<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/137126>137126</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [flang] Flang is unable to lower to LLVM IR
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            flang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          inaki-amatria
      </td>
    </tr>
</table>

<pre>
    - `flang` version is: `flang version 21.0.0git (git@github.com:inaki-amatria/llvm-project.git 054ee17f88fcd4dd8d646740b975ef1d2f4ea3aa)`
- Reduced test case:
```fortran
! foo.f90
program main
  use external_types
contains
 subroutine foo()
    type(external_data_t) :: foo_list
  end
  subroutine bar(bar_patch)
    type(patch_t) :: bar_patch
  end
end

! bar.f90
module model
  type :: subset_range_t
    type(patch_t), pointer :: p => null()
  end type
  type :: grid_vertices_t
 type(subset_range_t) :: domain
  end type
  type :: patch_t
 type(grid_vertices_t) :: verts
  end type
end

module var_metadata
  use model
  type :: var_metadata_t
    type(subset_range_t) :: access
  end type
end

module var
  use var_metadata
  type :: var_t
 type(var_metadata_t) :: md
  end type
  type :: var_ptr_t
    type(var_t), pointer :: p => null()
  end type
end

module var_list
  use var
  type :: var_list_t
    type(var_ptr_t) :: var
  end type
  type :: var_list_ptr_t
    type(var_list_t), pointer :: p => null()
  end type
end

module external_types
  use var_list
  type :: external_data_t
    type(var_list_ptr_t) :: list
  end type
end
```
- `flang` invocation is: `flang -fc1 -emit-llvm bar.f90 foo.f90`
- Expected behavior is: The code lowers to LLVM IR successfully
- Actual behavior: Lowering aborts with the following backtrace:
```
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /home/inaki/repos/llvm-project/build/bin/flang -fc1 -emit-llvm bar.f90 foo.f90
 #0 0x00006517c534a6b6 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/inaki/repos/llvm-project/build/bin/flang+0x27656b6)
 #1 0x00006517c534818e llvm::sys::RunSignalHandlers() (/home/inaki/repos/llvm-project/build/bin/flang+0x276318e)
 #2 0x00006517c534b014 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
 #3 0x000077fd16c4bcd0 (/usr/lib/libc.so.6+0x3dcd0)
 #4 0x00006517ca44bb78 mlir::Operation::~Operation() (/home/inaki/repos/llvm-project/build/bin/flang+0x7866b78)
 #5 0x00006517ca44c58d llvm::ilist_traits<mlir::Operation>::deleteNode(mlir::Operation*) (/home/inaki/repos/llvm-project/build/bin/flang+0x786758d)
 #6 0x00006517ca39e457 mlir::Block::clear() Block.cpp:0:0
 #7 0x00006517ca39e32d mlir::Block::~Block() (/home/inaki/repos/llvm-project/build/bin/flang+0x77b932d)
 #8 0x00006517ca45fde3 mlir::Region::~Region() (/home/inaki/repos/llvm-project/build/bin/flang+0x787ade3)
 #9 0x00006517ca44bb48 mlir::Operation::~Operation() (/home/inaki/repos/llvm-project/build/bin/flang+0x7866b48)
#10 0x00006517ca44c58d llvm::ilist_traits<mlir::Operation>::deleteNode(mlir::Operation*) (/home/inaki/repos/llvm-project/build/bin/flang+0x786758d)
#11 0x00006517ca39e457 mlir::Block::clear() Block.cpp:0:0
#12 0x00006517ca39e32d mlir::Block::~Block() (/home/inaki/repos/llvm-project/build/bin/flang+0x77b932d)
#13 0x00006517ca45fde3 mlir::Region::~Region() (/home/inaki/repos/llvm-project/build/bin/flang+0x787ade3)
#14 0x00006517ca44bb48 mlir::Operation::~Operation() (/home/inaki/repos/llvm-project/build/bin/flang+0x7866b48)
