Click on the item in the Finder's sidebar with the house icon and verify that you are able to write to this folder in the Sharing & Permissions section of the Get Info window, and that it isn't locked; if it is already set this way and you get that error, choose Utilities from the Finder's Go menu, open the AppleScript Editor, and run the following:
do shell script "mkdir ~/.Trash"
If you get a message stating that the folder exists, run the following:
set theUID to (do shell script "echo $UID")
do shell script "chown " & theUID & " ~/.Trash" with administrator privileges
do shell script "chmod u+rwx ~/.Trash"
tell application "Finder" to quit
delay 2
tell application "Finder" to run
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