2005-07-05 Atsushi Enomoto <atsushi@ximian.com>
[mono.git] / mcs / mcs / convert.cs
index bab50e1ff9442749b2b8460985678170ad251a86..09b56abea571f6d9475bc7913a03054cebce792f 100644 (file)
@@ -97,7 +97,7 @@ namespace Mono.CSharp {
                        // from the null type to any reference-type.
                        if (expr_type == TypeManager.null_type){
                                if (target_type.IsPointer)
-                                       return new EmptyCast (expr, target_type);
+                                       return new EmptyCast (NullPointer.Null, target_type);
                                        
                                if (!target_type.IsValueType)
                                        return new NullCast (expr, target_type);
@@ -303,7 +303,7 @@ namespace Mono.CSharp {
 
                        if (expr_type == TypeManager.sbyte_type){
                                //
-                               // From sbyte to short, int, long, float, double.
+                               // From sbyte to short, int, long, float, double, decimal
                                //
                                if (real_target_type == TypeManager.int32_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_I4);
@@ -315,9 +315,11 @@ namespace Mono.CSharp {
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
                                if (real_target_type == TypeManager.short_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_I2);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
                        } else if (expr_type == TypeManager.byte_type){
                                //
-                               // From byte to short, ushort, int, uint, long, ulong, float, double
+                               // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
                                // 
                                if ((real_target_type == TypeManager.short_type) ||
                                    (real_target_type == TypeManager.ushort_type) ||
@@ -333,9 +335,12 @@ namespace Mono.CSharp {
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
                                if (real_target_type == TypeManager.double_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
+                               
                        } else if (expr_type == TypeManager.short_type){
                                //
-                               // From short to int, long, float, double
+                               // From short to int, long, float, double, decimal
                                // 
                                if (real_target_type == TypeManager.int32_type)
                                        return new EmptyCast (expr, target_type);
@@ -345,9 +350,12 @@ namespace Mono.CSharp {
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
                                if (real_target_type == TypeManager.float_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
+                               
                        } else if (expr_type == TypeManager.ushort_type){
                                //
-                               // From ushort to int, uint, long, ulong, float, double
+                               // From ushort to int, uint, long, ulong, float, double, decimal
                                //
                                if (real_target_type == TypeManager.uint32_type)
                                        return new EmptyCast (expr, target_type);
@@ -362,9 +370,11 @@ namespace Mono.CSharp {
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
                                if (real_target_type == TypeManager.float_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
                        } else if (expr_type == TypeManager.int32_type){
                                //
-                               // From int to long, float, double
+                               // From int to long, float, double, decimal
                                //
                                if (real_target_type == TypeManager.int64_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_I8);
@@ -372,9 +382,11 @@ namespace Mono.CSharp {
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
                                if (real_target_type == TypeManager.float_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
                        } else if (expr_type == TypeManager.uint32_type){
                                //
-                               // From uint to long, ulong, float, double
+                               // From uint to long, ulong, float, double, decimal
                                //
                                if (real_target_type == TypeManager.int64_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_U8);
@@ -386,6 +398,8 @@ namespace Mono.CSharp {
                                if (real_target_type == TypeManager.float_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
                                                               OpCodes.Conv_R4);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
                        } else if (expr_type == TypeManager.int64_type){
                                //
                                // From long/ulong to float, double
@@ -393,7 +407,9 @@ namespace Mono.CSharp {
                                if (real_target_type == TypeManager.double_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
                                if (real_target_type == TypeManager.float_type)
-                                       return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);     
+                                       return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
                        } else if (expr_type == TypeManager.uint64_type){
                                //
                                // From ulong to float, double
@@ -403,10 +419,12 @@ namespace Mono.CSharp {
                                                               OpCodes.Conv_R8);
                                if (real_target_type == TypeManager.float_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R_Un,
-                                                              OpCodes.Conv_R4);        
+                                                              OpCodes.Conv_R4);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
                        } else if (expr_type == TypeManager.char_type){
                                //
-                               // From char to ushort, int, uint, long, ulong, float, double
+                               // From char to ushort, int, uint, long, ulong, float, double, decimal
                                // 
                                if ((real_target_type == TypeManager.ushort_type) ||
                                    (real_target_type == TypeManager.int32_type) ||
@@ -420,6 +438,8 @@ namespace Mono.CSharp {
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R4);
                                if (real_target_type == TypeManager.double_type)
                                        return new OpcodeCast (expr, target_type, OpCodes.Conv_R8);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr);
                        } else if (expr_type == TypeManager.float_type){
                                //
                                // float to double
@@ -472,11 +492,12 @@ namespace Mono.CSharp {
                        if (expr_type == target_type)
                                return true;
 
