1 files changed, 76 insertions, 0 deletions
diff --git a/src/tools/miri/tests/pass/coercions.rs b/src/tools/miri/tests/pass/coercions.rs
new file mode 100644
index 00000000000..db0d2ffd44b
--- /dev/null
+++ b/src/tools/miri/tests/pass/coercions.rs
@@ -0,0 +1,76 @@
+#![feature(coerce_unsized, unsize)]
+
+use std::marker::Unsize;
+use std::ops::CoerceUnsized;
+
+fn identity_coercion(x: &(dyn Fn(u32) -> u32 + Send)) -> &dyn Fn(u32) -> u32 {
+    x
+}
+fn fn_coercions(f: &fn(u32) -> u32) -> (unsafe fn(u32) -> u32, &(dyn Fn(u32) -> u32 + Send)) {
+    (*f, f)
+}
+
+fn simple_array_coercion(x: &[u8; 3]) -> &[u8] {
+    x
+}
+
+fn square(a: u32) -> u32 {
+    a * a
+}
+
+#[derive(PartialEq, Eq)]
+struct PtrWrapper<'a, T: 'a + ?Sized>(u32, u32, (), &'a T);
+impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<PtrWrapper<'a, U>> for PtrWrapper<'a, T> {}
+
+struct TrivPtrWrapper<'a, T: 'a + ?Sized>(&'a T);
+impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<TrivPtrWrapper<'a, U>>
+    for TrivPtrWrapper<'a, T>
+{
+}
+
+fn coerce_ptr_wrapper(p: PtrWrapper<[u8; 3]>) -> PtrWrapper<[u8]> {
+    p
+}
+
+fn coerce_triv_ptr_wrapper(p: TrivPtrWrapper<[u8; 3]>) -> TrivPtrWrapper<[u8]> {
+    p
+}
+
+fn coerce_fat_ptr_wrapper(
+    p: PtrWrapper<dyn Fn(u32) -> u32 + Send>,
+) -> PtrWrapper<dyn Fn(u32) -> u32> {
+    p
+}
+
+fn coerce_ptr_wrapper_poly<'a, T, Trait: ?Sized>(p: PtrWrapper<'a, T>) -> PtrWrapper<'a, Trait>
+where
+    PtrWrapper<'a, T>: CoerceUnsized<PtrWrapper<'a, Trait>>,
+{
+    p
+}
+
+fn main() {
+    let a = [0, 1, 2];
+    let square_local: fn(u32) -> u32 = square;
+    let (f, g) = fn_coercions(&square_local);
+    // cannot use `square as *const ()` because we can't know whether the compiler duplicates
+    // functions, so two function pointers are only equal if they result from the same function
+    // to function pointer cast
+    assert_eq!(f as *const (), square_local as *const ());
+    assert_eq!(g(4), 16);
+    assert_eq!(identity_coercion(g)(5), 25);
+
+    assert_eq!(simple_array_coercion(&a), &a);
+    let w = coerce_ptr_wrapper(PtrWrapper(2, 3, (), &a));
+    assert!(w == PtrWrapper(2, 3, (), &a) as PtrWrapper<[u8]>);
+
+    let w = coerce_triv_ptr_wrapper(TrivPtrWrapper(&a));
+    assert_eq!(&w.0, &a);
+
+    let z = coerce_fat_ptr_wrapper(PtrWrapper(2, 3, (), &square_local));
+    assert_eq!((z.3)(6), 36);
+
+    let z: PtrWrapper<dyn Fn(u32) -> u32> =
+        coerce_ptr_wrapper_poly(PtrWrapper(2, 3, (), &square_local));
+    assert_eq!((z.3)(6), 36);
+}