This error occurs when there was a recursive trait requirement that overflowed before it could be evaluated. Often this means that there is unbounded recursion in resolving some type bounds.
For example, in the following code:
trait Foo {} struct Bar<T>(T); impl<T> Foo for T where Bar<T>: Foo {}
To determine if a T
is Foo
, we need to check if Bar<T>
is Foo
. However, to do this check, we need to determine that Bar<Bar<T>>
is Foo
. To determine this, we check if Bar<Bar<Bar<T>>>
is Foo
, and so on. This is clearly a recursive requirement that can't be resolved directly.
Consider changing your trait bounds so that they're less self-referential.