Auto merge of #32054 - seanmonstar:impl-debug-core, r=alexcrichton

libcore: add Debug implementations to most missing types

Also adds `#![deny(missing_debug_implementations)]` to the core crate.

cc #31869

17 files changed, 319 insertions, 34 deletions

diff --git a/src/libcore/char.rs b/src/libcore/char.rs
index abae121ea7f..5b39fa42c6e 100644
--- a/src/libcore/char.rs
+++ b/src/libcore/char.rs
@@ -416,14 +416,14 @@ pub fn encode_utf16_raw(mut ch: u32, dst: &mut [u16]) -> Option<usize> {
 ///
 /// [`escape_unicode()`]: ../../std/primitive.char.html#method.escape_unicode
 /// [`char`]: ../../std/primitive.char.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct EscapeUnicode {
     c: char,
     state: EscapeUnicodeState
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 enum EscapeUnicodeState {
     Backslash,
     Type,
@@ -496,13 +496,13 @@ impl Iterator for EscapeUnicode {
 ///
 /// [`escape_default()`]: ../../std/primitive.char.html#method.escape_default
 /// [`char`]: ../../std/primitive.char.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct EscapeDefault {
     state: EscapeDefaultState
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 enum EscapeDefaultState {
     Backslash(char),
     Char(char),
diff --git a/src/libcore/fmt/builders.rs b/src/libcore/fmt/builders.rs
index b562e658b62..5ad1e2009b3 100644
--- a/src/libcore/fmt/builders.rs
+++ b/src/libcore/fmt/builders.rs
@@ -54,6 +54,7 @@ impl<'a, 'b: 'a> fmt::Write for PadAdapter<'a, 'b> {
 ///
 /// Constructed by the `Formatter::debug_struct` method.
 #[must_use]
+#[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugStruct<'a, 'b: 'a> {
     fmt: &'a mut fmt::Formatter<'b>,
@@ -120,6 +121,7 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
 ///
 /// Constructed by the `Formatter::debug_tuple` method.
 #[must_use]
+#[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugTuple<'a, 'b: 'a> {
     fmt: &'a mut fmt::Formatter<'b>,
@@ -231,6 +233,7 @@ impl<'a, 'b: 'a> DebugInner<'a, 'b> {
 ///
 /// Constructed by the `Formatter::debug_set` method.
 #[must_use]
+#[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugSet<'a, 'b: 'a> {
     inner: DebugInner<'a, 'b>,
@@ -279,6 +282,7 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
 ///
 /// Constructed by the `Formatter::debug_list` method.
 #[must_use]
+#[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugList<'a, 'b: 'a> {
     inner: DebugInner<'a, 'b>,
@@ -327,6 +331,7 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
 ///
 /// Constructed by the `Formatter::debug_map` method.
 #[must_use]
+#[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugMap<'a, 'b: 'a> {
     fmt: &'a mut fmt::Formatter<'b>,
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index 7f7bfe73c51..d2da16624ca 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -14,7 +14,7 @@
 
 use prelude::v1::*;
 
-use cell::{Cell, RefCell, Ref, RefMut, BorrowState};
+use cell::{UnsafeCell, Cell, RefCell, Ref, RefMut, BorrowState};
 use marker::PhantomData;
 use mem;
 use num::flt2dec;
@@ -25,6 +25,7 @@ use str;
 
 #[unstable(feature = "fmt_flags_align", issue = "27726")]
 /// Possible alignments returned by `Formatter::align`
+#[derive(Debug)]
 pub enum Alignment {
     /// Indication that contents should be left-aligned.
     Left,
@@ -152,6 +153,7 @@ impl<'a, W: Write + ?Sized> Write for &'a mut W {
 /// A struct to represent both where to emit formatting strings to and how they
 /// should be formatted. A mutable version of this is passed to all formatting
 /// traits.
+#[allow(missing_debug_implementations)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Formatter<'a> {
     flags: u32,
@@ -175,6 +177,7 @@ enum Void {}
 /// compile time it is ensured that the function and the value have the correct
 /// types, and then this struct is used to canonicalize arguments to one type.
 #[derive(Copy)]
+#[allow(missing_debug_implementations)]
 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
            issue = "0")]
 #[doc(hidden)]
@@ -1585,7 +1588,9 @@ impl<T: ?Sized> Debug for PhantomData<T> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Copy + Debug> Debug for Cell<T> {
     fn fmt(&self, f: &mut Formatter) -> Result {
-        write!(f, "Cell {{ value: {:?} }}", self.get())
+        f.debug_struct("Cell")
+            .field("value", &self.get())
+            .finish()
     }
 }
 
