TS 5.1.0 dev type inference regression when combining conditional/intersection/recursive type #53211
Description
Bug Report
Vue team is witnessing a new weird type behavior difference when upgrading TypeScript.
The typing difference is very subtle. I'm sorry I cannot provide a more concise example here. (The example has already been reduced from 500+ lines to 70 lines ).
The original usage is simple https://tsplay.dev/mxjRXw. I have attached the standalone example in the issue. All critical parts are commented.
🔎 Search Terms
Sorry I could not find a good search term.
🕗 Version & Regression Information
- This changed between versions 4.9.2 and 5.1.0dev
⏯ Playground Link
💻 Code
type ComponentPublicInstance<C, Options> = {
$options: Options & 'intersection anything' // intersection here is critical
} & ExtractComputedReturns<C> // this type intersection is important
type WhatEver<T> = T extends 1 ? true : false
type MixinToOptionTypes<T> = T extends ComponentOptionsBase<
infer C, 1, 1
>
? OptionTypesType<C>
: never
type IntersectionMixin<T> = WhatEver<T> extends true // a conditional is required here for reproduction
? OptionTypesType<{}>
: MixinToOptionTypes<T>
type CreateComponentPublicInstance<
Mixin extends 1 ,
Extends extends 1,
> = ComponentPublicInstance<
(IntersectionMixin<Mixin> & IntersectionMixin<Extends>)['C'],
ComponentOptionsBase<{}, Mixin, Extends>
>
interface ComponentOptionsBase<
_C extends ComputedOptions,
Mixin extends 1,
Extends extends 1,
> {
data?: (
this: CreateComponentPublicInstance<
Mixin,
Extends
>,
) => {} // a function property is required, method syntax cannot reproduce.
}
type ComputedGetter = (...args: any[]) => any
type ComputedOptions = Record<
string,
ComputedGetter | {get: ComputedGetter } // a union type for getter is required
>
type ExtractComputedReturns<T extends any> = {
[key in keyof T]: T[key] extends { get: (...args: any[]) => infer TReturn }
? TReturn
: T[key] extends (...args: any[]) => infer TReturn
? TReturn
: never
}
type OptionTypesType<C = {}> = { C: C }
type Mixin = 1; type Extend = 1;
type A1 = ComponentOptionsBase<any,Mixin,Extend> &{sth?:never}
export type Test1 = A1 extends ComponentOptionsBase<any,any,any>?'yes':'no'
// ^? expect Yes, got No in TS 5.1.0, but Yes in 4.9.5
// following types are for reference. They behave the same.
type A2 = ComponentOptionsBase<any,Mixin,Extend>
export type Test2 = A2 extends ComponentOptionsBase<any,any,any>?'yes':'no'
// ^? yes
type A3 = ComponentOptionsBase<any,Mixin,any> &{sth?:never}
export type Test3 = A3 extends ComponentOptionsBase<any,any,any>?'yes':'no'
// ^? yes
type A4 = ComponentOptionsBase<any,any,Extend> &{sth?:never}
export type Test4 = A4 extends ComponentOptionsBase<any,any,any>?'yes':'no'
// ^? yes🙁 Actual behavior
A1 should always be 'yes' in TS 5.1.0.
🙂 Expected behavior
A1 is 'no' in TS5.1.0, but 'yes' in TS4.9.5