Fix Trac #3118: missing alternative

[ghc-hetmet.git] / compiler / basicTypes / MkId.lhs

diff --git a/compiler/basicTypes/MkId.lhs b/compiler/basicTypes/MkId.lhs
index 1fe712b..986542b 100644 (file)
--- a/compiler/basicTypes/MkId.lhs
+++ b/compiler/basicTypes/MkId.lhs
@@ -35,7 +35,7 @@ module MkId (
         unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId,
         lazyId, lazyIdUnfolding, lazyIdKey,
 
-        mkRuntimeErrorApp,
+        mkRuntimeErrorApp, mkImpossibleExpr,
         rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID,
         nON_EXHAUSTIVE_GUARDS_ERROR_ID, nO_METHOD_BINDING_ERROR_ID,
         pAT_ERROR_ID, eRROR_ID, rEC_SEL_ERROR_ID,
@@ -53,7 +53,7 @@ import Type
 import TypeRep
 import Coercion
 import TcType
-import CoreUtils
+import CoreUtils       ( exprType, mkCoerce )
 import CoreUnfold
 import Literal
 import TyCon
@@ -977,6 +977,10 @@ mkRuntimeErrorApp err_id res_ty err_msg
   where
     err_string = Lit (mkMachString err_msg)
 
+mkImpossibleExpr :: Type -> CoreExpr
+mkImpossibleExpr res_ty
+  = mkRuntimeErrorApp rUNTIME_ERROR_ID res_ty "Impossible case alternative"
+
 rEC_SEL_ERROR_ID                = mkRuntimeErrorId recSelErrorName
 rUNTIME_ERROR_ID                = mkRuntimeErrorId runtimeErrorName
 iRREFUT_PAT_ERROR_ID            = mkRuntimeErrorId irrefutPatErrorName