This PR is specified by PowerShell/PowerShell-RFC#192

PR Summary

Resolves #3241.

Implements && and ||.

A statement like cmd1 && cmd2 should behave like cmd1; if ($?) { cmd2 }.

After discussion with the @PowerShell/powershell-committee, this feature has the following charateristics:

• cmd1 && cmd2 behaves like cmd1; if ($?) { cmd2 }
• cmd1 || cmd2 behaves like cmd1; if (-not $?) { cmd2 }
• cmd1 && cmd2 && cmd3 is left associative: [cmd1 && cmd2] && cmd3
• No control flow statements in pipeline chains; only pipelines. Control flow statements are still possible with subexpressions in pipelines (cmd1 && $(break)). These were taken out due to the inconsitencies they posed at a grammatical, data structure and semantic level.
• Assignment is consistent with other assignment in PowerShell, so that a script terminating error will not result in a partial assignment, but a pipeline-terminating error will.
• This syntax is available as the PSPipelineChainOperators experimental feature

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: or [ WIP ] to the beginning of the title (the WIP bot will keep its status check at Pending while the prefix is present) and remove the prefix when the PR is ready.
• Breaking changes
  • None
  • OR
  • Experimental feature(s) needed
    • Experimental feature name(s): PSPipelineChainOperators
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    • Issue filed: Document &&/|| operators MicrosoftDocs/PowerShell-Docs#4853
• Testing - New and feature
  • N/A or can only be tested interactively
  • OR
  • Make sure you've added a new test if existing tests do not effectively test the code changed