+
                        // First numeric conversions 
 
                        if (expr_type == TypeManager.sbyte_type){
                                //
-                               // From sbyte to short, int, long, float, double.
+                               // From sbyte to short, int, long, float, double, decimal
                                //
                                if ((target_type == TypeManager.int32_type) || 
                                    (target_type == TypeManager.int64_type) ||
@@ -488,7 +509,7 @@ namespace Mono.CSharp {
                                
                        } else if (expr_type == TypeManager.byte_type){
                                //
-                               // From byte to short, ushort, int, uint, long, ulong, float, double
+                               // From byte to short, ushort, int, uint, long, ulong, float, double, decimal
                                // 
                                if ((target_type == TypeManager.short_type) ||
                                    (target_type == TypeManager.ushort_type) ||
@@ -503,7 +524,7 @@ namespace Mono.CSharp {
        
                        } else if (expr_type == TypeManager.short_type){
                                //
-                               // From short to int, long, float, double
+                               // From short to int, long, double, float, decimal
                                // 
                                if ((target_type == TypeManager.int32_type) ||
                                    (target_type == TypeManager.int64_type) ||
@@ -514,7 +535,7 @@ namespace Mono.CSharp {
                                        
                        } else if (expr_type == TypeManager.ushort_type){
                                //
-                               // From ushort to int, uint, long, ulong, float, double
+                               // From ushort to int, uint, long, ulong, double, float, decimal
                                //
                                if ((target_type == TypeManager.uint32_type) ||
                                    (target_type == TypeManager.uint64_type) ||
@@ -527,7 +548,7 @@ namespace Mono.CSharp {
                                    
                        } else if (expr_type == TypeManager.int32_type){
                                //
-                               // From int to long, float, double
+                               // From int to long, double, float, decimal
                                //
                                if ((target_type == TypeManager.int64_type) ||
                                    (target_type == TypeManager.double_type) ||
@@ -537,7 +558,7 @@ namespace Mono.CSharp {
                                        
                        } else if (expr_type == TypeManager.uint32_type){
                                //
-                               // From uint to long, ulong, float, double
+                               // From uint to long, ulong, double, float, decimal
                                //
                                if ((target_type == TypeManager.int64_type) ||
                                    (target_type == TypeManager.uint64_type) ||
@@ -549,7 +570,7 @@ namespace Mono.CSharp {
                        } else if ((expr_type == TypeManager.uint64_type) ||
                                   (expr_type == TypeManager.int64_type)) {
                                //
-                               // From long/ulong to float, double
+                               // From long/ulong to double, float, decimal
                                //
                                if ((target_type == TypeManager.double_type) ||
                                    (target_type == TypeManager.float_type) ||
@@ -558,7 +579,7 @@ namespace Mono.CSharp {
                                    
                        } else if (expr_type == TypeManager.char_type){
                                //
-                               // From char to ushort, int, uint, long, ulong, float, double
+                               // From char to ushort, int, uint, ulong, long, float, double, decimal
                                // 
                                if ((target_type == TypeManager.ushort_type) ||
                                    (target_type == TypeManager.int32_type) ||
@@ -578,6 +599,21 @@ namespace Mono.CSharp {
                                        return true;
                        }       
                        
