bevyengine/bevy · error · ArgError

expected `{expected}` but received `{received}` (@ argument

Error message

expected `{expected}` but received `{received}` (@ argument index {index})

What it means

ArgError::UnexpectedType — while converting a reflected argument for a dynamic function call, the argument's type did not match the parameter's expected type. The payload carries the argument index plus the expected and received type paths.

Source

Thrown at crates/bevy_reflect/src/func/args/error.rs:13

use alloc::borrow::Cow;

use thiserror::Error;

use crate::func::args::Ownership;

/// An error that occurs when converting an [argument].
///
/// [argument]: crate::func::args::Arg
#[derive(Debug, Error, PartialEq)]
pub enum ArgError {
    /// The argument is not the expected type.
    #[error("expected `{expected}` but received `{received}` (@ argument index {index})")]
    UnexpectedType {
        /// Argument index.
        index: usize,
        /// Expected argument type path.
        expected: Cow<'static, str>,
        /// Received argument type path.
        received: Cow<'static, str>,
    },
    /// The argument has the wrong ownership.
    #[error("expected {expected} value but received {received} value (@ argument index {index})")]
    InvalidOwnership {
        /// Argument index.
        index: usize,
        /// Expected ownership.
        expected: Ownership,
        /// Received ownership.
        received: Ownership,
    },

View on GitHub (pinned to 396ca72708)

Solutions

1. Pass an argument of the expected type at the failing index
2. Fix the function's argument signature to match what callers send
3. Convert the argument before calling

When it happens

Trigger: Thrown at crates/bevy_reflect/src/func/args/error.rs:13 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/b13fe675ee305c22. Report an issue: GitHub.