Keywords

Every reserved keyword, with a one-line description. Reserved words cannot be used as identifiers.

There are 59 reserved keywords.

Keyword	Meaning
Bool	The boolean base type.
Duration	The time-span base type, in milliseconds (5.minutes).
Effect	The effectful-computation type, Effect[T].
Err	The error variant of Result.
Float	The floating-point base type.
Instant	The absolute-time base type, in epoch milliseconds (Clock.now()).
Int	The integer base type.
JsonError	The JSON-decode error type, Result[T, JsonError] from Json.decode.
None	The empty variant of Option.
Ok	The success variant of Result.
Option	The optional-value type, Option[T].
Result	The success-or-error type, Result[T, E].
Some	The present variant of Option.
String	The string base type.
ValidationError	The error type returned by a refined type’s .of.
actor	Declare an actor — a boundary contract a handler consumes via by.
adapter	Declare an adapter — the host boundary (capability contract + binding).
agent	Declare a stateful, keyed agent inside a context.
and	Combine refinement predicates (where A and B).
as	Alias a consumed context (consumes X as Y).
assert	Assert a condition inside a test case.
binding	Name an adapter’s TypeScript binding module (binding "<module>").
by	Name the actor a handler consumes (on … by <name>: <Actor>).
capability	Declare a capability (a dependency interface) in a context.
commons	Declare a pure, stateless module of types and functions.
consumes	Declare a dependency on another context’s services.
context	Declare a deployable context (services, agents, capabilities).
cron	The cron protocol on a service header (from cron).
else	The alternative branch of an if expression.
enum	Declare a payloadless sum type (enum { A, B }).
expect	Reserved keyword.
exports	Declare which types a context exposes, and how.
false	The boolean literal false.
fn	Declare a function.
from	Name the protocol a service conforms to (service X from http).
given	Declare the capabilities a handler requires.
http	The HTTP protocol on a service header (from http).
if	A conditional expression.
implies	Logical implication (P implies Q ≡ `!P
invariant	Declare an agent invariant — a predicate that must hold of every committed state.
is	Test a value against a variant pattern, yielding a Bool.
let	Bind a local value (let x = …, or let x <- … for an effect).
match	Pattern-match over a sum type, Result, or Option.
mocks	Provide a mock capability implementation in a test.
on	Begin a handler declaration (on call, on GET(…), on message, on open/on close).
opaque	Declare an opaque type, or export a type opaquely.
protocol	Reserved keyword (protocols are a closed, compiler-known set).
provides	Provide an implementation of a capability.
queue	The queue protocol on a service header (from queue("name")).
record	Reserved keyword (records are written type X = { … }).
self	The current agent instance, inside a handler.
service	Declare a service (a group of handlers) in a context.
test	Declare a test block or a test case.
transparent	Export a type with its structure visible (exports transparent { … }).
true	The boolean literal true.
type	Declare a type: alias, record, sum, opaque, or refined.
uses	Bring a commons into scope.
where	Attach refinement predicates to a base type.
wires	List the contexts a test integration stands up as Workers.