@@ -1594,9 +1599,15 @@ impl<T: ?Sized + Debug> Debug for RefCell<T> {
     fn fmt(&self, f: &mut Formatter) -> Result {
         match self.borrow_state() {
             BorrowState::Unused | BorrowState::Reading => {
-                write!(f, "RefCell {{ value: {:?} }}", self.borrow())
+                f.debug_struct("RefCell")
+                    .field("value", &self.borrow())
+                    .finish()
+            }
+            BorrowState::Writing => {
+                f.debug_struct("RefCell")
+                    .field("value", &"<borrowed>")
+                    .finish()
             }
-            BorrowState::Writing => write!(f, "RefCell {{ <borrowed> }}"),
         }
     }
 }
@@ -1615,5 +1626,12 @@ impl<'b, T: ?Sized + Debug> Debug for RefMut<'b, T> {
     }
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<T: ?Sized + Debug> Debug for UnsafeCell<T> {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        f.pad("UnsafeCell")
+    }
+}
+
 // If you expected tests to be here, look instead at the run-pass/ifmt.rs test,
 // it's a lot easier than creating all of the rt::Piece structures here.
diff --git a/src/libcore/fmt/rt/v1.rs b/src/libcore/fmt/rt/v1.rs
index f889045a3f5..6b31e040622 100644
--- a/src/libcore/fmt/rt/v1.rs
+++ b/src/libcore/fmt/rt/v1.rs
@@ -13,6 +13,7 @@
 //!
 //! These definitions are similar to their `ct` equivalents, but differ in that
 //! these can be statically allocated and are slightly optimized for the runtime
+#![allow(missing_debug_implementations)]
 
 #[derive(Copy, Clone)]
 pub struct Argument {
diff --git a/src/libcore/hash/mod.rs b/src/libcore/hash/mod.rs
index 3c219692bc4..4d0fed98334 100644
--- a/src/libcore/hash/mod.rs
+++ b/src/libcore/hash/mod.rs
@@ -73,6 +73,7 @@
 
 use prelude::v1::*;
 
+use fmt;
 use marker;
 use mem;
 
@@ -215,6 +216,13 @@ pub trait BuildHasher {
 #[stable(since = "1.7.0", feature = "build_hasher")]
 pub struct BuildHasherDefault<H>(marker::PhantomData<H>);
 