#15 0x00006517ca44c6a0 mlir::Operation::erase() (/home/inaki/repos/llvm-project/build/bin/flang+0x78676a0)
#16 0x00006517c5388543 Fortran::frontend::CodeGenAction::beginSourceFileAction() (/home/inaki/repos/llvm-project/build/bin/flang+0x27a3543)
#17 0x00006517c538366f Fortran::frontend::FrontendAction::beginSourceFile(Fortran::frontend::CompilerInstance&, Fortran::frontend::FrontendInputFile const&) (/home/inaki/repos/llvm-project/build/bin/flang+0x279e66f)
#18 0x00006517c5363203 Fortran::frontend::CompilerInstance::executeAction(Fortran::frontend::FrontendAction&) (/home/inaki/repos/llvm-project/build/bin/flang+0x277e203)
#19 0x00006517c53879cd Fortran::frontend::executeCompilerInvocation(Fortran::frontend::CompilerInstance*) (/home/inaki/repos/llvm-project/build/bin/flang+0x27a29cd)
#20 0x00006517c4ea70d4 fc1_main(llvm::ArrayRef<char const*>, char const*) (/home/inaki/repos/llvm-project/build/bin/flang+0x22c20d4)
#21 0x00006517c4ea62f6 main (/home/inaki/repos/llvm-project/build/bin/flang+0x22c12f6)
#22 0x000077fd16c35488 (/usr/lib/libc.so.6+0x27488)
#23 0x000077fd16c3554c __libc_start_main (/usr/lib/libc.so.6+0x2754c)
#24 0x00006517c4ea53a5 _start (/home/inaki/repos/llvm-project/build/bin/flang+0x22c03a5)
Segmentation fault (core dumped)
```
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzUWF1v2zoS_TX0CxGDIilKevCDm8a7Bbq7RXKxrwZFjmxuZdEgqTR5ub99QUm2ZMXJ7RYG7l2gjfXBOXPOzGj4Ib03uwZghdJPKP28kG3YW7cyjfxu7uRBBmfkorT6dXWHkSBVLZsdEgQ_g_PGNth4xNbnN-fHNFmSJdmZgBHNdyYgHm_2bblU9oDY-gIf0U1dPx_ujs7-B1RYRjOScoAkq_K8UpprnWvBRcZJWWQpVImmFQfJpES0QIIgsr7Dj6BbBRoH8AEr6QGxNSLr-Lr7V1kXnGziI5rgytplVUTLo7M7Jw_4IE18iXHrAcNLANfIehtej-ARWSvbBGmaeIl9WzrbBtNAhEE0jyyiJcZxOKL52VzLILcB0QJHNmwdDba18aEbD43ufieApXSI5qV026MMav8GuXt6gTiOHSH7v4PUUrpB6sHqtgZ8sBrqbnQEPeH4tvQQtk42O9iG97wieo-P1jQB3MnwiBH7jNgDbtq6nkQDGt3bzz3tnNHbZ3DBKPC9q8HPjMMoUttzet6FPZEc4eaORrz40M_hzlEb4vQs3fYAQcYknivjevCmQ-fBe1eUVAr8z7A4O3_DaM5hqn7GafR70B8HMhoeg5vr6PF_tQSuBff8IQzarjKJg65R6RlOUjrYfyirA3tH2-DoVgLftJAxhWfdU3rznnGd31z1tJfMmJwaX9cdp83bNM9WyXClf99VKsF3cDDhLrbkU-s4d8sB7OHlCCqAxiXs5bOxbsD5bQ9YWQ24tj_AeRws_vr13__AXx6xb7tir9q6fu0w1iq0sj4jRPOv0co0OyxL64LHP0zY47CPXbau7Y_4ppTqe3BSzZs7IutvXx_WTw-xjR1MwBKX7Q47OFoXIo99CMfIEdENopvJZNRPPrM5CNGN8b4Fj-gGy0Zj06i61dCxUU76_chkicj6KUj1Hev2cOx5kSUixbdhYpFu1x6gCX2o6WZvDxAdxDkQ0U3k6N_6L1tT6_hrGkQ3P5ceEvEZweSFEEJEmmQqZVyKUuBOZFcy_tX3F9-caULH_LcuojQfBzn5Y2t9cCAPiIr4QZimL7tY-78uAdFP5IVmIhWlGL4hRFkyY5wnOVxj_Ng2T2bXyPrvstE1ON9_ibcixZIcRlJ0RqokCccX7hHNu6jcY292pqls_DLX8f7ZGt1dFoOFX6pjrA3S_e8dsMFBllU6EYqXSpNBSutdZG7K_q9aersUHU2mlSYjST4lKTkvyyzHh9q4PmD_OoLrPvT-9vfx_naBy3IhyiwfOaUzTirN9SSbpu-zTpr4RdxfJfvQP9FQQ4B_Wh2L89rAPsQ3UpGluR5ViAsVrACeZpPIfqqt-t5fqhq6RVuk0j2-kutsjsaovo72e399w_xkZcHoRFl-mZ-00sAmXB5hNxbMcHPLasmkBjayKd5UMP9TKpgPFRzbEfm_r-CoIrlZBUc0-hep4MiF_WUqOLJ524P__Ap-04OFJO9zAhe3yzelkwlJRjrici7N85QzvBk25B2FytkmxIVrd3dvNfwNmrUaOZawM82TbZ2CjalheHXL-V-ylE_Sms04MyGqjzhvhrsPSCOafyj6cDQ1uC-ND7KJC7Ju4fUTLr80xzZEB1jZxofO8FZRKUCIaoxKfhkVwSj5g0zORPUF9wKqDWMSfz6st5SWASWThBezhGeF0h9JG0SMCk-7qv81zTebAmgmaaHGRkkvJjIOMiOa40ol2-40ZbrgXzsnXx-hQuxe7aU7FdI6zmT0Hl8-uxVdqijRfKSbzOgKWonuXO5W7hJaidEdvVyAs5Tn-R8uwGnG87HRUjbHSLnC22202fogXdhO-H-EmnI1ovJZIFImU9zj3SoUhMm0d_gEu7g97Q8EKtnWnQ9lHXQ7WjjV02mvvdArpgtWyAWskoynPMsYEYv9SksGIFhWEA4UQILgBUkI07xiLC3yhVlRQlPCKSeC51QsC56pLKmKTGRpAbJCnMBBmnoZdSyt2y26bfgqYVlCxaKWJdS-O6umdFBDUfp54Vad8LLdecRJXJ75ESKYUHcH3L1F-hlvut208bhtZFkDDrY_sZgcWCxaV69-_dBgIPy8ov8NAAD__3EJHa8">