+                       if (expr.eclass == ExprClass.MethodGroup){
+                               if (TypeManager.IsDelegateType (target_type) && RootContext.Version != LanguageVersion.ISO_1){
+                                       MethodGroupExpr mg = expr as MethodGroupExpr;
+                                       if (mg != null){
+                                               //
+                                               // This should not happen frequently, so we can create an object
+                                               // to test compatibility
+                                               //
+                                               Expression c = ImplicitDelegateCreation.Create (
+                                                       ec, mg, target_type, true, Location.Null);
+                                               return c != null;
+                                       }
+                               }
+                       }
+                       
                        if (ImplicitReferenceConversionExists (expr, target_type))
                                return true;
 
@@ -656,17 +692,10 @@ namespace Mono.CSharp {
                                if (conv != null)
                                        return true;
                        }
-                       
+
                        return false;
                }
 
-               //
-               // Used internally by FindMostEncompassedType, this is used
-               // to avoid creating lots of objects in the tight loop inside
-               // FindMostEncompassedType
-               //
-               static EmptyExpression priv_fmet_param;
-               
                /// <summary>
                ///  Finds "most encompassed type" according to the spec (13.4.2)
                ///  amongst the methods in the MethodGroupExpr
@@ -675,31 +704,40 @@ namespace Mono.CSharp {
                {
                        Type best = null;
 
-                       if (priv_fmet_param == null)
-                               priv_fmet_param = new EmptyExpression ();
+                       if (types.Count == 0)
+                               return null;
 
-                       foreach (Type t in types){
-                               priv_fmet_param.SetType (t);
-                               
+                       if (types.Count == 1)
+                               return (Type) types [0];
+
+                       EmptyExpression expr = EmptyExpression.Grab ();
+
+                       foreach (Type t in types) {
                                if (best == null) {
                                        best = t;
                                        continue;
                                }
-                               
-                               if (ImplicitStandardConversionExists (ec, priv_fmet_param, best))
+
+                               expr.SetType (t);
+                               if (ImplicitStandardConversionExists (ec, expr, best))
                                        best = t;
                        }
 
+                       expr.SetType (best);
+                       foreach (Type t in types) {
+                               if (best == t)
+                                       continue;
+                               if (!ImplicitStandardConversionExists (ec, expr, t)) {
+                                       best = null;
+                                       break;
+                               }
+                       }
+
+                       EmptyExpression.Release (expr);
+
                        return best;
                }
-
-               //
-               // Used internally by FindMostEncompassingType, this is used
-               // to avoid creating lots of objects in the tight loop inside
-               // FindMostEncompassingType
-               //
-               static EmptyExpression priv_fmee_ret;
-               
+       
                /// <summary>
                ///  Finds "most encompassing type" according to the spec (13.4.2)
                ///  amongst the types in the given set
@@ -708,77 +746,63 @@ namespace Mono.CSharp {
                {
                        Type best = null;
 
-                       if (priv_fmee_ret == null)
-                               priv_fmee_ret = new EmptyExpression ();
+                       if (types.Count == 0)
+                               return null;
+
+                       if (types.Count == 1)
+                               return (Type) types [0];
 
-                       foreach (Type t in types){
-                               priv_fmee_ret.SetType (best);
+                       EmptyExpression expr = EmptyExpression.Grab ();
 
+                       foreach (Type t in types) {
                                if (best == null) {
                                        best = t;
                                        continue;
                                }
 
-                               if (ImplicitStandardConversionExists (ec, priv_fmee_ret, t))
+                               expr.SetType (best);
+                               if (ImplicitStandardConversionExists (ec, expr, t))
                                        best = t;
                        }
-                       
+
+                       foreach (Type t in types) {
+                               if (best == t)
+                                       continue;
+                               expr.SetType (t);
+                               if (!ImplicitStandardConversionExists (ec, expr, best)) {
+                                       best = null;
+                                       break;
+                               }
+                       }
+
+                       EmptyExpression.Release (expr);
+
                        return best;
                }
 
