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.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/libstd/rand/mod.rs b/src/libstd/rand/mod.rs
index f48325218fb..b853e83de5d 100644
--- a/src/libstd/rand/mod.rs
+++ b/src/libstd/rand/mod.rs
@@ -59,6 +59,7 @@
 #![unstable(feature = "rand", issue = "0")]
 
 use cell::RefCell;
+use fmt;
 use io;
 use mem;
 use rc::Rc;
@@ -143,6 +144,12 @@ pub struct ThreadRng {
     rng: Rc<RefCell<ThreadRngInner>>,
 }
 
+impl fmt::Debug for ThreadRng {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("ThreadRng { .. }")
+    }
+}
+
 /// Retrieve the lazily-initialized thread-local random number
 /// generator, seeded by the system. Intended to be used in method
 /// chaining style, e.g. `thread_rng().gen::<isize>()`.