Implement `fmt::Debug` for all structures in libstd.

Part of https://github.com/rust-lang/rust/issues/31869.

Also turn on the `missing_debug_implementations` lint at the crate
level.

3 files changed, 187 insertions, 2 deletions

diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index 0b310eb2585..2fa3a9c4844 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1276,6 +1276,15 @@ impl<'a, K, V> Clone for Iter<'a, K, V> {
     }
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K: Debug, V: Debug> fmt::Debug for Iter<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 /// HashMap mutable values iterator.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IterMut<'a, K: 'a, V: 'a> {
@@ -1285,7 +1294,7 @@ pub struct IterMut<'a, K: 'a, V: 'a> {
 /// HashMap move iterator.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<K, V> {
-    inner: table::IntoIter<K, V>,
+    pub(super) inner: table::IntoIter<K, V>,
 }
 
 /// HashMap keys iterator.
@@ -1302,6 +1311,15 @@ impl<'a, K, V> Clone for Keys<'a, K, V> {
     }
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K: Debug, V: Debug> fmt::Debug for Keys<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 /// HashMap values iterator.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Values<'a, K: 'a, V: 'a> {
@@ -1316,10 +1334,19 @@ impl<'a, K, V> Clone for Values<'a, K, V> {
     }
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K: Debug, V: Debug> fmt::Debug for Values<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 /// HashMap drain iterator.
 #[stable(feature = "drain", since = "1.6.0")]
 pub struct Drain<'a, K: 'a, V: 'a> {
-    inner: table::Drain<'a, K, V>,
+    pub(super) inner: table::Drain<'a, K, V>,
 }
 
 /// Mutable HashMap values iterator.
@@ -1557,6 +1584,18 @@ impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, K, V> FusedIterator for IterMut<'a, K, V> {}
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K, V> fmt::Debug for IterMut<'a, K, V>
+    where K: fmt::Debug,
+          V: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.inner.iter())
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<K, V> Iterator for IntoIter<K, V> {
     type Item = (K, V);
@@ -1580,6 +1619,15 @@ impl<K, V> ExactSizeIterator for IntoIter<K, V> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<K, V> FusedIterator for IntoIter<K, V> {}
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<K: Debug, V: Debug> fmt::Debug for IntoIter<K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.inner.iter())
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, K, V> Iterator for Keys<'a, K, V> {
     type Item = &'a K;
@@ -1649,6 +1697,18 @@ impl<'a, K, V> ExactSizeIterator for ValuesMut<'a, K, V> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, K, V> FusedIterator for ValuesMut<'a, K, V> {}
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K, V> fmt::Debug for ValuesMut<'a, K, V>
+    where K: fmt::Debug,
+          V: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.inner.inner.iter())
+            .finish()
+    }
+}
+
 #[stable(feature = "drain", since = "1.6.0")]
 impl<'a, K, V> Iterator for Drain<'a, K, V> {
     type Item = (K, V);
@@ -1672,6 +1732,18 @@ impl<'a, K, V> ExactSizeIterator for Drain<'a, K, V> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, K, V> FusedIterator for Drain<'a, K, V> {}
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K, V> fmt::Debug for Drain<'a, K, V>
+    where K: fmt::Debug,
+          V: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.inner.iter())
+            .finish()
+    }
+}
+
 impl<'a, K, V> Entry<'a, K, V> {
     #[stable(feature = "rust1", since = "1.0.0")]
     /// Ensures a value is in the entry by inserting the default if empty, and returns
@@ -2148,6 +2220,13 @@ impl Default for RandomState {
     }
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl fmt::Debug for RandomState {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("RandomState { .. }")
+    }
+}
+
 impl<K, S, Q: ?Sized> super::Recover<Q> for HashMap<K, (), S>
     where K: Eq + Hash + Borrow<Q>,
           S: BuildHasher,
diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index 72af612f569..341b050862f 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -948,6 +948,15 @@ impl<'a, K> ExactSizeIterator for Iter<'a, K> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, K> FusedIterator for Iter<'a, K> {}
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K: fmt::Debug> fmt::Debug for Iter<'a, K> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<K> Iterator for IntoIter<K> {
     type Item = K;
@@ -968,6 +977,16 @@ impl<K> ExactSizeIterator for IntoIter<K> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<K> FusedIterator for IntoIter<K> {}
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<K: fmt::Debug> fmt::Debug for IntoIter<K> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let entries_iter = self.iter.inner.iter().map(|(k, _)| k);
+        f.debug_list()
+            .entries(entries_iter)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, K> Iterator for Drain<'a, K> {
     type Item = K;
@@ -988,6 +1007,16 @@ impl<'a, K> ExactSizeIterator for Drain<'a, K> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, K> FusedIterator for Drain<'a, K> {}
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, K: fmt::Debug> fmt::Debug for Drain<'a, K> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let entries_iter = self.iter.inner.iter().map(|(k, _)| k);
+        f.debug_list()
+            .entries(entries_iter)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T, S> Clone for Intersection<'a, T, S> {
     fn clone(&self) -> Intersection<'a, T, S> {
@@ -1021,6 +1050,18 @@ impl<'a, T, S> Iterator for Intersection<'a, T, S>
     }
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, T, S> fmt::Debug for Intersection<'a, T, S>
+    where T: fmt::Debug + Eq + Hash,
+          S: BuildHasher,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, T, S> FusedIterator for Intersection<'a, T, S>
     where T: Eq + Hash,
@@ -1068,6 +1109,18 @@ impl<'a, T, S> FusedIterator for Difference<'a, T, S>
 {
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, T, S> fmt::Debug for Difference<'a, T, S>
+    where T: fmt::Debug + Eq + Hash,
+          S: BuildHasher,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T, S> Clone for SymmetricDifference<'a, T, S> {
     fn clone(&self) -> SymmetricDifference<'a, T, S> {
@@ -1097,6 +1150,18 @@ impl<'a, T, S> FusedIterator for SymmetricDifference<'a, T, S>
 {
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, T, S> fmt::Debug for SymmetricDifference<'a, T, S>
+    where T: fmt::Debug + Eq + Hash,
+          S: BuildHasher,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T, S> Clone for Union<'a, T, S> {
     fn clone(&self) -> Union<'a, T, S> {
@@ -1111,6 +1176,18 @@ impl<'a, T, S> FusedIterator for Union<'a, T, S>
 {
 }
 
