Declaration includes incorrect 'any' types for inferred nested property members

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TypeScript Version: 3.5.3

Search Terms: declaration any inferred type

Code

I'm using some helper functions to construct type guards where the type predicate is inferred:

const isObject = (value: unknown): value is { [key: string]: unknown } =>
    typeof value === 'object' && value !== null
  
const isObjectWith = <S>(
  predicates: {
    readonly [P in keyof Required<S>]: (value: unknown) => value is S[P]
  },
) => (value: unknown): value is S =>
    isObject(value) && entries(predicates).every(([k, p]) => p(value[k]))

const isNumber = (x: unknown): x is number => typeof x === 'number'

const entries = <V extends object>(object: V): ReadonlyArray<readonly [string & keyof V, V[string & keyof V]]> =>
  Object.entries(object) as Array<[string & keyof V, V[string & keyof V]]>

export const isFoo = isObjectWith({
  a: isNumber,
})

export const isBar = isObjectWith({
  b: isFoo,
})

Expected behavior:
The .d.ts file should contain all the inferred property types:

export declare const isFoo: (value: unknown) => value is {
    a: number;
};
export declare const isBar: (value: unknown) => value is {
    b: {
        a: number;
    };
};
//# sourceMappingURL=repro.d.ts.map

Actual behavior:

The .d.ts file contains any for the nested property type:

export declare const isFoo: (value: unknown) => value is {
    a: number;
};
export declare const isBar: (value: unknown) => value is {
    b: {
        a: any;
    };
};
//# sourceMappingURL=repro.d.ts.map

Interestingly, if I force TypeScript to "evaluate" the inferred type using a mapped type, I get the correct result:

const _isFoo = isObjectWith({
  a: isNumber,
})
type GuardedType<T> = T extends (value: any) =>
  value is infer S ? { [K in keyof S]: S[K] }
  : never
export const isFoo: (value: unknown) => value is GuardedType<typeof _isFoo> = _isFoo

Related Issues: #19565