error: entry symbol `main` declared multiple times
  --> $DIR/dupe-symbols-7.rs:7:1
   |
LL | fn main(){}
   | ^^^^^^^^^
   |
   = help: did you use `#[no_mangle]` on `fn main`? Use `#![no_main]` to suppress the usual Rust-generated entry point

error: aborting due to 1 previous error