Implement Random for tuple

Implement `Random` for tuples of arity 12 or less. Each element is
expected to implement `Random`.

Author: sorairolake

library/core/src/primitive_docs.rs

@@ -1082,11 +1082,13 @@ mod prim_str {}
 /// * [`Debug`]
 /// * [`Default`]
 /// * [`Hash`]
+/// * [`Random`]
 /// * [`From<[T; N]>`][from]
 ///
 /// [from]: convert::From
 /// [`Debug`]: fmt::Debug
 /// [`Hash`]: hash::Hash
+/// [`Random`]: random::Random
 ///
 /// The following traits are implemented for tuples of any length. These traits have
 /// implementations that are automatically generated by the compiler, so are not limited by

library/core/src/tuple.rs

@@ -2,6 +2,7 @@
 
 use crate::cmp::Ordering::{self, *};
 use crate::marker::{ConstParamTy_, StructuralPartialEq, UnsizedConstParamTy};
+use crate::random::{Random, RandomSource};
 
 // Recursive macro for implementing n-ary tuple functions and operations
 //
@@ -122,6 +123,16 @@ macro_rules! tuple_impls {
             }
         }
 
+        maybe_tuple_doc! {
+            $($T)+ @
+            #[unstable(feature = "random", issue = "130703")]
+            impl<$($T: Random),+> Random for ($($T,)+) {
+                fn random(source: &mut (impl RandomSource + ?Sized)) -> Self {
+                    ($({ let x: $T = Random::random(source); x},)+)
+                }
+            }
+        }
+
         maybe_tuple_doc! {
             $($T)+ @
             #[stable(feature = "array_tuple_conv", since = "1.71.0")]