A Record<string, T> reference makes a recursive discriminated union with an array branch reject valid array values ("must be an array (was object)") — regression in 2.2.2

[karolrybak]

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🔎 Search Terms

=== query: must be an array ===
=== query: discriminated union Record ===
=== query: recursive union ===
=== query: Record discriminated ===
=== query: was object ===

🧩 Context

arktype	@ark/schema	result
2.2.1	0.56.0	✅ OK
2.2.2	0.56.1	❌ ERR
2.2.3	0.56.2	❌ ERR

The regression is introduced in 2.2.2 (@ark/schema 0.56.0 → 0.56.1).

🧑‍💻 Repro

import { scope, type } from "arktype";

const Node = scope({
  Number: { type: "'number'" },
  Array:  { type: "'array'", item: "Node" },
  Unit:   { type: "'unit'" },
  Container: { things: "Record<string, Node>" }, // ← remove this line → works
  Node: "Number | Array | Unit",
}).export().Node;

// A perfectly valid Node of the `array` variant:
const out = Node({ type: "array", item: { type: "number" } });

console.log(out instanceof type.errors ? "ERR: " + out.summary : "OK");
// 2.2.1 → "OK"
// 2.2.2 / 2.2.3 → "ERR: must be an array (was object)"

Minimization notes

The bug requires all of:

1. a discriminated union with ≥ 3 branches (2 branches do not trigger it);
2. one branch being an array type whose item recurses into the union
   ({ type: "'array'", item: "Node" });
3. a Record<string, Node> reference somewhere in the same scope.

Remove (3), or drop to 2 branches → the same value validates fine. It does not
depend on validation order — the mis-resolution is baked in at scope-build time.

Possibly related

This is the same fragile area as cyclic/recursive discriminated-union
discrimination:

• Discriminated union with circular references reports errors from wrong branch #1547 (fixed by Allow cyclic unions to discriminate on nested paths #1553, merged 2025-12-23) — cyclic union reports errors from
  the wrong branch. That fix is already present in the working 2.2.1, so this
  is a separate, newer regression.
• [bug] inconsistent errors for unions with cycles #1630 (open) — "inconsistent errors for unions with cycles" (error quality).
  Notably, [bug] inconsistent errors for unions with cycles #1630's pattern (a union variant with a Part[] field) with a
  valid value crashes on 2.2.1 (TypeError: this.<Alias>Apply is not a function) but is OK on 2.2.2 — so 2.2.2 fixed that crash while introducing
  the Record + array-branch false-rejection reported here.
• fix(schema): prevent crash validating unions of object arrays #1638 (open PR) — a different crash on unions of object arrays (Array union TypeError #1458).

[pullfrog]

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