Add tuple trait tests

src/test/ui/explore-issue-38412.stderr

@@ -43,19 +43,19 @@ LL |     t.2;
    = note: see issue #38412 <https://github.com/rust-lang/rust/issues/38412> for more information
    = help: add `#![feature(unstable_undeclared)]` to the crate attributes to enable
 
-error[E0616]: field `3` of struct `Tuple` is private
+error[E0616]: field `3` of struct `pub_and_stability::Tuple` is private
   --> $DIR/explore-issue-38412.rs:36:7
    |
 LL |     t.3;
    |       ^ private field
 
-error[E0616]: field `4` of struct `Tuple` is private
+error[E0616]: field `4` of struct `pub_and_stability::Tuple` is private
   --> $DIR/explore-issue-38412.rs:37:7
    |
 LL |     t.4;
    |       ^ private field
 
-error[E0616]: field `5` of struct `Tuple` is private
+error[E0616]: field `5` of struct `pub_and_stability::Tuple` is private
   --> $DIR/explore-issue-38412.rs:38:7
    |
 LL |     t.5;

src/test/ui/tuple/builtin-fail.rs

@@ -0,0 +1,19 @@
+#![feature(tuple_trait)]
+
+fn assert_is_tuple<T: std::marker::Tuple + ?Sized>() {}
+
+struct TupleStruct(i32, i32);
+
+fn from_param_env<T>() {
+    assert_is_tuple::<T>();
+    //~^ ERROR `T` is not a tuple
+}
+
+fn main() {
+    assert_is_tuple::<i32>();
+    //~^ ERROR `i32` is not a tuple
+    assert_is_tuple::<(i32)>();
+    //~^ ERROR `i32` is not a tuple
+    assert_is_tuple::<TupleStruct>();
+    //~^ ERROR `TupleStruct` is not a tuple
+}

src/test/ui/tuple/builtin-fail.stderr

@@ -0,0 +1,55 @@
+error[E0277]: `T` is not a tuple
+  --> $DIR/builtin-fail.rs:8:23
+   |
+LL |     assert_is_tuple::<T>();
+   |                       ^ the trait `Tuple` is not implemented for `T`
+   |
+note: required by a bound in `assert_is_tuple`
+  --> $DIR/builtin-fail.rs:3:23
+   |
+LL | fn assert_is_tuple<T: std::marker::Tuple + ?Sized>() {}
+   |                       ^^^^^^^^^^^^^^^^^^ required by this bound in `assert_is_tuple`
+help: consider restricting type parameter `T`
+   |
+LL | fn from_param_env<T: std::marker::Tuple>() {
+   |                    ++++++++++++++++++++
+
+error[E0277]: `i32` is not a tuple
+  --> $DIR/builtin-fail.rs:13:23
+   |
+LL |     assert_is_tuple::<i32>();
+   |                       ^^^ the trait `Tuple` is not implemented for `i32`
+   |
+note: required by a bound in `assert_is_tuple`
+  --> $DIR/builtin-fail.rs:3:23
+   |
+LL | fn assert_is_tuple<T: std::marker::Tuple + ?Sized>() {}
+   |                       ^^^^^^^^^^^^^^^^^^ required by this bound in `assert_is_tuple`
+
+error[E0277]: `i32` is not a tuple
+  --> $DIR/builtin-fail.rs:15:24
+   |
+LL |     assert_is_tuple::<(i32)>();
+   |                        ^^^ the trait `Tuple` is not implemented for `i32`
+   |
+note: required by a bound in `assert_is_tuple`
+  --> $DIR/builtin-fail.rs:3:23
+   |
+LL | fn assert_is_tuple<T: std::marker::Tuple + ?Sized>() {}
+   |                       ^^^^^^^^^^^^^^^^^^ required by this bound in `assert_is_tuple`
+
+error[E0277]: `TupleStruct` is not a tuple
+  --> $DIR/builtin-fail.rs:17:23
+   |
+LL |     assert_is_tuple::<TupleStruct>();
+   |                       ^^^^^^^^^^^ the trait `Tuple` is not implemented for `TupleStruct`
+   |
+note: required by a bound in `assert_is_tuple`
+  --> $DIR/builtin-fail.rs:3:23
+   |
+LL | fn assert_is_tuple<T: std::marker::Tuple + ?Sized>() {}
+   |                       ^^^^^^^^^^^^^^^^^^ required by this bound in `assert_is_tuple`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/tuple/builtin.rs

@@ -0,0 +1,20 @@
+// check-pass
+
+#![feature(tuple_trait)]
+
+fn assert_is_tuple<T: std::marker::Tuple + ?Sized>() {}
+
+struct Unsized([u8]);
+
+fn from_param_env<T: std::marker::Tuple + ?Sized>() {
+    assert_is_tuple::<T>();
+}
+
+fn main() {
+    assert_is_tuple::<()>();
+    assert_is_tuple::<(i32,)>();
+    assert_is_tuple::<(Unsized,)>();
+    from_param_env::<()>();
+    from_param_env::<(i32,)>();
+    from_param_env::<(Unsized,)>();
+}