[project @ 2003-01-13 17:01:22 by simonpj]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcExpr.lhs

diff --git a/ghc/compiler/typecheck/TcExpr.lhs b/ghc/compiler/typecheck/TcExpr.lhs
index 9b913d8..025c7dc 100644 (file)
--- a/ghc/compiler/typecheck/TcExpr.lhs
+++ b/ghc/compiler/typecheck/TcExpr.lhs
@@ -13,7 +13,7 @@ import {-# SOURCE #-} TcSplice( tcSpliceExpr, tcBracket )
 import HsSyn           ( HsReify(..), ReifyFlavour(..) )
 import TcType          ( isTauTy )
 import TcEnv           ( bracketOK, tcMetaTy, tcLookupGlobal,
-                         wellStaged, metaLevel )
+                         checkWellStaged, metaLevel )
 import TcSimplify      ( tcSimplifyBracket )
 import Name            ( isExternalName )
 import qualified DsMeta
@@ -798,12 +798,17 @@ tcId name -- Look up the Id and instantiate its type
       Brack use_lvl ps_var lie_var
        | use_lvl > bind_lvl && not (isExternalName name)
        ->      -- E.g. \x -> [| h x |]
-                       -- We must behave as if the reference to x was
-                       --      h $(lift x)     
-                       -- We use 'x' itself as the splice proxy, used by 
-                       -- the desugarer to stitch it all back together
-                       -- NB: isExernalName is true of top level things, 
-                       -- and false of nested bindings
+               -- We must behave as if the reference to x was
+               --      h $(lift x)     
+               -- We use 'x' itself as the splice proxy, used by 
+               -- the desugarer to stitch it all back together.
+               -- If 'x' occurs many times we may get many identical
+               -- bindings of the same splice proxy, but that doesn't
+               -- matter, although it's a mite untidy.
+               --
+               -- NB: During type-checking, isExernalName is true of 
+               -- top level things, and false of nested bindings
+               -- Top-level things don't need lifting.
        
        let
            id_ty = idType id
@@ -826,11 +831,7 @@ tcId name  -- Look up the Id and instantiate its type
        returnM (HsVar id, id_ty))
 
       other -> 
-       let
-          use_lvl = metaLevel use_stage
-       in
-       checkTc (wellStaged bind_lvl use_lvl)
-               (badStageErr id bind_lvl use_lvl)       `thenM_`
+       checkWellStaged (quotes (ppr id)) bind_lvl use_stage    `thenM_`
 #endif
        -- This is the bit that handles the no-Template-Haskell case
        case isDataConWrapId_maybe id of
@@ -1047,12 +1048,6 @@ Boring and alphabetical:
 arithSeqCtxt expr
   = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
 
-
-badStageErr id bind_lvl use_lvl
-  = ptext SLIT("Stage error:") <+> quotes (ppr id) <+> 
-       hsep   [ptext SLIT("is bound at stage") <+> ppr bind_lvl,
-               ptext SLIT("but used at stage") <+> ppr use_lvl]
-
 parrSeqCtxt expr
   = hang (ptext SLIT("In a parallel array sequence:")) 4 (ppr expr)
 
@@ -1120,7 +1115,6 @@ missingStrictFields con fields
     header = ptext SLIT("Constructor") <+> quotes (ppr con) <+> 
             ptext SLIT("does not have the required strict field(s)") 
          
-
 missingFields :: DataCon -> [FieldLabel] -> SDoc
 missingFields con fields
   = ptext SLIT("Fields of") <+> quotes (ppr con) <+> ptext SLIT("not initialised:")