bevyengine/bevy · error · FunctionError

received {received} arguments but expected one of {expected:

Error message

received {received} arguments but expected one of {expected:?}

What it means

FunctionError::ArgCountMismatch — a dynamic function/mut function was called with a number of arguments matching none of its registered overload signatures. Payloads: the received count and the set of expected counts.

Source

Thrown at crates/bevy_reflect/src/func/error.rs:20

use crate::func::{
    args::{ArgCount, ArgError},
    Return,
};
use alloc::borrow::Cow;
use bevy_platform::collections::HashSet;
use thiserror::Error;

/// An error that occurs when calling a [`DynamicFunction`] or [`DynamicFunctionMut`].
///
/// [`DynamicFunction`]: crate::func::DynamicFunction
/// [`DynamicFunctionMut`]: crate::func::DynamicFunctionMut
#[derive(Debug, Error, PartialEq)]
pub enum FunctionError {
    /// An error occurred while converting an argument.
    #[error(transparent)]
    ArgError(#[from] ArgError),
    /// The number of arguments provided does not match the expected number.
    #[error("received {received} arguments but expected one of {expected:?}")]
    ArgCountMismatch {
        /// Expected argument count. [`ArgCount`] for overloaded functions will contain multiple possible counts.
        expected: ArgCount,
        /// Number of arguments received.
        received: usize,
    },
    /// No overload was found for the given set of arguments.
    #[error("no overload found for arguments with signature `{received:?}`, expected one of `{expected:?}`")]
    NoOverload {
        /// The set of available argument signatures.
        expected: HashSet<ArgumentSignature>,
        /// The received argument signature.
        received: ArgumentSignature,
    },
}

/// The result of calling a [`DynamicFunction`] or [`DynamicFunctionMut`].
///

View on GitHub (pinned to 396ca72708)

Solutions

1. Pass exactly the arguments the function expects
2. Inspect the function's signature info before calling

When it happens

Trigger: Thrown at crates/bevy_reflect/src/func/error.rs:20 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of bevyengine/bevy@396ca72708 (2026-08-20). Data as JSON: /api/errors/92d6a7feb0c04fc7. Report an issue: GitHub.