error

type struct Name { ... }
type enum Name { ... }
type trait Name { ... }
type union Name { ... }

Begins a type declaration; the keyword that follows says which kind. On its own, type Name = Existing; declares an alias.

type enum Name {
    Unit,
    Payload(T),
    Named { x: i32 },
}

An algebraic data type. Variants may be bare or carry a tuple or struct payload, and a match on an enum must cover every variant. Name::Variant names a variant; methods are added with implement enum Name { ... }.

type enum RandomError {
    EntropyUnavailable;
    EmptyRange;
    InvalidWeights;
}

What went wrong in a fallible random operation.

implement struct Name { ... }
implement trait Trait for Type { ... }
implement u64 { ... }

Adds methods to a type outside its declaration. implement struct T (or enum, or a bare primitive) opens an inherent block; implement trait Tr for T supplies a trait's methods for one type. Resolution is at compile time - no dynamic dispatch.

implement enum Name { ... }

Names the enum an inherent block extends - the only way to give an enum methods.

type enum RandomError {
    EntropyUnavailable;
    EmptyRange;
    InvalidWeights;
}

What went wrong in a fallible random operation.

RandomError::describe(&this) -> Str

A short, stable description of the failure, as a borrowed Str. The convergent accessor every stdlib error type exposes (describe(&this) -> Str); Display/Debug for RandomError delegate to it. Borrows a static string literal, so the view outlives any RandomError.

&this
mut &this
this

The receiver of a method. Its first parameter declares how the method takes it: &this borrows read-only, mut &this borrows exclusively, and this / mut this move the value in and consume it. In the body, this.field reaches the members.

type struct Str {
    bytes: u8*;
    length: u64;
}

Str: a borrowed UTF-8 string slice.

RandomError::rank(&this) -> i32

Discriminant rank, for equality.

primitive i32

32-bit signed integer.

import a::b;
import a::b::{ X, Y };
import a::b as c;
import a::b::*;

Brings a module, or selected items from it, into scope. One path per declaration: use the brace form for several items, as to alias, and * for everything public (prefer the brace form; wildcards invite name collisions).

namespace std;

std: the Cryo standard library.

namespace std::random;

std::random: pseudo-random and OS-backed randomness.

namespace std::random::error;

std::random::error: failures the random library can report.

RandomError::describe(&this) -> Str

A short, stable description of the failure, as a borrowed Str. The convergent accessor every stdlib error type exposes (describe(&this) -> Str); Display/Debug for RandomError delegate to it. Borrows a static string literal, so the view outlives any RandomError.

type trait Display {
    fmt<W>(&this, f: mut &Formatter<W>) -> Result<(), FmtError>
    where W: FmtWrite;
}

Display / Debug / Formatter.

RandomError::rank(&this) -> i32

Discriminant rank, for equality.

implement trait Trait for Type { ... }

Introduces a trait implementation: the block supplies, for one concrete type, the method bodies the trait requires.

type trait Eq {
    equals(&this, other: &This) -> boolean;
}

Types that support value equality. equals(a, b) must be reflexive, symmetric, and transitive.

implement trait Trait for Type { ... }

Names the type a trait implementation is for. The block that follows supplies the bodies the trait requires.