Add more implementations of ExactSizeIterator when iterating built-in…

… Python data structures.

newsfragments/2676.added.md

@@ -0,0 +1 @@
+Implemented `ExactSizeIterator` for `PyListIterator`, `PyDictIterator`, `PySetIterator` and `PyFrozenSetIterator`

src/types/dict.rs

@@ -308,11 +308,17 @@ impl<'py> Iterator for PyDictIterator<'py> {
 
  #[inline]
  fn size_hint(&self) -> (usize, Option<usize>) {
- let len = self.len as usize;
+ let len = self.len();
  (len, Some(len))
  }
 }
 
+impl<'py> ExactSizeIterator for PyDictIterator<'py> {
+ fn len(&self) -> usize {
+ self.len as usize
+ }
+}
+
 impl<'a> std::iter::IntoIterator for &'a PyDict {
  type Item = (&'a PyAny, &'a PyAny);
  type IntoIter = PyDictIterator<'a>;

src/types/frozenset.rs

@@ -117,7 +117,7 @@ mod impl_ {
  }
 
  pub struct PyFrozenSetIterator<'py> {
- set: &'py PyAny,
+ set: &'py PyFrozenSet,
  pos: ffi::Py_ssize_t,
  }
 
@@ -141,11 +141,14 @@ mod impl_ {
 
  #[inline]
  fn size_hint(&self) -> (usize, Option<usize>) {
- let len = self.set.len().unwrap_or_default();
- (
- len.saturating_sub(self.pos as usize),
- Some(len.saturating_sub(self.pos as usize)),
- )
+ let len = self.len();
+ (len, Some(len))
+ }
+ }
+
+ impl<'py> ExactSizeIterator for PyFrozenSetIterator<'py> {
+ fn len(&self) -> usize {
+ self.set.len().saturating_sub(self.pos as usize)
  }
  }
 }

src/types/list.rs

@@ -321,12 +321,14 @@ impl<'a> Iterator for PyListIterator<'a> {
 
  #[inline]
  fn size_hint(&self) -> (usize, Option<usize>) {
- let len = self.list.len();
+ let len = self.len();
+ (len, Some(len))
+ }
+}
 
- (
- len.saturating_sub(self.index),
- Some(len.saturating_sub(self.index)),
- )
+impl<'a> ExactSizeIterator for PyListIterator<'a> {
+ fn len(&self) -> usize {
+ self.list.len().saturating_sub(self.index)
  }
 }
 

src/types/set.rs

@@ -165,7 +165,7 @@ mod impl_ {
 mod impl_ {
  use super::*;
  pub struct PySetIterator<'py> {
- set: &'py super::PyAny,
+ set: &'py super::PySet,
  pos: ffi::Py_ssize_t,
  used: ffi::Py_ssize_t,
  }
@@ -215,11 +215,14 @@ mod impl_ {
 
  #[inline]
  fn size_hint(&self) -> (usize, Option<usize>) {
- let len = self.set.len().unwrap_or_default();
- (
- len.saturating_sub(self.pos as usize),
- Some(len.saturating_sub(self.pos as usize)),
- )
+ let len = self.len();
+ (len, Some(len))
+ }
+ }
+
+ impl<'py> ExactSizeIterator for PySetIterator<'py> {
+ fn len(&self) -> usize {
+ self.set.len().saturating_sub(self.pos as usize)
  }
  }
 }

src/types/tuple.rs

@@ -241,16 +241,14 @@ impl<'a> Iterator for PyTupleIterator<'a> {
 
  #[inline]
  fn size_hint(&self) -> (usize, Option<usize>) {
- (
- self.length.saturating_sub(self.index as usize),
- Some(self.length.saturating_sub(self.index as usize)),
- )
+ let len = self.len();
+ (len, Some(len))
  }
 }
 
 impl<'a> ExactSizeIterator for PyTupleIterator<'a> {
  fn len(&self) -> usize {
- self.length - self.index
+ self.length.saturating_sub(self.index)
  }
 }