Method call arity mismatch

Why this fires

The call passes the wrong number of arguments for the function being called:

fn greet(name: str, greeting: str) -> str {
    return "${greeting}, ${name}"
}

fn main() {
    print(greet("Ada"))
//        ^^^^^^^^^^^^ error: arity mismatch — expected 2 arguments, got 1
}

Arity is a hard error: the compiler can't pick a reasonable interpretation when the argument count is wrong, so it reports the mismatch and stops type-checking the call.

Fix it

1. Pass the missing arguments

print(greet("Ada", "Hello"))

2. Use default values on the signature

If most call sites want the same value, declare a default:

fn greet(name: str, greeting: str = "Hello") -> str {
    return "${greeting}, ${name}"
}

greet("Ada")                     // ok — greeting defaults to "Hello"
greet("Ada", "Bom dia")          // ok — greeting overridden

3. Use a variadic / rest parameter

For functions that genuinely take any number of arguments:

fn join(separator: str, ...parts: str) -> str { ... }

join(", ", "a", "b", "c")

See also

• TE111 — the count is right but a type doesn't match.
• /docs/functions — default arguments, variadics, optional parameters.