Reject out of range constant conversion to nullable enum.

mcs/errors/cs0030-15.cs

@@ -0,0 +1,12 @@
+// CS0030: Cannot convert type `long' to `System.DayOfWeek?'
+// Line: 10
+
+using System;
+
+class C
+{
+    static void Main ()
+    {
+		var dow = (DayOfWeek?) long.MaxValue;
+    }
+}

mcs/mcs/cfold.cs

@@ -149,7 +149,7 @@ static public Constant BinaryFold (ResolveContext ec, Binary.Operator oper,
 					case Binary.Operator.ExclusiveOr:
 						result = BinaryFold (ec, oper, ((EnumConstant)left).Child, ((EnumConstant)right).Child, loc);
 						if (result != null)
-							result = result.TryReduce (ec, lt);
+							result = result.Reduce (ec, lt);
 						return result;
 
 					///
@@ -158,7 +158,7 @@ static public Constant BinaryFold (ResolveContext ec, Binary.Operator oper,
 					case Binary.Operator.Subtraction:
 						result = BinaryFold (ec, oper, ((EnumConstant)left).Child, ((EnumConstant)right).Child, loc);
 						if (result != null)
-							result = result.TryReduce (ec, EnumSpec.GetUnderlyingType (lt));
+							result = result.Reduce (ec, EnumSpec.GetUnderlyingType (lt));
 						return result;
 
 					///
@@ -340,7 +340,7 @@ static public Constant BinaryFold (ResolveContext ec, Binary.Operator oper,
 					if (result == null)
 						return null;
 
-					result = result.TryReduce (ec, lt);
+					result = result.Reduce (ec, lt);
 					if (result == null)
 						return null;
 
@@ -459,7 +459,7 @@ static public Constant BinaryFold (ResolveContext ec, Binary.Operator oper,
 					if (result == null)
 						return null;
 
-					result = result.TryReduce (ec, lt);
+					result = result.Reduce (ec, lt);
 					if (result == null)
 						return null;
 

mcs/mcs/constant.cs

@@ -251,10 +251,12 @@ protected override Expression DoResolve (ResolveContext rc)
 			return this;
 		}
 
-		/// <summary>
-		///   Attempts to do a compile-time folding of a constant cast.
-		/// </summary>
-		public Constant TryReduce (ResolveContext ec, TypeSpec target_type)
+		//
+		// Attempts to do a compile-time folding of a constant cast and handles
+		// error reporting for constant overlows only, on normal conversion
+		// errors returns null
+		// 
+		public Constant Reduce (ResolveContext ec, TypeSpec target_type)
 		{
 			try {
 				return TryReduceConstant (ec, target_type);
@@ -271,6 +273,15 @@ public Constant TryReduce (ResolveContext ec, TypeSpec target_type)
 			}
 		}
 
+		public Constant TryReduce (ResolveContext rc, TypeSpec targetType)
+		{
+			try {
+				return TryReduceConstant (rc, targetType);
+			} catch (OverflowException) {
+				return null;
+			}
+		}
+
 		Constant TryReduceConstant (ResolveContext ec, TypeSpec target_type)
 		{
 			if (Type == target_type) {

mcs/mcs/convert.cs

@@ -1196,7 +1196,7 @@ static Expression UserDefinedConversion (ResolveContext ec, Expression source, T
 			if (s_x != source_type) {
 				var c = source as Constant;
 				if (c != null) {
-					source = c.TryReduce (ec, s_x);
+					source = c.Reduce (ec, s_x);
 					if (source == null)
 						c = null;
 				}
@@ -1990,21 +1990,28 @@ static public Expression ExplicitConversionCore (ResolveContext ec, Expression e
 				if (expr_type == real_target)
 					return EmptyCast.Create (expr, target_type);
 
-				ne = ImplicitNumericConversion (expr, real_target);
-				if (ne != null)
-					return EmptyCast.Create (ne, target_type);
-
-				ne = ExplicitNumericConversion (ec, expr, real_target);
-				if (ne != null)
-					return EmptyCast.Create (ne, target_type);
+				Constant c = expr as Constant;
+				if (c != null) {
+					c = c.TryReduce (ec, real_target);
+					if (c != null)
+						return c;
+				} else {
+					ne = ImplicitNumericConversion (expr, real_target);
+					if (ne != null)
+						return EmptyCast.Create (ne, target_type);
 
-				//
-				// LAMESPEC: IntPtr and UIntPtr conversion to any Enum is allowed
-				//
-				if (expr_type.BuiltinType == BuiltinTypeSpec.Type.IntPtr || expr_type.BuiltinType == BuiltinTypeSpec.Type.UIntPtr) {
-					ne = ExplicitUserConversion (ec, expr, real_target, loc);
+					ne = ExplicitNumericConversion (ec, expr, real_target);
 					if (ne != null)
-						return ExplicitConversionCore (ec, ne, target_type, loc);
+						return EmptyCast.Create (ne, target_type);
+
+					//
+					// LAMESPEC: IntPtr and UIntPtr conversion to any Enum is allowed
+					//
+					if (expr_type.BuiltinType == BuiltinTypeSpec.Type.IntPtr || expr_type.BuiltinType == BuiltinTypeSpec.Type.UIntPtr) {
+						ne = ExplicitUserConversion (ec, expr, real_target, loc);
+						if (ne != null)
+							return ExplicitConversionCore (ec, ne, target_type, loc);
+					}
 				}
 			} else {
 				ne = ExplicitNumericConversion (ec, expr, target_type);

mcs/mcs/expression.cs

@@ -1702,7 +1702,7 @@ protected override Expression DoResolve (ResolveContext ec)
 
 			Constant c = expr as Constant;
 			if (c != null) {
-				c = c.TryReduce (ec, type);
+				c = c.Reduce (ec, type);
 				if (c != null)
 					return c;
 			}
@@ -2661,7 +2661,7 @@ Constant EnumLiftUp (ResolveContext ec, Constant left, Constant right, Location
 					return left;
 
 				if (left.IsZeroInteger)
-					return left.TryReduce (ec, right.Type);
+					return left.Reduce (ec, right.Type);
 
 				break;
 

mcs/mcs/statement.cs

@@ -1225,7 +1225,7 @@ public override bool Resolve (BlockContext ec)
 				res = c;
 			} else {
 				TypeSpec type = ec.Switch.SwitchType;
-				res = c.TryReduce (ec, type);
+				res = c.Reduce (ec, type);
 				if (res == null) {
 					c.Error_ValueCannotBeConverted (ec, type, true);
 					return false;