Infinite loop -- narrowed down to single file with no imports

[UppaJung]

TypeScript Version: [email protected]

I did.

Search Terms: infinite loop

I found one other recent report of an infinite loop, but that reporter wasn't able to isolate the problem. I've got this one nailed to a file with one important and one line that can be commented out to make the infinite loop go away.

Code

// A *self-contained* demonstration of the problem follows...
// Test this by running `tsc --target es6` on the command-line, rather than through another build tool such as Gulp, Webpack, etc.

export enum PubSubRecordIsStoredInRedisAsA {
  redisHash = "redisHash",
  jsonEncodedRedisString = "jsonEncodedRedisString"
}

export interface PubSubRecord<NAME extends string, RECORD, IDENTIFIER extends Partial<RECORD>> {
  name: NAME;
  record: RECORD;
  identifier: IDENTIFIER;
  storedAs: PubSubRecordIsStoredInRedisAsA;
  maxMsToWaitBeforePublishing: number;
}

type NameFieldConstructor<SO_FAR> =
  SO_FAR extends {name: any} ? {} : {
    name: <TYPE>(t?: TYPE) => BuildPubSubRecordType<SO_FAR & {name: TYPE}>
  }

const buildNameFieldConstructor = <SO_FAR>(soFar: SO_FAR) => (
  "name" in soFar ? {} : {
    name: <TYPE>(instance: TYPE = undefined) =>
      buildPubSubRecordType(Object.assign({}, soFar, {name: instance as TYPE}) as SO_FAR & {name: TYPE}) as BuildPubSubRecordType<SO_FAR & {name: TYPE}>
  }
);

type StoredAsConstructor<SO_FAR> =
  SO_FAR extends {storedAs: any} ? {} : {
    storedAsJsonEncodedRedisString: () => BuildPubSubRecordType<SO_FAR & {storedAs: PubSubRecordIsStoredInRedisAsA.jsonEncodedRedisString}>;
    storedRedisHash: () => BuildPubSubRecordType<SO_FAR & {storedAs: PubSubRecordIsStoredInRedisAsA.redisHash}>;
  }

const buildStoredAsConstructor = <SO_FAR>(soFar: SO_FAR) => (
  "storedAs" in soFar ? {} : {
    storedAsJsonEncodedRedisString: () =>
      buildPubSubRecordType(Object.assign({}, soFar, {storedAs: PubSubRecordIsStoredInRedisAsA.jsonEncodedRedisString})) as
        BuildPubSubRecordType<SO_FAR & {storedAs: PubSubRecordIsStoredInRedisAsA.jsonEncodedRedisString}>,
    storedAsRedisHash: () =>
      buildPubSubRecordType(Object.assign({}, soFar, {storedAs: PubSubRecordIsStoredInRedisAsA.redisHash})) as
        BuildPubSubRecordType<SO_FAR & {storedAs: PubSubRecordIsStoredInRedisAsA.redisHash}>,
  }
);

type IdentifierFieldConstructor<SO_FAR> =
  SO_FAR extends {identifier: any} ? {} :
  SO_FAR extends {record: any} ? {
    identifier: <TYPE extends Partial<SO_FAR["record"]>>(t?: TYPE) => BuildPubSubRecordType<SO_FAR & {identifier: TYPE}>
  } : {}

const buildIdentifierFieldConstructor = <SO_FAR>(soFar: SO_FAR) => (
  "identifier" in soFar || (!("record" in soFar)) ? {} : {
    identifier: <TYPE>(instance: TYPE = undefined) =>
      buildPubSubRecordType(Object.assign({}, soFar, {identifier: instance as TYPE}) as SO_FAR & {identifier: TYPE}) as BuildPubSubRecordType<SO_FAR & {identifier: TYPE}>
  }
);

type RecordFieldConstructor<SO_FAR> =
  SO_FAR extends {record: any} ? {} : {
    record: <TYPE>(t?: TYPE) => BuildPubSubRecordType<SO_FAR & {record: TYPE}>
  }

const buildRecordFieldConstructor = <SO_FAR>(soFar: SO_FAR) => (
  "record" in soFar ? {} : {
    record: <TYPE>(instance: TYPE = undefined) =>
      buildPubSubRecordType(Object.assign({}, soFar, {record: instance as TYPE}) as SO_FAR & {record: TYPE}) as BuildPubSubRecordType<SO_FAR & {record: TYPE}>
  }
);

type MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR> =
  SO_FAR extends {maxMsToWaitBeforePublishing: any} ? {} : {
    maxMsToWaitBeforePublishing: (t: number) => BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: number}>,
    neverDelayPublishing: () => BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: 0}>,
  }

