The compiler changed the type of my variable based on its usage. Usage in code I didn't write. There was no warning about this (even with clippy). The program crashed at runtime.
I found this amusing because it doesn't happen in dynamic languages, and it doesn't happen in languages where you have to specify the types. But Rust, with its emphasis on safety, somehow lured me into this trap within the first 15 minutes of programming.
I found it more amusing because in my other attempts at Rust, the compiler rejected my code constantly (which was valid and worked fine), but then also silently modified my program without warning to crash at runtime.
I saw an article by the developers of the Flow language, which suffered from a similar issue until it was fixed. They called it Spooky Action at a Distance.
This being said, I like Rust and its goals overall. I just wish it was a little more explicit with the types, and a little more configurable on the compiler strictness side. Many of its errors are actually just warnings, depending on your program. It feels disrespectful for a compiler to insist it knows better than the programmer, and to refuse to even compile the program.