-               //
-               // Used to avoid creating too many objects
-               //
-               static EmptyExpression priv_fms_expr;
-               
                /// <summary>
                ///   Finds the most specific source Sx according to the rules of the spec (13.4.4)
                ///   by making use of FindMostEncomp* methods. Applies the correct rules separately
                ///   for explicit and implicit conversion operators.
                /// </summary>
-               static public Type FindMostSpecificSource (EmitContext ec, MethodGroupExpr me,
+               static public Type FindMostSpecificSource (EmitContext ec, IList list,
                                                           Expression source, bool apply_explicit_conv_rules,
                                                           Location loc)
                {
                        ArrayList src_types_set = new ArrayList ();
                        
-                       if (priv_fms_expr == null)
-                               priv_fms_expr = new EmptyExpression ();
-
                        //
                        // If any operator converts from S then Sx = S
                        //
                        Type source_type = source.Type;
-                       foreach (MethodBase mb in me.Methods){
-                               ParameterData pd = Invocation.GetParameterData (mb);
+                       foreach (MethodBase mb in list){
+                               ParameterData pd = TypeManager.GetParameterData (mb);
                                Type param_type = pd.ParameterType (0);
 
                                if (param_type == source_type)
                                        return param_type;
 
-                               if (apply_explicit_conv_rules) {
-                                       //
-                                       // From the spec :
-                                       // Find the set of applicable user-defined conversion operators, U.  This set
-                                       // consists of the
-                                       // user-defined implicit or explicit conversion operators declared by
-                                       // the classes or structs in D that convert from a type encompassing
-                                       // or encompassed by S to a type encompassing or encompassed by T
-                                       //
-                                       priv_fms_expr.SetType (param_type);
-                                       if (ImplicitStandardConversionExists (ec, priv_fms_expr, source_type))
-                                               src_types_set.Add (param_type);
-                                       else {
-                                               if (ImplicitStandardConversionExists (ec, source, param_type))
-                                                       src_types_set.Add (param_type);
-                                       }
-                               } else {
-                                       //
-                                       // Only if S is encompassed by param_type
-                                       //
-                                       if (ImplicitStandardConversionExists (ec, source, param_type))
-                                               src_types_set.Add (param_type);
-                               }
+                               src_types_set.Add (param_type);
                        }
                        
                        //
@@ -804,59 +828,25 @@ namespace Mono.CSharp {
                        else
                                return FindMostEncompassedType (ec, src_types_set);
                }
-
-               //
-               // Useful in avoiding proliferation of objects
-               //
-               static EmptyExpression priv_fmt_expr;
                
                /// <summary>
                ///  Finds the most specific target Tx according to section 13.4.4
                /// </summary>
-               static public Type FindMostSpecificTarget (EmitContext ec, MethodGroupExpr me,
+               static public Type FindMostSpecificTarget (EmitContext ec, IList list,
                                                           Type target, bool apply_explicit_conv_rules,
                                                           Location loc)
                {
                        ArrayList tgt_types_set = new ArrayList ();
                        
-                       if (priv_fmt_expr == null)
-                               priv_fmt_expr = new EmptyExpression ();
-                       
                        //
                        // If any operator converts to T then Tx = T
                        //
-                       foreach (MethodInfo mi in me.Methods){
+                       foreach (MethodInfo mi in list){
                                Type ret_type = mi.ReturnType;
-
                                if (ret_type == target)
                                        return ret_type;
 
-                               if (apply_explicit_conv_rules) {
-                                       //
-                                       // From the spec :
-                                       // Find the set of applicable user-defined conversion operators, U.
-                                       //
-                                       // This set consists of the
-                                       // user-defined implicit or explicit conversion operators declared by
-                                       // the classes or structs in D that convert from a type encompassing
-                                       // or encompassed by S to a type encompassing or encompassed by T
-                                       //
-                                       priv_fms_expr.SetType (ret_type);
-                                       if (ImplicitStandardConversionExists (ec, priv_fms_expr, target))
-                                               tgt_types_set.Add (ret_type);
-                                       else {
-                                               priv_fms_expr.SetType (target);
-                                               if (ImplicitStandardConversionExists (ec, priv_fms_expr, ret_type))
-                                                       tgt_types_set.Add (ret_type);
-                                       }
-                               } else {
-                                       //
-                                       // Only if T is encompassed by param_type
-                                       //
-                                       priv_fms_expr.SetType (ret_type);
-                                       if (ImplicitStandardConversionExists (ec, priv_fms_expr, target))
-                                               tgt_types_set.Add (ret_type);
-                               }
+                               tgt_types_set.Add (ret_type);
                        }
 
