While working on LeetCode's Pascal's Triangle, I ran into a classic head-scratcher involving Interfaces, Concrete Classes, and Generic Invariance. If you've ever been tripped up by errors like ...

𝗖𝗹𝗮𝘂𝗱𝗲 𝗪𝗿𝗼𝘁𝗲 𝗧𝗵𝗲 𝗪𝗿𝗼𝗻𝗴 𝗗𝗮𝘁𝗲𝘀 I got an interview invite. I used Claude Code to draft my reply. Claude gave me five dates. They looked perfect. I hit send. The recruiter replied.