LibJS: Integrate labels into the Interpreter

The interpreter now considers a statement or block's label when
considering whether or not to break. All statements can be labelled.

Libraries/LibJS/AST.cpp

@@ -282,9 +282,9 @@ Value ForStatement::execute(Interpreter& interpreter) const
             if (interpreter.exception())
                 return {};
             if (interpreter.should_unwind()) {
-                if (interpreter.should_unwind_until(ScopeType::Continuable)) {
+                if (interpreter.should_unwind_until(ScopeType::Continuable, m_label)) {
                     interpreter.stop_unwind();
-                } else if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+                } else if (interpreter.should_unwind_until(ScopeType::Breakable, m_label)) {
                     interpreter.stop_unwind();
                     break;
                 } else {
@@ -303,9 +303,9 @@ Value ForStatement::execute(Interpreter& interpreter) const
             if (interpreter.exception())
                 return {};
             if (interpreter.should_unwind()) {
-                if (interpreter.should_unwind_until(ScopeType::Continuable)) {
+                if (interpreter.should_unwind_until(ScopeType::Continuable, m_label)) {
                     interpreter.stop_unwind();
-                } else if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+                } else if (interpreter.should_unwind_until(ScopeType::Breakable, m_label)) {
                     interpreter.stop_unwind();
                     break;
                 } else {
@@ -370,9 +370,9 @@ Value ForInStatement::execute(Interpreter& interpreter) const
             if (interpreter.exception())
                 return {};
             if (interpreter.should_unwind()) {
-                if (interpreter.should_unwind_until(ScopeType::Continuable)) {
+                if (interpreter.should_unwind_until(ScopeType::Continuable, m_label)) {
                     interpreter.stop_unwind();
-                } else if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+                } else if (interpreter.should_unwind_until(ScopeType::Breakable, m_label)) {
                     interpreter.stop_unwind();
                     break;
                 } else {
@@ -437,9 +437,9 @@ Value ForOfStatement::execute(Interpreter& interpreter) const
         if (interpreter.exception())
             return {};
         if (interpreter.should_unwind()) {
-            if (interpreter.should_unwind_until(ScopeType::Continuable)) {
+            if (interpreter.should_unwind_until(ScopeType::Continuable, m_label)) {
                 interpreter.stop_unwind();
-            } else if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+            } else if (interpreter.should_unwind_until(ScopeType::Breakable, m_label)) {
                 interpreter.stop_unwind();
                 break;
             } else {
@@ -1635,7 +1635,7 @@ Value SwitchStatement::execute(Interpreter& interpreter) const
             if (interpreter.exception())
                 return {};
             if (interpreter.should_unwind()) {
-                if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+                if (interpreter.should_unwind_until(ScopeType::Breakable, m_label)) {
                     interpreter.stop_unwind();
                     return {};
                 }
@@ -1655,13 +1655,13 @@ Value SwitchCase::execute(Interpreter& interpreter) const
 
 Value BreakStatement::execute(Interpreter& interpreter) const
 {
-    interpreter.unwind(ScopeType::Breakable);
+    interpreter.unwind(ScopeType::Breakable, m_target_label);
     return js_undefined();
 }
 
 Value ContinueStatement::execute(Interpreter& interpreter) const
 {
-    interpreter.unwind(ScopeType::Continuable);
+    interpreter.unwind(ScopeType::Continuable, m_target_label);
     return js_undefined();
 }
 

Libraries/LibJS/Interpreter.cpp

@@ -72,8 +72,11 @@ Value Interpreter::run(const Statement& statement, ArgumentVector arguments, Sco
     m_last_value = js_undefined();
     for (auto& node : block.children()) {
         m_last_value = node.execute(*this);
-        if (m_unwind_until != ScopeType::None)
+        if (should_unwind()) {
+            if (should_unwind_until(ScopeType::Breakable, block.label()))
+                stop_unwind();
             break;
+        }
     }
 
     bool did_return = m_unwind_until == ScopeType::Function;

Libraries/LibJS/Interpreter.h

@@ -91,9 +91,18 @@ public:
 
