private static void ConvertUnboxStruct(AstExpression node, XTypeReference resultType, XTypeSystem typeSystem)
{
// Structs must never be null. We have to handle structs here, since a newobj
// might need generic arguments. These would be difficult to provide at "UnboxFromGeneric",
// but will be automatically filled in by the GenericInstanceConverter
// convert to (temp$ = (T)x) != null ? temp$ : default(T)
// replace any unbox, but keep if otherwise.
var clone = node.Code == AstCode.Unbox ? new AstExpression(node.Arguments[0]) : new AstExpression(node);
// make sure we don't evaluate the expression twice.
var tempVar = new AstGeneratedVariable("temp$", "") { Type = typeSystem.Object };
// T(x)
var txExpr = new AstExpression(node.SourceLocation, AstCode.SimpleCastclass, resultType, clone)
.SetType(resultType);
// temporary storage
var storeTempVar = new AstExpression(node.SourceLocation, AstCode.Stloc, tempVar, txExpr) { ExpectedType = resultType };
var loadTempVar = new AstExpression(node.SourceLocation, AstCode.Ldloc, tempVar)
.SetType(resultType);
// default (T)
var defaultT = new AstExpression(node.SourceLocation, AstCode.DefaultValue, resultType).SetType(resultType);
var constructor = StructCallConverter.GetDefaultValueCtor(resultType.Resolve());
StructCallConverter.ConvertDefaultValue(defaultT, constructor);
// Combine
var conditional = new AstExpression(node.SourceLocation, AstCode.Conditional, resultType,
storeTempVar, loadTempVar, defaultT)
.SetType(resultType);
node.CopyFrom(conditional);
}
