Apple

What is puzzling is not the fact that set dest to quoted form of POSIX path of ((sourcefolder as text) & theName)
fails in a System Events block.
I know for months that we aren’t supposed to use OSAX features in a tell application block.
But I know also that Apple explained that
tell me to set dest to quoted form of POSIX path of ((sourcefolder as text) & theName)
is THE way to get rid of this rule.

So, the official scheme doesn’t work.

You're overlooking the fact that System Events also defines the term POSIX path, and I suspect that's the cause of what you are seeing in this case.

As long as the item at the path exists, you can use this without error:

tell application "System Events"

set dest to POSIX path of disk item ((sourcefolder as text) & theName)

end tell

The other alternative is ensure that System Events's POSIX path is not used:

tell application "System Events"

using terms from scripting additions

set dest to POSIX path of ((sourcefolder as text) & theName)

end using terms from

end tell

As a side note to your actual code, using either the shell's mkdir or ASObjC is easier in this situation because you don't need to check whether the folder already exists; they just make it if it's not there already:

use scripting additions

use framework "Foundation"

set theResult to current application's NSFileManager's defaultManager()'s ¬

createDirectoryAtPath:(POSIX path of ((sourcefolder as text) & theName)) ¬

withIntermediateDirectories:true attributes:(missing value) |error|:(missing value)

--
Shane Stanley <email@hidden>
<www.macosxautomation.com/applescript/apps/>

References:
	>I made a nightmare (From: Yvan KOENIG <email@hidden>)
	>Re: I made a nightmare (From: "S. J. Cunningham" <email@hidden>)
	>Re: I made a nightmare (From: Yvan KOENIG <email@hidden>)