+#[stable(since = "1.9.0", feature = "core_impl_debug")]
+impl<H> fmt::Debug for BuildHasherDefault<H> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BuildHasherDefault")
+    }
+}
+
 #[stable(since = "1.7.0", feature = "build_hasher")]
 impl<H: Default + Hasher> BuildHasher for BuildHasherDefault<H> {
     type Hasher = H;
diff --git a/src/libcore/hash/sip.rs b/src/libcore/hash/sip.rs
index 342071f1b51..a1a306d5c7d 100644
--- a/src/libcore/hash/sip.rs
+++ b/src/libcore/hash/sip.rs
@@ -30,6 +30,7 @@ use super::Hasher;
 /// Although the SipHash algorithm is considered to be generally strong,
 /// it is not intended for cryptographic purposes. As such, all
 /// cryptographic uses of this implementation are _strongly discouraged_.
+#[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct SipHasher {
     k0: u64,
diff --git a/src/libcore/iter.rs b/src/libcore/iter.rs
index def44e1a9ce..72421e94a43 100644
--- a/src/libcore/iter.rs
+++ b/src/libcore/iter.rs
@@ -303,6 +303,7 @@ use clone::Clone;
 use cmp;
 use cmp::{Ord, PartialOrd, PartialEq, Ordering};
 use default::Default;
+use fmt;
 use marker;
 use mem;
 use num::{Zero, One};
@@ -2929,7 +2930,7 @@ impl<A, B> ExactSizeIterator for Zip<A, B>
 ///
 /// [`rev()`]: trait.Iterator.html#method.rev
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Rev<T> {
@@ -2961,7 +2962,7 @@ impl<I> DoubleEndedIterator for Rev<I> where I: DoubleEndedIterator {
 /// [`Iterator`]: trait.Iterator.html
 #[stable(feature = "iter_cloned", since = "1.1.0")]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct Cloned<I> {
     it: I,
 }
@@ -3002,7 +3003,7 @@ impl<'a, I, T: 'a> ExactSizeIterator for Cloned<I>
 ///
 /// [`cycle()`]: trait.Iterator.html#method.cycle
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Cycle<I> {
@@ -3040,7 +3041,7 @@ impl<I> Iterator for Cycle<I> where I: Clone + Iterator {
 ///
 /// [`chain()`]: trait.Iterator.html#method.chain
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Chain<A, B> {
@@ -3062,7 +3063,7 @@ pub struct Chain<A, B> {
 //
 //  The fourth state (neither iterator is remaining) only occurs after Chain has
 //  returned None once, so we don't need to store this state.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 enum ChainState {
     // both front and back iterator are remaining
     Both,
@@ -3184,7 +3185,7 @@ impl<A, B> DoubleEndedIterator for Chain<A, B> where
 ///
 /// [`zip()`]: trait.Iterator.html#method.zip
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Zip<A, B> {
@@ -3307,6 +3308,15 @@ pub struct Map<I, F> {
     f: F,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Map")
+            .field("iter", &self.iter)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B, I: Iterator, F> Iterator for Map<I, F> where F: FnMut(I::Item) -> B {
     type Item = B;
@@ -3347,6 +3357,15 @@ pub struct Filter<I, P> {
     predicate: P,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, P> fmt::Debug for Filter<I, P> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Filter")
+            .field("iter", &self.iter)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<I: Iterator, P> Iterator for Filter<I, P> where P: FnMut(&I::Item) -> bool {
     type Item = I::Item;
@@ -3398,6 +3417,15 @@ pub struct FilterMap<I, F> {
     f: F,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("FilterMap")
+            .field("iter", &self.iter)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
     where F: FnMut(I::Item) -> Option<B>,
@@ -3443,7 +3471,7 @@ impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F>
 ///
 /// [`enumerate()`]: trait.Iterator.html#method.enumerate
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Enumerate<I> {
@@ -3517,7 +3545,7 @@ impl<I> DoubleEndedIterator for Enumerate<I> where
 ///
 /// [`peekable()`]: trait.Iterator.html#method.peekable
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Peekable<I: Iterator> {
@@ -3676,6 +3704,16 @@ pub struct SkipWhile<I, P> {
     predicate: P,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("SkipWhile")
+            .field("iter", &self.iter)
+            .field("flag", &self.flag)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<I: Iterator, P> Iterator for SkipWhile<I, P>
     where P: FnMut(&I::Item) -> bool
@@ -3716,6 +3754,16 @@ pub struct TakeWhile<I, P> {
     predicate: P,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, P> fmt::Debug for TakeWhile<I, P> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("TakeWhile")
+            .field("iter", &self.iter)
+            .field("flag", &self.flag)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<I: Iterator, P> Iterator for TakeWhile<I, P>
     where P: FnMut(&I::Item) -> bool
@@ -3752,7 +3800,7 @@ impl<I: Iterator, P> Iterator for TakeWhile<I, P>
 ///
 /// [`skip()`]: trait.Iterator.html#method.skip
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Skip<I> {
@@ -3843,7 +3891,7 @@ impl<I> DoubleEndedIterator for Skip<I> where I: DoubleEndedIterator + ExactSize
 ///
 /// [`take()`]: trait.Iterator.html#method.take
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Take<I> {
@@ -3914,6 +3962,16 @@ pub struct Scan<I, St, F> {
     state: St,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, St: fmt::Debug, F> fmt::Debug for Scan<I, St, F> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Scan")
+            .field("iter", &self.iter)
+            .field("state", &self.state)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B, I, St, F> Iterator for Scan<I, St, F> where
     I: Iterator,
@@ -3951,6 +4009,19 @@ pub struct FlatMap<I, U: IntoIterator, F> {
     backiter: Option<U::IntoIter>,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, U: IntoIterator, F> fmt::Debug for FlatMap<I, U, F>
+    where U::IntoIter: fmt::Debug
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("FlatMap")
+            .field("iter", &self.iter)
+            .field("frontiter", &self.frontiter)
+            .field("backiter", &self.backiter)
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<I: Iterator, U: IntoIterator, F> Iterator for FlatMap<I, U, F>
     where F: FnMut(I::Item) -> U,
@@ -4014,7 +4085,7 @@ impl<I: DoubleEndedIterator, U, F> DoubleEndedIterator for FlatMap<I, U, F> wher
 ///
 /// [`fuse()`]: trait.Iterator.html#method.fuse
 /// [`Iterator`]: trait.Iterator.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Fuse<I> {
@@ -4109,6 +4180,15 @@ pub struct Inspect<I, F> {
     f: F,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<I: fmt::Debug, F> fmt::Debug for Inspect<I, F> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Inspect")
+            .field("iter", &self.iter)
+            .finish()
+    }
+}
+
 impl<I: Iterator, F> Inspect<I, F> where F: FnMut(&I::Item) {
     #[inline]
     fn do_inspect(&mut self, elt: Option<I::Item>) -> Option<I::Item> {
@@ -4272,7 +4352,7 @@ step_impl_no_between!(u64 i64);
 /// The resulting iterator handles overflow by stopping. The `A`
 /// parameter is the type being iterated over, while `R` is the range
 /// type (usually one of `std::ops::{Range, RangeFrom, RangeInclusive}`.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[unstable(feature = "step_by", reason = "recent addition",
            issue = "27741")]
 pub struct StepBy<A, R> {
@@ -4679,7 +4759,7 @@ impl<A: Step + One> DoubleEndedIterator for ops::RangeInclusive<A> where
 /// This `struct` is created by the [`repeat()`] function. See its documentation for more.
 ///
 /// [`repeat()`]: fn.repeat.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Repeat<A> {
     element: A
@@ -4761,6 +4841,13 @@ pub fn repeat<T: Clone>(elt: T) -> Repeat<T> {
 #[stable(feature = "iter_empty", since = "1.2.0")]
 pub struct Empty<T>(marker::PhantomData<T>);
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<T> fmt::Debug for Empty<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("Empty")
+    }
+}
+
 #[stable(feature = "iter_empty", since = "1.2.0")]
 impl<T> Iterator for Empty<T> {
     type Item = T;
@@ -4830,7 +4917,7 @@ pub fn empty<T>() -> Empty<T> {
 /// This `struct` is created by the [`once()`] function. See its documentation for more.
 ///
 /// [`once()`]: fn.once.html
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[stable(feature = "iter_once", since = "1.2.0")]
 pub struct Once<T> {
     inner: ::option::IntoIter<T>
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 1d5bb4d55b3..f199909dfa9 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -56,6 +56,7 @@
 
