The following Powershell script demonstrates the issue:
$hash = @{'a' = 1; 'b' = 2}
Write-Host $hash['a'] # => 1
Write-Host $hash.a # => 1
# Two ways of printing using quoted strings.
Write-Host "$($hash['a'])" # => 1
Write-Host "$($hash.a)" # => 1
# And the same two ways Expanding a single-quoted string.
$ExecutionContext.InvokeCommand.ExpandString('$($hash[''a''])') # => 1
$ExecutionContext.InvokeCommand.ExpandString('$($hash.a)') # => Oh no!
Exception calling "ExpandString" with "1" argument(s): "Object reference not set to an instance of an object."
At line:1 char:1
+ $ExecutionContext.InvokeCommand.ExpandString('$($hash.a)')
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : NullReferenceException
Anyone know why the $hash.key syntax works everywhere but inside explicit expansion? Can this be fixed, or do I have to suck it up and live with the $hash[''key''] syntax?