private void EmitTypeBinaryExpression(Expression expr)
{
var node = (TypeBinaryExpression)expr;
if (node.NodeType == ExpressionType.TypeEqual)
{
EmitExpression(node.ReduceTypeEqual());
return;
}
var type = node.Expression.Type;
// Try to determine the result statically
var result = ConstantCheck.AnalyzeTypeIs(node);
if (result == AnalyzeTypeIsResult.KnownTrue ||
result == AnalyzeTypeIsResult.KnownFalse)
{
// Result is known statically, so just emit the expression for
// its side effects and return the result
EmitExpressionAsVoid(node.Expression);
_ilg.EmitBoolean(result == AnalyzeTypeIsResult.KnownTrue);
return;
}
if (result == AnalyzeTypeIsResult.KnownAssignable)
{
// We know the type can be assigned, but still need to check
// for null at runtime
if (type.IsNullableType())
{
EmitAddress(node.Expression, type);
_ilg.EmitHasValue(type);
return;
}
Debug.Assert(!type.IsValueType);
EmitExpression(node.Expression);
_ilg.Emit(OpCodes.Ldnull);
_ilg.Emit(OpCodes.Ceq);
_ilg.Emit(OpCodes.Ldc_I4_0);
_ilg.Emit(OpCodes.Ceq);
return;
}
Debug.Assert(result == AnalyzeTypeIsResult.Unknown);
// Emit a full runtime "isinst" check
EmitExpression(node.Expression);
if (type.IsValueType)
{
_ilg.Emit(OpCodes.Box, type);
}
_ilg.Emit(OpCodes.Isinst, node.TypeOperand);
_ilg.Emit(OpCodes.Ldnull);
_ilg.Emit(OpCodes.Cgt_Un);
}
