Enum Error 

#[non_exhaustive]
pub enum Error {
    StepLimit {
        limit: u64,
    },
    InvalidPattern {
        arm: usize,
        node: usize,
        reason: Reason,
    },
    Model {
        reason: &'static str,
    },
    TooLarge,
}

Why a check could not produce a Report.

Examples

use match_lang::{check, Arm, Error, Model, Pat, Reason, Signature};

struct Bytes;

impl Model for Bytes {
    type Ty = ();
    fn signature(&self, _: &()) -> Signature<()> {
        Signature::Int { min: 0, max: 255 }
    }
    fn fields(&self, _: &(), _: u32, _: &mut Vec<()>) {}
}

let err = check(&Bytes, &(), &[Arm::new(Pat::int(300))]).unwrap_err();
assert_eq!(err, Error::InvalidPattern { arm: 0, node: 0, reason: Reason::OutOfDomain });

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

StepLimit

The analysis took more steps than the step limit allows. Deciding exhaustiveness is NP-hard in general, so some matrices (typically many columns of overlapping or-patterns or ranges) need exponential work; the limit turns them into this error instead of a hang. Raise the limit if the match is legitimate, or report it to the user as too complex to check.

Fields

limit: u64

The limit that was exceeded.

InvalidPattern

A pattern does not fit the type it is matched against. This is a type error the language’s checker should have caught; nothing was analysed.

Fields

arm: usize

The index of the arm.

node: usize

The preorder index of the offending node within the arm’s pattern (see Pat).

reason: Reason

What is wrong with it.

Model

The model answered inconsistently: the same type got different signatures or field counts during one check, or a signature was itself invalid (an Int with min > max). Fix the model.

Fields

reason: &'static str

What was inconsistent.

TooLarge

The patterns, or the matrix built from them, need more than u32::MAX - 1 nodes, rows, or cells.

Trait Implementations

impl Clone for Error

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Error

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

Formats the value using the given formatter.

impl Display for Error

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

Formats the value using the given formatter.

impl Eq for Error

impl Error for Error

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 PartialEq for Error

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Error