/// <summary>
/// Pops the value on the stack, converts it from one type to another, then pushes the
/// result onto the stack. Undefined is converted to the given default value.
/// </summary>
/// <param name="generator"> The IL generator. </param>
/// <param name="fromType"> The type to convert from. </param>
/// <param name="targetParameter"> The type to convert to and the default value, if there is one. </param>
private static void EmitTypeConversion(ILGenerator generator, Type fromType, BinderArgument argument)
{
// Emit either the default value if there is one, otherwise emit "undefined".
if (argument.HasDefaultValue)
{
// Check if the input value is undefined.
var elseClause = generator.CreateLabel();
generator.Duplicate();
generator.BranchIfNull(elseClause);
generator.Duplicate();
generator.LoadField(ReflectionHelpers.Undefined_Value);
generator.CompareEqual();
generator.BranchIfTrue(elseClause);
// Convert as per normal.
EmitTypeConversion(generator, fromType, argument.Type);
// Jump to the end.
var endOfIf = generator.CreateLabel();
generator.Branch(endOfIf);
generator.DefineLabelPosition(elseClause);
// Pop the existing value and emit the default value.
generator.Pop();
EmitUndefined(generator, argument);
// Define the end of the block.
generator.DefineLabelPosition(endOfIf);
}
else
{
// Convert as per normal.
EmitTypeConversion(generator, fromType, argument.Type);
}
}
/// <summary>
/// Pushes the result of converting <c>undefined</c> to the given type onto the stack.
/// </summary>
/// <param name="il"> The IL generator. </param>
/// <param name="targetParameter"> The type to convert to, and optionally a default value. </param>
private static void EmitUndefined(ILGenerator il, BinderArgument argument)
{
// Emit either the default value if there is one, otherwise emit "undefined".
if (argument.HasDefaultValue == true)
{
// Emit the default value.
EmitHelpers.EmitValue(il, argument.DefaultValue);
}
else
{
// Convert Undefined to the target type and emit.
EmitHelpers.EmitUndefined(il);
EmitTypeConversion(il, typeof(object), argument.Type);
}
}