+ bad_locals :: [Name]
+ bad_locals = [n | (n,LocalDef) <- defined_but_not_used]
+
+ bad_imp_names :: [(Name,Provenance)]
+ bad_imp_names = [(n,p) | (n,p@(UserImport mod _ True)) <- defined_but_not_used,
+ not (module_unused mod)]
+
+ deprec_used deprec_env = [ (n,txt)
+ | n <- nameSetToList mentioned_names,
+ not (isLocallyDefined n),
+ Just txt <- [lookupNameEnv deprec_env n] ]
+
+ -- inst_mods are directly-imported modules that
+ -- contain instance decl(s) that the renamer decided to suck in
+ -- It's not necessarily redundant to import such modules.
+ --
+ -- NOTE: Consider
+ -- module This
+ -- import M ()
+ --
+ -- The import M() is not *necessarily* redundant, even if
+ -- we suck in no instance decls from M (e.g. it contains
+ -- no instance decls, or This contains no code). It may be
+ -- that we import M solely to ensure that M's orphan instance
+ -- decls (or those in its imports) are visible to people who
+ -- import This. Sigh.
+ -- There's really no good way to detect this, so the error message
+ -- in RnEnv.warnUnusedModules is weakened instead
+ inst_mods = [m | InstD (InstDecl _ _ _ (Just dfun) _) <- imported_decls,
+ let m = nameModule dfun,
+ m `elem` direct_import_mods
+ ]
+
+ minimal_imports :: FiniteMap Module AvailEnv
+ minimal_imports0 = emptyFM
+ minimal_imports1 = foldNameSet add_name minimal_imports0 really_used_names
+ minimal_imports = foldr add_inst_mod minimal_imports1 inst_mods
+
+ add_name n acc = case maybeUserImportedFrom n of
+ Nothing -> acc
+ Just m -> addToFM_C plusAvailEnv acc m
+ (unitAvailEnv (mk_avail n))
+ add_inst_mod m acc
+ | m `elemFM` acc = acc -- We import something already
+ | otherwise = addToFM acc m emptyAvailEnv
+ -- Add an empty collection of imports for a module
+ -- from which we have sucked only instance decls
+
+ mk_avail n = case lookupNameEnv avail_env n of
+ Just (AvailTC m _) | n==m -> AvailTC n [n]
+ | otherwise -> AvailTC m [n,m]
+ Just avail -> Avail n
+ Nothing -> pprPanic "mk_avail" (ppr n)
+
+ -- unused_imp_mods are the directly-imported modules
+ -- that are not mentioned in minimal_imports
+ unused_imp_mods = [m | m <- direct_import_mods,
+ not (maybeToBool (lookupFM minimal_imports m)),
+ moduleName m /= pRELUDE_Name]
+
+ module_unused :: Module -> Bool
+ module_unused mod = mod `elem` unused_imp_mods
+