Compiler does not stop

[kakkun61]

The compiler does not stop compiling this code.

enum A {
    A(B)
}

enum B {
    B1, B2(B)
}

fn main() {
}

I expected following compilation error.

error: illegal recursive enum type; wrap the inner value in a box to make it representable
enum B {
    B1, B2(B)
}

commits which I confirm with: 758c5e8 & a2db7c1

[bblum]

This is related to but not the same as #2063. The problem here is that while B is an illegal type, that check is not run until after A is checked.

The compiler should instead maintain a cache of "types which have been occurs-checked", and for forward-references like this, additionally check the nested type if it doesn't appear in the cache yet.

[alexcrichton]

Closing as a dupe of #2063. There's a whole array of issues with recursive unbounded-sized types, but I don't think it helps much to keep separate issues open for all of them when they're likely all related. This will be linked in #2063 though, and I will comment that this should be taken care of as well.