Recover gracefully from a Template Haskell programmers error

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

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index 497ba23..388828e 100644 (file)
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -11,7 +11,7 @@ module TcEnv(
        tcExtendGlobalEnv, 
        tcExtendGlobalValEnv,
        tcLookupLocatedGlobal,  tcLookupGlobal, 
-       tcLookupGlobalId, tcLookupTyCon, tcLookupClass, tcLookupDataCon,
+       tcLookupField, tcLookupTyCon, tcLookupClass, tcLookupDataCon,
        tcLookupLocatedGlobalId, tcLookupLocatedTyCon,
        tcLookupLocatedClass, 
        
@@ -121,16 +121,19 @@ tcLookupGlobal name
                tcImportDecl name       -- Go find it in an interface
        }}}}}
 
-tcLookupGlobalId :: Name -> TcM Id
--- Never used for Haskell-source DataCons, hence no ADataCon case
-tcLookupGlobalId name
+tcLookupField :: Name -> TcM Id                -- Returns the selector Id
+tcLookupField name
   = tcLookupGlobal name                `thenM` \ thing ->
-    return (tyThingId thing)
+    case thing of
+       AnId id -> return id
+       other   -> wrongThingErr "field name" (AGlobal thing) name
 
 tcLookupDataCon :: Name -> TcM DataCon
-tcLookupDataCon con_name
-  = tcLookupGlobal con_name    `thenM` \ thing ->
-    return (tyThingDataCon thing)
+tcLookupDataCon name
+  = tcLookupGlobal name        `thenM` \ thing ->
+    case thing of
+       ADataCon con -> return con
+       other        -> wrongThingErr "data constructor" (AGlobal thing) name
 
 tcLookupClass :: Name -> TcM Class
 tcLookupClass name