Integer width mismatch

Meaning

Binary arithmetic and bitwise operands must use compatible exact integer types. Prismio does not silently widen them.

Signedness matters as well as width. Int is signed 32-bit and is not interchangeable with U32; Isize/Usize vary with target pointer width.

Why it happens

The error often appears when a fixed-width value crosses an API boundary, an unannotated literal receives an unexpected context, or a length/index type is mixed with ordinary Int arithmetic. Prismio avoids C-style promotion so the conversion decision stays visible.

Invalid code

fn main() -> Int {
    let wide: I64 = 10
    let normal: Int = 5
    let result = wide + normal
    return 0
}

Correct code

fn main() -> Int {
    let wide: I64 = 10
    let normal: Int = 5
    let result = wide + normal as I64
    return result as Int
}

Common fixes

Cast one operand to the other's type, or choose one width at the data boundary and use it consistently.

Prefer widening to a type that can represent both values. Before narrowing, validate the range in application logic. Parenthesize a cast when precedence could be unclear: (small as Int) + normal.

Do not fix a signedness mismatch merely by choosing the unsigned side if negative values are meaningful. Pick the domain type first, then convert deliberately.