Merge commit 'd5e2a7aca5' into clippyup

tests/ui/uninit.rs

@@ -3,13 +3,15 @@
 
 use std::mem::{self, MaybeUninit};
 
+union MyOwnMaybeUninit {
+    value: u8,
+    uninit: (),
+}
+
 fn main() {
     let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
 
-    // edge case: For now we lint on empty arrays
-    let _: [u8; 0] = unsafe { MaybeUninit::uninit().assume_init() };
-
-    // edge case: For now we accept unit tuples
+    // This is OK, because ZSTs do not contain data.
     let _: () = unsafe { MaybeUninit::uninit().assume_init() };
 
     // This is OK, because `MaybeUninit` allows uninitialized data.
@@ -21,6 +23,19 @@ fn main() {
     // This is OK, because all constitutent types are uninit-compatible.
     let _: (MaybeUninit<usize>, [MaybeUninit<bool>; 2]) = unsafe { MaybeUninit::uninit().assume_init() };
 
+    // This is OK, because our own MaybeUninit is just as fine as the one from core.
+    let _: MyOwnMaybeUninit = unsafe { MaybeUninit::uninit().assume_init() };
+
+    // This is OK, because empty arrays don't contain data.
+    let _: [u8; 0] = unsafe { MaybeUninit::uninit().assume_init() };
+
     // Was a false negative.
     let _: usize = unsafe { mem::MaybeUninit::uninit().assume_init() };
+
+    polymorphic::<()>();
+
+    fn polymorphic<T>() {
+        // We are conservative around polymorphic types.
+        let _: T = unsafe { mem::MaybeUninit::uninit().assume_init() };
+    }
 }