Specify the reason for import for the backpack's extra imports

2 files changed, 13 insertions, 9 deletions

diff --git a/compiler/GHC/Rename/Names.hs b/compiler/GHC/Rename/Names.hs
index fa19bdc600..a50701b764 100644
--- a/compiler/GHC/Rename/Names.hs
+++ b/compiler/GHC/Rename/Names.hs
@@ -185,14 +185,14 @@ with yes we have gone with no for now.
 -- the return types represent.
 -- Note: Do the non SOURCE ones first, so that we get a helpful warning
 -- for SOURCE ones that are unnecessary
-rnImports :: [LImportDecl GhcPs]
+rnImports :: [(LImportDecl GhcPs, SDoc)]
           -> RnM ([LImportDecl GhcRn], GlobalRdrEnv, ImportAvails, AnyHpcUsage)
 rnImports imports = do
     tcg_env <- getGblEnv
     -- NB: want an identity module here, because it's OK for a signature
     -- module to import from its implementor
     let this_mod = tcg_mod tcg_env
-    let (source, ordinary) = partition is_source_import imports
+    let (source, ordinary) = partition (is_source_import . fst) imports
         is_source_import d = ideclSource (unLoc d) == IsBoot
     stuff1 <- mapAndReportM (rnImportDecl this_mod) ordinary
     stuff2 <- mapAndReportM (rnImportDecl this_mod) source
@@ -293,14 +293,14 @@ Running generateModules from #14693 with DEPTH=16, WIDTH=30 finishes in
 --
 --  4. A boolean 'AnyHpcUsage' which is true if the imported module
 --     used HPC.
-rnImportDecl  :: Module -> LImportDecl GhcPs
+rnImportDecl  :: Module -> (LImportDecl GhcPs, SDoc)
              -> RnM (LImportDecl GhcRn, GlobalRdrEnv, ImportAvails, AnyHpcUsage)
 rnImportDecl this_mod
              (L loc decl@(ImportDecl { ideclName = loc_imp_mod_name
                                      , ideclPkgQual = mb_pkg
                                      , ideclSource = want_boot, ideclSafe = mod_safe
                                      , ideclQualified = qual_style, ideclImplicit = implicit
-                                     , ideclAs = as_mod, ideclHiding = imp_details }))
+                                     , ideclAs = as_mod, ideclHiding = imp_details }), import_reason)
   = setSrcSpanA loc $ do
 
     when (isJust mb_pkg) $ do
@@ -312,7 +312,7 @@ rnImportDecl this_mod
     -- If there's an error in loadInterface, (e.g. interface
     -- file not found) we get lots of spurious errors from 'filterImports'
     let imp_mod_name = unLoc loc_imp_mod_name
-        doc = ppr imp_mod_name <+> text "is directly imported"
+        doc = ppr imp_mod_name <+> import_reason
 
     -- Check for self-import, which confuses the typechecker (#9032)
     -- ghc --make rejects self-import cycles already, but batch-mode may not
diff --git a/compiler/GHC/Tc/Module.hs b/compiler/GHC/Tc/Module.hs
index 450e97819a..d5e0f3255d 100644
--- a/compiler/GHC/Tc/Module.hs
+++ b/compiler/GHC/Tc/Module.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE MultiWayIf #-}
+{-# LANGUAGE TupleSections #-}
 
 {-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
 
@@ -278,8 +279,11 @@ tcRnModuleTcRnM hsc_env mod_sum
                 $ (simpleImportDecl mod_name)
                   { ideclHiding = Just (False, noLocA [])}
               ; mkImport _ = panic "mkImport" }
-        ; let { all_imports = prel_imports ++ import_decls
-                       ++ map mkImport (raw_sig_imports ++ raw_req_imports) }
+        ; let { withReason t imps = map (,text t) imps }
+        ; let { all_imports = withReason "is implicitly imported" prel_imports
+                  ++ withReason "is directly imported" import_decls
+                  ++ withReason "is an extra sig import" (map mkImport raw_sig_imports)
+                  ++ withReason "is an implicit req import" (map mkImport raw_req_imports) }
         ; -- OK now finally rename the imports
           tcg_env <- {-# SCC "tcRnImports" #-}
                      tcRnImports hsc_env all_imports
@@ -360,7 +364,7 @@ implicitPreludeWarn
 ************************************************************************
 -}
 
-tcRnImports :: HscEnv -> [LImportDecl GhcPs] -> TcM TcGblEnv
+tcRnImports :: HscEnv -> [(LImportDecl GhcPs, SDoc)] -> TcM TcGblEnv
 tcRnImports hsc_env import_decls
   = do  { (rn_imports, rdr_env, imports, hpc_info) <- rnImports import_decls ;
 
@@ -2610,7 +2614,7 @@ tcRnImportDecls :: HscEnv
 tcRnImportDecls hsc_env import_decls
  =  runTcInteractive hsc_env $
     do { gbl_env <- updGblEnv zap_rdr_env $
-                    tcRnImports hsc_env import_decls
+                    tcRnImports hsc_env $ map (,text "is directly imported") import_decls
        ; return (tcg_rdr_env gbl_env) }
   where
     zap_rdr_env gbl_env = gbl_env { tcg_rdr_env = emptyGlobalRdrEnv }