C# Constant.ConvertImplicitly方法代码示例

		static bool ConvertPromotion (ResolveContext rc, ref Constant prim, ref Constant second, TypeSpec type)
		{
			Constant c = prim.ConvertImplicitly (type);
			if (c != null) {
				prim = c;
				return true;
			}

			if (type.BuiltinType == BuiltinTypeSpec.Type.UInt) {
				type = rc.BuiltinTypes.Long;
				prim = prim.ConvertImplicitly (type);
				second = second.ConvertImplicitly (type);
				return prim != null && second != null;
			}

			return false;
		}

		static bool ConvertPromotion (ref Constant prim, ref Constant second, Type type)
		{
			Constant c = prim.ConvertImplicitly (type);
			if (c != null) {
				prim = c;
				return true;
			}

			if (type == TypeManager.uint32_type) {
				type = TypeManager.int64_type;
				prim = prim.ConvertImplicitly (type);
				second = second.ConvertImplicitly (type);
				return prim != null && second != null;
			}

			return false;
		}

		//
		// Performs the numeric promotions on the left and right expresions
		// and deposits the results on `lc' and `rc'.
		//
		// On success, the types of `lc' and `rc' on output will always match,
		// and the pair will be one of:
		//
		// TODO: BinaryFold should be called as an optimization step only,
		// error checking here is weak
		//		
		static bool DoBinaryNumericPromotions (ResolveContext rc, ref Constant left, ref Constant right)
		{
			TypeSpec ltype = left.Type;
			TypeSpec rtype = right.Type;

			foreach (TypeSpec t in rc.BuiltinTypes.BinaryPromotionsTypes) {
				if (t == ltype)
					return t == rtype || ConvertPromotion (rc, ref right, ref left, t);

				if (t == rtype)
					return t == ltype || ConvertPromotion (rc, ref left, ref right, t);
			}

			left = left.ConvertImplicitly (rc.BuiltinTypes.Int);
			right = right.ConvertImplicitly (rc.BuiltinTypes.Int);
			return left != null && right != null;
		}

		//
		// Performs the numeric promotions on the left and right expresions
		// and deposits the results on `lc' and `rc'.
		//
		// On success, the types of `lc' and `rc' on output will always match,
		// and the pair will be one of:
		//
		static bool DoBinaryNumericPromotions (ref Constant left, ref Constant right)
		{
			Type ltype = left.Type;
			Type rtype = right.Type;

			foreach (Type t in binary_promotions) {
				if (t == ltype)
					return t == rtype || ConvertPromotion (ref right, ref left, t);

				if (t == rtype)
					return t == ltype || ConvertPromotion (ref left, ref right, t);
			}

			left = left.ConvertImplicitly (TypeManager.int32_type);
			right = right.ConvertImplicitly (TypeManager.int32_type);
			return left != null && right != null;
		}

		//
		// Performs the numeric promotions on the left and right expresions
		// and deposits the results on `lc' and `rc'.
		//
		// On success, the types of `lc' and `rc' on output will always match,
		// and the pair will be one of:
		//
		// TODO: BinaryFold should be called as an optimization step only,
		// error checking here is weak
		//		
		static bool DoBinaryNumericPromotions (ResolveContext rc, ref Constant left, ref Constant right)
		{
			TypeSpec ltype = left.Type;
			TypeSpec rtype = right.Type;

			// PlayScript - AS has bool as an additional binary promotion type.
			TypeSpec[] binaryPromotionsTypes = (rc.FileType == SourceFileType.PlayScript ? 
			                                    rc.BuiltinTypes.AsBinaryPromotionsTypes : rc.BuiltinTypes.BinaryPromotionsTypes);

			foreach (TypeSpec t in binaryPromotionsTypes) {
				if (t == ltype)
					return t == rtype || ConvertPromotion (rc, ref right, ref left, t);

				if (t == rtype)
					return t == ltype || ConvertPromotion (rc, ref left, ref right, t);
			}

			left = left.ConvertImplicitly (rc.BuiltinTypes.Int, rc);
			right = right.ConvertImplicitly (rc.BuiltinTypes.Int, rc);
			return left != null && right != null;
		}

		public virtual Constant ConvertInitializer (ResolveContext rc, Constant expr)
		{
			return expr.ConvertImplicitly (MemberType);
		}

