Check if duplicate fields map correctly

[immibis]

According to @skyboy, if a class has a field with the same name (and maybe descriptor?) as a superclass, it will be remapped incorrectly. EG:

class A {int a;}
class B extends A {int a;}

where A/a:I has a mapping and B/a:I doesn't, it shouldn't use the A/a mapping for B/a, but does it?

[skyboy]

More elaborately: accesses to B/a will get remapped to A/a, which may then fail due to modifiers like private and final. The structure I had it in was of this fashion:

class A {private int a;}
class B {private static int a; static void init(){a = 0;}}