arktype•7d ago

type inference resolves types from scopes to never in union

When using types from scopes in a union, arktype will resolve some of them to be "never", however if you insert their definition directly it resolves the type correctly Here is an example. If you paste this in the playground and hover of the out, the type will resolve to "never" in some places. Interestingly the .expression tab in the playground resolves the native Typescript expression correctly Is this a bug or am I misusing scopes in some way?

import { type } from "arktype";

const formScope = type.scope({
  "form.number": "string.numeric.parse",
  "form.integer": "string.integer.parse",
  "form.string": "string > 0",
  "form.checkbox": type("true|false|undefined", "=>", (c) => (c === undefined ? false : c)),
  "form.date": /^\d{2}\.\d{2}\.\d{4}$/,
  "form.year": type(/^\d{4}$/, "=>", (c) => Number.parseInt(c, 10)),
  "form.yearmonth": /^\d{2}\/\d{4}$/ ,
  "form.yesno.yes": "'yes'",
  "form.yesno.no": "'no'",
  "form.yesno": ["form.yesno.yes | form.yesno.no", "=>", (c) => c === "yes"],
 });

const arkScope = type.scope({
  ...formScope.export(),
});

const ark = arkScope;

const Thing = ark.type
  .or(
    ark.type
      .or(
        {
          hasWorkPermit: "form.yesno.yes",
          workPermit: {
            validUntil: "form.yearmonth",
          },
        },
        {
          hasWorkPermit: "form.yesno.no",
        },
      )
      .and({
        hasTemporaryResidence: "form.yesno.yes",
        temporaryResidence: {
          validUntil: "form.yearmonth",
        },
      }),
    {
      hasTemporaryResidence: "form.yesno.no",
    },
  )
  .and({
    inGermanySince: "form.yearmonth",
  });

const out = Thing({})

import { type } from "arktype";

const formScope = type.scope({
  "form.number": "string.numeric.parse",
  "form.integer": "string.integer.parse",
  "form.string": "string > 0",
  "form.checkbox": type("true|false|undefined", "=>", (c) => (c === undefined ? false : c)),
  "form.date": /^\d{2}\.\d{2}\.\d{4}$/,
  "form.year": type(/^\d{4}$/, "=>", (c) => Number.parseInt(c, 10)),
  "form.yearmonth": /^\d{2}\/\d{4}$/ ,
  "form.yesno.yes": "'yes'",
  "form.yesno.no": "'no'",
  "form.yesno": ["form.yesno.yes | form.yesno.no", "=>", (c) => c === "yes"],
 });

const arkScope = type.scope({
  ...formScope.export(),
});

const ark = arkScope;

const Thing = ark.type
  .or(
    ark.type
      .or(
        {
          hasWorkPermit: "form.yesno.yes",
          workPermit: {
            validUntil: "form.yearmonth",
          },
        },
        {
          hasWorkPermit: "form.yesno.no",
        },
      )
      .and({
        hasTemporaryResidence: "form.yesno.yes",
        temporaryResidence: {
          validUntil: "form.yearmonth",
        },
      }),
    {
      hasTemporaryResidence: "form.yesno.no",
    },
  )
  .and({
    inGermanySince: "form.yearmonth",
  });

const out = Thing({})

14 Replies

Flosi21OP•7d ago

I did some digging and the problem seems to be that in the NaryUnionParser the scope is not passed to type.infer When i change (nary.ts: line 22 )

    <const a, const b, r = Type<type.infer<a> | type.infer<b>, $>>(
        a: type.validate<a, $>,
        b: type.validate<b, $>
    ): r extends infer _ ? _ : never

    <const a, const b, r = Type<type.infer<a> | type.infer<b>, $>>(
        a: type.validate<a, $>,
        b: type.validate<b, $>
    ): r extends infer _ ? _ : never

    <const a, const b, r = Type<type.infer<a, $> | type.infer<b, $>, $>>(
        a: type.validate<a, $>,
        b: type.validate<b, $>
    ): r extends infer _ ? _ : never

    <const a, const b, r = Type<type.infer<a, $> | type.infer<b, $>, $>>(
        a: type.validate<a, $>,
        b: type.validate<b, $>
    ): r extends infer _ ? _ : never

it works. Is there are reason why the scope is not passed to type.infer here?

ssalbdivad•7d ago

You're right, that is a mistake! Would be happy to accept a PR (double check other n-ary operations as well to make sure scope is passed + add test) otherwise will fix in next release Good digging 👍

ssalbdivad•7d ago

One warning, if you name keywords like this with ., people might expect it to be a submodule, which is a built-in version of that syntax: https://arktype.io/docs/scopes#submodules

ArkType

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Flosi21OP•7d ago

thanks a lot for the quick response, I will open a pull request for this issue 🙂 https://github.com/arktypeio/arktype/issues/1422

GitHub

type inference resolves custom types from scopes to be "never" when...

Report a bug 🔎 Search Terms never union discriminated union scope 🧩 Context ArkType version: 2.1.19 TypeScript version (5.1+): 5.7.3 Other context you think may be relevant (JS flavor, OS, etc.): 🧑...

Flosi21OP•7d ago

another quick question: is there a reason why we do not reuse the inferredX properties when defining r?

inferredA = type.infer<a, $>,
        inferredB = type.infer<b, $>,
        inferredC = type.infer<c, $>,
        r = Type<inferNaryMerge<[type.infer<a>, type.infer<b>, type.infer<c>]>, $>

inferredA = type.infer<a, $>,
        inferredB = type.infer<b, $>,
        inferredC = type.infer<c, $>,
        r = Type<inferNaryMerge<[type.infer<a>, type.infer<b>, type.infer<c>]>, $>

ssalbdivad•7d ago

I want to say no, as long as it doesn't cause any types to break its certainly cleaner (though probably negligible in terms of perf due to caching) Actually this change overall could be quite good for perf if you're not using the default scope because the missing $ arg could cause the def to be parsed twice

Flosi21OP•7d ago

nice 😌

Flosi21OP•6d ago

the PR is now ready for review :) https://github.com/arktypeio/arktype/pull/1423

GitHub

#1422: fix nary type inference for scopes by Flosi23 · Pull Reques...

fixes: #1422 Added scope $ to all nary type inference. TODO: add tests

Flosi21OP•6d ago

addressed and pushed your requested changes 🙂

ssalbdivad•6d ago

Awesome thanks so much- very much appreciate your thoroughness here!

Flosi21OP•6d ago