fix operator= of linear_set

alib2std/src/extensions/linear_set.hpp

@@ -603,6 +603,7 @@ public:
 	linear_set& operator= (const linear_set& x) {
 		m_data = x.m_data;
 		m_comp = x.m_comp;
+		return *this;
 	}
 	/**
@@ -616,6 +617,7 @@ public:
 	linear_set& operator= (linear_set&& x) {
 		m_data = std::move ( x.m_data );
 		m_comp = std::move ( x.m_comp );
+		return *this;
 	}
 	/**
@@ -629,6 +631,7 @@ public:
 	linear_set& operator= (std::initializer_list<T> il) {
 		m_data = std::move ( il );
 		std::sort ( m_data.begin ( ), m_data.end ( ), m_comp );
+		return *this;
 	}
 	/**