Merge pull request #4888 from ethereum/disallow_single_statement_vardecl_if_while_for

Disallow single statement var decl in if/while/for without blocks

2 files changed, 25 insertions, 2 deletions

diff --git a/libsolidity/analysis/SyntaxChecker.cpp b/libsolidity/analysis/SyntaxChecker.cpp
index ac4fa72b..0bc20f2e 100644
--- a/libsolidity/analysis/SyntaxChecker.cpp
+++ b/libsolidity/analysis/SyntaxChecker.cpp
@@ -138,9 +138,25 @@ void SyntaxChecker::endVisit(ModifierDefinition const& _modifier)
 	m_placeholderFound = false;
 }
 
-bool SyntaxChecker::visit(WhileStatement const&)
+void SyntaxChecker::checkSingleStatementVariableDeclaration(ASTNode const& _statement)
+{
+	auto varDecl = dynamic_cast<VariableDeclarationStatement const*>(&_statement);
+	if (varDecl)
+		m_errorReporter.syntaxError(_statement.location(), "Variable declarations can only be used inside blocks.");
+}
+
+bool SyntaxChecker::visit(IfStatement const& _ifStatement)
+{
+	checkSingleStatementVariableDeclaration(_ifStatement.trueStatement());
+	if (Statement const* _statement = _ifStatement.falseStatement())
+		checkSingleStatementVariableDeclaration(*_statement);
+	return true;
+}
+
+bool SyntaxChecker::visit(WhileStatement const& _whileStatement)
 {
 	m_inLoopDepth++;
+	checkSingleStatementVariableDeclaration(_whileStatement.body());
 	return true;
 }
 
@@ -149,9 +165,10 @@ void SyntaxChecker::endVisit(WhileStatement const&)
 	m_inLoopDepth--;
 }
 
-bool SyntaxChecker::visit(ForStatement const&)
+bool SyntaxChecker::visit(ForStatement const& _forStatement)
 {
 	m_inLoopDepth++;
+	checkSingleStatementVariableDeclaration(_forStatement.body());
 	return true;
 }
 
diff --git a/libsolidity/analysis/SyntaxChecker.h b/libsolidity/analysis/SyntaxChecker.h
index 897df676..f5716bf9 100644
--- a/libsolidity/analysis/SyntaxChecker.h
+++ b/libsolidity/analysis/SyntaxChecker.h
@@ -52,6 +52,12 @@ private:
 	virtual bool visit(ModifierDefinition const& _modifier) override;
 	virtual void endVisit(ModifierDefinition const& _modifier) override;
 
+	/// Reports an error if _statement is a VariableDeclarationStatement.
+	/// Used by if/while/for to check for single statement variable declarations
+	/// without a block.
+	void checkSingleStatementVariableDeclaration(ASTNode const& _statement);
+
+	virtual bool visit(IfStatement const& _ifStatement) override;
 	virtual bool visit(WhileStatement const& _whileStatement) override;
 	virtual void endVisit(WhileStatement const& _whileStatement) override;
 	virtual bool visit(ForStatement const& _forStatement) override;