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Severity: warning
Category: Object types
Stage: Stage 1

Description

When a freshly-created object literal is assigned directly to a variable or parameter whose type annotation does not include a particular property, the extra property is almost certainly a typo or a misunderstanding of the target type. SJS emits this warning — rather than a hard error — because the assignment is structurally valid (the required properties are present), but the excess property will be silently discarded, which is usually unintentional.

This check applies only to fresh object literals at the point of assignment. It does not apply when a previously-bound variable of a wider type is assigned to a narrower type.

Example

// ✗ warning
type Point = { x: number; y: number }

let p: Point = { x: 1, y: 2, z: 3 }   // SJS-W006 — `z` is excess
// ✗ warning
function move(p: Point): void { }

move({ x: 0, y: 0, label: "origin" })  // SJS-W006 — `label` is excess

Suppression / Fix

Remove the excess property from the literal:

// ✓ correct
let p: Point = { x: 1, y: 2 }

If the target type should include the property, update the type annotation:

// ✓ correct — extend the type
type Point3D = { x: number; y: number; z: number }
let p: Point3D = { x: 1, y: 2, z: 3 }

If you need to temporarily widen the value, assign it to a variable first so it is no longer a fresh literal at the assignment site:

// ✓ correct — passes through a wider intermediate binding
const raw = { x: 1, y: 2, z: 3 }
let p: Point = raw    // no warning — raw is not a fresh literal here

Related codes

  • SJS-E002 — missing required property on object type
  • SJS-E005 — property type mismatch
Documentation