 #![no_core]
 #![deny(missing_docs)]
+#![deny(missing_debug_implementations)]
 #![cfg_attr(not(stage0), deny(warnings))]
 
 #![feature(allow_internal_unstable)]
diff --git a/src/libcore/num/flt2dec/mod.rs b/src/libcore/num/flt2dec/mod.rs
index b9a7afc400d..b549f334242 100644
--- a/src/libcore/num/flt2dec/mod.rs
+++ b/src/libcore/num/flt2dec/mod.rs
@@ -222,6 +222,7 @@ impl<'a> Part<'a> {
 
 /// Formatted result containing one or more parts.
 /// This can be written to the byte buffer or converted to the allocated string.
+#[allow(missing_debug_implementations)]
 #[derive(Clone)]
 pub struct Formatted<'a> {
     /// A byte slice representing a sign, either `""`, `"-"` or `"+"`.
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 56b84fd6a64..dd60e8797a9 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -763,7 +763,7 @@ impl<'a, T> IntoIterator for &'a mut Option<T> {
 // The Option Iterators
 /////////////////////////////////////////////////////////////////////////////
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 struct Item<A> {
     opt: Option<A>
 }
@@ -796,6 +796,7 @@ impl<A> ExactSizeIterator for Item<A> {}
 
 /// An iterator over a reference of the contained item in an Option.
 #[stable(feature = "rust1", since = "1.0.0")]
+#[derive(Debug)]
 pub struct Iter<'a, A: 'a> { inner: Item<&'a A> }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -826,6 +827,7 @@ impl<'a, A> Clone for Iter<'a, A> {
 
 /// An iterator over a mutable reference of the contained item in an Option.
 #[stable(feature = "rust1", since = "1.0.0")]
+#[derive(Debug)]
 pub struct IterMut<'a, A: 'a> { inner: Item<&'a mut A> }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -848,7 +850,7 @@ impl<'a, A> DoubleEndedIterator for IterMut<'a, A> {
 impl<'a, A> ExactSizeIterator for IterMut<'a, A> {}
 
