PartialEq

The PartialEq macro generates an equals() method for field-by-field structural equality comparison. This is analogous to Rust’s PartialEq trait, enabling value-based equality semantics instead of reference equality.

Generated Output

Type	Generated Code	Description
Class	`classNameEquals(a, b)` + `static equals(a, b)`	Standalone function + static wrapper method
Enum	`enumNameEquals(a: EnumName, b: EnumName): boolean`	Standalone function using strict equality
Interface	`interfaceNameEquals(a: InterfaceName, b: InterfaceName): boolean`	Standalone function comparing fields
Type Alias	`typeNameEquals(a: TypeName, b: TypeName): boolean`	Standalone function with type-appropriate comparison

Comparison Strategy

The generated equality check:

Identity check: a === b returns true immediately
Field comparison: Compares each non-skipped field

Type-Specific Comparisons

Type	Comparison Method
Primitives	Strict equality (`===`)
Arrays	Length + element-by-element (recursive)
`Date`	`getTime()` comparison
`Map`	Size + entry-by-entry comparison
`Set`	Size + membership check
Objects	Calls `equals()` if available, else `===`

Field-Level Options

The @partialEq decorator supports:

skip - Exclude the field from equality comparison

Example

Before (Your Code)

/** @derive(PartialEq, Hash) */
class User {
    id: number;
    name: string;

    /** @partialEq({ skip: true }) @hash({ skip: true }) */
    cachedScore: number;
}

After (Generated)

class User {
    id: number;
    name: string;

    cachedScore: number;

    static equals(a: User, b: User): boolean {
        return userEquals(a, b);
    }

    static hashCode(value: User): number {
        return userHashCode(value);
    }
}

export function userEquals(a: User, b: User): boolean {
    if (a === b) return true;
    return a.id === b.id && a.name === b.name;
}

export function userHashCode(value: User): number {
    let hash = 17;
    hash =
        (hash * 31 +
            (Number.isInteger(value.id)
                ? value.id | 0
                : value.id
                      .toString()
                      .split('')
                      .reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0))) |
        0;
    hash =
        (hash * 31 +
            (value.name ?? '').split('').reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0)) |
        0;
    return hash;
}

Generated output:

class User {
    id: number;
    name: string;

    cachedScore: number;

    static equals(a: User, b: User): boolean {
        return userEquals(a, b);
    }

    static hashCode(value: User): number {
        return userHashCode(value);
    }
}

export function userEquals(a: User, b: User): boolean {
    if (a === b) return true;
    return a.id === b.id && a.name === b.name;
}

export function userHashCode(value: User): number {
    let hash = 17;
    hash =
        (hash * 31 +
            (Number.isInteger(value.id)
                ? value.id | 0
                : value.id
                      .toString()
                      .split('')
                      .reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0))) |
        0;
    hash =
        (hash * 31 +
            (value.name ?? '').split('').reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0)) |
        0;
    return hash;
}

Equality Contract

When implementing PartialEq, consider also implementing Hash:

Reflexivity: a.equals(a) is always true
Symmetry: a.equals(b) implies b.equals(a)
Hash consistency: Equal objects must have equal hash codes

To maintain the hash contract, skip the same fields in both PartialEq and Hash:

Before (Your Code)

/** @derive(PartialEq, Hash) */
class User {
    id: number;
    name: string;

    /** @partialEq({ skip: true }) @hash({ skip: true }) */
    cachedScore: number;
}

After (Generated)

class User {
    id: number;
    name: string;

    cachedScore: number;

    static equals(a: User, b: User): boolean {
        return userEquals(a, b);
    }

    static hashCode(value: User): number {
        return userHashCode(value);
    }
}

export function userEquals(a: User, b: User): boolean {
    if (a === b) return true;
    return a.id === b.id && a.name === b.name;
}

export function userHashCode(value: User): number {
    let hash = 17;
    hash =
        (hash * 31 +
            (Number.isInteger(value.id)
                ? value.id | 0
                : value.id
                      .toString()
                      .split('')
                      .reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0))) |
        0;
    hash =
        (hash * 31 +
            (value.name ?? '').split('').reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0)) |
        0;
    return hash;
}

Generated output:

class User {
    id: number;
    name: string;

    cachedScore: number;

    static equals(a: User, b: User): boolean {
        return userEquals(a, b);
    }

    static hashCode(value: User): number {
        return userHashCode(value);
    }
}

export function userEquals(a: User, b: User): boolean {
    if (a === b) return true;
    return a.id === b.id && a.name === b.name;
}

export function userHashCode(value: User): number {
    let hash = 17;
    hash =
        (hash * 31 +
            (Number.isInteger(value.id)
                ? value.id | 0
                : value.id
                      .toString()
                      .split('')
                      .reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0))) |
        0;
    hash =
        (hash * 31 +
            (value.name ?? '').split('').reduce((h, c) => (h * 31 + c.charCodeAt(0)) | 0, 0)) |
        0;
    return hash;
}