                        //
@@ -865,13 +855,17 @@ namespace Mono.CSharp {
                        if (apply_explicit_conv_rules) {
                                ArrayList candidate_set = new ArrayList ();
 
+                               EmptyExpression expr = EmptyExpression.Grab ();
+
                                foreach (Type ret_type in tgt_types_set){
-                                       priv_fmt_expr.SetType (ret_type);
+                                       expr.SetType (ret_type);
                                        
-                                       if (ImplicitStandardConversionExists (ec, priv_fmt_expr, target))
+                                       if (ImplicitStandardConversionExists (ec, expr, target))
                                                candidate_set.Add (ret_type);
                                }
 
+                               EmptyExpression.Release (expr);
+
                                if (candidate_set.Count != 0)
                                        return FindMostEncompassingType (ec, candidate_set);
                        }
@@ -903,82 +897,90 @@ namespace Mono.CSharp {
                        return UserDefinedConversion (ec, source, target, loc, true);
                }
 
-               static DoubleHash explicit_conv = new DoubleHash (100);
-               static DoubleHash implicit_conv = new DoubleHash (100);
+               static void AddConversionOperators (EmitContext ec, ArrayList list, 
+                                                   Expression source, Type target_type, 
+                                                   bool look_for_explicit,
+                                                   MethodGroupExpr mg)
+               {
+                       if (mg == null)
+                               return;
+
+                       Type source_type = source.Type;
+                       EmptyExpression expr = EmptyExpression.Grab ();
+                       foreach (MethodInfo m in mg.Methods) {
+                               ParameterData pd = TypeManager.GetParameterData (m);
+                               Type return_type = m.ReturnType;
+                               Type arg_type = pd.ParameterType (0);
+
+                               if (source_type != arg_type) {
+                                       if (!ImplicitStandardConversionExists (ec, source, arg_type)) {
+                                               if (!look_for_explicit)
+                                                       continue;
+                                               expr.SetType (arg_type);
+                                               if (!ImplicitStandardConversionExists (ec, expr, source_type))
+                                                       continue;
+                                       }
+                               }
+
+                               if (target_type != return_type) {
+                                       expr.SetType (return_type);
+                                       if (!ImplicitStandardConversionExists (ec, expr, target_type)) {
+                                               if (!look_for_explicit)
+                                                       continue;
+                                               expr.SetType (target_type);
+                                               if (!ImplicitStandardConversionExists (ec, expr, return_type))
+                                                       continue;
+                                       }
+                               }
+
+                               list.Add (m);
+                       }
+
+                       EmptyExpression.Release (expr);
+               }
+
                /// <summary>
-               ///   Computes the MethodGroup for the user-defined conversion
+               ///   Computes the list of the user-defined conversion
                ///   operators from source_type to target_type.  `look_for_explicit'
                ///   controls whether we should also include the list of explicit
                ///   operators
                /// </summary>
-               static MethodGroupExpr GetConversionOperators (EmitContext ec,
-                                                              Type source_type, Type target_type,
-                                                              Location loc, bool look_for_explicit)
+               static IList GetConversionOperators (EmitContext ec,
+                                                    Expression source, Type target_type,
+                                                    Location loc, bool look_for_explicit)
                {
-                       Expression mg1 = null, mg2 = null;
-                       Expression mg5 = null, mg6 = null, mg7 = null, mg8 = null;
-                       string op_name;
+                       ArrayList ret = new ArrayList (4);
 
