Enum A3Error 

pub enum A3Error {
    Parse(Error),
    Serialize(Error),
    Validate(Vec<String>),
}

The single error type returned by every fallible function in this crate.

In Rust, errors are values — there are no exceptions. Every function that can fail returns Result<T, A3Error>, which is either Ok(value) or Err(A3Error::...). The caller decides how to handle it.

#[derive(Debug)] lets you print the error with {:?} formatting. #[derive(Error)] (from thiserror) implements std::error::Error for us.

Variants

Parse(Error)

Returned when the input string is not valid JSON.

#[error("...")] defines the human-readable message produced by .to_string() or the {} format specifier.

{0} refers to the first (and only) field of this variant by position. serde_json::Error is the underlying parse error from the JSON library.

#[from] implements From<serde_json::Error> for A3Error automatically, enabling the ? operator to convert deserialization errors into this variant without an explicit .map_err(...) call.

Serialize(Error)

Returned when a validated crate::A3 cannot be serialized to JSON.

In practice this variant is unreachable for well-typed A3 values, but it is kept distinct from A3Error::Parse so that error messages accurately reflect the failure mode — serialization, not parsing.

Validate(Vec<String>)

Returned when input is structurally valid JSON but violates A3 rules.

We collect all validation errors into a Vec<String> so that a caller sees every problem at once, not just the first one encountered.

{0:#?} uses the “alternate” debug formatter, which prints each element on its own line — readable for a list of error messages.

Trait Implementations

impl Debug for A3Error

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

Formats the value using the given formatter.

impl Display for A3Error

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

Formats the value using the given formatter.

impl Error for A3Error

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<Error> for A3Error

fn from(source: Error) -> Self

Converts to this type from the input type.