Solidity ForStatements expressions are now optional

libsolidity/AST_accept.h

@@ -271,9 +271,12 @@ void ForStatement::accept(ASTVisitor& _visitor)
 {
 	if (_visitor.visit(*this))
 	{
-		m_initExpression->accept(_visitor);
-		m_condExpression->accept(_visitor);
-		m_loopExpression->accept(_visitor);
+		if (m_initExpression)
+			m_initExpression->accept(_visitor);
+		if (m_condExpression)
+			m_condExpression->accept(_visitor);
+		if (m_loopExpression)
+			m_loopExpression->accept(_visitor);
 		m_body->accept(_visitor);
 	}
 	_visitor.endVisit(*this);
@@ -283,9 +286,12 @@ void ForStatement::accept(ASTConstVisitor& _visitor) const
 {
 	if (_visitor.visit(*this))
 	{
-		m_initExpression->accept(_visitor);
-		m_condExpression->accept(_visitor);
-		m_loopExpression->accept(_visitor);
+		if (m_initExpression)
+			m_initExpression->accept(_visitor);
+		if (m_condExpression)
+			m_condExpression->accept(_visitor);
+		if (m_loopExpression)
+			m_loopExpression->accept(_visitor);
 		m_body->accept(_visitor);
 	}
 	_visitor.endVisit(*this);

libsolidity/Parser.cpp

@@ -374,14 +374,25 @@ ASTPointer<WhileStatement> Parser::parseWhileStatement()
 ASTPointer<ForStatement> Parser::parseForStatement()
 {
 	ASTNodeFactory nodeFactory(*this);
+	ASTPointer<ASTNode> initExpression;
+	ASTPointer<Expression> conditionExpression;
+	ASTPointer<ExpressionStatement> loopExpression;
 	expectToken(Token::FOR);
 	expectToken(Token::LPAREN);
-	ASTPointer<ASTNode> initExpression = parseVardefOrExprstatement();
+
+	// LTODO: Maybe here have some predicate like peekExpression() instead of checking for semicolon and RPAREN?
+	if (m_scanner->getCurrentToken() != Token::SEMICOLON)
+		initExpression = parseVardefOrExprstatement();
 	expectToken(Token::SEMICOLON);
-	ASTPointer<Expression> conditionExpression = parseExpression();
+
+	if (m_scanner->getCurrentToken() != Token::SEMICOLON)
+		conditionExpression = parseExpression();
 	expectToken(Token::SEMICOLON);
-	ASTPointer<ExpressionStatement> loopExpression = parseExpressionStatement();
+
+	if (m_scanner->getCurrentToken() != Token::RPAREN)
+		loopExpression = parseExpressionStatement();
 	expectToken(Token::RPAREN);
+
 	ASTPointer<Statement> body = parseStatement();
 	nodeFactory.setEndPositionFromNode(body);
 	return nodeFactory.createNode<ForStatement>(initExpression,

libsolidity/grammar.txt

@@ -20,7 +20,7 @@ Statement = IfStatement | WhileStatement | Block |
 
 IfStatement = 'if' '(' Expression ')' Statement ( 'else' Statement )?
 WhileStatement = 'while' '(' Expression ')' Statement
-ForStatement = 'for' '(' VardefOrExpressionstatement ';' Expression ';' Expressionstatement ')' Statement
+ForStatement = 'for' '(' (VardefOrExpressionstatement)? ';' (Expression)? ';' (Expressionstatement)? ')' Statement
 Continue = 'continue' ';'
 Break = 'break' ';'
 Return = 'return' Expression? ';'

test/solidityParser.cpp

@@ -397,6 +397,18 @@ BOOST_AUTO_TEST_CASE(for_loop_simple_initexpr)
 	BOOST_CHECK_NO_THROW(parseTextExplainError(text));
 }
 
+BOOST_AUTO_TEST_CASE(for_loop_simple_noexpr)
+{
+	char const* text = "contract test {\n"
+					   "  function fun(uint256 a) {\n"
+					   "    uint256 i =0;\n"
+					   "    for (;;)\n"
+					   "    { uint256 x = i; break; continue; }\n"
+					   "  }\n"
+					   "}\n";
+	BOOST_CHECK_NO_THROW(parseTextExplainError(text));
+}
+
 BOOST_AUTO_TEST_CASE(if_statement)
 {
 	char const* text = "contract test {\n"