add nodiscard to features2d clone funcs

modules/features2d/include/opencv2/features2d.hpp

@@ -1082,7 +1082,7 @@ public:
     that is, copies both parameters and train data. If emptyTrainData is true, the method creates an
     object copy with the current parameters but with empty train data.
      */
-    CV_WRAP virtual Ptr<DescriptorMatcher> clone( bool emptyTrainData=false ) const = 0;
+    CV_WRAP CV_NODISCARD_STD virtual Ptr<DescriptorMatcher> clone( bool emptyTrainData=false ) const = 0;
 
     /** @brief Creates a descriptor matcher of a given type with the default parameters (using default
     constructor).
@@ -1142,7 +1142,7 @@ protected:
     static bool isPossibleMatch( InputArray mask, int queryIdx, int trainIdx );
     static bool isMaskedOut( InputArrayOfArrays masks, int queryIdx );
 
-    static Mat clone_op( Mat m ) { return m.clone(); }
+    CV_NODISCARD_STD static Mat clone_op( Mat m ) { return m.clone(); }
     void checkMasks( InputArrayOfArrays masks, int queryDescriptorsCount ) const;
 
     //! Collection of descriptors from train images.
@@ -1183,7 +1183,7 @@ public:
      */
     CV_WRAP static Ptr<BFMatcher> create( int normType=NORM_L2, bool crossCheck=false ) ;
 
-    virtual Ptr<DescriptorMatcher> clone( bool emptyTrainData=false ) const CV_OVERRIDE;
+    CV_NODISCARD_STD virtual Ptr<DescriptorMatcher> clone( bool emptyTrainData=false ) const CV_OVERRIDE;
 protected:
     virtual void knnMatchImpl( InputArray queryDescriptors, std::vector<std::vector<DMatch> >& matches, int k,
         InputArrayOfArrays masks=noArray(), bool compactResult=false ) CV_OVERRIDE;
@@ -1222,7 +1222,7 @@ public:
 
     CV_WRAP static Ptr<FlannBasedMatcher> create();
 
-    virtual Ptr<DescriptorMatcher> clone( bool emptyTrainData=false ) const CV_OVERRIDE;
+    CV_NODISCARD_STD virtual Ptr<DescriptorMatcher> clone( bool emptyTrainData=false ) const CV_OVERRIDE;
 protected:
     static void convertToDMatches( const DescriptorCollection& descriptors,
                                    const Mat& indices, const Mat& distances,

modules/python/src2/hdr_parser.py

@@ -432,11 +432,18 @@ class CppHeaderParser(object):
         # filter off some common prefixes, which are meaningless for Python wrappers.
         # note that we do not strip "static" prefix, which does matter;
         # it means class methods, not instance methods
-        decl_str = self.batch_replace(decl_str, [("static inline", ""), ("inline", ""), ("explicit ", ""),
+        decl_str = self.batch_replace(decl_str, [("static inline", ""),
-                                                 ("CV_EXPORTS_W", ""), ("CV_EXPORTS", ""), ("CV_CDECL", ""),
+                                                 ("inline", ""),
-                                                 ("CV_WRAP ", " "), ("CV_INLINE", ""),
+                                                 ("explicit ", ""),
-                                                 ("CV_DEPRECATED", ""), ("CV_DEPRECATED_EXTERNAL", "")]).strip()
+                                                 ("CV_EXPORTS_W", ""),
-
+                                                 ("CV_EXPORTS", ""),
+                                                 ("CV_CDECL", ""),
+                                                 ("CV_WRAP ", " "),
+                                                 ("CV_INLINE", ""),
+                                                 ("CV_DEPRECATED", ""),
+                                                 ("CV_DEPRECATED_EXTERNAL", ""),
+                                                 ("CV_NODISCARD_STD", ""),
+                                                 ("CV_NODISCARD", "")]).strip()
 
         if decl_str.strip().startswith('virtual'):
             virtual_method = True