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 { ... }.

FmtError::Io(IoError)

The byte sink rejected the write. IoError carries kind + errno.

FmtError::Alloc(AllocError)

A heap-backed sink (String, Array<u8>) could not grow.

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.

&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.

primitive boolean

true / false. Not interchangeable with integers. 1 byte.

FmtError::describe(&this) -> Str

A short, stable description of what went wrong, as a borrowed Str. The convergent accessor every stdlib error type exposes (describe(&this) -> Str); Display/Debug for FmtError delegate to it.

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

Str: a borrowed UTF-8 string slice.

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::fmt;

fmt: formatting values as text.

namespace std::fmt::error;

FmtError: the failure kind for formatted-text writes.

type struct String<A = GlobalAlloc> {
    buffer: RawBuffer<u8, A>;
    length: u64;
}

String: owned, heap-allocated, length-typed UTF-8.

String::push<T>(mut &this, item: T) -> void

Append item to the string as its **text** representation, dispatched at compile time via static match (T) - no runtime cost, no trait bound, because the available arms ARE the accepted types: - Str / string - the view's / C string's UTF-8 bytes verbatim (a string's terminating NUL is not copied).

FmtError::describe(&this) -> Str

A short, stable description of what went wrong, as a borrowed Str. The convergent accessor every stdlib error type exposes (describe(&this) -> Str); Display/Debug for FmtError delegate to it.

FmtError::Io(IoError)

The byte sink rejected the write. IoError carries kind + errno.

FmtError::Alloc(AllocError)

A heap-backed sink (String, Array<u8>) could not grow.

type struct Array<T, A = GlobalAlloc> where A: Allocator {
    ptr: T*;
    length: i64;
    capacity: i64;
    alloc: A;
}

Array<T, A>: growable, heap-backed, contiguous sequence.

primitive u8

8-bit unsigned integer.

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

Display / Debug / Formatter.

implement trait Trait for Type { ... }

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

implement trait Trait for Type { ... }

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

namespace std::io;

io: byte-level input/output.