const buildMaxMsToWaitBeforePublishingFieldConstructor = <SO_FAR>(soFar: SO_FAR): MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR> => (
  "maxMsToWaitBeforePublishing" in soFar ? {} : {
    maxMsToWaitBeforePublishing: (instance: number = 0) =>
      buildPubSubRecordType(Object.assign({}, soFar, {maxMsToWaitBeforePublishing: instance})) as BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: number}>,
    neverDelayPublishing: () =>
      buildPubSubRecordType(Object.assign({}, soFar, {maxMsToWaitBeforePublishing: 0})) as BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: 0}>,
  }
) as MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR>;

type TypeConstructor<SO_FAR> =
  SO_FAR extends {identifier: any, record: any, maxMsToWaitBeforePublishing: number, storedAs: PubSubRecordIsStoredInRedisAsA} ? {
    type: SO_FAR,
    fields: Set<keyof SO_FAR>,
    hasField: (fieldName: string | number | symbol) => fieldName is keyof SO_FAR
  } : {}

const buildType = <SO_FAR>(soFar: SO_FAR) => (
  "identifier" in soFar && "object" in soFar && "maxMsToWaitBeforePublishing" in soFar && "PubSubRecordIsStoredInRedisAsA" in soFar ? {} : {
    type: soFar,
    fields: () => new Set(Object.keys(soFar) as (keyof SO_FAR)[]),
    hasField: (fieldName: string | number | symbol) => fieldName in soFar
  }
);

type BuildPubSubRecordType<SO_FAR> =
  NameFieldConstructor<SO_FAR> &
  IdentifierFieldConstructor<SO_FAR> &
  RecordFieldConstructor<SO_FAR> &
  StoredAsConstructor<SO_FAR> & // infinite loop goes away when you comment out this line
  MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR> &
  TypeConstructor<SO_FAR>

const buildPubSubRecordType = <SO_FAR>(soFar: SO_FAR) => Object.assign(
  {},
  buildNameFieldConstructor(soFar),
  buildIdentifierFieldConstructor(soFar),
  buildRecordFieldConstructor(soFar),
  buildStoredAsConstructor(soFar),
  buildMaxMsToWaitBeforePublishingFieldConstructor(soFar),
  buildType(soFar)
) as BuildPubSubRecordType<SO_FAR>;
const PubSubRecordType = buildPubSubRecordType({});

Expected behavior:
Compiles.

Actual behavior:
The compiler fails to terminate (at least for as long as I was willing to wait.)

Playground Link:

Related Issues:

Possibly #26612

[UppaJung]

Here's a smaller (similar, but different) test case to provide another means of attack.

Note the comment that says "Replace this line with the four below and the infinite loop goes away"

type PubSubRecordIsStoredInRedisAsA = "redisHash" | "jsonEncodedRedisString";

export interface PubSubRecord<NAME extends string, RECORD, IDENTIFIER extends Partial<RECORD>> {
  name: NAME;
  record: RECORD;
  identifier: IDENTIFIER;
  storedAs: PubSubRecordIsStoredInRedisAsA;
  maxMsToWaitBeforePublishing: number;
}

type StoredAsConstructor<SO_FAR> =
  SO_FAR extends {storedAs: PubSubRecordIsStoredInRedisAsA} ? {} : {
    storedAsJsonEncodedRedisString: () => BuildPubSubRecordType<SO_FAR & {storedAs: "jsonEncodedRedisString"}>;
    storedRedisHash: () => BuildPubSubRecordType<SO_FAR & {storedAs: "redisHash"}>;
  }

const buildStoredAsConstructor = <SO_FAR>(
  soFar: SO_FAR
) => (
  "storedAs" in soFar ? {} : {
    storedAsJsonEncodedRedisString: () =>
      buildPubSubRecordType(Object.assign({}, soFar, {storedAs: "jsonEncodedRedisString"})) as
        BuildPubSubRecordType<SO_FAR & {storedAs: "jsonEncodedRedisString"}>,
    storedAsRedisHash: () =>
      buildPubSubRecordType(Object.assign({}, soFar, {storedAs: "redisHash"})) as
        BuildPubSubRecordType<SO_FAR & {storedAs: "redisHash"}>,
  }
); // Replace this line with the four below and the compiler's infinite loop goes away
// ) as SO_FAR extends {storedAs: PubSubRecordIsStoredInRedisAsA} ? {} : {
//     storedAsJsonEncodedRedisString: () => BuildPubSubRecordType<SO_FAR & {storedAs: "jsonEncodedRedisString"}>;
//     storedRedisHash: () => BuildPubSubRecordType<SO_FAR & {storedAs: "redisHash"}>;
// };

type IdentifierFieldConstructor<SO_FAR> =
  SO_FAR extends {identifier: any} ? {} :
  SO_FAR extends {record: any} ? {
    identifier: <TYPE extends Partial<SO_FAR["record"]>>(t?: TYPE) => BuildPubSubRecordType<SO_FAR & {identifier: TYPE}>
  } : {}

