FAIL_FAST crash in conhost after shrinking the buffer height

[j4james]

Windows Terminal version

Commit cfdea71

Windows build number

10.0.19044.2006

Other Software

No response

Steps to reproduce

1. Open a cmd shell in conhost.
2. Open the console Properties dialog.
3. On the Layout tab, set the Screen Buffer height to 50, and the Window height to 24.
4. Also make sure the Wrap text output on resize option is UNCHECKED.
5. Back in the shell, keep pressing enter until you've filled up all 50 lines of the buffer.
6. Open the Properties again, and set the Screen Buffer height to 24.
7. Back in the shell, type any letter.

Expected Behavior

I'd expect to see the letter that I typed being output at the prompt.

Actual Behavior

The console crashes with the FAIL_FAST check here:

terminal/src/host/_stream.cpp

Line 252 in cfdea71

FAIL_FAST_IF(!(coordCursor.Y == bufferSize.Y));

[j4james]

I thought at first this was a regression, but once I realised that step 4 was necessary, I was able to reproduce this in my inbox conhost as well. So if it is a regression, it's at least not a very recent one.

[BDisp]

This is also happening on conhost by using the System.Console on a C# project and resizing the console height by mouse to zero it will crash with a pipe not connected error. I don't know if it's possible to restore the console on the catch exception handler.

[lhecker]

Related to #14298.