song/StringFilter: move `negated` flag from containing class

src/song/OptimizeFilter.cxx

@@ -58,11 +58,11 @@ OptimizeSongFilter(ISongFilterPtr f) noexcept
 			/* #TagSongFilter has its own "negated" flag,
 			   so we can drop the #NotSongFilter
 			   container */
-			tf->negated = !tf->negated;
+			tf->ToggleNegated();
 			return child;
 		} else if (auto *uf = dynamic_cast<UriSongFilter *>(child.get())) {
 			/* same for #UriSongFilter */
-			uf->negated = !uf->negated;
+			uf->ToggleNegated();
 			return child;
 		}
 

src/song/StringFilter.cxx

@@ -23,8 +23,8 @@
 
 #include <assert.h>
 
-bool
-StringFilter::Match(const char *s) const noexcept
+inline bool
+StringFilter::MatchWithoutNegation(const char *s) const noexcept
 {
 #if !CLANG_CHECK_VERSION(3,6)
 	/* disabled on clang due to -Wtautological-pointer-compare */
@@ -41,3 +41,9 @@ StringFilter::Match(const char *s) const noexcept
 			: value == s;
 	}
 }
+
+bool
+StringFilter::Match(const char *s) const noexcept
+{
+	return MatchWithoutNegation(s) != negated;
+}

src/song/StringFilter.hxx

@@ -38,14 +38,16 @@ class StringFilter {
 	 */
 	bool substring;
 
+	bool negated;
+
 public:
 	template<typename V>
-	StringFilter(V &&_value, bool _fold_case, bool _substring)
+	StringFilter(V &&_value, bool _fold_case, bool _substring, bool _negated)
 		:value(std::forward<V>(_value)),
 		 fold_case(_fold_case
 			   ? IcuCompare(value.c_str())
 			   : IcuCompare()),
-		 substring(_substring) {}
+		 substring(_substring), negated(_negated) {}
 
 	bool empty() const noexcept {
 		return value.empty();
@@ -59,8 +61,24 @@ public:
 		return fold_case;
 	}
 
+	bool IsNegated() const noexcept {
+		return negated;
+	}
+
+	void ToggleNegated() noexcept {
+		negated = !negated;
+	}
+
+	const char *GetOperator() const noexcept {
+		return negated ? "!=" : "==";
+	}
+
 	gcc_pure
 	bool Match(const char *s) const noexcept;
+
+private:
+	gcc_pure
+	bool MatchWithoutNegation(const char *s) const noexcept;
 };
 
 #endif

src/song/TagSongFilter.cxx

@@ -31,7 +31,8 @@ TagSongFilter::ToExpression() const noexcept
 		? "any"
 		: tag_item_names[type];
 
-	return std::string("(") + name + " " + (negated ? "!=" : "==") + " \"" + EscapeFilterString(filter.GetValue()) + "\")";
+	return std::string("(") + name + " " + filter.GetOperator()
+		+ " \"" + EscapeFilterString(filter.GetValue()) + "\")";
 }
 
 bool
@@ -89,5 +90,5 @@ TagSongFilter::MatchNN(const Tag &tag) const noexcept
 bool
 TagSongFilter::Match(const LightSong &song) const noexcept
 {
-	return MatchNN(song.tag) != negated;
+	return MatchNN(song.tag);
 }

src/song/TagSongFilter.hxx

@@ -34,18 +34,15 @@ struct LightSong;
 class TagSongFilter final : public ISongFilter {
 	TagType type;
 
-	bool negated;
-
 	StringFilter filter;
 
-	friend ISongFilterPtr OptimizeSongFilter(ISongFilterPtr) noexcept;
-
 public:
 	template<typename V>
 	TagSongFilter(TagType _type, V &&_value, bool fold_case, bool substring,
-		      bool _negated)
-		:type(_type), negated(_negated),
-		 filter(std::forward<V>(_value), fold_case, substring) {}
+		      bool negated)
+		:type(_type),
+		 filter(std::forward<V>(_value), fold_case, substring,
+			negated) {}
 
 	TagType GetTagType() const {
 		return type;
@@ -60,7 +57,11 @@ public:
 	}
 
 	bool IsNegated() const noexcept {
-		return negated;
+		return filter.IsNegated();
+	}
+
+	void ToggleNegated() noexcept {
+		filter.ToggleNegated();
 	}
 
 	ISongFilterPtr Clone() const noexcept override {

src/song/UriSongFilter.cxx

@@ -25,11 +25,12 @@
 std::string
 UriSongFilter::ToExpression() const noexcept
 {
-	return std::string("(file ") + (negated ? "!=" : "==") + " \"" + EscapeFilterString(filter.GetValue()) + "\")";
+	return std::string("(file ") + filter.GetOperator()
+		+ " \"" + EscapeFilterString(filter.GetValue()) + "\")";
 }
 
 bool
 UriSongFilter::Match(const LightSong &song) const noexcept
 {
-	return filter.Match(song.GetURI().c_str()) != negated;
+	return filter.Match(song.GetURI().c_str());
 }

src/song/UriSongFilter.hxx

@@ -26,16 +26,12 @@
 class UriSongFilter final : public ISongFilter {
 	StringFilter filter;
 
-	bool negated;
-
-	friend ISongFilterPtr OptimizeSongFilter(ISongFilterPtr) noexcept;
-
 public:
 	template<typename V>
 	UriSongFilter(V &&_value, bool fold_case, bool substring,
-		      bool _negated)
-		:filter(std::forward<V>(_value), fold_case, substring),
-		 negated(_negated) {}
+		      bool negated)
+		:filter(std::forward<V>(_value), fold_case, substring,
+			negated) {}
 
 	const auto &GetValue() const noexcept {
 		return filter.GetValue();
@@ -46,7 +42,11 @@ public:
 	}
 
 	bool IsNegated() const noexcept {
-		return negated;
+		return filter.IsNegated();
+	}
+
+	void ToggleNegated() noexcept {
+		filter.ToggleNegated();
 	}
 
 	ISongFilterPtr Clone() const noexcept override {