Count occurrences

text.count(needle) returns an i64 without allocating. Matches are literal and do not overlap. An empty needle counts Unicode scalar boundaries:

def main() -> Result[(), IoError]:
    print("banana".count("ana"))?
    print("aaaaa".count("aa"))?
    print("é🙂".count(""))?
    print("".count(""))?
    print("text".count("missing"))?
    Ok(())

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The method borrows both strings and takes exactly one pattern argument.