 /// An iterator over the item contained inside an Option.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<A> { inner: Item<A> }
 
diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs
index 3cbeac450e2..ec72809acab 100644
--- a/src/libcore/ptr.rs
+++ b/src/libcore/ptr.rs
@@ -520,6 +520,7 @@ impl<T: ?Sized> PartialOrd for *mut T {
 /// modified without a unique path to the `Unique` reference. Useful
 /// for building abstractions like `Vec<T>` or `Box<T>`, which
 /// internally use raw pointers to manage the memory that they own.
+#[allow(missing_debug_implementations)]
 #[unstable(feature = "unique", reason = "needs an RFC to flesh out design",
            issue = "27730")]
 pub struct Unique<T: ?Sized> {
@@ -592,6 +593,7 @@ impl<T> fmt::Pointer for Unique<T> {
 /// of this wrapper has shared ownership of the referent. Useful for
 /// building abstractions like `Rc<T>` or `Arc<T>`, which internally
 /// use raw pointers to manage the memory that they own.
+#[allow(missing_debug_implementations)]
 #[unstable(feature = "shared", reason = "needs an RFC to flesh out design",
            issue = "27730")]
 pub struct Shared<T: ?Sized> {
diff --git a/src/libcore/raw.rs b/src/libcore/raw.rs
index 84467be6eca..20c85b5efc1 100644
--- a/src/libcore/raw.rs
+++ b/src/libcore/raw.rs
@@ -59,6 +59,7 @@ use mem;
 /// println!("data pointer = {:?}, length = {}", repr.data, repr.len);
 /// ```
 #[repr(C)]
+#[allow(missing_debug_implementations)]
 pub struct Slice<T> {
     pub data: *const T,
     pub len: usize,
@@ -143,6 +144,7 @@ impl<T> Clone for Slice<T> {
 /// ```
 #[repr(C)]
 #[derive(Copy, Clone)]
+#[allow(missing_debug_implementations)]
 pub struct TraitObject {
     pub data: *mut (),
     pub vtable: *mut (),
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index 09f612c20ec..7f8cf531d26 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -799,6 +799,7 @@ impl<'a, T, E> IntoIterator for &'a mut Result<T, E> {
 /////////////////////////////////////////////////////////////////////////////
 
 /// An iterator over a reference to the `Ok` variant of a `Result`.
+#[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Iter<'a, T: 'a> { inner: Option<&'a T> }
 
@@ -830,6 +831,7 @@ impl<'a, T> Clone for Iter<'a, T> {
 }
 
 /// An iterator over a mutable reference to the `Ok` variant of a `Result`.
+#[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IterMut<'a, T: 'a> { inner: Option<&'a mut T> }
 
@@ -856,6 +858,7 @@ impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
 impl<'a, T> ExactSizeIterator for IterMut<'a, T> {}
 
 /// An iterator over the value in a `Ok` variant of a `Result`.
+#[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<T> { inner: Option<T> }
 
