LibJS: Add support for public fields in classes

Userland/Libraries/LibJS/Tests/classes/class-public-fields.js

@@ -0,0 +1,87 @@
+test("basic functionality", () => {
+    class A {
+        number = 3;
+
+        string = "foo";
+
+        uninitialized;
+    }
+
+    const a = new A();
+    expect(a.number).toBe(3);
+    expect(a.string).toBe("foo");
+    expect(a.uninitialized).toBeUndefined();
+});
+
+test("extended name syntax", () => {
+    class A {
+        "field with space" = 1;
+
+        12 = "twelve";
+
+        [`he${"llo"}`] = 3;
+    }
+
+    const a = new A();
+    expect(a["field with space"]).toBe(1);
+    expect(a[12]).toBe("twelve");
+    expect(a.hello).toBe(3);
+});
+
+test("initializer has correct this value", () => {
+    class A {
+        this_val = this;
+
+        this_name = this.this_val;
+    }
+
+    const a = new A();
+    expect(a.this_val).toBe(a);
+    expect(a.this_name).toBe(a);
+});
+
+test("static fields", () => {
+    class A {
+        static simple = 1;
+        simple = 2;
+
+        static "with space" = 3;
+
+        static 24 = "two dozen";
+
+        static [`he${"llo"}`] = "friends";
+
+        static this_val = this;
+        static this_name = this.name;
+        static this_val2 = this.this_val;
+    }
+
+    expect(A.simple).toBe(1);
+    expect(A["with space"]).toBe(3);
+    expect(A[24]).toBe("two dozen");
+    expect(A.hello).toBe("friends");
+
+    expect(A.this_val).toBe(A);
+    expect(A.this_name).toBe("A");
+    expect(A.this_val2).toBe(A);
+
+    const a = new A();
+    expect(a.simple).toBe(2);
+});
+
+test("with super class", () => {
+    class A {
+        super_field = 3;
+    }
+
+    class B extends A {
+        references_super_field = super.super_field;
+        arrow_ref_super = () => (super.super_field = 4);
+    }
+
+    const b = new B();
+    expect(b.super_field).toBe(3);
+    expect(b.references_super_field).toBeUndefined();
+    b.arrow_ref_super();
+    expect(b.super_field).toBe(4);
+});