1 files changed, 56 insertions, 0 deletions
diff --git a/tests/ui/unsafe/unsafe-borrow.rs b/tests/ui/unsafe/unsafe-borrow.rs
new file mode 100644
index 00000000000..8dddc70be45
--- /dev/null
+++ b/tests/ui/unsafe/unsafe-borrow.rs
@@ -0,0 +1,56 @@
+// revisions: mirunsafeck thirunsafeck
+// [thirunsafeck]compile-flags: -Z thir-unsafeck
+
+#![feature(rustc_attrs)]
+#![allow(unused,dead_code)]
+
+fn tuple_struct() {
+    #[rustc_layout_scalar_valid_range_start(1)]
+    struct NonZero<T>(T);
+
+    let mut foo = unsafe { NonZero((1,)) };
+    let a = &mut foo.0.0;
+    //~^ ERROR: mutation of layout constrained field is unsafe
+}
+
+fn slice() {
+    #[rustc_layout_scalar_valid_range_start(1)]
+    struct NonZero<'a, T>(&'a mut [T]);
+
+    let mut nums = [1, 2, 3, 4];
+    let mut foo = unsafe { NonZero(&mut nums[..]) };
+    let a = &mut foo.0[2];
+    // ^ not unsafe because there is an implicit dereference here
+}
+
+fn array() {
+    #[rustc_layout_scalar_valid_range_start(1)]
+    struct NonZero<T>([T; 4]);
+
+    let nums = [1, 2, 3, 4];
+    let mut foo = unsafe { NonZero(nums) };
+    let a = &mut foo.0[2];
+    //~^ ERROR: mutation of layout constrained field is unsafe
+}
+
+fn block() {
+    #[rustc_layout_scalar_valid_range_start(1)]
+    struct NonZero<T>(T);
+
+    let foo = unsafe { NonZero((1,)) };
+    &mut { foo.0 }.0;
+    // ^ not unsafe because the result of the block expression is a new place
+}
+
+fn mtch() {
+    #[rustc_layout_scalar_valid_range_start(1)]
+    struct NonZero<T>(T);
+
+    let mut foo = unsafe { NonZero((1,)) };
+    match &mut foo {
+        NonZero((a,)) => *a = 0,
+        //~^ ERROR: mutation of layout constrained field is unsafe
+    }
+}
+
+fn main() {}