diff --git a/library/core/src/any.rs b/library/core/src/any.rs
index eef8f2046d33e..c9882d5350e2c 100644
--- a/library/core/src/any.rs
+++ b/library/core/src/any.rs
@@ -435,7 +435,7 @@ impl dyn Any + Send + Sync {
 /// While `TypeId` implements `Hash`, `PartialOrd`, and `Ord`, it is worth
 /// noting that the hashes and ordering will vary between Rust releases. Beware
 /// of relying on them inside of your code!
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct TypeId {
     t: u64,
@@ -464,6 +464,13 @@ impl TypeId {
     }
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+impl fmt::Debug for TypeId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("TypeId(_)")
+    }
+}
+
 /// Returns the name of a type as a string slice.
 ///
 /// # Note
diff --git a/library/core/src/mem/mod.rs b/library/core/src/mem/mod.rs
index 778e34e634f64..abfa657f76bbc 100644
--- a/library/core/src/mem/mod.rs
+++ b/library/core/src/mem/mod.rs
@@ -988,7 +988,7 @@ impl<T> hash::Hash for Discriminant<T> {
 #[stable(feature = "discriminant_value", since = "1.21.0")]
 impl<T> fmt::Debug for Discriminant<T> {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt.debug_tuple("Discriminant").field(&self.0).finish()
+        fmt.pad("Discriminant(_)")
     }
 }
 
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index 0ef848ff0c4c1..2493dd1dc44dd 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -985,7 +985,7 @@ pub fn park_timeout(dur: Duration) {
 ///
 /// [`id`]: Thread::id
 #[stable(feature = "thread_id", since = "1.19.0")]
-#[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
+#[derive(Eq, PartialEq, Clone, Copy, Hash)]
 pub struct ThreadId(NonZeroU64);
 
 impl ThreadId {
@@ -1025,6 +1025,13 @@ impl ThreadId {
     }
 }
 
+#[stable(feature = "thread_id", since = "1.19.0")]
+impl fmt::Debug for ThreadId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.pad("ThreadId(_)")
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Thread
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/library/std/src/time.rs b/library/std/src/time.rs
index 89addae078948..3c9cc5614bf16 100644
--- a/library/std/src/time.rs
+++ b/library/std/src/time.rs
@@ -410,7 +410,9 @@ impl Sub<Instant> for Instant {
 #[stable(feature = "time2", since = "1.8.0")]
 impl fmt::Debug for Instant {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.0.fmt(f)
+        // Instant is an opaque type and only useful with `Duration`. So it
+        // would be misleading to show implementation detail in the output.
+        f.pad("Instant(_)")
     }
 }