-                       op_name = "op_Implicit";
-
-                       MethodGroupExpr union3;
-                       object r;
-                       if ((look_for_explicit ? explicit_conv : implicit_conv).Lookup (source_type, target_type, out r))
-                               return (MethodGroupExpr) r;
-                       
-                       mg1 = Expression.MethodLookup (ec, source_type, op_name, loc);
-                       if (source_type.BaseType != null)
-                               mg2 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
-
-                       if (mg1 == null)
-                               union3 = (MethodGroupExpr) mg2;
-                       else if (mg2 == null)
-                               union3 = (MethodGroupExpr) mg1;
-                       else
-                               union3 = Invocation.MakeUnionSet (mg1, mg2, loc);
+                       Type source_type = source.Type;
 
-                       mg1 = Expression.MethodLookup (ec, target_type, op_name, loc);
-                       if (mg1 != null){
-                               if (union3 != null)
-                                       union3 = Invocation.MakeUnionSet (union3, mg1, loc);
-                               else
-                                       union3 = (MethodGroupExpr) mg1;
+                       if (source_type != TypeManager.decimal_type) {
+                               AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
+                                       Expression.MethodLookup (
+                                               ec, source_type, "op_Implicit", loc) as MethodGroupExpr);
+                               if (look_for_explicit) {
+                                       AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
+                                               Expression.MethodLookup (
+                                                       ec, source_type, "op_Explicit", loc) as MethodGroupExpr);
+                               }
                        }
 
-                       if (target_type.BaseType != null)
-                               mg1 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
-                       
-                       if (mg1 != null){
-                               if (union3 != null)
-                                       union3 = Invocation.MakeUnionSet (union3, mg1, loc);
-                               else
-                                       union3 = (MethodGroupExpr) mg1;
+                       if (target_type != TypeManager.decimal_type) {
+                               AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
+                                       Expression.MethodLookup (
+                                               ec, target_type, "op_Implicit", loc) as MethodGroupExpr);
+                               if (look_for_explicit) {
+                                       AddConversionOperators (ec, ret, source, target_type, look_for_explicit,
+                                               Expression.MethodLookup (
+                                                       ec, target_type, "op_Explicit", loc) as MethodGroupExpr);
+                               }
                        }
 
