Imagine the following code:

int a = a + 1;

Currently this compiles and runs, the output is 1. This shouldn't be allowed and should throw a compile error along the lines of "usage of undefined variable 'a'". The value in the initializer expression seems to be the default value of the type, so for the case above, it's 0, for strings it would be "", null for reference types, etc. My type analyzer caught only a single occurance of this, Scripts/Game/UI/Components/MainMenu/SCR_CommunitySubMenu.c line 112,

string content = content + m_Feedback.GetValue();