+%************************************************************************
+%* *
+\subsection{Provenance and export info}
+%* *
+%************************************************************************
+
+The GlobalRdrEnv gives maps RdrNames to Names. There is a separate
+one for each module, corresponding to that module's top-level scope.
+
+\begin{code}
+type GlobalRdrEnv = RdrNameEnv [(Name,Provenance)] -- The list is because there may be name clashes
+ -- These only get reported on lookup,
+ -- not on construction
+\end{code}
+
+The "provenance" of something says how it came to be in scope.
+
+\begin{code}
+data Provenance
+ = LocalDef -- Defined locally
+
+ | NonLocalDef -- Defined non-locally
+ ImportReason
+ PrintUnqualified
+
+data ImportReason
+ = UserImport Module SrcLoc Bool -- Imported from module M on line L
+ -- Note the M may well not be the defining module
+ -- for this thing!
+ -- The Bool is true iff the thing was named *explicitly* in the import spec,
+ -- rather than being imported as part of a group; e.g.
+ -- import B
+ -- import C( T(..) )
+ -- Here, everything imported by B, and the constructors of T
+ -- are not named explicitly; only T is named explicitly.
+ -- This info is used when warning of unused names.
+
+ | ImplicitImport -- Imported implicitly for some other reason
+
+
+type PrintUnqualified = Bool -- True <=> the unqualified name of this thing is
+ -- in scope in this module, so print it
+ -- unqualified in error messages
+\end{code}
+
+\begin{code}
+hasBetterProv :: Provenance -> Provenance -> Bool
+-- Choose
+-- a local thing over an imported thing
+-- a user-imported thing over a non-user-imported thing
+-- an explicitly-imported thing over an implicitly imported thing
+hasBetterProv LocalDef _ = True
+hasBetterProv (NonLocalDef (UserImport _ _ True) _) _ = True
+hasBetterProv (NonLocalDef (UserImport _ _ _ ) _) (NonLocalDef ImplicitImport _) = True
+hasBetterProv _ _ = False
+
+pprNameProvenance :: Name -> Provenance -> SDoc
+pprProvenance name LocalDef = ptext SLIT("defined at") <+> ppr (nameSrcLoc name)
+pprProvenance name (NonLocalDef why _) = sep [ppr_reason why,
+ nest 2 (parens (ppr_defn (nameSrcLoc name)))]
+
+ppr_reason ImplicitImport = ptext SLIT("implicitly imported")
+ppr_reason (UserImport mod loc _) = ptext SLIT("imported from") <+> ppr mod <+> ptext SLIT("at") <+> ppr loc
+
+ppr_defn loc | isGoodSrcLoc loc = ptext SLIT("at") <+> ppr loc
+ | otherwise = empty
+\end{code}