|
static private ImplicitConvert ( |
||
| expression | ||
| expectedType | ||
| return | ||
internal static Expression ImplicitConvert(Expression expression, Type expectedType)
{
if (expectedType == null)
{
return expression;
}
if (expectedType.IsGenericParameter)
{
if (!expectedType.IsAppropriate(expression.Type))
{
return null;
}
}
else
{
if ((expectedType.IsAppropriate(expression.Type) && expression.Type.IsValueType && !expectedType.IsValueType)
|| expectedType.GetMethod("op_Implicit", BindingFlags.Public | BindingFlags.Static, null, new [] { expression.Type, }, null) != null
)
{
return Convert(expression, expectedType);
}
if (!expectedType.IsAppropriate(expression.Type))
{
if (Nullable.GetUnderlyingType(expectedType).Let(t => t != null && t == expression.Type))
{
return Convert(expression, typeof(Nullable<>).MakeGenericType(expression.Type));
}
else if (Nullable.GetUnderlyingType(expression.Type).Let(t => t != null && t == expectedType))
{
return Convert(expression, Nullable.GetUnderlyingType(expression.Type));
}
return ConvertNumericType(expression.Type, expectedType)
.Null(t => Convert(expression, t));
}
}
return expression;
}
/// <summary>
/// Reduces this node to a simpler expression, with (if possible) additional symbol tables.
/// </summary>
/// <param name="expression">The reducing expression.</param>
/// <param name="symbols">The additional symbol table for reducing. If <paramref name="expression"/> is not <see cref="YacqExpression"/>, this parameter is ignored.</param>
/// <param name="expectedType">The type which is expected as the type of reduced expression.</param>
/// <returns>The reduced expression.</returns>
public static Expression Reduce(this Expression expression, SymbolTable symbols, Type expectedType = null)
{
return(expression != null
? expression is YacqExpression
? ((YacqExpression)expression).Reduce(symbols, expectedType)
: YacqExpression.ImplicitConvert(expression, expectedType)
: null);
}