add `relaxed_struct_unsize` feature gate

3 files changed, 25 insertions, 0 deletions

diff --git a/src/test/ui/feature-gates/feature-gate-relaxed_struct_unsize.rs b/src/test/ui/feature-gates/feature-gate-relaxed_struct_unsize.rs
new file mode 100644
index 00000000000..0cfd0a0b978
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-relaxed_struct_unsize.rs
@@ -0,0 +1,10 @@
+// Test that we allow unsizing even if there is an unchanged param in the
+// field getting unsized.
+struct A<T, U: ?Sized + 'static>(T, B<T, U>);
+struct B<T, U: ?Sized>(T, U);
+
+fn main() {
+    let x: A<[u32; 1], [u32; 1]> = A([0; 1], B([0; 1], [0; 1]));
+    let y: &A<[u32; 1], [u32]> = &x; //~ ERROR mismatched types
+    assert_eq!(y.1.1.len(), 1);
+}
diff --git a/src/test/ui/feature-gates/feature-gate-relaxed_struct_unsize.stderr b/src/test/ui/feature-gates/feature-gate-relaxed_struct_unsize.stderr
new file mode 100644
index 00000000000..f62def47726
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-relaxed_struct_unsize.stderr
@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/feature-gate-relaxed_struct_unsize.rs:8:34
+   |
+LL |     let y: &A<[u32; 1], [u32]> = &x;
+   |            -------------------   ^^ expected slice `[u32]`, found array `[u32; 1]`
+   |            |
+   |            expected due to this
+   |
+   = note: expected reference `&A<[u32; 1], [u32]>`
+              found reference `&A<[u32; 1], [u32; 1]>`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/unsized/unchanged-param.rs b/src/test/ui/unsized/unchanged-param.rs
index 93c7af68ac3..83199e8112e 100644
--- a/src/test/ui/unsized/unchanged-param.rs
+++ b/src/test/ui/unsized/unchanged-param.rs
@@ -1,3 +1,4 @@
+#![feature(relaxed_struct_unsize)]
 // run-pass
 // Test that we allow unsizing even if there is an unchanged param in the
 // field getting unsized.