diff --git a/src/libcore/slice.rs b/src/libcore/slice.rs
index ca9a618793a..aa555b44e89 100644
--- a/src/libcore/slice.rs
+++ b/src/libcore/slice.rs
@@ -38,6 +38,7 @@ use cmp::{Ordering, PartialEq, PartialOrd, Eq, Ord};
 use cmp::Ordering::{Less, Equal, Greater};
 use cmp;
 use default::Default;
+use fmt;
 use intrinsics::assume;
 use iter::*;
 use ops::{FnMut, self, Index};
@@ -877,6 +878,15 @@ pub struct Iter<'a, T: 'a> {
     _marker: marker::PhantomData<&'a T>,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("Iter")
+            .field(&self.as_slice())
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<'a, T: Sync> Sync for Iter<'a, T> {}
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -925,6 +935,15 @@ pub struct IterMut<'a, T: 'a> {
     _marker: marker::PhantomData<&'a mut T>,
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("IterMut")
+            .field(&make_slice!(self.ptr, self.end))
+            .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<'a, T: Sync> Sync for IterMut<'a, T> {}
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -980,6 +999,16 @@ pub struct Split<'a, T:'a, P> where P: FnMut(&T) -> bool {
     finished: bool
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for Split<'a, T, P> where P: FnMut(&T) -> bool {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Split")
+            .field("v", &self.v)
+            .field("finished", &self.finished)
+            .finish()
+    }
+}
+
 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T, P> Clone for Split<'a, T, P> where P: Clone + FnMut(&T) -> bool {
@@ -1053,6 +1082,16 @@ pub struct SplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
     finished: bool
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("SplitMut")
+            .field("v", &self.v)
+            .field("finished", &self.finished)
+            .finish()
+    }
+}
+
 impl<'a, T, P> SplitIter for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
     #[inline]
     fn finish(&mut self) -> Option<&'a mut [T]> {
@@ -1127,6 +1166,7 @@ impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
 /// An private iterator over subslices separated by elements that
 /// match a predicate function, splitting at most a fixed number of
 /// times.
+#[derive(Debug)]
 struct GenericSplitN<I> {
     iter: I,
     count: usize,
@@ -1162,6 +1202,15 @@ pub struct SplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
     inner: GenericSplitN<Split<'a, T, P>>
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitN<'a, T, P> where P: FnMut(&T) -> bool {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("SplitN")
+            .field("inner", &self.inner)
+            .finish()
+    }
+}
+
 /// An iterator over subslices separated by elements that match a
 /// predicate function, limited to a given number of splits, starting
 /// from the end of the slice.
@@ -1170,6 +1219,15 @@ pub struct RSplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
     inner: GenericSplitN<Split<'a, T, P>>
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitN<'a, T, P> where P: FnMut(&T) -> bool {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("RSplitN")
+            .field("inner", &self.inner)
+            .finish()
+    }
+}
+
 /// An iterator over subslices separated by elements that match a predicate
 /// function, limited to a given number of splits.
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1177,6 +1235,15 @@ pub struct SplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
     inner: GenericSplitN<SplitMut<'a, T, P>>
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for SplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("SplitNMut")
+            .field("inner", &self.inner)
+            .finish()
+    }
+}
+
 /// An iterator over subslices separated by elements that match a
 /// predicate function, limited to a given number of splits, starting
 /// from the end of the slice.
@@ -1185,6 +1252,15 @@ pub struct RSplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
     inner: GenericSplitN<SplitMut<'a, T, P>>
 }
 
+#[stable(feature = "core_impl_debug", since = "1.9.0")]
+impl<'a, T: 'a + fmt::Debug, P> fmt::Debug for RSplitNMut<'a, T, P> where P: FnMut(&T) -> bool {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("RSplitNMut")
+            .field("inner", &self.inner)
+            .finish()
+    }
+}
+
 macro_rules! forward_iterator {
     ($name:ident: $elem:ident, $iter_of:ty) => {
         #[stable(feature = "rust1", since = "1.0.0")]
@@ -1212,6 +1288,7 @@ forward_iterator! { SplitNMut: T, &'a mut [T] }
 forward_iterator! { RSplitNMut: T, &'a mut [T] }
 
 /// An iterator over overlapping subslices of length `size`.
+#[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Windows<'a, T:'a> {
     v: &'a [T],
@@ -1305,6 +1382,7 @@ impl<'a, T> ExactSizeIterator for Windows<'a, T> {}
 ///
 /// When the slice len is not evenly divided by the chunk size, the last slice
 /// of the iteration will be the remainder.
+#[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Chunks<'a, T:'a> {
     v: &'a [T],
@@ -1405,6 +1483,7 @@ impl<'a, T> ExactSizeIterator for Chunks<'a, T> {}
 /// An iterator over a slice in (non-overlapping) mutable chunks (`size`
 /// elements at a time). When the slice len is not evenly divided by the chunk
 /// size, the last slice of the iteration will be the remainder.
+#[derive(Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct ChunksMut<'a, T:'a> {
     v: &'a mut [T],
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 4ea85c6b6ac..8e467f52fa4 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -323,7 +323,7 @@ Section: Iterators
 /// Created with the method [`chars()`].
 ///
 /// [`chars()`]: ../../std/primitive.str.html#method.chars
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Chars<'a> {
     iter: slice::Iter<'a, u8>
@@ -468,7 +468,7 @@ impl<'a> Chars<'a> {
 }
 
 /// Iterator for a string's characters and their byte offsets.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct CharIndices<'a> {
     front_offset: usize,
@@ -533,7 +533,7 @@ impl<'a> CharIndices<'a> {
 ///
 /// [`bytes()`]: ../../std/primitive.str.html#method.bytes
 #[stable(feature = "rust1", since = "1.0.0")]
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct Bytes<'a>(Cloned<slice::Iter<'a, u8>>);
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -663,6 +663,17 @@ macro_rules! generate_pattern_iterators {
         pub struct $forward_iterator<'a, P: Pattern<'a>>($internal_iterator<'a, P>);
 
