Minor code style tweaks

No functional change.

src/types.h

@@ -324,8 +324,8 @@ inline Value& operator+=(Value& v, int i) { return v = v + i; }
 inline Value& operator-=(Value& v, int i) { return v = v - i; }
 
 /// Additional operators to add a Direction to a Square
-inline Square operator+(Square s, Direction d) { return Square(int(s) + int(d)); }
-inline Square operator-(Square s, Direction d) { return Square(int(s) - int(d)); }
+constexpr Square operator+(Square s, Direction d) { return Square(int(s) + int(d)); }
+constexpr Square operator-(Square s, Direction d) { return Square(int(s) - int(d)); }
 inline Square& operator+=(Square& s, Direction d) { return s = s + d; }
 inline Square& operator-=(Square& s, Direction d) { return s = s - d; }
 
@@ -448,7 +448,7 @@ constexpr PieceType promotion_type(Move m) {
   return PieceType(((m >> 12) & 3) + KNIGHT);
 }
 
-inline Move make_move(Square from, Square to) {
+constexpr Move make_move(Square from, Square to) {
   return Move((from << 6) + to);
 }
 

src/uci.h

@@ -56,7 +56,7 @@ public:
   void operator<<(const Option&);
   operator double() const;
   operator std::string() const;
-  bool operator==(const char*);
+  bool operator==(const char*) const;
 
 private:
   friend std::ostream& operator<<(std::ostream&, const OptionsMap&);

src/ucioption.cpp

@@ -134,7 +134,7 @@ Option::operator std::string() const {
   return currentValue;
 }
 
-bool Option::operator==(const char* s) {
+bool Option::operator==(const char* s) const {
   assert(type == "combo");
   return    !CaseInsensitiveLess()(currentValue, s)
          && !CaseInsensitiveLess()(s, currentValue);