Removes unnecessary overloaded operator

Author: fredrikbk

include/taco/index_notation/index_notation.h

@@ -173,15 +173,19 @@ class Access : public IndexExpr {
   const std::vector<IndexVar>& getIndexVars() const;
 
   /// Assign the result of an expression to a left-hand-side tensor access.
+  /// ```
+  /// a(i) = b(i) * c(i);
+  /// ```
   Assignment operator=(const IndexExpr&);
+
+  // Must override the default Access operator=, otherwise it is a copy.
   Assignment operator=(const Access&);
 
   /// Accumulate the result of an expression to a left-hand-side tensor access.
   /// ```
   /// a(i) += B(i,j) * c(j);
   /// ```
   void operator+=(const IndexExpr&);
-  void operator+=(const Access&);
 
 private:
   const Node* getPtr() const;

src/index_notation/index_notation.cpp

@@ -250,10 +250,6 @@ void Access::operator+=(const IndexExpr& expr) {
   const_cast<AccessNode*>(getPtr())->setIndexExpression(expr, true);
 }
 
-void Access::operator+=(const Access& expr) {
-  operator+=(static_cast<IndexExpr>(expr));
-}
-
 
 // class Sum
 Reduction::Reduction(const Node* n) : IndexExpr(n) {