         $(#[$common_stability_attribute])*
+        impl<'a, P: Pattern<'a>> fmt::Debug for $forward_iterator<'a, P>
+            where P::Searcher: fmt::Debug
+        {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                f.debug_tuple(stringify!($forward_iterator))
+                    .field(&self.0)
+                    .finish()
+            }
+        }
+
+        $(#[$common_stability_attribute])*
         impl<'a, P: Pattern<'a>> Iterator for $forward_iterator<'a, P> {
             type Item = $iterty;
 
@@ -686,6 +697,17 @@ macro_rules! generate_pattern_iterators {
         pub struct $reverse_iterator<'a, P: Pattern<'a>>($internal_iterator<'a, P>);
 
         $(#[$common_stability_attribute])*
+        impl<'a, P: Pattern<'a>> fmt::Debug for $reverse_iterator<'a, P>
+            where P::Searcher: fmt::Debug
+        {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                f.debug_tuple(stringify!($reverse_iterator))
+                    .field(&self.0)
+                    .finish()
+            }
+        }
+
+        $(#[$common_stability_attribute])*
         impl<'a, P: Pattern<'a>> Iterator for $reverse_iterator<'a, P>
             where P::Searcher: ReverseSearcher<'a>
         {
@@ -746,6 +768,7 @@ derive_pattern_clone!{
     clone SplitInternal
     with |s| SplitInternal { matcher: s.matcher.clone(), ..*s }
 }
+
 struct SplitInternal<'a, P: Pattern<'a>> {
     start: usize,
     end: usize,
@@ -754,6 +777,18 @@ struct SplitInternal<'a, P: Pattern<'a>> {
     finished: bool,
 }
 
+impl<'a, P: Pattern<'a>> fmt::Debug for SplitInternal<'a, P> where P::Searcher: fmt::Debug {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("SplitInternal")
+            .field("start", &self.start)
+            .field("end", &self.end)
+            .field("matcher", &self.matcher)
+            .field("allow_trailing_empty", &self.allow_trailing_empty)
+            .field("finished", &self.finished)
+            .finish()
+    }
+}
+
 impl<'a, P: Pattern<'a>> SplitInternal<'a, P> {
     #[inline]
     fn get_end(&mut self) -> Option<&'a str> {
@@ -852,12 +887,22 @@ derive_pattern_clone!{
     clone SplitNInternal
     with |s| SplitNInternal { iter: s.iter.clone(), ..*s }
 }
+
 struct SplitNInternal<'a, P: Pattern<'a>> {
     iter: SplitInternal<'a, P>,
     /// The number of splits remaining
     count: usize,
 }
 
+impl<'a, P: Pattern<'a>> fmt::Debug for SplitNInternal<'a, P> where P::Searcher: fmt::Debug {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("SplitNInternal")
+            .field("iter", &self.iter)
+            .field("count", &self.count)
+            .finish()
+    }
+}
+
 impl<'a, P: Pattern<'a>> SplitNInternal<'a, P> {
     #[inline]
     fn next(&mut self) -> Option<&'a str> {
@@ -902,8 +947,17 @@ derive_pattern_clone!{
     clone MatchIndicesInternal
     with |s| MatchIndicesInternal(s.0.clone())
 }
+
 struct MatchIndicesInternal<'a, P: Pattern<'a>>(P::Searcher);
 
+impl<'a, P: Pattern<'a>> fmt::Debug for MatchIndicesInternal<'a, P> where P::Searcher: fmt::Debug {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("MatchIndicesInternal")
+            .field(&self.0)
+            .finish()
+    }
+}
+
 impl<'a, P: Pattern<'a>> MatchIndicesInternal<'a, P> {
     #[inline]
     fn next(&mut self) -> Option<(usize, &'a str)> {
@@ -944,8 +998,17 @@ derive_pattern_clone!{
     clone MatchesInternal
     with |s| MatchesInternal(s.0.clone())
 }
+
 struct MatchesInternal<'a, P: Pattern<'a>>(P::Searcher);
 
