[BUG]: Crash on invalid snippet upon using the member access operator

[isuckatcs]

Bug description

The following invalid snippet hits an assertion during parsing/sema. The crash only happens if the member access operator (a.x) is present.

@register_passable
struct S:
    var x: Int

    fn __init__() -> S:
        let a = Self
        a.x = 0

mojo: /__w/modular/modular/third-party/llvm-project/llvm/include/llvm/Support/Casting.h:566: decltype(auto) llvm::cast(const From &) [To = M::KGEN::DeclRefType, From = mlir::Type]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
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: mojo repro.mojo
1.      Crash resolving decl body at loc(".../repro.mojo":5:5)
    >>     fn __init__() -> S:
           ^.......................
    >>         let a = Self
    >>         a.x = 0
       ...............<
2.      Crash parsing statement at loc(".../repro.mojo":7:9)
    >>         a.x = 0
               ^......<

Steps to reproduce

• run the snippet in the description with mojo

System information

- Ubuntu 22.04.3 LTS (WSL 2)
- mojo 0.6.1 (876ded2e)
- modular 0.3.1 (589ce200)

[junweizeng]

The original code snippet seems unable to reproduce the error. Following is the corrected code snippet.

@register_passable
struct S:
    var x: Int

    fn __init__() -> S:
        let a = Self
        a.x = 0

Steps to reproduce and complete crash report is as follows:

$ mojo build test.mojo
mojo: /__w/modular/modular/third-party/llvm-project/llvm/include/llvm/Support/Casting.h:566: decltype(auto) llvm::cast(const From &) [To = M::KGEN::DeclRefType, From = mlir::Type]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.
[6055:6055:20231230,234755.738277:ERROR file_io_posix.cc:144] open /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq: No such file or directory (2)
[6055:6055:20231230,234755.738352:ERROR file_io_posix.cc:144] open /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq: No such file or directory (2)
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: mojo test.mojo
1.      Crash resolving decl body at loc("/path/to/test.mojo":5:5)
    >>     fn __init__() -> S:
           ^..................
    >>         let a = Self
    >>         a.x = 0
       ...............<
2.      Crash parsing statement at loc("/path/to/test.mojo":7:9)
    >>         a.x = 0
               ^......<
 #0 0x000055c0350feee7 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x60fee7)
 #1 0x000055c0350fcabe (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x60dabe)
 #2 0x000055c0350ff5bf (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x6105bf)
 #3 0x00007fe7a6d44520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007fe7a6d989fc pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x969fc)
 #5 0x00007fe7a6d44476 gsignal (/lib/x86_64-linux-gnu/libc.so.6+0x42476)
 #6 0x00007fe7a6d2a7f3 abort (/lib/x86_64-linux-gnu/libc.so.6+0x287f3)
 #7 0x00007fe7a6d2a71b (/lib/x86_64-linux-gnu/libc.so.6+0x2871b)
 #8 0x00007fe7a6d3be96 (/lib/x86_64-linux-gnu/libc.so.6+0x39e96)
 #9 0x000055c03679cdf3 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x1caddf3)
#10 0x000055c0355a489a (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xab589a)
#11 0x000055c0355a4114 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xab5114)
#12 0x000055c0355a6013 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xab7013)
#13 0x000055c03558e3ee (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xa9f3ee)
#14 0x000055c03558e10f (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xa9f10f)
#15 0x000055c035591f9e (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xaa2f9e)
#16 0x000055c0355901bb (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xaa11bb)
#17 0x000055c0355e4eff (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xaf5eff)
#18 0x000055c0355e60b8 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xaf70b8)
#19 0x000055c0355f4b97 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xb05b97)
#20 0x000055c0355f42bb (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xb052bb)
#21 0x000055c0355a0c3a (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xab1c3a)
#22 0x000055c0355b0a1d (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xac1a1d)
#23 0x000055c0355b1a51 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xac2a51)
#24 0x000055c0355992d9 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xaaa2d9)
#25 0x000055c0355cf2bc (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xae02bc)
#26 0x000055c0355cc0d8 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xadd0d8)
#27 0x000055c0355cbf76 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xadcf76)
#28 0x000055c03556b7c9 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xa7c7c9)
#29 0x000055c035585bce (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xa96bce)
#30 0x000055c0355863d8 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xa973d8)
#31 0x000055c03552c7f4 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xa3d7f4)
#32 0x000055c03552cb60 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0xa3db60)
#33 0x000055c0350c77bf (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x5d87bf)
#34 0x000055c0350b3c6b (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x5c4c6b)
#35 0x000055c0350c68c9 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x5d78c9)
#36 0x000055c0350ad352 (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x5be352)
#37 0x00007fe7a6d2bd90 (/lib/x86_64-linux-gnu/libc.so.6+0x29d90)
#38 0x00007fe7a6d2be40 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e40)
#39 0x000055c0350ac92e (/home/jwzeng/.modular/pkg/packages.modular.com_mojo/bin/mojo+0x5bd92e)
Aborted

System information

Ubuntu 22.04.3 LTS (WSL 2)

mojo 0.6.1 (876ded2e)

modular 0.3.1 (589ce200)

[ematejska]

Thank you for the nice reproducer!