Multiline prompt behaves incorrectly on macOS

[tLXvGt]

Steps to reproduce

Run:
function prompt { "Hello, World`r`nHi> " }

Expected behavior

On Windows PowerShell correctly prompts me with 2 lines:

Hello, World
Hi> [cursor]

I can write anything and prompt will stay the same.

Actual behavior

On macOS PowerShell correctly prompts me with 2 lines:

Hello, World
Hi> [cursor]

However, when I press any key prompt copies first line into second one and prompt looks like this:

Hello, World
Hell[cursor]

Environment data

> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      6.0.0-alpha
PSEdition                      Core
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   3.0.0.0
GitCommitId                    v6.0.0-alpha.18
CLRVersion
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

[lzybkr]

This is another symptom PowerShell/PSReadLine#468. When that issue is fixed, this one will be as well.

[daxian-dbw]

I believe this is addressed by #3867