diff options
| -rw-r--r-- | library/core/src/iter/adapters/intersperse.rs | 2 | ||||
| -rw-r--r-- | library/core/tests/iter.rs | 12 |
2 files changed, 14 insertions, 0 deletions
diff --git a/library/core/src/iter/adapters/intersperse.rs b/library/core/src/iter/adapters/intersperse.rs index 2143509d71d..b1170f32ba1 100644 --- a/library/core/src/iter/adapters/intersperse.rs +++ b/library/core/src/iter/adapters/intersperse.rs @@ -176,6 +176,8 @@ where if !needs_sep { if let Some(x) = iter.next() { accum = f(accum, x); + } else { + return accum; } } diff --git a/library/core/tests/iter.rs b/library/core/tests/iter.rs index fa259e68a43..78b4d1acaf5 100644 --- a/library/core/tests/iter.rs +++ b/library/core/tests/iter.rs @@ -3577,6 +3577,18 @@ fn test_intersperse_fold() { acc }); assert_eq!(v.as_slice(), [9, 2, 9, 3]); + + struct NoneAtStart(i32); // Produces: None, Some(2), Some(3), None, ... + impl Iterator for NoneAtStart { + type Item = i32; + fn next(&mut self) -> Option<i32> { + self.0 += 1; + Some(self.0).filter(|i| i % 3 != 1) + } + } + + let v = NoneAtStart(0).intersperse(1000).fold(0, |a, b| a + b); + assert_eq!(v, 0); } #[test] |