visit struct fields in uninit fallback check

2 files changed, 55 insertions, 1 deletions

diff --git a/tests/ui/uninit_vec.rs b/tests/ui/uninit_vec.rs
index 0cc77a8775d..464f88140bd 100644
--- a/tests/ui/uninit_vec.rs
+++ b/tests/ui/uninit_vec.rs
@@ -150,4 +150,36 @@ fn main() {
             vec.set_len(10);
         }
     }
+
+    fn nested_union<T>() {
+        let mut vec: Vec<UnsafeCell<MaybeUninit<T>>> = Vec::with_capacity(1);
+        unsafe {
+            vec.set_len(1);
+        }
+    }
+
+    struct Recursive<T>(*const Recursive<T>, MaybeUninit<T>);
+    fn recursive_union<T>() {
+        // Make sure we don't stack overflow on recursive types.
+        // The pointer acts as the base case because it can't be uninit regardless of its pointee.
+
+        let mut vec: Vec<Recursive<T>> = Vec::with_capacity(1);
+        //~^ uninit_vec
+        unsafe {
+            vec.set_len(1);
+        }
+    }
+
+    #[repr(u8)]
+    enum Enum<T> {
+        Variant(T),
+    }
+    fn union_in_enum<T>() {
+        // Enums can have a discriminant that can't be uninit, so this should still warn
+        let mut vec: Vec<Enum<T>> = Vec::with_capacity(1);
+        //~^ uninit_vec
+        unsafe {
+            vec.set_len(1);
+        }
+    }
 }
diff --git a/tests/ui/uninit_vec.stderr b/tests/ui/uninit_vec.stderr
index e8b77d653f0..e7c81cf792f 100644
--- a/tests/ui/uninit_vec.stderr
+++ b/tests/ui/uninit_vec.stderr
@@ -125,5 +125,27 @@ LL |             vec.set_len(10);
    |
    = help: initialize the buffer or wrap the content in `MaybeUninit`
 
-error: aborting due to 12 previous errors
+error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
+  --> tests/ui/uninit_vec.rs:166:9
+   |
+LL |         let mut vec: Vec<Recursive<T>> = Vec::with_capacity(1);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |             vec.set_len(1);
+   |             ^^^^^^^^^^^^^^
+   |
+   = help: initialize the buffer or wrap the content in `MaybeUninit`
+
+error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
+  --> tests/ui/uninit_vec.rs:179:9
+   |
+LL |         let mut vec: Vec<Enum<T>> = Vec::with_capacity(1);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |             vec.set_len(1);
+   |             ^^^^^^^^^^^^^^
+   |
+   = help: initialize the buffer or wrap the content in `MaybeUninit`
+
+error: aborting due to 14 previous errors