infinite size recursive struct using a fixed-size array ICEs instead of an error

[thestinger]

struct Foo {
    bar: [Option<Foo> * 2]
}

[jdm]

Probably related to #3778.

[graydon]

accepted for production ready

[bblum]

Modernized:

use std::sys;
struct Foo {
        bar: [Option<Foo>, ..2]
}
fn main() {
    error!("%?", sys::size_of::<Foo>());
}

I had to use the type Foo instead of just defining it, but it does indeed stack overflow the compiler.

[bblum]

The recursion is between middle::trans::type_of::sizing_type_of and middle::trans::adt::represent_type and middle::trans::adt::mk_struct.

I thought this was going to be the same bug as #7587, but it is not, since that one is in type_contents and this one is in trans.

[bblum]

Fixed-size array not necessary, actually. Dup of #3779.