Infinite loop on expanding cycle for struct types

[TIHan]

[<Struct>]
type MyStruct<'T> =

    val field : YourStruct<MyStruct<MyStruct<'T>>>

and [<Struct>] YourStruct<'T> =

    val field : 'T

If you define this in F#, it will cause an infinite loop in the compiler and you will have to kill your process for it to stop.

We expect to receive an error when defining this type.

[dsyme]

Nice catch. There's code to catch this sort of thing an it catches a lot of cases but it's surprisingly hard to get right!

[dsyme]

How did you find this one?

[TIHan]

@RikkiGibson had a test case for C#, and I tried in F# and we blew up :)

[RikkiGibson]

One weird trick discovered by a type theorist—compiler devs hate him!