LibJS: Add static initializers to classes

Author: https://github.com/davidot
Commit: 6b2accce31
Pull-request: https://github.com/SerenityOS/serenity/pull/10470
Issue: https://github.com/SerenityOS/serenity/issues/7044
Issue: https://github.com/SerenityOS/serenity/issues/8574
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibJS/Tests/classes/class-static-initializers.js

@@ -0,0 +1,48 @@
+test("basic functionality", () => {
+    var called = false;
+    class A {
+        static {
+            expect(called).toBeFalse();
+            expect(this.name).toBe("A");
+            called = true;
+        }
+    }
+
+    expect(called).toBeTrue();
+    new A();
+    expect(called).toBeTrue();
+});
+
+test("called in order", () => {
+    var i = 0;
+    class A {
+        static {
+            expect(i).toBe(0);
+            i++;
+        }
+
+        static method() {
+            return 2;
+        }
+
+        static {
+            expect(i).toBe(1);
+            i++;
+        }
+    }
+
+    expect(i).toBe(2);
+    new A();
+    expect(i).toBe(2);
+});
+
+test("correct this", () => {
+    var thisValue = null;
+    class A {
+        static {
+            thisValue = this;
+        }
+    }
+
+    expect(thisValue).toBe(A);
+});