//.........这里部分代码省略.........
				if (lt == InternalType.NullLiteral)
					return right;

				if (rt == InternalType.NullLiteral)
					return left;

				//
				// If both sides are strings, then concatenate, if
				// one is a string, and the other is not, then defer
				// to runtime concatenation
				//
				if (lt.BuiltinType == BuiltinTypeSpec.Type.String || rt.BuiltinType == BuiltinTypeSpec.Type.String){
					if (lt == rt)
						return new StringConstant (ec.BuiltinTypes, (string)left.GetValue () + (string)right.GetValue (),
							left.Location);
					
					return null;
				}

				//
				// handle "E operator + (E x, U y)"
				// handle "E operator + (Y y, E x)"
				//
				EnumConstant lc = left as EnumConstant;
				EnumConstant rc = right as EnumConstant;
				if (lc != null || rc != null){
					if (lc == null) {
						lc = rc;
						lt = lc.Type;
						right = left;
					}

					// U has to be implicitly convetible to E.base
					right = right.ConvertImplicitly (lc.Child.Type);
					if (right == null)
						return null;

					result = BinaryFold (ec, oper, lc.Child, right, loc);
					if (result == null)
						return null;

					result = result.TryReduce (ec, lt);
					if (result == null)
						return null;

					return new EnumConstant (result, lt);
				}

				if (!DoBinaryNumericPromotions (ec, ref left, ref right))
					return null;

				try {
					if (left is DoubleConstant){
						double res;
						
						if (ec.ConstantCheckState)
							res = checked (((DoubleConstant) left).Value +
								       ((DoubleConstant) right).Value);
						else
							res = unchecked (((DoubleConstant) left).Value +
									 ((DoubleConstant) right).Value);

						return new DoubleConstant (ec.BuiltinTypes, res, left.Location);
					}
					if (left is FloatConstant){
						float res;

//.........这里部分代码省略.........

			case Binary.Operator.Addition:
				//
				// If both sides are strings, then concatenate, if
				// one is a string, and the other is not, then defer
				// to runtime concatenation
				//
				if (lt == TypeManager.string_type || rt == TypeManager.string_type){
					if (lt == TypeManager.string_type && rt == TypeManager.string_type)
						return new StringConstant (
							((StringConstant) left).Value +
							((StringConstant) right).Value, left.Location);
					
					return null;
				}

				if (lt == TypeManager.null_type && lt == rt)
					return left;

				//
				// handle "E operator + (E x, U y)"
				// handle "E operator + (Y y, E x)"
				//
				EnumConstant lc = left as EnumConstant;
				EnumConstant rc = right as EnumConstant;
				if (lc != null || rc != null){
					if (lc == null) {
						lc = rc;
						lt = lc.Type;
						right = left;
					}

					// U has to be implicitly convetible to E.base
					right = right.ConvertImplicitly (lc.Child.Type);
					if (right == null)
						return null;

					result = BinaryFold (ec, oper, lc.Child, right, loc);
					if (result == null)
						return null;

					result = result.TryReduce (ec, lt, loc);
					if (result == null)
						return null;

					return new EnumConstant (result, lt);
				}

				if (!DoBinaryNumericPromotions (ref left, ref right))
					return null;

				try {
					if (left is DoubleConstant){
						double res;
						
						if (ec.ConstantCheckState)
							res = checked (((DoubleConstant) left).Value +
								       ((DoubleConstant) right).Value);
						else
							res = unchecked (((DoubleConstant) left).Value +
									 ((DoubleConstant) right).Value);
						
						return new DoubleConstant (res, left.Location);
					}
					if (left is FloatConstant){
						float res;