[project @ 2003-01-10 14:20:41 by simonpj]

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

diff --git a/ghc/compiler/typecheck/TcSplice.lhs b/ghc/compiler/typecheck/TcSplice.lhs
index e0e7fbc..a5ebd6e 100644 (file)
--- a/ghc/compiler/typecheck/TcSplice.lhs
+++ b/ghc/compiler/typecheck/TcSplice.lhs
@@ -35,6 +35,7 @@ import TysWiredIn     ( mkListTy )
 import DsMeta          ( exprTyConName, declTyConName, decTyConName, qTyConName )
 import ErrUtils (Message)
 import Outputable
+import Panic           ( showException )
 import GHC.Base                ( unsafeCoerce# )       -- Should have a better home in the module hierarchy
 import Monad (liftM)
 \end{code}
@@ -128,17 +129,21 @@ tcSpliceExpr name expr res_ty
 -- inner escape before dealing with the outer one
 
 tcTopSplice expr res_ty
-  = tcMetaTy exprTyConName             `thenM` \ meta_exp_ty ->
-    setStage topSpliceStage (
-       getLIE (tcMonoExpr expr meta_exp_ty)
-    )                                  `thenM` \ (expr', lie) ->
+  = checkNoErrs (
+       -- checkNoErrs: must not try to run the thing
+       --              if the type checker fails!
+
+       tcMetaTy exprTyConName          `thenM` \ meta_exp_ty ->
+       setStage topSpliceStage (
+         getLIE (tcMonoExpr expr meta_exp_ty)
+        )                              `thenM` \ (expr', lie) ->
 
        -- Solve the constraints
-    tcSimplifyTop lie                  `thenM` \ const_binds ->
-    let 
-       q_expr = mkHsLet const_binds expr'
-    in
-    zonkTopExpr q_expr                 `thenM` \ zonked_q_expr ->
+       tcSimplifyTop lie               `thenM` \ const_binds ->
+
+       -- Wrap the bindings around it and zonk
+       zonkTopExpr (mkHsLet const_binds expr')
+    )                                  `thenM` \ zonked_q_expr ->
 
        -- Run the expression
     traceTc (text "About to run" <+> ppr zonked_q_expr)        `thenM_`
@@ -216,9 +221,6 @@ runMetaD :: TypecheckedHsExpr       -- Of type Q [Dec]
         -> TcM [Meta.Dec]      -- Of type [Dec]
 runMetaD e = runMeta e
 
-tcRunQ :: Meta.Q a -> TcM a
-tcRunQ thing = ioToTcRn (Meta.runQ thing)
-
 runMeta :: TypecheckedHsExpr   -- Of type X
        -> TcM t                -- Of type t
 runMeta expr
@@ -238,16 +240,20 @@ runMeta expr
        type_env = tcg_type_env tcg_env
        rdr_env  = tcg_rdr_env tcg_env
     in
-    ioToTcRn (HscMain.compileExpr 
-               hsc_env pcs this_mod 
-               rdr_env type_env expr)  `thenM` \ hval ->
-
-    tryM (tcRunQ (unsafeCoerce# hval)) `thenM` \ either_tval ->
+       -- Wrap the compile-and-run in an exception-catcher
+       -- Compiling might fail if linking fails
+       -- Running might fail if it throws an exception
+    tryM (ioToTcRn (do
+       hval <- HscMain.compileExpr 
+                     hsc_env pcs this_mod 
+                     rdr_env type_env expr
+        Meta.runQ (unsafeCoerce# hval)         -- Coerce it to Q t, and run it
+    ))                                 `thenM` \ either_tval ->
 
     case either_tval of
-         Left exn -> failWithTc (vcat [text "Exception when running compile-time code:", 
+         Left exn -> failWithTc (vcat [text "Exception when trying to run compile-time code:", 
                                        nest 4 (vcat [text "Code:" <+> ppr expr,
-                                                     text ("Exn: " ++ show exn)])])
+                                                     text ("Exn: " ++ Panic.showException exn)])])
          Right v  -> returnM v
 \end{code}