-                       MethodGroupExpr union4 = null;
-
-                       if (look_for_explicit) {
-                               op_name = "op_Explicit";
-
-                               mg5 = Expression.MemberLookup (ec, source_type, op_name, loc);
-                               if (source_type.BaseType != null)
-                                       mg6 = Expression.MethodLookup (ec, source_type.BaseType, op_name, loc);
-                               
-                               mg7 = Expression.MemberLookup (ec, target_type, op_name, loc);
-                               if (target_type.BaseType != null)
-                                       mg8 = Expression.MethodLookup (ec, target_type.BaseType, op_name, loc);
-                               
-                               MethodGroupExpr union5 = Invocation.MakeUnionSet (mg5, mg6, loc);
-                               MethodGroupExpr union6 = Invocation.MakeUnionSet (mg7, mg8, loc);
-
-                               union4 = Invocation.MakeUnionSet (union5, union6, loc);
-                       }
-                       
-                       MethodGroupExpr ret = Invocation.MakeUnionSet (union3, union4, loc);
-                       (look_for_explicit ? explicit_conv : implicit_conv).Insert (source_type, target_type, ret);
                        return ret;
                }
-               
+
+               static DoubleHash explicit_conv = new DoubleHash (100);
+               static DoubleHash implicit_conv = new DoubleHash (100);
+
                /// <summary>
                ///   User-defined conversions
                /// </summary>
@@ -986,42 +988,62 @@ namespace Mono.CSharp {
                                                                Type target, Location loc,
                                                                bool look_for_explicit)
                {
-                       MethodGroupExpr union;
                        Type source_type = source.Type;
-                       MethodBase method = null;
-
-                       union = GetConversionOperators (ec, source_type, target, loc, look_for_explicit);
-                       if (union == null)
-                               return null;
-                       
-                       Type most_specific_source, most_specific_target;
-
-                       most_specific_source = FindMostSpecificSource (ec, union, source, look_for_explicit, loc);
-                       if (most_specific_source == null)
-                               return null;
-
-                       most_specific_target = FindMostSpecificTarget (ec, union, target, look_for_explicit, loc);
-                       if (most_specific_target == null) 
-                               return null;
-
-                       int count = 0;
-
-                       
-                       foreach (MethodBase mb in union.Methods){
-                               ParameterData pd = Invocation.GetParameterData (mb);
-                               MethodInfo mi = (MethodInfo) mb;
+                       MethodInfo method = null;
+                       Type most_specific_source = null;
+                       Type most_specific_target = null;
+
+                       object o;
+                       DoubleHash hash = look_for_explicit ? explicit_conv : implicit_conv;
+
+                       if (!(source is Constant) && hash.Lookup (source_type, target, out o)) {
+                               method = (MethodInfo) o;
+                               if (method != null) {
+                                       ParameterData pd = TypeManager.GetParameterData (method);
+                                       most_specific_source = pd.ParameterType (0);
+                                       most_specific_target = method.ReturnType;
+                               }
+                       } else {
+                               IList ops = GetConversionOperators (ec, source, target, loc, look_for_explicit);
+                               if (ops == null || ops.Count == 0) {
+                                       method = null;
+                                       goto skip;
+                               }
+                                       
+                               most_specific_source = FindMostSpecificSource (ec, ops, source, look_for_explicit, loc);
+                               if (most_specific_source == null) {
+                                       method = null;
+                                       goto skip;
+                               }
+                               
+                               most_specific_target = FindMostSpecificTarget (ec, ops, target, look_for_explicit, loc);
+                               if (most_specific_target == null) {
+                                       method = null;
+                                       goto skip;
+                               }
+                               
+                               int count = 0;
                                
-                               if (pd.ParameterType (0) == most_specific_source &&
-                                   mi.ReturnType == most_specific_target) {
-                                       method = mb;
-                                       count++;
+                               foreach (MethodInfo m in ops) {
+                                       ParameterData pd = TypeManager.GetParameterData (m);
+                                       
+                                       if (pd.ParameterType (0) == most_specific_source &&
+                                           m.ReturnType == most_specific_target) {
+                                               method = m;
+                                               count++;
+                                       }
                                }
+                               if (count > 1)
+                                       method = null;
+                               
+                       skip:
+                               if (!(source is Constant))
+                                       hash.Insert (source_type, target, method);
                        }
-                       
-                       if (method == null || count > 1)
+
+                       if (method == null)
                                return null;
                        
-                       
                        //
                        // This will do the conversion to the best match that we
                        // found.  Now we need to perform an implict standard conversion
@@ -1037,7 +1059,7 @@ namespace Mono.CSharp {
                                return null;
 
                        Expression e;
-                       e =  new UserCast ((MethodInfo) method, source, loc);
+                       e =  new UserCast (method, source, loc);
                        if (e.Type != target){
                                if (!look_for_explicit)
                                        e = ImplicitConversionStandard (ec, e, target, loc);
@@ -1100,7 +1122,8 @@ namespace Mono.CSharp {
                                if (RootContext.Version != LanguageVersion.ISO_1){
                                        MethodGroupExpr mg = expr as MethodGroupExpr;
                                        if (mg != null)
-                                               return ImplicitDelegateCreation.Create (ec, mg, target_type, loc);
+                                               return ImplicitDelegateCreation.Create (
+                                                       ec, mg, target_type, false, loc);
                                }
                        }
 
@@ -1141,7 +1164,7 @@ namespace Mono.CSharp {
                                
                                if (target_type.IsPointer) {
                                        if (expr_type == TypeManager.null_type)
-                                               return new EmptyCast (expr, target_type);
+                                               return new EmptyCast (NullPointer.Null, target_type);
 
