Unable to assign string-embedded default value to type including scoped keyword

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default value scope alias not assignable literal

🧩 Context

• ArkType version: 2.0.0-beta.0
• TypeScript version (5.1+): 5.4.5
• Other context you think may be relevant (JS flavor, OS, etc.):

🧑‍💻 Repro

This test currently fails because we are not able to infer specialNumber in this context:

it("validated default in scope", () => {
  const $ = scope({
    specialNumber: "number",
    // "5 is not assignable to specialNumber "
    obj: { foo: "string", bar: "specialNumber = 5" },
  });
});

This is due to this workaround in ark/type/parser/objectLiteral.ts in validateDefaultValueString:

type validateDefaultValueString =
// other context
[
  // check against the output of the type since morphs will not occur
  // we currently can't parse string embedded defaults for non-global keywords
  distillOut<inferString<baseDef, {}, args>>,
  // a default value should never have In/Out, so which side we choose is irrelevant
  // we will never need a scope here as we're just trying to infer a UnitLiteral
  distillOut<inferString<defaultDef, {}, args>>
] extends [infer base, infer defaultValue]

The reason we need to pass {} in the top def instead of $ (which fixes the issue) is that passing $ and then comparing the values breaks other inference, namely thunks and piping (you should see errors across the repo if you change this back to $).

For now the workaround is to just use a tuple default, e.g:

it("validated default in scope", () => {
  const $ = scope({
    specialNumber: "number",
    obj: { foo: "string", bar: ["specialNumber", "=", 5] },
  });
});

This may not be resolvable without changes to TS, but could be fixed by #1017