/// <summary>
/// Attempts to coerce the operand types on a binary operation for some special type and value cases as treated by JsonValue:
/// "true" and "false" can be converted to boolean.
/// Guid, DateTime and other types can be converted to string.
/// </summary>
/// <param name="thisOperand">The first operand.</param>
/// <param name="otherOperand">The second operand</param>
/// <param name="coercedType">On success, this parameter contains the coerced type.</param>
/// <returns>true if the coercion is performed, false otherwise.</returns>
private static bool TryCoerceSpecialTypes(DynamicMetaObject thisOperand, DynamicMetaObject otherOperand, out Type coercedType)
{
JsonValue thisValue = thisOperand.Value as JsonValue;
JsonValue otherValue = otherOperand.Value as JsonValue;
if (thisValue is JsonPrimitive)
{
Type thisType = thisValue.Read().GetType();
if (thisType != otherOperand.LimitType)
{
if (otherOperand.LimitType == typeof(string) || (thisType == typeof(string) && otherValue == null))
{
object value;
if (thisValue.TryReadAs(otherOperand.LimitType, out value))
{
coercedType = otherOperand.LimitType;
return(true);
}
}
}
}
coercedType = default(Type);
return(false);
}
/// <summary>
/// Updates the <see cref="Expression"/> tree for the operands of the specified operation.
/// </summary>
/// <param name="operation">The operation to evalutes.</param>
/// <param name="thisOperand">The first operand.</param>
/// <param name="otherOperand">The second operand.</param>
/// <param name="thisExpression">The <see cref="Expression"/> for the first operand.</param>
/// <param name="otherExpression">The <see cref="Expression"/> for the second operand.</param>
private static void GetBinaryOperandExpressions(ExpressionType operation, DynamicMetaObject thisOperand, DynamicMetaObject otherOperand, ref Expression thisExpression, ref Expression otherExpression)
{
JsonValue thisValue = thisOperand.Value as JsonValue;
JsonValue otherValue = otherOperand.Value as JsonValue;
Type thisType = thisValue.Read().GetType();
Type otherType = otherValue != null?otherValue.Read().GetType() : otherOperand.Value.GetType();
Type coercedType;
if (JsonValueDynamicMetaObject.TryCoerceType(operation, thisType, otherType, out coercedType))
{
thisType = otherType = coercedType;
}
else if (JsonValueDynamicMetaObject.TryCoerceSpecialTypes(thisOperand, otherOperand, out coercedType))
{
thisType = otherType = coercedType;
}
thisExpression = Expression.Convert(thisExpression, thisOperand.LimitType);
thisExpression = Expression.Convert(Expression.Call(thisExpression, ReadAsMethodInfo, new Expression[] { Expression.Constant(thisType) }), thisType);
otherExpression = Expression.Convert(otherExpression, otherOperand.LimitType);
if (otherValue != null)
{
otherExpression = Expression.Convert(Expression.Call(otherExpression, ReadAsMethodInfo, new Expression[] { Expression.Constant(otherType) }), otherType);
}
else if (otherOperand.LimitType != otherType)
{
otherExpression = Expression.Convert(otherExpression, otherType);
}
}
/// <summary>
/// Gets the return type for unary operations.
/// </summary>
/// <param name="binder">The unary operation binder.</param>
/// <returns>The type representing the operation return type.</returns>
private Type GetUnaryOperationReturnType(UnaryOperationBinder binder)
{
JsonValue thisValue = this.Value as JsonValue;
Type returnType = binder.ReturnType == typeof(object) ? thisValue.Read().GetType() : binder.ReturnType;
//// The DLR sets the binder.ReturnType for the unary 'Not' operation as 'object' as opposed to 'bool',
//// we need to detect this case and fix up the type to enable boolean conversions from strings.
if (returnType == typeof(string) && binder.Operation == ExpressionType.Not)
{
bool boolVal;
if (thisValue.TryReadAs <bool>(out boolVal))
{
returnType = typeof(bool);
}
}
return(returnType);
}