+
+%*********************************************************
+%* *
+ Splices
+%* *
+%*********************************************************
+
+Note [Splices]
+~~~~~~~~~~~~~~
+Consider
+ f = ...
+ h = ...$(thing "f")...
+
+The splice can expand into literally anything, so when we do dependency
+analysis we must assume that it might mention 'f'. So we simply treat
+all locally-defined names as mentioned by any splice. This is terribly
+brutal, but I don't see what else to do. For example, it'll mean
+that every locally-defined thing will appear to be used, so no unused-binding
+warnings. But if we miss the dependency, then we might typecheck 'h' before 'f',
+and that will crash the type checker because 'f' isn't in scope.
+
+Currently, I'm not treating a splice as also mentioning every import,
+which is a bit inconsistent -- but there are a lot of them. We might
+thereby get some bogus unused-import warnings, but we won't crash the
+type checker. Not very satisfactory really.
+
+\begin{code}
+rnSplice :: HsSplice RdrName -> RnM (HsSplice Name, FreeVars)
+rnSplice (HsSplice n expr)
+ = do { checkTH expr "splice"
+ ; loc <- getSrcSpanM
+ ; n' <- newLocalBndrRn (L loc n)
+ ; (expr', fvs) <- rnLExpr expr
+
+ -- Ugh! See Note [Splices] above
+ ; lcl_rdr <- getLocalRdrEnv
+ ; gbl_rdr <- getGlobalRdrEnv
+ ; let gbl_names = mkNameSet [gre_name gre | gre <- globalRdrEnvElts gbl_rdr,
+ isLocalGRE gre]
+ lcl_names = mkNameSet (occEnvElts lcl_rdr)
+
+ ; return (HsSplice n' expr', fvs `plusFV` lcl_names `plusFV` gbl_names) }
+
+checkTH :: Outputable a => a -> String -> RnM ()
+#ifdef GHCI
+checkTH _ _ = return () -- OK
+#else
+checkTH e what -- Raise an error in a stage-1 compiler
+ = addErr (vcat [ptext (sLit "Template Haskell") <+> text what <+>
+ ptext (sLit "illegal in a stage-1 compiler"),
+ nest 2 (ppr e)])
+#endif
+\end{code}