Fix #541

Author: alfonsogarciacaro

src/fsharp/PatternMatchCompilation.fs

@@ -920,7 +920,7 @@ let CompilePatternBasic
 
              if nonNil topgtvs then error(InternalError("Unexpected generalized type variables when compiling an active pattern",m));
              let rty = apinfo.ResultType g m resTys
-             let v,vexp = mkCompGenLocal m "activePatternResult" rty
+             let v,vexp = mkCompGenLocal m ("activePatternResult"^string (newUnique())) rty
              if topv.IsMemberOrModuleBinding then 
                  AdjustValToTopVal v topv.ActualParent ValReprInfo.emptyValData;
              let argexp = GetSubExprOfInput subexpr