Struct FromValueError

pub struct FromValueError { /* private fields */ }

Error type for failed value conversions.

This error is returned when attempting to convert a CEL Value to a Rust type using the FromValue trait, but the conversion fails due to type mismatch.

Error Information

The error contains:

• Source value: The original CEL value that could not be converted
• Target type: String description of the intended conversion target
• Context: Additional information about why the conversion failed

Common Causes

• Type mismatch: Trying to convert Value::String to i64
• Invalid format: Trying to convert malformed data
• Constraint violation: Value doesn’t meet type constraints

Examples

use cel_cxx::{Value, FromValue, FromValueError};

let string_val = Value::String("not_a_number".to_string().into());
let result = i64::from_value(&string_val);

match result {
    Ok(num) => println!("Converted: {}", num),
    Err(error) => {
        println!("Cannot convert value: {}", error);
    }
}

Implementations

impl FromValueError

pub fn new(value: Value, to: impl ToString) -> Self

Create a new conversion error with a custom target type description.

Arguments

• value - The CEL value that could not be converted
• to - Description of the target type (will be converted to string)

Examples

use cel_cxx::{Value, FromValueError};

let error = FromValueError::new(Value::String("text".to_string().into()), "integer");
// Error created successfully with custom type description

pub fn new_typed<T: TypedValue>(value: Value) -> Self

Create a new conversion error with automatic type name detection.

This method uses the TypedValue trait to automatically determine the CEL type information of the target type, providing more consistent error messages.

Type Parameters

• T - The target type that implements TypedValue

Arguments

• value - The CEL value that could not be converted

Examples

use cel_cxx::{Value, FromValueError};

let error = FromValueError::new_typed::<i64>(Value::String("text".to_string().into()));
// error contains type information for the target type

Trait Implementations

impl Clone for FromValueError

fn clone(&self) -> FromValueError

Returns a duplicate of the value.

const fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FromValueError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for FromValueError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for FromValueError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<FromMapKeyError> for FromValueError

fn from(error: FromMapKeyError) -> Self

Converts to this type from the input type.

impl From<FromValueError> for Error

fn from(error: FromValueError) -> Self

Converts to this type from the input type.