Generates a syntax error when declaring a variable declaration's LHS has no named components

libsolidity/analysis/SyntaxChecker.cpp

@@ -22,6 +22,7 @@
 #include <libsolidity/analysis/SemVerHandler.h>
 #include <libsolidity/interface/ErrorReporter.h>
 #include <libsolidity/interface/Version.h>
+#include <boost/algorithm/cxx11/all_of.hpp>
 
 using namespace std;
 using namespace dev;
@@ -254,6 +255,18 @@ bool SyntaxChecker::visit(FunctionTypeName const& _node)
 	return true;
 }
 
+bool SyntaxChecker::visit(VariableDeclarationStatement const& _statement)
+{
+	// Report if none of the variable components in the tuple have a name (only possible via deprecated "var")
+	if (boost::algorithm::all_of_equal(_statement.declarations(), nullptr))
+		m_errorReporter.syntaxError(
+			_statement.location(),
+			"The use of the \"var\" keyword is disallowed. The declaration part of the statement can be removed, since it is empty."
+		);
+
+	return true;
+}
+
 bool SyntaxChecker::visit(StructDefinition const& _struct)
 {
 	if (_struct.members().empty())

libsolidity/analysis/SyntaxChecker.h

@@ -69,6 +69,8 @@ private:
 	virtual bool visit(FunctionDefinition const& _function) override;
 	virtual bool visit(FunctionTypeName const& _node) override;
 
+	virtual bool visit(VariableDeclarationStatement const& _statement) override;
+
 	virtual bool visit(StructDefinition const& _struct) override;
 
 	ErrorReporter& m_errorReporter;