I'm having the same or similar problem as described by #17726 right now.
Crashes at this line: https://github.com/mono/mono/blob/b7a308f660de8174b64697a422abfc7315d07b8c/mcs/class/corlib/System.Reflection.Emit/AssemblyBuilder.cs#L752
The ReflectionTypeLoadException has one exception attached with this error message:
Type '__callback_factory__class__' is not finished
It happens after calling
var types = from a in assemblies
from ti in a.DefinedTypes
where ti.IsDefined(typeof(TypeAliasAttribute), false)
And iterating over the enumerable (e.g. by using foreach or calling ToList()).
I observed this behavior on Android only. Tested on iOS and works.
var types = from a in assemblies from ti in a.DefinedTypes select ti;
Is enough for me to get a crashing app.
Seems to be a specific assembly that leads to the crash. Just noticed the browsed assemblies can be reduced to one specific by now. Unfortunately I can't tell, which assembly lead to the error.
Created attachment 17118 [details]
small app that shows this issue