/// <summary>
/// If the specified type is some specific Nullable(T) type, returns its underlying type.
/// Otherwise, returns the supplied type.
/// </summary>
/// <param name="target">The type</param>
/// <exception cref="ArgumentNullException"><paramref name="target"/> is null</exception>
public static Type GetUnderlyingType(this Type target)
{
if (target == null)
{
throw new ArgumentNullException("target");
}
return(target.IsNullableType() ? UnboxableNullable.GetUnderlyingType(target) : target);
}
/// <summary>
/// Attempts to auto-adjust the size of argument to the desired type.
/// Integers grow up to Int64, Double or Decimal, floats grow up to Decimal.
/// </summary>
/// <param name="root">Optional, corresponding parse tree node</param>
/// <param name="expr">Expression whose value is to be adjusted, must be of numeric value type</param>
/// <param name="targetType">Desired type</param>
/// <param name="adjusted">New or same expression</param>
/// <exception cref="ArgumentNullException"><paramref name="expr"/> is null</exception>
/// <exception cref="ArgumentNullException"><paramref name="targetType"/> is null</exception>
public static bool TryAdjustReturnType(ParseTreeNode root, Expression expr, Type targetType, out Expression adjusted)
{
if (expr == null)
{
throw new ArgumentNullException("expr");
}
if (targetType == null)
{
throw new ArgumentNullException("targetType");
}
// do we actually have to adjust them?
if (ReferenceEquals(expr.Type, targetType))
{
adjusted = expr;
return(true);
}
if (expr.IsVoid())
{
adjusted = GetDefaultExpression(targetType);
return(true);
}
if (targetType.IsNullableType())
{
if (expr.IsNullableType())
{
var variable = Expression.Variable(expr.Type);
var setvar = Expression.Assign(variable, expr);
var hasvalue = Expression.Field(variable, "HasValue");
Expression value = Expression.Field(variable, "Value");
Expression adjustedValue;
if (TryAdjustReturnType(root, value, UnboxableNullable.GetUnderlyingType(targetType), out adjustedValue))
{
adjusted = Expression.Block(
targetType,
new [] { variable },
setvar,
Expression.Condition(hasvalue, MakeNewNullable(targetType, adjustedValue), MakeNewNullable(targetType)));
return(true);
}
}
else
{
Expression adjustedValue;
if (TryAdjustReturnType(root, expr, UnboxableNullable.GetUnderlyingType(targetType), out adjustedValue))
{
adjusted = MakeNewNullable(targetType, adjustedValue);
return(true);
}
}
}
else if (expr.IsNullableType())
{
var nonnullable = expr.RemoveNullability();
return(TryAdjustReturnType(root, nonnullable, targetType, out adjusted));
}
else
{
return(TryAdjustNumericType(root, expr, targetType, out adjusted));
}
adjusted = null;
return(false);
}