TypeScript Subtraction

type RemoveModifiers<T> = {
  -readonly [P in keyof T]-?: T[P];
};

interface SourceType {
    readonly id?: number;
    readonly name?: string;
}

// The compiler evaluates this by stripping both 'readonly' and '?'
type ProcessedType = {
    -readonly [K in keyof SourceType]-?: SourceType[K];
};

// Resulting type equivalent:
// type ProcessedType = {
//     id: number;
//     name: string;
// }

const numA: number = 10;
const numB: number = 5;
const resultNum: number = numA - numB; // Valid

const bigA: bigint = 10n;
const bigB: bigint = 5n;
const resultBig: bigint = bigA - bigB; // Valid

enum Status { Pending = 1, Active = 2 }
const resultEnum: number = Status.Active - Status.Pending; // Valid

// Compiler Error ts(2365): Operator '-' cannot be applied to types 'number' and 'bigint'.
const invalidMixed = numA - bigA; 

// Compiler Error ts(2362): The left-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.
const invalidString = "10" - 5; 

const positive: number = 42;
const negative: number = -positive; // Evaluates to -42

const bigVal: bigint = 42n;
const negBig: bigint = -bigVal; // Evaluates to -42n

enum Offset { Base = 5 }
const negEnum: number = -Offset.Base; // Evaluates to -5

// Compiler Error ts(2356): An arithmetic operand must be of type 'any', 'number', 'bigint' or an enum type.
const invalidUnary = -"hello";