Clarify the original fn main() -> ()

Co-authored-by: Josh Triplett <[email protected]>

Author: cuviper

posts/2022-05-19-Rust-1.61.0.md

@@ -30,7 +30,7 @@ Please [report] any bugs you might come across!
 
 ### Custom exit codes from `main`
 
-In the beginning, Rust `main` functions could only return the unit `()`, always indicating success
+In the beginning, Rust `main` functions could only return the unit type `()` (either implicitly or explicitly), always indicating success
 in the exit status, and if you wanted otherwise you had to call `process::exit(code)`. Since Rust
 1.26, `main` has been allowed to return a `Result`, where `Ok` translated to a C `EXIT_SUCCESS` and
 `Err` to `EXIT_FAILURE` (also debug-printing the error). Under the hood, these alternate return