Incorrect type inference of deep nested types

[captain-yossarian]

Bug Report

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💻 Code

type ZERO = 0
type Next<T> = T extends ZERO ? { v: ZERO } : (T extends { v: infer U } ? { v: Next<U> } : never)

type ONE = Next<ZERO>
type TWO = Next<ONE>
type THREE = Next<TWO>
type FOUR = Next<THREE>
type FIVE = Next<FOUR>
type SIX = Next<FIVE>
type SEVEN = Next<SIX>
type EIGHT = Next<SEVEN>
type NINE = Next<EIGHT>
type TEN = Next<NINE>

type TEq<T, P> = T extends P ? (P extends T ? true : never) : never

let v1: TEq<TWO, TWO> = true // correct: types is equal
let v3: TEq<SIX, SEVEN> = true // error: why type of v3 inferred as true?

type Result = TEq<SIX, SEVEN>

type Result_the_same_type = {
    v: {
        v: {
            v: {
                v: {
                    v: {
                        v: ZERO;
                    };
                };
            };
        };
    };
} extends {
    v: {
        v: {
            v: {
                v: {
                    v: {
                        v: {
                            v: ZERO
                        };
                    };
                };
            };
        };
    };
} ? true : false // false

/**
 * Why Result is true
 * and Result_the_same_type is false
 */

As you see Result and Result_the_same_type are structuraly equal.

🙁 Actual behavior

Result is true
Result_the_same_type is false

🙂 Expected behavior

Result should be false

[RyanCavanaugh]

See #35533 (comment)

[DarkGenius]

See #35533 (comment)

Is there some workaround for this case?

[captain-yossarian]

@DarkGenius what about:

type AllowedLevels = 1 | 2 | 3 | 4 | 5;

type Levels<T, Cache extends Array<any> = []> = {

  [P in keyof T]: T[P] extends object ? Levels<T[P], [...Cache, 1]> : Cache

}[keyof T];

type Allowed<T> = Levels<T> extends { length: AllowedLevels } ? true : false;

type Result=Allowed<SIX> // true
type Result2=Allowed<SEVEN> // false

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.