Can you please copy the error message exactly? The first one is not a valid type.
#What is the difference between these types
ornate drum
Or, hm, it is syntactically valid but useless.
Vec<(String, i32)> is a vector of tuples
https://doc.rust-lang.org/book/ch03-02-data-types.html#the-tuple-type
Vec<String, i32>, depending on your perspective, either means nothing or means “a Vec whose memory allocator is an i32”, which is nonsense
So there is no reason ever to write Vec<String, i32>. If it appears somewhere, it is a mistake.