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SW12001: Incompatible declaration assignment

A variable that holds one ref or animation is assigned a different one.

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This error occurs when a variable that holds one ref, keyframes, or view transition definition is later assigned a different one. The compiler tracks which definitions a variable can hold, and the assignment breaks that record. The message includes the explanation from TypeScript.

Reported

let current = style.ref("card");
current = style.ref("panel");
style({ [current("hover")]: "underline" });

SW12001: incompatible declaration identities: TS2322: Type 'StyleRef<string>' is not assignable to type 'StyleRef<"stillwind-identity/v1:eyJraW5kIjoicmVmIiwibW9kdWxlSWQiOiJSZWZlcmVuY2UudHN4Iiwic3RhcnQiOjQ2LCJlbmQiOjUzLCJiaW5kaW5nTmFtZSI6ImN1cnJlbnQifQ">'. Type 'string' is not assignable to type '"stillwind-identity/v1:eyJraW5kIjoicmVmIiwibW9kdWxlSWQiOiJSZWZlcmVuY2UudHN4Iiwic3RhcnQiOjQ2LCJlbmQiOjUzLCJiaW5kaW5nTmFtZSI6ImN1cnJlbnQifQ"'. Preserve declaration candidates with an explicit union or a generic parameter.

Source format: Jsx

Fixed

const card = style.ref("card");
const panel = style.ref("panel");
let current: typeof card | typeof panel = card;
current = panel;
style({ [current("hover")]: "underline" });

How to fix

  • Declare each definition in its own const, and give the variable an explicit union of their types, as in the example.
  • In a function that accepts several definitions, use a generic parameter instead of a wider type.
  • Keep the types that TypeScript infers when you pass definitions through exports.