Enum PresetError 

pub enum PresetError {
    Toml(Error),
    UnknownSystem(String),
    Expr {
        param: String,
        err: ExprError,
    },
    Config(String),
    Io(String),
}

Why a preset failed to load. Every variant is recoverable — the caller keeps the previous good preset.

Variants

Toml(Error)

The TOML itself was malformed.

UnknownSystem(String)

system named a built-in that does not exist.

Expr

A parameter’s expression failed to compile.

Fields

param: String

The parameter whose expression was invalid.

err: ExprError

The compile error.

Config(String)

A structural-config table ([curve]/[generator]) was invalid — an unknown family, an out-of-range value, an undefined grammar symbol.

Io(String)

The preset file could not be read (message from the I/O error).

Implementations

impl PresetError

pub fn span(&self) -> Option<Range<usize>>

The byte range in the preset source this error points at, when the parser gave one.

Only the TOML arm can have one: every other variant is raised by the loader’s own validation, which runs against parsed values rather than against the document, and a value carries no position. A caller turns the offset into a line and column against the source it read — which it still has and this module never did.

pub fn param(&self) -> Option<&str>

The parameter whose expression failed to compile, for the arm that has one.

The name is already in Display’s sentence; this is the same fact as a field, so a structured consumer does not have to read it back out of prose.

Trait Implementations

impl Debug for PresetError

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

Formats the value using the given formatter.

impl Display for PresetError

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

Formats the value using the given formatter.

impl Error for PresetError

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.