LibJS: Actually leave the current function scope on "return"

We now unwind until the nearest function-level scope on the scope stack
when executing a return statement.

3 files changed, 13 insertions, 6 deletions

diff --git a/Libraries/LibJS/AST.cpp b/Libraries/LibJS/AST.cpp
index d3b34dc027..f89b3b0f5a 100644
--- a/Libraries/LibJS/AST.cpp
+++ b/Libraries/LibJS/AST.cpp
@@ -81,7 +81,7 @@ Value CallExpression::execute(Interpreter& interpreter) const
 Value ReturnStatement::execute(Interpreter& interpreter) const
 {
     auto value = argument() ? argument()->execute(interpreter) : js_undefined();
-    interpreter.do_return();
+    interpreter.unwind(ScopeType::Function);
     return value;
 }
 
diff --git a/Libraries/LibJS/Interpreter.cpp b/Libraries/LibJS/Interpreter.cpp
index ac80f688b0..f602336bc4 100644
--- a/Libraries/LibJS/Interpreter.cpp
+++ b/Libraries/LibJS/Interpreter.cpp
@@ -61,8 +61,13 @@ Value Interpreter::run(const Statement& statement, Vector<Argument> arguments, S
     Value last_value = js_undefined();
     for (auto& node : block.children()) {
         last_value = node.execute(*this);
+        if (m_unwind_until != ScopeType::None)
+            break;
     }
 
+    if (m_unwind_until == scope_type)
+        m_unwind_until = ScopeType::None;
+
     exit_scope(block);
     return last_value;
 }
@@ -80,11 +85,10 @@ void Interpreter::exit_scope(const ScopeNode& scope_node)
 {
     while (m_scope_stack.last().scope_node.ptr() != &scope_node)
         m_scope_stack.take_last();
-}
 
-void Interpreter::do_return()
-{
-    dbg() << "FIXME: Implement Interpreter::do_return()";
+    // If we unwind all the way, just reset m_unwind_until so that future "return" doesn't break.
+    if (m_scope_stack.is_empty())
+        m_unwind_until = ScopeType::None;
 }
 
 void Interpreter::declare_variable(const FlyString& name, DeclarationType declaration_type)
diff --git a/Libraries/LibJS/Interpreter.h b/Libraries/LibJS/Interpreter.h
index 1aa7b87f05..fab56397d1 100644
--- a/Libraries/LibJS/Interpreter.h
+++ b/Libraries/LibJS/Interpreter.h
@@ -37,6 +37,7 @@
 namespace JS {
 
 enum class ScopeType {
+    None,
     Function,
     Block,
 };
@@ -74,7 +75,7 @@ public:
 
     Heap& heap() { return m_heap; }
 
-    void do_return();
+    void unwind(ScopeType type) { m_unwind_until = type; }
 
     Value get_variable(const FlyString& name);
     void set_variable(const FlyString& name, Value, bool first_assignment = false);
@@ -114,6 +115,8 @@ private:
     Object* m_string_prototype { nullptr };
     Object* m_object_prototype { nullptr };
     Object* m_array_prototype { nullptr };
+
+    ScopeType m_unwind_until { ScopeType::None };
 };
 
 }