Naming

Every name has one spelling, decided by what kind of thing it names.

Identifiers are ASCII letters, digits and underscores, and can't start with a digit. The compiler checks the case and suggests the right spelling.

A name must convert to its file name and back unchanged, so a name can't have two capitals in a row: write VatRate, not VATRate.

Reserved words

The words that control flow or open a declaration are reserved. None of them can name a declaration, field, parameter, variable or variant, and using one as a name is syntax.expected_name. They are action, and, assert, attempt, constant, decline, else, emit, entity, fails, false, fixture, for, function, if, in, library, match, mut, none, not, or, package, propagate, provide, public, query, reject, resource, return, routes, schedule, seed, subscriber, test, true, type, use and var.

A setting the language defines may still use a reserved word as its key, such as package: Stripe.v2024_06_20 in a connection or test: in configuration.

Words that are names everywhere else

Some words mean something only where the language expects them, and can be used as names anywhere else:

• asc and desc, a query's order;
• end, in templates;
• matches, the pattern operator;
• input and value;
• the words that open a declaration with no name: acceptance, application, authentication, config, flags, locales, migration, policy, principal and suggestions (Suggestions).

include, pick, omit and optional build a type's fields (Values and types), so they can name anything but a field. The standard-library and generated namespaces (list, clock, config and the rest) can't name a domain or a library.