Program crashes on second hot reload with stackalloc on method body

[isadorasophia]

Version Used: 17.7 Preview 3

Steps to Reproduce:

1. Debug the following app

namespace ExceptionSample
{
    internal class Program
    {
        static void Main(string[] args)
        {
            bool something = false;
            if (!something) // break here
            { 
                // edit 1: add lines here
                Span<bool> stuff = stackalloc bool[64];
                // edit 2: add lines
            }
        }
    }
}

2. Add lines on first edit and apply code changes
3. Add lines on second edit and apply code changes

Expected Behavior:
Successfully applied changes.

Actual Behavior:
App immediately crashes and exits with:

Fatal error. Unspecified error (0x80004005 (E_FAIL))
   at ExceptionSample.Program.Main(System.String[])

Remarks
The hot reload itself was successful:

13:37 25.53 Starting session.
13:37 35.38 Checking for updates...
13:37 35.42 Applying updates...
13:37 35.43 ConsoleApp39 (2): Sending updates to running application.
13:37 35.43 Changes were successfully applied.
13:37 35.53 ConsoleApp39 (2): Updates applied successfully.
13:37 47.40 Checking for updates...
13:37 47.45 Applying updates...
13:37 47.45 ConsoleApp39 (2): Sending updates to running application.
13:37 47.45 ConsoleApp39 (2): Updates applied successfully.
13:37 47.45 Changes were successfully applied.
13:37 48.18 Ending session.

[isadorasophia]

@tmat fyi

[tmat]

Simpler repro:

using System;

internal class Program
{
    static void Main()
    {
        Span<bool> stuff = stackalloc bool[64];
    }
}

Insert comment anywhere in the variable declaration statement.

Deltas we emit:
Repro.zip

The compiler doesn't correctly map variables (the IL should be unchanged):

Original:

Method 'Program.Main' (0x06000006)
  Locals: System.Span`1<bool>, System.Span`1<bool> (#1b)
{
  // Code size       17 (0x11)
  .maxstack  2
  IL_0000:  nop
  IL_0001:  ldc.i4.s   64
  IL_0003:  conv.u
  IL_0004:  localloc
  IL_0006:  ldc.i4.s   64
  IL_0008:  newobj     'System.Span`1<bool>..ctor' (0x0a00000e)
  IL_000d:  stloc.1
  IL_000e:  ldloc.1
  IL_000f:  stloc.0
  IL_0010:  ret
}

Delta:

Method 'Program.Main' (0x06000006)
  Locals: System.Span`1<bool>, System.Span`1<bool>, System.Span`1<bool> (#19d/1:1)
{
  // Code size       17 (0x11)
  .maxstack  2
  IL_0000:  nop
  IL_0001:  ldc.i4.s   64
  IL_0003:  conv.u
  IL_0004:  localloc
  IL_0006:  ldc.i4.s   64
  IL_0008:  newobj     'System.Span`1<bool>..ctor' (0x0a000014/1:1)
  IL_000d:  stloc.2
  IL_000e:  ldloc.2
  IL_000f:  stloc.0
  IL_0010:  ret
}