Section 5: Type Declarations

Goal: User-defined types

SPEC: spec/08-types.md, spec/09-properties-of-types.md, spec/10-declarations.md

Status: In-progress — Structs (5.1), sum types (5.2), newtypes (5.3), generics (5.4), built-in generics (5.6), derive (5.7), visibility (5.8), associated functions (5.9) all working in evaluator. Compound type inference (5.5) entirely pending. LLVM tests missing. Verified 2026-02-10.

SYNC POINT: Adding a new built-in type (e.g., Duration, Size, CPtr, Nursery) requires updates across ori_ir (type variant), ori_types (registration + method signatures), ori_eval (runtime representation + method dispatch), ori_llvm (type layout + codegen), and library/std/ (prelude or module definitions). This section primarily covers user-defined types, but built-in types added by other sections (11, 16, 17, 18) follow the same pattern.

5.1 Struct Types

5.2 Sum Types (Enums) — COMPLETED 2026-01-28

5.3 Newtypes

Proposal: proposals/approved/newtype-pattern-proposal.md

5.4 Generic Types

5.5 Compound Types

Note: tests/spec/types/collections.ori is ENTIRELY COMMENTED OUT — type checker doesn’t support collection type inference yet. Lists, tuples, maps work in the evaluator but type checker support is pending.

5.6 Built-in Generic Types

5.7 `with` Clause on Type Declarations (Capability Unification)

Proposal: proposals/approved/capability-unification-generics-proposal.md — Phase 1

Replace #derive(Trait) with type T: Trait = .... Derivation moves from attribute syntax into the type declaration grammar as a : trait clause.

SUPERSEDES: Previous syntax #derive(Eq, Clone) and #[derive(Eq, Clone)] are both replaced by type T: Eq, Clone = { ... }.

Syntax Migration

Existing Derive Functionality (carries forward)

5.8 Visibility

5.9 Associated Functions

Proposal: proposals/approved/associated-functions-language-feature.md

Generalize associated functions to work for ANY type with an impl block, removing hardcoded type checks. Enables syntax like Point.origin(), Builder.new(), Duration.from_seconds(s: 10).

Migration

Implement: Remove is_type_name_for_associated_functions() hardcoded checks [done] (2026-02-10)
- Rust Tests: ori_types/src/infer/ (calls) — general type name resolution
- Ori Tests: tests/spec/types/associated_functions.ori — user types (Point, Builder, Counter, Rectangle, Pair) all work

Parsing

Implement: Parse Type.method(...) syntax in expression position [done] (2026-02-10)
- Rust Tests: ori_parse/src/grammar/postfix.rs — type-prefixed method call
- Ori Tests: Point.origin(), Builder.new(), Counter.zero(), Rectangle.square(size: 5)
Implement: Distinguish type name vs value in resolution [done] (2026-02-10)
- Rust Tests: ori_types/src/infer/ — type vs value resolution
- Ori Tests: test_instance_vs_associated — Pair.create() (type) vs p.sum() (value)

Associated Function Registry

Implement: Track methods without self in impl blocks [done] (2026-02-10)
- Rust Tests: ori_types/src/check/ (method registry) — associated function registry
- Ori Tests: Point.origin(), Point.new(), Builder.new(), Counter.zero(), Counter.starting_at(), Rectangle.square/from_dimensions/unit(), Pair.create()
Implement: Built-in associated functions for Duration [done] (2026-02-10)
- Ori Tests: tests/spec/types/associated_functions.ori — Duration.from_seconds(s: 5) verified
- Duration.from_nanoseconds(ns:), from_microseconds(us:), from_milliseconds(ms:)
- Duration.from_seconds(s:), from_minutes(m:), from_hours(h:)
Implement: Built-in associated functions for Size [done] (2026-02-10)
- Ori Tests: tests/spec/types/associated_functions.ori — Size.from_megabytes(mb: 2) verified
- Size.from_bytes(b:), from_kilobytes(kb:), from_megabytes(mb:)
- Size.from_gigabytes(gb:), from_terabytes(tb:)

Generic Types

Implement: Full type arguments required for generic associated functions
- Ori Tests: Not tested — Option<int>.some(value: 42) pattern not verified
- Example: Option<int>.some(value: 42)

Self Return Type

Implement: Allow Self as return type in associated functions [done] (2026-02-10)
- Ori Tests: tests/spec/types/associated_functions.ori — Point.origin() -> Self, Builder.new() -> Self, Counter.zero() -> Self, Counter.increment(self) -> Self

Trait Associated Functions

Implement: Traits can define associated functions without self
- Rust Tests: ori_types/src/check/registration/traits.rs — trait associated functions
- Ori Tests: Not tested — trait Default { @default () -> Self } pattern
- Example: trait Default { @default () -> Self }

LLVM Support

LLVM Support: Codegen for associated function calls
- LLVM Rust Tests: ori_llvm/tests/associated_function_tests.rs (file does not exist)
- AOT Tests: No AOT coverage yet

5.10 Section Completion Checklist

Exit Criteria: User-defined structs and enums work Status: Evaluator support complete for core features. Type checker compound inference and several derive impls pending. Verified 2026-02-10.