                                        if (expr_type == TypeManager.void_ptr_type)
                                                return new EmptyCast (expr, target_type);
@@ -1243,8 +1266,8 @@ namespace Mono.CSharp {
                        if (source.Name == target.Name){
                                Report.ExtraInformation (loc,
                                         String.Format (
-                                               "The type {0} has two conflicting definitons, one comes from {0} and the other from {1}",
-                                               source.Assembly.FullName, target.Assembly.FullName));
+                                               "The type {0} has two conflicting definitions, one comes from {1} and the other from {2}",
+                                               source.Name, source.Assembly.FullName, target.Assembly.FullName));
                                                         
                        }
                        Report.Error (29, loc, "Cannot convert implicitly from {0} to `{1}'",
@@ -1479,9 +1502,11 @@ namespace Mono.CSharp {
                                        return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_U8);
                                if (real_target_type == TypeManager.char_type)
                                        return new ConvCast (ec, expr, target_type, ConvCast.Mode.R4_CH);
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr, true);
                        } else if (expr_type == TypeManager.double_type){
                                //
-                               // From double to byte, byte, short,
+                               // From double to sbyte, byte, short,
                                // ushort, int, uint, long, ulong,
                                // char, float or decimal
                                //
@@ -1505,10 +1530,26 @@ namespace Mono.CSharp {
                                        return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_CH);
                                if (real_target_type == TypeManager.float_type)
                                        return new ConvCast (ec, expr, target_type, ConvCast.Mode.R8_R4);
-                       } 
-
-                       // decimal is taken care of by the op_Explicit methods.
-
+                               if (real_target_type == TypeManager.decimal_type)
+                                       return new CastToDecimal (ec, expr, true);
+                       } else if (expr_type == TypeManager.decimal_type) {
+                               //
+                               // From decimal to sbyte, byte, short, ushort, int, uint,
+                               // long, ulong, char, double or float
+                               //
+                               if (real_target_type == TypeManager.sbyte_type ||
+                                   real_target_type == TypeManager.byte_type ||
+                                   real_target_type == TypeManager.short_type ||
+                                   real_target_type == TypeManager.ushort_type ||
+                                   real_target_type == TypeManager.int32_type ||
+                                   real_target_type == TypeManager.uint32_type ||
+                                   real_target_type == TypeManager.int64_type ||
+                                   real_target_type == TypeManager.uint64_type ||
+                                   real_target_type == TypeManager.char_type ||
+                                   real_target_type == TypeManager.double_type ||
+                                   real_target_type == TypeManager.float_type)
+                                       return new CastFromDecimal (ec, expr, target_type);
+                       }
                        return null;
                }
 
@@ -1773,20 +1814,21 @@ namespace Mono.CSharp {
                                        return ne;
                        }
 
-               skip_explicit:
                        if (ec.InUnsafe){
                                if (target_type.IsPointer){
                                        if (expr_type.IsPointer)
                                                return new EmptyCast (expr, target_type);
                                        
                                        if (expr_type == TypeManager.sbyte_type ||
-                                           expr_type == TypeManager.byte_type ||
                                            expr_type == TypeManager.short_type ||
-                                           expr_type == TypeManager.ushort_type ||
                                            expr_type == TypeManager.int32_type ||
+                                           expr_type == TypeManager.int64_type)
+                                               return new OpcodeCast (expr, target_type, OpCodes.Conv_I);
+
+                                       if (expr_type == TypeManager.ushort_type ||
                                            expr_type == TypeManager.uint32_type ||
                                            expr_type == TypeManager.uint64_type ||
-                                           expr_type == TypeManager.int64_type)
+                                           expr_type == TypeManager.byte_type)
                                                return new OpcodeCast (expr, target_type, OpCodes.Conv_U);
                                }
                                if (expr_type.IsPointer){
@@ -1840,7 +1882,7 @@ namespace Mono.CSharp {
                                              TypeManager.CSharpName (target_type) + "'");
                                return null;
                        }
-                               
+
                        Error_CannotConvertType (loc, original_expr_type, target_type);
                        return null;
                }