LibJS: Make "break" actually work inside "switch"

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/e3b92caa6d9

Libraries/LibJS/AST.cpp

@@ -980,8 +980,13 @@ Value SwitchStatement::execute(Interpreter& interpreter) const
             statement.execute(interpreter);
             if (interpreter.exception())
                 return {};
-            if (interpreter.should_unwind())
+            if (interpreter.should_unwind()) {
+                if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+                    interpreter.stop_unwind();
+                    return {};
+                }
                 return {};
+            }
         }
     }
 

Libraries/LibJS/Interpreter.h

@@ -86,6 +86,8 @@ public:
     Heap& heap() { return m_heap; }
 
     void unwind(ScopeType type) { m_unwind_until = type; }
+    void stop_unwind() { m_unwind_until = ScopeType::None; }
+    bool should_unwind_until(ScopeType type) const { return m_unwind_until == type; }
     bool should_unwind() const { return m_unwind_until != ScopeType::None; }
 
     Optional<Value> get_variable(const FlyString& name);

Libraries/LibJS/Tests/switch-break.js

@@ -0,0 +1,25 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    var i = 0;
+    var three;
+    var five;
+
+    for (; i < 9; ) {
+        switch (i) {
+        case 3:
+            three = i;
+            break;
+        case 5:
+            five = i;
+            break;
+        }
+        ++i;
+    }
+    assert(three === 3);
+    assert(five === 5);
+
+    console.log("PASS");
+} catch {
+}
+