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oxlint-plugin-effect

no-manual-discriminant-construction

Intent: a union’s variant is built by its constructor, never as an object literal with the discriminant.

// ❌ no
const error = { _tag: "NotFound", id }


// ✅ yes
const error = new NotFound({ id })


// ❌ no, with `discriminants: ["_tag", "eventType"]`
const event = { eventType: "PaymentStarted", id, payment }


// ✅ yes
const event = PaymentStartedEvent.make({ id, payment })

Trigger: an object literal with a discriminant property (also "type" or ["type"]) whose value is a string literal. The discriminants are the names in discriminants.

Exemptions and blind spots: values that are not literals ("Ready" as const included). Literals that are patterns or raw input, also nested: the arguments of Match.when, Match.not, of .with(…) on a ts-pattern match(…) chain, the expected value of an expect(…) matcher or expect.* helper, the input of Schema.decode*(X)(…)/Schema.encode*(X)(…), the argument of JSON.stringify, and an argument whose parameter is annotated unknown in a function declared in the same file (a fake API’s raw body). Transport payloads written as literals fire, as does raw data passed to an imported function or through a variable, and a name added to discriminants fires on objects outside closed unions: the list is a choice of the codebase. See schema-struct-with-tag (effecttsgo) for Schema.Struct with a _tag field.

Why: a literal skips the constructor, so it carries none of the class’s prototype, equality or validation, and drifts silently when the type changes.

Options:

Fix: none