oxc-project/oxc · warning

capacity overflow

Error message

capacity overflow

What it means

Diagnostic from oxlint's vue/require-slots-as-functions rule (crates/oxc_linter/src/rules/vue/require_slots_as_functions.rs). In Vue 3 each entry of `this.$slots` is a function returning VNodes (in Vue 2 it was a VNode or array). Using a slot as a plain property — rendering or passing `this.$slots.default` without calling it — breaks under Vue 3. The rule flags member reads on `$slots` (via `this`-object analysis in component options) that are not invoked as functions.

Source

Thrown at crates/oxc_allocator/src/vec2/raw_vec.rs:858

#[inline]
fn alloc_guard(alloc_size: usize) -> Result<(), AllocError> {
    if size_of::<usize>() < 8 {
        if alloc_size > isize::MAX as usize {
            return Err(AllocError::CapacityOverflow);
        }
    } else if alloc_size > u32::MAX as usize {
        return Err(AllocError::CapacityOverflow);
    }
    Ok(())
}

// One central function responsible for reporting capacity overflows. This'll
// ensure that the code generation related to these panics is minimal as there's
// only one location which panics rather than a bunch throughout the module.
#[cold]
#[inline(never)]
fn capacity_overflow() -> ! {
    panic!("capacity overflow")
}

/// Handle collection allocation errors
///
// Causing a collection alloc error is rare case, so marked as `#[cold]` and `#[inline(never)]`
// to make the call site function as small as possible, so it can be inlined.
#[inline(never)]
#[cold]
fn handle_error(error: AllocError) -> ! {
    match error {
        AllocError::CapacityOverflow => capacity_overflow(),
        // TODO: call `handle_alloc_error` instead of `panic!` once the AllocErr stored a Layout,
        AllocError::AllocErr => panic!("encountered allocation error"),
    }
}

#[cfg(test)]
mod tests {

View on GitHub (pinned to e1e7af627c)

Solutions

1. Invoke the slot: `this.$slots.default?.()`.
2. When only testing presence, `!!this.$slots.default` is fine, but rendering must call it.
3. In setup-style code use `const slots = useSlots(); slots.default?.()` for the same access.

Example fix

// before
render() { return h('div', this.$slots.default); }

// after
render() { return h('div', this.$slots.default?.()); }

// warn on $slots member reads that are not immediately called
const re = /\$slots\.[A-Za-z_$][\w$]*(\?)?\s*(?!\()/g;
for (const m of source.matchAll(re)) {
  console.warn(`call the slot function: ${m[0]}()`);
}

When it happens

Trigger: Inside a Vue component options object (methods, computed, render): `this.$slots.default` used as a value, e.g. `h('div', this.$slots.default)` or `renderIt(this.$slots.default)` without a call. The correct form is `this.$slots.default?.()`.

Common situations: Vue 2 to Vue 3 migrations where slots were arrays/vnodes; render functions and functional components reading slots; library code that supported both Vue versions.

Related errors

• Cannot create a `NonEmptyStack` from an empty iterator
• Change to `throw new TypeError(...)`
• Could not find the reuseWorker option in ${path}
• `VirtualFree` failed during cleanup: {err}
• `VirtualFree` failed: {err}

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/38f7d31b47083136. Report an issue: GitHub.