commitlint: do not use empty class for None

Empty classes result in strange issues that turn the
TS compiler into not very helpful. E.g.:
https://stackoverflow.com/questions/78953267/why-is-typescript-not-throwing-a-compile-time-error-when-constructor-is-not-used

NOTE: we still mark the new methods as deprecated to
give a hint that `instanceof` usage is better. These
tooltips will be properly shown by IDEs and linters
according to:
https://stackoverflow.com/a/62991642/544947

commitlint/fpHelpers.ts

@@ -1,9 +1,35 @@
-export class None {}
+interface IOption {
+    /**
+     * @deprecated it is better to use `if (foo instanceof None)` so that you can access the .value in the `else` case
+     **/
+    IsNone(): boolean;
+    /**
+     * @deprecated it is better to use `if (!(foo instanceof None))` so that you can access the .value inside the `if` block
+     **/
+    IsSome(): boolean;
+}
+
+export class None {
+    public IsNone(): boolean {
+        return true;
+    }
+    public IsSome(): boolean {
+        return false;
+    }
+}
 export class Some<T> {
     value: T;
 
     constructor(val: T) {
         this.value = val;
     }
+
+    public IsNone(): boolean {
+        return false;
+    }
+    public IsSome(): boolean {
+        return true;
+    }
 }
-export type Option<T> = None | Some<T>;
+
+export type Option<T> = (None | Some<T>) & IOption;

commitlint/tests/testHelpers.ts

@@ -19,6 +19,15 @@ test("testing Options", () => {
     expect(typeGuard(bar)).toBe("4");
 });
 
+test("testing Is methods", () => {
+    let foo: Option<number> = new None();
+    let bar: Option<number> = new Some(2);
+    expect(foo.IsNone()).toBe(true);
+    expect(bar.IsNone()).toBe(false);
+    expect(foo.IsSome()).toBe(false);
+    expect(bar.IsSome()).toBe(true);
+});
+
 export function runCommitLintOnMsg(inputMsg: string) {
     // FIXME: should we .lowerCase().startsWith("win") in case it starts
     // returning Win64 in the future? thing is, our CI doesn't like this