LibJS: Add support for "continue" inside "for" statements :^)

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/9ebd066ac84

Libraries/LibJS/AST.cpp

@@ -215,6 +215,16 @@ Value ForStatement::execute(Interpreter& interpreter) const
             last_value = interpreter.run(*m_body);
             if (interpreter.exception())
                 return {};
+            if (interpreter.should_unwind()) {
+                if (interpreter.should_unwind_until(ScopeType::Continuable)) {
+                    interpreter.stop_unwind();
+                } else if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+                    interpreter.stop_unwind();
+                    break;
+                } else {
+                    return {};
+                }
+            }
             if (m_update) {
                 m_update->execute(interpreter);
                 if (interpreter.exception())
@@ -226,6 +236,16 @@ Value ForStatement::execute(Interpreter& interpreter) const
             last_value = interpreter.run(*m_body);
             if (interpreter.exception())
                 return {};
+            if (interpreter.should_unwind()) {
+                if (interpreter.should_unwind_until(ScopeType::Continuable)) {
+                    interpreter.stop_unwind();
+                } else if (interpreter.should_unwind_until(ScopeType::Breakable)) {
+                    interpreter.stop_unwind();
+                    break;
+                } else {
+                    return {};
+                }
+            }
             if (m_update) {
                 m_update->execute(interpreter);
                 if (interpreter.exception())
@@ -759,7 +779,7 @@ Value VariableDeclaration::execute(Interpreter& interpreter) const
     return {};
 }
 
-Value VariableDeclarator::execute(Interpreter &) const
+Value VariableDeclarator::execute(Interpreter&) const
 {
     // NOTE: This node is handled by VariableDeclaration.
     ASSERT_NOT_REACHED();
@@ -1005,6 +1025,12 @@ Value BreakStatement::execute(Interpreter& interpreter) const
     return {};
 }
 
+Value ContinueStatement::execute(Interpreter& interpreter) const
+{
+    interpreter.unwind(ScopeType::Continuable);
+    return {};
+}
+
 void SwitchStatement::dump(int indent) const
 {
     ASTNode::dump(indent);

Libraries/LibJS/AST.h

@@ -814,4 +814,14 @@ private:
     virtual const char* class_name() const override { return "BreakStatement"; }
 };
 
+class ContinueStatement final : public Statement {
+public:
+    ContinueStatement() {}
+
+    virtual Value execute(Interpreter&) const override;
+
+private:
+    virtual const char* class_name() const override { return "ContinueStatement"; }
+};
+
 }

Libraries/LibJS/Interpreter.h

@@ -43,6 +43,7 @@ enum class ScopeType {
     Block,
     Try,
     Breakable,
+    Continuable,
 };
 
 struct Variable {

Libraries/LibJS/Lexer.cpp

@@ -48,6 +48,7 @@ Lexer::Lexer(StringView source)
         s_keywords.set("catch", TokenType::Catch);
         s_keywords.set("class", TokenType::Class);
         s_keywords.set("const", TokenType::Const);
+        s_keywords.set("continue", TokenType::Continue);
         s_keywords.set("default", TokenType::Default);
         s_keywords.set("delete", TokenType::Delete);
         s_keywords.set("do", TokenType::Do);

Libraries/LibJS/Parser.cpp

@@ -208,6 +208,8 @@ NonnullRefPtr<Statement> Parser::parse_statement()
         return parse_try_statement();
     case TokenType::Break:
         return parse_break_statement();
+    case TokenType::Continue:
+         return parse_continue_statement();
     case TokenType::Switch:
         return parse_switch_statement();
     case TokenType::Do:
@@ -686,6 +688,13 @@ NonnullRefPtr<BreakStatement> Parser::parse_break_statement()
     return create_ast_node<BreakStatement>();
 }
 
+NonnullRefPtr<ContinueStatement> Parser::parse_continue_statement()
+{
+    consume(TokenType::Continue);
+    // FIXME: Handle labels.
+    return create_ast_node<ContinueStatement>();
+}
+
 NonnullRefPtr<ConditionalExpression> Parser::parse_conditional_expression(NonnullRefPtr<Expression> test)
 {
     consume(TokenType::QuestionMark);
@@ -938,6 +947,7 @@ bool Parser::match_statement() const
         || type == TokenType::CurlyOpen
         || type == TokenType::Switch
         || type == TokenType::Break
+        || type == TokenType::Continue
         || type == TokenType::Var;
 }
 

Libraries/LibJS/Parser.h

@@ -58,6 +58,7 @@ public:
     NonnullRefPtr<SwitchStatement> parse_switch_statement();
     NonnullRefPtr<SwitchCase> parse_switch_case();
     NonnullRefPtr<BreakStatement> parse_break_statement();
+    NonnullRefPtr<ContinueStatement> parse_continue_statement();
     NonnullRefPtr<DoWhileStatement> parse_do_while_statement();
     NonnullRefPtr<ConditionalExpression> parse_conditional_expression(NonnullRefPtr<Expression> test);
 

Libraries/LibJS/Tests/continue-basic.js

@@ -0,0 +1,14 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    var j = 0;
+    for (var i = 0; i < 9; ++i) {
+        if (i == 3)
+            continue;
+        ++j;
+    }
+    assert(j == 8);
+    console.log("PASS");
+} catch {
+}
+

Libraries/LibJS/Token.h

@@ -50,6 +50,7 @@ namespace JS {
     __ENUMERATE_JS_TOKEN(Colon)                       \
     __ENUMERATE_JS_TOKEN(Comma)                       \
     __ENUMERATE_JS_TOKEN(Const)                       \
+    __ENUMERATE_JS_TOKEN(Continue)                    \
     __ENUMERATE_JS_TOKEN(CurlyClose)                  \
     __ENUMERATE_JS_TOKEN(CurlyOpen)                   \
     __ENUMERATE_JS_TOKEN(Default)                     \