LYR-SEM0026

the wrong number of type arguments

error · spec 03-types

A generic type, alias or function is given more or fewer type arguments than it declares type parameters (after defaults), or a function that is not generic is given type arguments.

Explanation

Cell<T> takes one type argument and Pair<A, B> two; a type parameter with a default may be left out. A function that is not generic takes none.

Write as many type arguments as the declaration has parameters, or leave them out where the context or the arguments determine them. A call writes them all or none: _ stands for one the inference is to fill — arrayOf<string, _>(3, f) writes T and leaves E, what f throws, to the call. Where a call writes too few, lyric fix adds a _ for each one left out.

Wrong

struct Cell<T> { v: T }

fn main(): void {
    let b: Cell<int, int> = Cell { v = 1 };
    let _ = b.v;
}

Right

struct Cell<T> { v: T }

fn main(): void {
    let b: Cell<int> = Cell { v = 1 };
    let _ = b.v;
}