js__typescript__jest/src/core/types.ts

export interface Literal {
  type: "literal";
  value: number;
}

export type BinaryOperators = "+" | "-" | "*" | "/";

export interface BinaryOperation {
  type: "binary";
  operator: BinaryOperators;
  left: Expression;
  right: Expression;
}

export type Expression = Literal | BinaryOperation;