi && has_code)
+    whenGHCi    = when (hasLib && withGHCiLib    lbi && has_code)
+    whenShared  = when (hasLib && withSharedLib  lbi && has_code)
 
 -- -----------------------------------------------------------------------------
 -- Registering

Cabal/Distribution/Simple/GHC/Internal.hs

@@ -289,6 +289,11 @@ componentGhcOptions verbosity lbi bi clbi odir =
         LibComponentLocalBuildInfo { componentCompatPackageKey = pk }
           -> toFlag pk
         _ -> mempty,
+      ghcOptInstantiatedWith = case clbi of
+        LibComponentLocalBuildInfo { componentInstantiatedWith = insts }
+          -> insts
+        _ -> [],
+      ghcOptNoCode          = toFlag $ componentIsIndefinite clbi,
       ghcOptPackageDBs      = withPackageDB lbi,
       ghcOptPackages        = toNubListR $ mkGhcOptPackages clbi,
       ghcOptSplitObjs       = toFlag (splitObjs lbi),