Why do I need to escape the last single quote in this Powershell here-string?

Question

According to Powershell "about quoting rules":

A here-string is a single-quoted or double-quoted string in which quotation marks are interpreted literally.

However the following here-string results in a TerminatorExpectedAtEndOfString exception in Powershell version 5.0 (build 10586, revision 117). In a Powershell version 2.0 it works as expected:

$herestr=@"
'"'
"@
Write-Host $herestr

If I quote the last single quote with a backtick (`) the here-string works as expected in both version 2.0 and 5.0.

$herestr=@"
'"`'
"@
Write-Host $herestr

Why do I need to escape the last single quote in a here-string?

Answer 1

I believe it is a bug in PowerShell parser. It looks like when it in statement parse mode, it first try to interpret first thing as BareWord string literal. And if it failed, then it produce error. You can workaround this by putting extra space before or after equal sign:

$herestr =@"
'"'
"@

or

$herestr= @"
'"'
"@

Or by using parenthesis:

[void]($herestr=@"
'"'
"@)

Note, as parenthesis is not assignment or increment/decrement, them will write result of expression into pipeline, unlike bare assignment expression, so you need to explicitly ignore it with [void] or any other method.