+impl<'a, P: Pattern<'a>> fmt::Debug for MatchesInternal<'a, P> where P::Searcher: fmt::Debug {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("MatchesInternal")
+            .field(&self.0)
+            .finish()
+    }
+}
+
 impl<'a, P: Pattern<'a>> MatchesInternal<'a, P> {
     #[inline]
     fn next(&mut self) -> Option<&'a str> {
@@ -988,7 +1051,7 @@ generate_pattern_iterators! {
 ///
 /// [`lines()`]: ../../std/primitive.str.html#method.lines
 #[stable(feature = "rust1", since = "1.0.0")]
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct Lines<'a>(Map<SplitTerminator<'a, char>, LinesAnyMap>);
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1019,7 +1082,7 @@ impl<'a> DoubleEndedIterator for Lines<'a> {
 /// [`lines_any()`]: ../../std/primitive.str.html#method.lines_any
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_deprecated(since = "1.4.0", reason = "use lines()/Lines instead now")]
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 #[allow(deprecated)]
 pub struct LinesAny<'a>(Lines<'a>);
 
@@ -1242,7 +1305,7 @@ static UTF8_CHAR_WIDTH: [u8; 256] = [
 /// Struct that contains a `char` and the index of the first byte of
 /// the next `char` in a string.  This can be used as a data structure
 /// for iterating over the UTF-8 bytes of a string.
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug)]
 #[unstable(feature = "str_char",
            reason = "existence of this struct is uncertain as it is frequently \
                      able to be replaced with char.len_utf8() and/or \
diff --git a/src/libcore/str/pattern.rs b/src/libcore/str/pattern.rs
index abad29cb775..b803539e12b 100644
--- a/src/libcore/str/pattern.rs
+++ b/src/libcore/str/pattern.rs
@@ -20,6 +20,7 @@
 use prelude::v1::*;
 
 use cmp;
+use fmt;
 use usize;
 
 // Pattern
@@ -275,7 +276,7 @@ impl<'a> CharEq for &'a [char] {
 
 struct CharEqPattern<C: CharEq>(C);
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 struct CharEqSearcher<'a, C: CharEq> {
     char_eq: C,
     haystack: &'a str,
@@ -415,7 +416,7 @@ macro_rules! searcher_methods {
 /////////////////////////////////////////////////////////////////////////////
 
 /// Associated type for `<char as Pattern<'a>>::Searcher`.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct CharSearcher<'a>(<CharEqPattern<char> as Pattern<'a>>::Searcher);
 
 unsafe impl<'a> Searcher<'a> for CharSearcher<'a> {
@@ -440,7 +441,7 @@ impl<'a> Pattern<'a> for char {
 // Todo: Change / Remove due to ambiguity in meaning.
 
 /// Associated type for `<&[char] as Pattern<'a>>::Searcher`.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct CharSliceSearcher<'a, 'b>(<CharEqPattern<&'b [char]> as Pattern<'a>>::Searcher);
 
 unsafe impl<'a, 'b> Searcher<'a> for CharSliceSearcher<'a, 'b> {
@@ -467,6 +468,17 @@ impl<'a, 'b> Pattern<'a> for &'b [char] {
 pub struct CharPredicateSearcher<'a, F>(<CharEqPattern<F> as Pattern<'a>>::Searcher)
     where F: FnMut(char) -> bool;
 
+impl<'a, F> fmt::Debug for CharPredicateSearcher<'a, F>
+    where F: FnMut(char) -> bool
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("CharPredicateSearcher")
+            .field("haystack", &self.0.haystack)
+            .field("char_indices", &self.0.char_indices)
+            .field("ascii_only", &self.0.ascii_only)
+            .finish()
+    }
+}
 unsafe impl<'a, F> Searcher<'a> for CharPredicateSearcher<'a, F>
     where F: FnMut(char) -> bool
 {
diff --git a/src/libcore/sync/atomic.rs b/src/libcore/sync/atomic.rs
index 2055ca7adf3..7ae129eaf48 100644
--- a/src/libcore/sync/atomic.rs
+++ b/src/libcore/sync/atomic.rs
@@ -162,7 +162,7 @@ unsafe impl<T> Sync for AtomicPtr<T> {}
 /// Rust's memory orderings are [the same as
 /// LLVM's](http://llvm.org/docs/LangRef.html#memory-model-for-concurrent-operations).
 #[stable(feature = "rust1", since = "1.0.0")]
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug)]
 pub enum Ordering {
     /// No ordering constraints, only atomic operations. Corresponds to LLVM's
     /// `Monotonic` ordering.