     Heap& heap() { return m_heap; }
 
-    void unwind(ScopeType type) { m_unwind_until = type; }
+    void unwind(ScopeType type, FlyString label = {})
+    {
+        m_unwind_until = type;
+        m_unwind_until_label = label;
+    }
     void stop_unwind() { m_unwind_until = ScopeType::None; }
-    bool should_unwind_until(ScopeType type) const { return m_unwind_until == type; }
+    bool should_unwind_until(ScopeType type, FlyString label) const
+    {
+        if (m_unwind_until_label.is_null())
+            return m_unwind_until == type;
+        return m_unwind_until == type && m_unwind_until_label == label;
+    }
     bool should_unwind() const { return m_unwind_until != ScopeType::None; }
 
     Value get_variable(const FlyString& name);
@@ -189,6 +198,7 @@ private:
     Exception* m_exception { nullptr };
 
     ScopeType m_unwind_until { ScopeType::None };
+    FlyString m_unwind_until_label;
 
     Console m_console;
 };

Libraries/LibJS/Parser.cpp

@@ -269,9 +269,11 @@ NonnullRefPtr<Statement> Parser::parse_statement()
         consume();
         return create_ast_node<EmptyStatement>();
     default:
-        auto result = try_parse_labelled_statement();
+        if (match(TokenType::Identifier)) {
-        if (!result.is_null())
+            auto result = try_parse_labelled_statement();
-            return result.release_nonnull();
+            if (!result.is_null())
+                return result.release_nonnull();
+        }
         if (match_expression()) {
             auto expr = parse_expression(0);
             consume_or_insert_semicolon();
@@ -1117,7 +1119,7 @@ NonnullRefPtr<BreakStatement> Parser::parse_break_statement()
         consume();
         return create_ast_node<BreakStatement>(target_label);
     }
-    if (match_identifier_name() && !m_parser_state.m_current_token.trivia().contains('\n'))
+    if (match(TokenType::Identifier) && !m_parser_state.m_current_token.trivia().contains('\n'))
         target_label = consume().value();
     consume_or_insert_semicolon();
     return create_ast_node<BreakStatement>(target_label);
@@ -1131,7 +1133,7 @@ NonnullRefPtr<ContinueStatement> Parser::parse_continue_statement()
         consume();
         return create_ast_node<ContinueStatement>(target_label);
     }
-    if (match_identifier_name() && !m_parser_state.m_current_token.trivia().contains('\n'))
+    if (match(TokenType::Identifier) && !m_parser_state.m_current_token.trivia().contains('\n'))
         target_label = consume().value();
     consume_or_insert_semicolon();
     return create_ast_node<ContinueStatement>(target_label);

Libraries/LibJS/Tests/automatic-semicolon-insertion.js

@@ -25,9 +25,13 @@ function bar() {
 }
 
 function foo() {
+    label:
     for (var i = 0; i < 4; i++) {
         break // semicolon inserted here
         continue // semicolon inserted here
+
+        break label // semicolon inserted here
+        continue label // semicolon inserted here
     }
 
     var j // semicolon inserted here
@@ -39,8 +43,25 @@ function foo() {
     1;
 var curly/* semicolon inserted here */}
 
+function baz() {
+    let counter = 0;
+    let outer;
+
+    outer:
+    for (let i = 0; i < 5; ++i) {
+        for (let j = 0; j < 5; ++j) {
+            continue // semicolon inserted here
+            outer // semicolon inserted here
+        }
+        counter++;
+    }
+
+    return counter;
+}
+
 try {
     assert(foo() === undefined);
+    assert(baz() === 5);
 
     console.log("PASS");
 } catch (e) {

Libraries/LibJS/Tests/labels.js

@@ -1,12 +1,42 @@
 load("test-common.js");
 
 try {
-    test:
+    test: {
-    {
         let o = 1;
         assert(o === 1);
+        break test;
+        assertNotReached();
     }
 
+    outer: {
+        {
+            break outer;
+        }
+        assertNotReached();
+    }
+
+    let counter = 0;
+    outer:
+    for (a of [1, 2, 3]) {
+        for (b of [4, 5, 6]) {
+            if (a === 2 && b === 5)
+                break outer;
+            counter++;
+        }
+    }
+    assert(counter === 4);
+
+    let counter = 0;
+    outer:
+    for (a of [1, 2, 3]) {
+        for (b of [4, 5, 6]) {
+            if (b === 6)
+                continue outer;
+            counter++;
+        }
+    }
+    assert(counter === 6);
+
     console.log("PASS");
 } catch (e) {
     console.log("FAIL: " + e);