+#[stable(feature = "std_debug", since = "1.15.0")]
+impl<'a, T, S> fmt::Debug for Union<'a, T, S>
+    where T: fmt::Debug + Eq + Hash,
+          S: BuildHasher,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list()
+            .entries(self.clone())
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T, S> Iterator for Union<'a, T, S>
     where T: Eq + Hash,
diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index a784d8e50f9..2cd9362a657 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -882,6 +882,15 @@ unsafe impl<'a, K: Sync, V: Sync> Sync for IterMut<'a, K, V> {}
 // but Send is the more useful bound
 unsafe impl<'a, K: Send, V: Send> Send for IterMut<'a, K, V> {}
 
+impl<'a, K: 'a, V: 'a> IterMut<'a, K, V> {
+    pub fn iter(&self) -> Iter<K, V> {
+        Iter {
+            iter: self.iter.clone(),
+            elems_left: self.elems_left,
+        }
+    }
+}
+
 /// Iterator over the entries in a table, consuming the table.
 pub struct IntoIter<K, V> {
     table: RawTable<K, V>,
@@ -891,6 +900,15 @@ pub struct IntoIter<K, V> {
 unsafe impl<K: Sync, V: Sync> Sync for IntoIter<K, V> {}
 unsafe impl<K: Send, V: Send> Send for IntoIter<K, V> {}
 
+impl<K, V> IntoIter<K, V> {
+    pub fn iter(&self) -> Iter<K, V> {
+        Iter {
+            iter: self.iter.clone(),
+            elems_left: self.table.size,
+        }
+    }
+}
+
 /// Iterator over the entries in a table, clearing the table.
 pub struct Drain<'a, K: 'a, V: 'a> {
     table: Shared<RawTable<K, V>>,
@@ -901,6 +919,17 @@ pub struct Drain<'a, K: 'a, V: 'a> {
 unsafe impl<'a, K: Sync, V: Sync> Sync for Drain<'a, K, V> {}
 unsafe impl<'a, K: Send, V: Send> Send for Drain<'a, K, V> {}
 
+impl<'a, K, V> Drain<'a, K, V> {
+    pub fn iter(&self) -> Iter<K, V> {
+        unsafe {
+            Iter {
+                iter: self.iter.clone(),
+                elems_left: (**self.table).size,
+            }
+        }
+    }
+}
+
 impl<'a, K, V> Iterator for Iter<'a, K, V> {
     type Item = (&'a K, &'a V);