api: impl ExactSizeIterator for SubCaptureMatches

PR #857

Author: jaehl

src/re_trait.rs

@@ -74,8 +74,19 @@ impl<'c> Iterator for SubCapturesPosIter<'c> {
         self.idx += 1;
         x
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.locs.len() - self.idx;
+        (len, Some(len))
+    }
+
+    fn count(self) -> usize {
+        self.len()
+    }
 }
 
+impl<'c> ExactSizeIterator for SubCapturesPosIter<'c> {}
+
 impl<'c> FusedIterator for SubCapturesPosIter<'c> {}
 
 /// `RegularExpression` describes types that can implement regex searching.

src/re_unicode.rs

@@ -1092,8 +1092,18 @@ impl<'c, 't> Iterator for SubCaptureMatches<'c, 't> {
             .next()
             .map(|cap| cap.map(|(s, e)| Match::new(self.caps.text, s, e)))
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.it.size_hint()
+    }
+
+    fn count(self) -> usize {
+        self.it.count()
+    }
 }
 
+impl<'c, 't> ExactSizeIterator for SubCaptureMatches<'c, 't> {}
+
 impl<'c, 't> FusedIterator for SubCaptureMatches<'c, 't> {}
 
 /// An iterator that yields all non-overlapping capture groups matching a