An incorrect number of generic arguments was provided.
Erroneous code example:
struct Foo<T> { x: T }
struct Bar { x: Foo } // error: wrong number of type arguments:
// expected 1, found 0
struct Baz<S, T> { x: Foo<S, T> } // error: wrong number of type arguments:
// expected 1, found 2
fn foo<T, U>(x: T, y: U) {}
fn f() {}
fn main() {
let x: bool = true;
foo::<bool>(x); // error: wrong number of type arguments:
// expected 2, found 1
foo::<bool, i32, i32>(x, 2, 4); // error: wrong number of type arguments:
// expected 2, found 3
f::<'static>(); // error: wrong number of lifetime arguments
// expected 0, found 1
}When using/declaring an item with generic arguments, you must provide the exact same number:
struct Foo<T> { x: T }
struct Bar<T> { x: Foo<T> } // ok!
struct Baz<S, T> { x: Foo<S>, y: Foo<T> } // ok!
fn foo<T, U>(x: T, y: U) {}
fn f() {}
fn main() {
let x: bool = true;
foo::<bool, u32>(x, 12); // ok!
f(); // ok!
}