Stack overflow with "recursive" associated type

[kyledewey]

On 3/4/2015 on playpen, the following code:

trait Foo {
    type A;
}

struct FooStruct;

impl Foo for FooStruct {
    type A = <FooStruct as Foo>::A;
}

fn main() { }

...gives the following error:

thread 'rustc' has overflowed its stack
Illegal instruction (core dumped)
playpen: application terminated with error code 132

This may be considered a duplicate of issue #20551, which notes a similar problem with recursive trait bounds. I figured this may be unique given that this involves a recursive associated type on a trait, rather than a recursive trait itself.

[kyledewey]

cc @nikomatsakis

[solson]

This was just rediscovered in the #rust IRC. Playpen link

[dylanede]

The code that that IRC example was simplified from was code that looked reasonably sane (and was quite far removed from simple recursion like this), so trying to come up with an error message instead of a crash would be quite handy.