Generic attributes: Attribute.GetCustomAttributes returns null when passed an unbound generic type #64335
Description
Description
Attribute.GetCustomAttributes normally returns an empty array when no attributes are found (or throws an exception if the parameters don't make sense).
However, Attribute.GetCustomAttributes(someType, typeof(SomeGenericAttribute<>)) returns null. This is unexpected, particularly as the nullable annotations say that it doesn't return null.
It's worth noting that this wasn't previously possible: it was simply not possible to create a generic type which derived from Attribute, and if you passed a type which wasn't derived from Attribute to Attribute.GetCustomAttributes, you got an exception telling you that. So I suspect this is an unhandled case which just fell through the cracks.
Reproduction Steps
Test.M();
public class Test
{
public static void M()
{
var attrs = Attribute.GetCustomAttributes(typeof(Test), typeof(TestAttribute<>));
Console.WriteLine(attrs == null); // true
}
}
public class TestAttribute<T> : Attribute { }Expected behavior
Attribute.GetCustomAttributes either returns an array, or throws an exception. It should not return null.
Actual behavior
Attribute.GetCustomAttributes returns null in this case.
Regression?
No. It was not previously possible to pass an unbound generic attribute type to Attribute.GetCustomAttributes.
Known Workarounds
No response
Configuration
No response
Other information
No response