[BUG] Crash when declaring a nested struct with a variable of the same type

[guna-sd]

Bug description

When declaring a struct that contains a variable of its own type, the code crashes. This issue is not limited to any specific struct but occurs with any struct that includes a variable of the same struct type. The expected behavior is for the code to compile without errors, but it results in a crash instead.

This issue appears to be related to the recursive nature of the struct declaration, where a struct contains a variable of its own type. This problem is critical as it affects the ability to define common data structures like linked lists, trees, and others that require self-referential types.

Steps to reproduce

issue code

@value
struct Node:
    var data: Int
    var next: Optional[Node]

Crash log

[34229:34229:20240612,222743.659602:WARNING process_reader_linux.cc:144] no stack mapping
Please submit a bug report to https://github.com/modularml/mojo/issues and include the crash backtrace along with all the relevant source codes.
Stack dump:
0. Program arguments: /home/guna/.modular/pkg/packages.modular.com_mojo/bin/mojo /home/guna/Projects/new/test.mojo
[34229:34230:20240612,222743.692664:ERROR directory_reader_posix.cc:42] opendir /home/guna/.modular/crashdb/attachments/542b6caf-68ed-4ad1-9bf0-6a0f03aa4c0d: No such file or directory (2)
#0 0x000059c6b1289438 (/home/guna/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x12a1438)
#1 0x000059c6b128725e (/home/guna/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x129f25e)
#2 0x000059c6b1289acd (/home/guna/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x12a1acd)
...
#255 0x000059c6b17c1950 (/home/guna/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x17d9950)
mojo crashed!
Please file a bug report.
Segmentation fault (core dumped)

System information

Ubuntu 24.04 LTS
mojo 24.4.0 (2cb57382)
modular 0.8.0 (39a426b5)

[ematejska]

Looks similar to #2208.

[ematejska]

Should this also error out? In the latest nightly build (mojo 2024.6.1405 (ceceb171), it compiles. @jeff @tatiana

[suahelen]

Should this also error out? In the latest nightly build (mojo 2024.6.1405 (ceceb171), it compiles. @jeff @tatiana

The struct definition seems to compile but as soon as I try to instantiate it in main the error is there again.