Run untyped splices in the renamer.

compiler/deSugar/DsExpr.lhs

@@ -557,6 +557,7 @@ Here is where we desugar the Template Haskell brackets and escapes
 \begin{code}
 -- Template Haskell stuff
 
+dsExpr (HsRnBracketOut _ _) = panic "dsExpr HsRnBracketOut"
 #ifdef GHCI
 dsExpr (HsBracketOut x ps) = dsBracket x ps
 #else

compiler/deSugar/DsMeta.hs

@@ -74,7 +74,7 @@ dsBracket :: HsBracket Name -> [PendingSplice] -> DsM CoreExpr
 dsBracket brack splices
   = dsExtendMetaEnv new_bit (do_brack brack)
   where
-    new_bit = mkNameEnv [(n, Splice (unLoc e)) | (n,e) <- splices]
+    new_bit = mkNameEnv [(n, Splice (unLoc e)) | PendingTcSplice n e <- splices]
 
     do_brack (VarBr _ n) = do { MkC e1  <- lookupOcc n ; return e1 }
     do_brack (ExpBr e)   = do { MkC e1  <- repLE e     ; return e1 }

compiler/hsSyn/HsExpr.lhs

@@ -236,6 +236,13 @@ data HsExpr id
 
   | HsBracket    (HsBracket id)
 
+    -- See Note [Pending Renamer Splices]
+  | HsRnBracketOut (HsBracket Name)     -- Output of the renamer is
+                                        -- the *original*
+                   [PendingSplice]      -- renamed expression, plus
+                                        -- _renamed_ splices to be
+                                        -- type checked
+
   | HsBracketOut (HsBracket Name)       -- Output of the type checker is
                                         -- the *original*
                  [PendingSplice]        -- renamed expression, plus
@@ -327,11 +334,50 @@ tupArgPresent :: HsTupArg id -> Bool
 tupArgPresent (Present {}) = True
 tupArgPresent (Missing {}) = False
 
-type PendingSplice = (Name, LHsExpr Id) -- Typechecked splices, waiting to be
-                                        -- pasted back in by the desugarer
-
+-- See Note [Pending Splices]
+data PendingSplice
+  = PendingRnExpSplice Name (LHsExpr Name)
+  | PendingRnTypeSplice Name (LHsExpr Name)
+  | PendingRnCrossStageSplice Name
+  | PendingTcSplice Name (LHsExpr Id)
+  deriving (Data, Typeable)
 \end{code}
 
+Note [Pending Splices]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Now that untyped brackets are not type checked, we need a mechanism to ensure
+that splices contained in untyped brackets *are* type checked. Therefore the
+renamer now renames every HsBracket into a HsRnBracketOut, which contains the
+splices that need to be type checked. There are three varieties of pending
+splices generated by the renamer:
+
+ * Pending expression splices (PendingRnExpSplice), e.g.,
+
+   [|$(f x) + 2|]
+
+ * Pending type splices (PendingRnTypeSplice), e.g.,
+
+   [|f :: $(g x)|]
+
+ * Pending cross-stage splices (PendingRnCrossStageSplice), e.g.,
+
+   \x -> [| x |]
+
+There is a fourth variety of pending splice, which is generated by the type
+checker:
+
+  * Pending *typed* expression splices, (PendingTcSplice), e.g.,
+
+    [||1 + $$(f 2)||]
+
+It would be possible to eliminate HsRnBracketOut and use HsBracketOut for the
+output of the renamer. However, when pretty printing the output of the renamer,
+e.g., in a type error message, we *do not* want to print out the pending
+splices. In contrast, when pretty printing the output of the type checker, we
+*do* want to print the pending splices. So splitting them up seems to make
+sense, although I hate to add another constructor to HsExpr.
+
 Note [Parens in HsSyn]
 ~~~~~~~~~~~~~~~~~~~~~~
 HsPar (and ParPat in patterns, HsParTy in types) is used as follows
@@ -536,11 +582,12 @@ ppr_expr (HsSCC lbl expr)
 ppr_expr (HsWrap co_fn e) = pprHsWrapper (pprExpr e) co_fn
 ppr_expr (HsType id)      = ppr id
 
-ppr_expr (HsSpliceE s)       = pprSplice s
-ppr_expr (HsBracket b)       = pprHsBracket b
-ppr_expr (HsBracketOut e []) = ppr e
-ppr_expr (HsBracketOut e ps) = ppr e $$ ptext (sLit "pending") <+> ppr ps
-ppr_expr (HsQuasiQuoteE qq)  = ppr qq
+ppr_expr (HsSpliceE s)        = pprSplice s
+ppr_expr (HsBracket b)        = pprHsBracket b
+ppr_expr (HsRnBracketOut e _) = ppr e
+ppr_expr (HsBracketOut e [])  = ppr e
+ppr_expr (HsBracketOut e ps)  = ppr e $$ ptext (sLit "pending") <+> ppr ps
+ppr_expr (HsQuasiQuoteE qq)   = ppr qq
 
 ppr_expr (HsProc pat (L _ (HsCmdTop cmd _ _ _)))
   = hsep [ptext (sLit "proc"), ppr pat, ptext (sLit "->"), ppr cmd]
@@ -622,6 +669,7 @@ hsExprNeedsParens (ExplicitList {})   = False
 hsExprNeedsParens (ExplicitPArr {})   = False
 hsExprNeedsParens (HsPar {})          = False
 hsExprNeedsParens (HsBracket {})      = False
+hsExprNeedsParens (HsRnBracketOut {}) = False
 hsExprNeedsParens (HsBracketOut _ []) = False
 hsExprNeedsParens (HsDo sc _ _)
        | isListCompExpr sc            = False
@@ -1362,6 +1410,12 @@ thBrackets pp_kind pp_body = char '[' <> pp_kind <> char '|' <+>
 
 thTyBrackets :: SDoc -> SDoc
 thTyBrackets pp_body = ptext (sLit "[||") <+> pp_body <+> ptext (sLit "||]")
+
+instance Outputable PendingSplice where
+  ppr (PendingRnExpSplice name expr)   = ppr (name, expr)
+  ppr (PendingRnTypeSplice name expr)  = ppr (name, expr)
+  ppr (PendingRnCrossStageSplice name) = ppr name
+  ppr (PendingTcSplice name expr)      = ppr (name, expr)
 \end{code}
 
 %************************************************************************

compiler/rename/RnExpr.lhs

@@ -110,7 +110,14 @@ rnExpr (HsVar v)
                                        -- OverloadedLists works correctly
               -> rnExpr (ExplicitList placeHolderType Nothing [])
               | otherwise
-              -> finishHsVar name } }
+              -> do { mb_bind_lvl <- lookupLocalOccThLvl_maybe v
+                    ; case mb_bind_lvl of
+                        { Nothing -> return ()
+                        ; Just bind_lvl
+                            | isExternalName name -> return ()
+                            | otherwise -> checkThLocalName name bind_lvl
+                        }
+                    ; finishHsVar name }}}
 
 rnExpr (HsIPVar v)
   = return (HsIPVar v, emptyFVs)