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Kinds (E3xxx)

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These checks cover the kind of each function and item: plain fn code, const code, pushdown fn story code and #[scene] scenes each have rules about what they may call, read and hold. These diagnostics also cover story variables, second-class references and closures, and the shape of choice! and text forms.

E3001 call-rule

Error. A function calls another function of a kind it may not call, such as a fn calling into the story, a pushdown fn calling a fn, or a const fn calling a fn.

kis
fn start() -> Int<0, 3> { 0 }


pushdown fn visit() {
    start();
}

Fix: move the call into a function of a kind that is allowed to make it. The only way from fn code into the story is nav::start of an entry scene.

E3002 step-outside-scene

Error. A function that is not a scene runs a step with s! or choice!. This includes closures and instant procedures.

kix
pushdown fn visit() {
    s!(t!["no"]);
}

Fix: mark the function #[scene], or move the step into a scene.

E3003 scene-call-outside-scene

Error. An instant procedure (a pushdown fn without #[scene]) calls a scene.

kis
#[scene]
pushdown fn Other() {}


pushdown fn visit() {
    Other();
}

Fix: call the scene from another #[scene] function, or mark the caller #[scene].

E3004 unbounded-loop

Error. An instant procedure uses while or another loop with no bound. Instant procedures may only use for over an array, or over a range with constant bounds.

kis
static mut ROUTE: Int<0, 3> = 0;


pushdown fn visit() {
    while ROUTE < 3 { ROUTE += 1; }
}

Fix: use a bounded loop such as for i in [1, 2] { ROUTE = i; }, or mark the function #[scene].

E3005 instant-recursion

Error. Instant procedures call each other in a cycle, either directly or through a function pointer.

kis
pushdown fn ping() { pong(); }
pushdown fn pong() { ping(); }

Fix: mark one of the functions #[scene] and pass through a step.

E3006 for-not-constant

Error. A for loop in story code iterates over a range whose bounds are not constant expressions.

kis
static mut ROUTE: Int<0, 3> = 0;


pushdown fn visit() {
    let n = ROUTE;
    for i in 0..n { }
}

Fix: iterate over an array, or over a range with constant bounds such as for i in 0..MAX { ... }.

E3007 story-variable-outside-story

Error. A story variable (static mut) is read or written outside pushdown fn code.

kis
static mut ROUTE: Int<0, 3> = 0;


fn system() {
    let route = ROUTE;
}

Fix: access the story variable only from a pushdown fn.

E3008 not-finite

Error. A story variable, an entry scene parameter, or the result of a tabulated const fn call has a type with too many values. Such types must be finite, such as bounded integers, bool and enums.

kis
static mut COUNT: u32 = 0;

Fix: use a bounded type, such as static mut COUNT: Int<0, 10> = 0;.

E3009 text-in-entry

Error. A parameter type or the return type of an entry scene contains Text. fn code can build text at runtime, so Text cannot cross into the story.

kis
enum Ending { Normal }


#[scene]
#[entry]
pushdown fn Named(name: Text) -> Ending {
    Ending::Normal
}

Fix: pass a finite value, such as an enum, and choose the text inside the story.

E3010 not-constant

Error. The initializer of a const (or of a static mut) is not a constant expression. Assignments and calls to fn functions are not constant expressions.

kis
const COUNTED: u32 = { let mut n = 0; n += 1; n };

Fix: write the initializer as a constant expression, such as const COUNTED: u32 = 1;.

E3011 bad-handle

Error. An immutable static holds something other than a Setting<T> or Meta<T> handle.

kis
static LIMIT_HANDLE: u32 = 3;

Fix: use const for a constant (const LIMIT: u32 = 3;) or static mut for a story variable.

E3012 reference-in-item

Error. The type of a const or static contains a reference.

kis
const BORROWED: &u32 = &1;

Fix: store the value itself, such as const BORROWED: u32 = 1;.

E3013 meta-in-const

Error. const code uses a Meta field. Meta is read by fn code and written by the story, and is never visible to const code.

kis
static CLEARED: Meta<bool> = meta(false);


const fn render(mut screen: Screen) -> Screen {
    let cleared = CLEARED;
    screen
}

Fix: read the meta value in fn code, or pass it to the const fn as a parameter.

E3014 second-class-reference

Error. Story code stores a reference in a local or returns one. In the story, references are second-class and can only be passed as arguments.

kis
struct Point { x: Int<0, 3>, y: Int<0, 3> }


pushdown fn alias(p: &mut Point) {
    let q = &p.x;
}

Fix: pass the reference directly as an argument, or copy the value out with let q = p.x;.

