[project @ 1996-04-30 17:34:02 by partain]

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

diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs
index c45d809..3ea432f 100644 (file)
--- a/ghc/compiler/typecheck/TcInstDcls.lhs
+++ b/ghc/compiler/typecheck/TcInstDcls.lhs
@@ -73,10 +73,11 @@ import PprType              ( GenType, GenTyVar, GenClass, GenClassOp, TyCon,
 import PprStyle
 import Pretty
 import RnUtils         ( RnEnv(..) )
-import TyCon           ( derivedFor )
+import TyCon           ( isSynTyCon, derivedFor )
 import Type            ( GenType(..),  ThetaType(..), mkTyVarTys,
                          splitSigmaTy, splitAppTy, isTyVarTy, matchTy, mkSigmaTy,
-                         getTyCon_maybe, maybeBoxedPrimType )
+                         getTyCon_maybe, maybeBoxedPrimType
+                       )
 import TyVar           ( GenTyVar, mkTyVarSet )
 import TysWiredIn      ( stringTy )
 import Unique          ( Unique )
@@ -889,7 +890,7 @@ We can also have instances for functions: @instance Foo (a -> b) ...@.
 \begin{code}
 scrutiniseInstanceType from_here clas inst_tau
        -- TYCON CHECK
-  | not (maybeToBool inst_tycon_maybe)
+  | not (maybeToBool inst_tycon_maybe) || isSynTyCon inst_tycon
   = failTc (instTypeErr inst_tau)
 
        -- IMPORTED INSTANCES ARE OK (but see tcInstDecl1)