extend type

Platform spec node

extend type

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Spec standingStandard

Owner

Piotr Mikstacki pmikstacki@cybernomad.it

Submitter

Piotr Mikstacki pmikstacki@cybernomad.it

Current document

ADRs

No architecture decision records under adr/ for this feature yet. Standard features must publish at least one ADR or keep a ## Decisions summary on the hub.

Articles

• Code style and naming Language-level naming and style conventions that affect readability and tooling consistency. article Proposed
• extend type Type extension syntax replacing impl blocks; public members only, full type scope access. article Standard Reviewed Wed May 20
• Modules and visibility File layout, `public`/`internal` boundaries, and how packages compose. The driver and package manager use the same module graph the typechecker sees. article Standard Reviewed Thu May 21
• Name resolution Scopes, imports, and shadowing tie syntax to symbols. Diagnostics for unresolved names must cite these rules verbatim. article Standard Reviewed Thu May 21

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Completeness

OKarea · 2 SpecSection(s) · 0 H2 heading(s)

Section id	Required	Found
scope	yes	yes
features	yes	yes

Full tree: run pnpm verify:platform-spec-layout (writes src/generated/platform-spec-layout-report.json).

Related spec docs

• Area
  Program structure

  Parent area

• Feature
  Compiler Mod SDK

  Generators emit extend-type members

• Feature
  Modules and visibility

  Visibility and module boundaries

Purpose

extend type is the normative mechanism for adding members to an existing type. It replaces prior impl-block extension patterns for user and generated code.

Syntax

extend type Account
{
    pub unit Deposit(f32 amount)
    {
        account.balance += amount;
    }
}

The extended type name (Account) must refer to an in-scope type declaration. The body may declare methods and other members allowed by the type system for that target.

Access rules

• Members inside extend type may access public members of the extended type only.
• Private member access is forbidden inside extend type bodies.
• extend type does not bypass module visibility; extension sites must satisfy normal import and visibility rules.

Compiler mods

Generator contracts may emit extend type blocks as typed AST contributions. Generated extensions follow the same access and visibility rules as hand-authored extensions.