const buildIdentifierFieldConstructor = <SO_FAR>(soFar: SO_FAR) => (
  "identifier" in soFar || (!("record" in soFar)) ? {} : {
    identifier: <TYPE>(instance: TYPE = undefined) =>
      buildPubSubRecordType(Object.assign({}, soFar, {identifier: instance as TYPE}) as SO_FAR & {identifier: TYPE}) as BuildPubSubRecordType<SO_FAR & {identifier: TYPE}>
  }
);

type RecordFieldConstructor<SO_FAR> =
  SO_FAR extends {record: any} ? {} : {
    record: <TYPE>(t?: TYPE) => BuildPubSubRecordType<SO_FAR & {record: TYPE}>
  }

const buildRecordFieldConstructor = <SO_FAR>(soFar: SO_FAR) => (
  "record" in soFar ? {} : {
    record: <TYPE>(instance: TYPE = undefined) =>
      buildPubSubRecordType(Object.assign({}, soFar, {record: instance as TYPE}) as SO_FAR & {record: TYPE}) as BuildPubSubRecordType<SO_FAR & {record: TYPE}>
  }
);

type MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR> =
  SO_FAR extends {maxMsToWaitBeforePublishing: any} ? {} : {
    maxMsToWaitBeforePublishing: (t: number) => BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: number}>,
    neverDelayPublishing: () => BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: 0}>,
  }

const buildMaxMsToWaitBeforePublishingFieldConstructor = <SO_FAR>(soFar: SO_FAR): MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR> => (
  "maxMsToWaitBeforePublishing" in soFar ? {} : {
    maxMsToWaitBeforePublishing: (instance: number = 0) =>
      buildPubSubRecordType(Object.assign({}, soFar, {maxMsToWaitBeforePublishing: instance})) as BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: number}>,
    neverDelayPublishing: () =>
      buildPubSubRecordType(Object.assign({}, soFar, {maxMsToWaitBeforePublishing: 0})) as BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: 0}>,
  }
) as MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR>;

type BuildPubSubRecordType<SO_FAR> =
  IdentifierFieldConstructor<SO_FAR> &
  RecordFieldConstructor<SO_FAR> &
  StoredAsConstructor<SO_FAR> &
  MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR>

const buildPubSubRecordType = <SO_FAR>(soFar: SO_FAR) => Object.assign(
  {},
  buildIdentifierFieldConstructor(soFar),
  buildRecordFieldConstructor(soFar),
  buildStoredAsConstructor(soFar),
  buildMaxMsToWaitBeforePublishingFieldConstructor(soFar),
) as BuildPubSubRecordType<SO_FAR>;
const PubSubRecordType = buildPubSubRecordType({});

[ghost]

Preliminary work on a smaller repro:

type StoredAsConstructor<SO_FAR> = {
  storedAsJsonEncodedRedisString: () => BuildPubSubRecordType<SO_FAR & {storedAs: "jsonEncodedRedisString"}>;
  storedRedisHash: () => BuildPubSubRecordType<SO_FAR & {storedAs: "redisHash"}>;
}

const buildStoredAsConstructor = <SO_FAR>(soFar: SO_FAR) => ({
  storedAsJsonEncodedRedisString: () => ({}) as BuildPubSubRecordType<SO_FAR & {storedAs: "jsonEncodedRedisString"}>,
});

type IdentifierFieldConstructor<SO_FAR> =
  SO_FAR extends {identifier: any} ? {} :
  SO_FAR extends {record: any} ? {
    identifier: <TYPE extends Partial<SO_FAR["record"]>>(t?: TYPE) => BuildPubSubRecordType<SO_FAR & {identifier: TYPE}>
  } : {}

type RecordFieldConstructor<SO_FAR> =
  SO_FAR extends {record: any} ? {}
  : { record: <TYPE>(t?: TYPE) => BuildPubSubRecordType<SO_FAR & {record: TYPE}> }

type MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR> =
  SO_FAR extends {maxMsToWaitBeforePublishing: any} ? {} : {
    maxMsToWaitBeforePublishing: (t: number) => BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: number}>,
    neverDelayPublishing: () => BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: 0}>,
  }

const buildMaxMsToWaitBeforePublishingFieldConstructor = <SO_FAR>(soFar: SO_FAR): MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR> => (
  {
    neverDelayPublishing: () =>
      buildPubSubRecordType(Object.assign({}, soFar, {maxMsToWaitBeforePublishing: 0})) as BuildPubSubRecordType<SO_FAR & {maxMsToWaitBeforePublishing: 0}>,
  }
) as MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR>;

type BuildPubSubRecordType<SO_FAR> =
  IdentifierFieldConstructor<SO_FAR> &
  RecordFieldConstructor<SO_FAR> &
  StoredAsConstructor<SO_FAR> &
  MaxMsToWaitBeforePublishingFieldConstructor<SO_FAR>

const buildPubSubRecordType = <SO_FAR>(soFar: SO_FAR) => ({}) as BuildPubSubRecordType<SO_FAR>;