public static void EmitConvert(XamlEmitContextWithLocals <IXamlILEmitter, XamlILNodeEmitResult> context, IXamlLineInfo node, IXamlType what,
IXamlType to, Func <bool, IXamlILEmitter> ld)
{
if (what.Equals(to))
{
ld(false);
}
else if (what == XamlPseudoType.Null)
{
if (to.IsValueType)
{
if (to.GenericTypeDefinition?.Equals(context.Configuration.WellKnownTypes.NullableT) == true)
{
using (var loc = context.GetLocalOfType(to))
ld(false)
.Pop()
.Ldloca(loc.Local)
.Emit(OpCodes.Initobj, to)
.Ldloc(loc.Local);
}
else
{
throw new XamlLoadException("Unable to convert {x:Null} to " + to.GetFqn(), node);
}
}
else
{
ld(false);
}
}
else if (what.IsValueType && to.IsValueType)
{
if (to.IsNullableOf(what))
{
ld(false).Emit(OpCodes.Newobj,
to.Constructors.First(c =>
c.Parameters.Count == 1 && c.Parameters[0].Equals(what)));
}
else if (what.IsNullableOf(what))
{
ld(true)
.EmitCall(what.FindMethod(m => m.Name == "get_Value"));
}
else
{
throw new XamlLoadException(
$"Don't know how to convert value type {what.GetFullName()} to value type {to.GetFullName()}",
node);
}
}
else if (!to.IsValueType && what.IsValueType)
{
if (!to.IsAssignableFrom(what))
{
throw new XamlLoadException(
$"Don't know how to convert value type {what.GetFullName()} to reference type {to.GetFullName()}",
node);
}
ld(false).Box(what);
}
else if (to.IsValueType && !what.IsValueType)
{
if (!(what.Namespace == "System" && what.Name == "Object"))
{
throw new XamlLoadException(
$"Don't know how to convert reference type {what.GetFullName()} to value type {to.GetFullName()}",
node);
}
ld(false).Unbox_Any(to);
}
else
{
if (to.IsAssignableFrom(what))
{
// Downcast, always safe
ld(false);
}
else if (what.IsInterface || what.IsAssignableFrom(to))
{
// Upcast or cast from interface, might throw InvalidCastException
ld(false).Emit(OpCodes.Castclass, to);
}
else
{
// Types are completely unrelated, e. g. string to List<int> conversion attempt
throw new XamlLoadException(
$"Don't know how to convert reference type {what.GetFullName()} to reference type {to.GetFullName()}",
node);
}
}
}