E3015 second-class-closure

Error. Story code stores a closure in a local. In the story, closures are second-class and can only be passed as arguments and called.

kis
pushdown fn twice(f: pushdown Fn()) {
    f();
    let g = f;
}

Fix: call f directly instead of binding it to a local.

E3016 aliased-mut-argument

Error. In story code, a place is passed as a &mut argument and also as another argument of the same call.

kis
struct Point { x: Int<0, 3>, y: Int<0, 3> }


pushdown fn shift(a: &mut Point, b: &Point) {
    a.x = b.y;
}


pushdown fn alias(p: &mut Point) {
    shift(p, p);
}

Fix: pass distinct places, such as shift(&mut a, &b);.

E3017 immutable-place

Error. Code assigns to a place whose root binding is not declared mutable.

kis
struct Point { x: Int<0, 3>, y: Int<0, 3> }


#[scene]
pushdown fn Moves() {
    let b = Point { x: 1, y: 2 };
    b.x = 3;
}

Fix: declare the binding mutable, as in let mut b = Point { x: 1, y: 2 };.

E3018 misplaced-attribute

Error. An attribute is used on an item it does not apply to. For example, #[scene] on a fn, #[entry] without #[scene], #[must_use] on a function, or #[shader_arg] on anything but a struct.

kis
#[scene] fn not_a_story() {}

Fix: put the attribute only where it applies, such as #[scene] pushdown fn not_a_story() {}.

E3019 choice-id

Error. Two choice! forms in the same function use the same id. Saves record the choice id, so it must be unique within its function.

kix
enum Map { A, B }


#[scene]
pushdown fn Main() {
    match choice!{ id = "map", t!["A"] => Map::A, t!["B"] => Map::B } { _ => {} }
    match choice!{ id = "map", t!["A"] => Map::A, t!["B"] => Map::B } { _ => {} }
}

Fix: give each choice its own id, such as id = "map2".

E3020 choice-arms

Error. A choice! lists the same variant in more than one arm. Each variant may be chosen at most once.

kix
enum Map { A, B }


#[scene]
pushdown fn Main() {
    match choice!{ id = "map", t!["A"] => Map::A, t!["A again"] => Map::A } {
        Map::A => {}
        _ => {}
    }
}

Fix: map each arm to a different variant.

E3021 ruby-readings

Error. A mono ruby does not give exactly one reading per character of its base text.

kix
#[scene]
pushdown fn Main() {
    s!(t![["漢字"]("か"|"ん"|"じ")]);
}

Fix: give one reading per character, such as s!(t![["漢字"]("かん"|"じ")]);.

E3022 effect-not-constant

Error. The effect argument of a text effect(base, e) is not a constant expression.

kis
use std::narrative::text::{effect, mark};


fn tagged(n: u8) -> Text {
    effect("a", mark(n))
}

Fix: pass a constant effect, such as effect("a", mark(1)).

W3023 unused-must-use

Warning. A value of a #[must_use] type, such as a Swap, is created and then dropped. The change it describes does not happen until it is used.

kis
const fn render(mut screen: Screen) -> Screen {
    screen.background().clear();
    screen
}

Fix: apply the change, as in screen.background().clear().apply_animation(cut());.

E3024 rng-outside-scene

Error. A function that is not a scene calls rng_choose. Only a scene can draw a random value.

kis
enum Coin { Heads, Tails }


pushdown fn flip() -> Coin {
    rng_choose::<Coin>()
}

Fix: mark the function #[scene], or draw the value in a scene and pass it in.

E3025 shader-arg-shape

Error. A #[shader_arg] struct is not a record struct with at least one named field, or it has type parameters. A shader reads its arguments as a WGSL struct with named members of fixed types; const parameters, such as an array length, are allowed.

kis
#[shader_arg]
struct Pair(Decimal, Decimal);

Fix: name the fields and drop type parameters: #[shader_arg] struct Pair { a: Decimal, b: Decimal }.

E3026 shader-arg-field

Error. A field of a #[shader_arg] struct has a type a shader cannot read, or is an array of length 0. Allowed field types are bool, i32, u32, Decimal, Rat, Color, Point, Offset, Size, Anchor, Angle, Duration, fieldless enums, other #[shader_arg] structs, and non-empty arrays of these.

kis
#[shader_arg]
struct Caption {
    text: String,
}

Fix: pass only numeric data to the shader, e.g. #[shader_arg] struct Caption { strength: Decimal }.

Last updated Oct 29, 2026