[frankmcsherry]

enum now declares sums and type declares aliases, so type Text = List(int); and type Pair = (int, int); name structural shapes.
A draft: the change is complete and tested; aliases inside lambdas wait on a corgi change.

The language

enum Member = User int | Group int;   -- a sum, with the variant syntax `type` used before
enum Node = Node List(int);           -- a one-variant sum needs no special form
type Text = List(int);                -- an alias
type Grant = (Member, Text);          -- aliases may name enums and other aliases
let grants = input 0 : (int, Grant);

• An alias resolves to its shape wherever a declared name may appear: input, import, var and output declarations, and enum payloads.
• Enums are structural: variant names are for reading and erase, so two enums with the same lane shapes are the same type. The README says so.
• Enums and aliases share one namespace and may be declared in any order. A cycle through either kind is an error, as is a duplicate name.
• type X = A | B; fails with "sums are declared with enum, not type". The old spelling is not kept.
• enum matches the text corgi already uses for sums (enum Name = … in … inside lambdas, and DDIR's declarations to corgi's Scope).

Inside lambdas

Lambda ascriptions such as (x : Text) are parsed by corgi, which has no aliases.
For now they fail with unknown enum 'Text'; alias `Text`: aliases are not yet available inside lambdas.
A corgi draft adds type Name = shape to corgi (frankmcsherry/WIP#149); a DDIR follow-up that hands aliases to corgi is tested against it and waits on moving DDIR's corgi pin.

Conversion and checks

• 34 files: 13 programs, 13 plan-pair snapshots, 7 Rust files and the README. Every declaration needed only the keyword, including the one-variant sums in binders.ddp and join_fallback.ddp.
• The regenerated snapshots differ only in the keyword.
• Six new tests: aliases in shapes and chains, aliases of enums and enum payloads naming aliases, alias and mixed cycles, duplicate names, the enum hint, the lambda error, and inline corgi enums.
• cargo test --release -p interactive passes; all nine example .expected outputs match at 1 to 4 workers.

Implemented by GPT-6 Sol (Codex); reviewed, tested and opened by Claude Code.

🤖 Generated with Claude Code

https://claude.ai/code/session_01H6wB4H99TLw4tqu4x48pXL