Intersection causes incorrect type compatability

[webstrand]

Bug Report

🔎 Search Terms

intersection assignability omit compatability

🕗 Version & Regression Information

• This changed between versions 3.8.3 and 3.9.7

⏯ Playground Link

Playground link with relevant code

💻 Code

type APIApplicationCommandSubcommandGroupOption = {
    options?: APIApplicationCommandSubcommandOption[];
}

type CommandSubcommandGroupOption = Omit<APIApplicationCommandSubcommandGroupOption, 'options'> & { // <-- so is this one
  options?: CommandSubcommandOption[]
}

type CommandSubcommandOption = { otherProps: unknown } & { // <-- this intersection is apparently critical
  options?: unknown[]
}

interface APIApplicationCommandSubcommandOption {
    options?: { foo: string }[];
    otherProps: unknown;
}

function transformSubcommandGroupOption1(option: CommandSubcommandGroupOption): APIApplicationCommandSubcommandGroupOption {
  return option; // no error, but there _should_ be an error here.
}

function transformSubcommandGroupOption2(option: CommandSubcommandGroupOption): APIApplicationCommandSubcommandGroupOption {
  return { ...option }; // error in 3.9.7
}

🙁 Actual behavior

The return option does not produce an error and the return { ...option } does produce an error.

🙂 Expected behavior

Both returns should behave the same. Ideally, both should produce an error because CommandSubcommandGroupOption is incompatible with APIApplicationCommandSubcommandGroupOption.

From help thread on Discord: https://discord.com/channels/508357248330760243/964236133330460772

[RyanCavanaugh]

Working out some bot kinks 😅

type APIApplicationCommandSubcommandGroupOption = {
    options?: APIApplicationCommandSubcommandOption[];
}

type CommandSubcommandGroupOption = Omit<APIApplicationCommandSubcommandGroupOption, 'options'> & { // <-- so is this one
  options?: CommandSubcommandOption[]
}

type CommandSubcommandOption = { otherProps: unknown } & { // <-- this intersection is apparently critical
  options?: unknown[]
}

interface APIApplicationCommandSubcommandOption {
    options?: { foo: string }[];
    otherProps: unknown;
}

function transformSubcommandGroupOption1(option: CommandSubcommandGroupOption): APIApplicationCommandSubcommandGroupOption {
  return option; // no error, but there _should_ be an error here.
}

function transformSubcommandGroupOption2(option: CommandSubcommandGroupOption): APIApplicationCommandSubcommandGroupOption {
  return { ...option }; // error in 3.9.7
}

[typescript-bot]

👋 Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of the repro in the issue body running against the nightly TypeScript.

---

Issue body code block by @webstrand

❌ Failed: -

• Type 'CommandSubcommandGroupOption' is not assignable to type 'APIApplicationCommandSubcommandGroupOption'. Types of property 'options' are incompatible. Type 'CommandSubcommandOption[] | undefined' is not assignable to type 'APIApplicationCommandSubcommandOption[] | undefined'. Type 'CommandSubcommandOption[]' is not assignable to type 'APIApplicationCommandSubcommandOption[]'. Type 'CommandSubcommandOption' is not assignable to type 'APIApplicationCommandSubcommandOption'. Types of property 'options' are incompatible. Type 'unknown[] | undefined' is not assignable to type '{ foo: string; }[] | undefined'. Type 'unknown[]' is not assignable to type '{ foo: string; }[]'. Type 'unknown' is not assignable to type '{ foo: string; }'.
• Type '{ options?: CommandSubcommandOption[]; }' is not assignable to type 'APIApplicationCommandSubcommandGroupOption'. Types of property 'options' are incompatible. Type 'CommandSubcommandOption[] | undefined' is not assignable to type 'APIApplicationCommandSubcommandOption[] | undefined'.

Historical Information

Version

Reproduction Outputs

4.2.2, 4.3.2, 4.4.2, 4.5.2, 4.6.2

❌ Failed: - Type '{ options?: CommandSubcommandOption[] | undefined; }' is not assignable to type 'APIApplicationCommandSubcommandGroupOption'. Types of property 'options' are incompatible. Type 'CommandSubcommandOption[] | undefined' is not assignable to type 'APIApplicationCommandSubcommandOption[] | undefined'. Type 'CommandSubcommandOption[]' is not assignable to type 'APIApplicationCommandSubcommandOption[]'. Type 'CommandSubcommandOption' is not assignable to type 'APIApplicationCommandSubcommandOption'. Types of property 'options' are incompatible. Type 'unknown[] | undefined' is not assignable to type '{ foo: string; }[] | undefined'. Type 'unknown[]' is not assignable to type '{ foo: string; }[]'. Type 'unknown' is not assignable to type '{ foo: string; }'.

[typescript-bot]

👋 Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of this repro running against the nightly TypeScript.

---

Comment by @RyanCavanaugh

❌ Failed: -

• Type 'CommandSubcommandGroupOption' is not assignable to type 'APIApplicationCommandSubcommandGroupOption'. Types of property 'options' are incompatible. Type 'CommandSubcommandOption[] | undefined' is not assignable to type 'APIApplicationCommandSubcommandOption[] | undefined'. Type 'CommandSubcommandOption[]' is not assignable to type 'APIApplicationCommandSubcommandOption[]'. Type 'CommandSubcommandOption' is not assignable to type 'APIApplicationCommandSubcommandOption'. Types of property 'options' are incompatible. Type 'unknown[] | undefined' is not assignable to type '{ foo: string; }[] | undefined'. Type 'unknown[]' is not assignable to type '{ foo: string; }[]'. Type 'unknown' is not assignable to type '{ foo: string; }'.
• Type '{ options?: CommandSubcommandOption[]; }' is not assignable to type 'APIApplicationCommandSubcommandGroupOption'. Types of property 'options' are incompatible. Type 'CommandSubcommandOption[] | undefined' is not assignable to type 'APIApplicationCommandSubcommandOption[] | undefined'.

Historical Information

Version

Reproduction Outputs

4.2.2, 4.3.2, 4.4.2, 4.5.2, 4.6.2

❌ Failed: - Type '{ options?: CommandSubcommandOption[] | undefined; }' is not assignable to type 'APIApplicationCommandSubcommandGroupOption'. Types of property 'options' are incompatible. Type 'CommandSubcommandOption[] | undefined' is not assignable to type 'APIApplicationCommandSubcommandOption[] | undefined'. Type 'CommandSubcommandOption[]' is not assignable to type 'APIApplicationCommandSubcommandOption[]'. Type 'CommandSubcommandOption' is not assignable to type 'APIApplicationCommandSubcommandOption'. Types of property 'options' are incompatible. Type 'unknown[] | undefined' is not assignable to type '{ foo: string; }[] | undefined'. Type 'unknown[]' is not assignable to type '{ foo: string; }[]'. Type 'unknown' is not assignable to type '{ foo: string; }'.

[andrewbranch]

@typescript-bot bisect good v3.8.3 bad v3.9.7

[typescript-bot]

The change between v3.8.3 and v3.9.7 occurred at b8baf48.