1 files changed, 169 insertions, 0 deletions
diff --git a/src/test/ui/lint/invalid_value.rs b/src/test/ui/lint/invalid_value.rs
new file mode 100644
index 000000000..57d8cbe7c
--- /dev/null
+++ b/src/test/ui/lint/invalid_value.rs
@@ -0,0 +1,169 @@
+// This test checks that calling `mem::{uninitialized,zeroed}` with certain types results
+// in a lint.
+
+#![feature(never_type, rustc_attrs)]
+#![allow(deprecated)]
+#![deny(invalid_value)]
+
+use std::mem::{self, MaybeUninit};
+use std::ptr::NonNull;
+use std::num::NonZeroU32;
+
+enum Void {}
+
+struct Ref(&'static i32);
+struct RefPair((&'static i32, i32));
+
+struct Wrap<T> { wrapped: T }
+enum WrapEnum<T> { Wrapped(T) }
+
+#[rustc_layout_scalar_valid_range_start(0)]
+#[rustc_layout_scalar_valid_range_end(128)]
+#[repr(transparent)]
+pub(crate) struct NonBig(u64);
+
+/// A two-variant enum, thus needs a tag and may not remain uninitialized.
+enum Fruit {
+    Apple,
+    Banana,
+}
+
+/// Looks like two variants but really only has one.
+enum OneFruit {
+    Apple(!),
+    Banana,
+}
+
+enum OneFruitNonZero {
+    Apple(!),
+    Banana(NonZeroU32),
+}
+
+enum TwoUninhabited {
+    A(!),
+    B(Void),
+}
+
+#[rustc_layout_scalar_valid_range_start(254)]
+#[rustc_layout_scalar_valid_range_end(1)]
+pub(crate) struct WrapAroundRange(u8);
+
+#[allow(unused)]
+fn generic<T: 'static>() {
+    unsafe {
+        let _val: &'static T = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: &'static T = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Wrap<&'static T> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: Wrap<&'static T> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+    }
+}
+
+fn main() {
+    unsafe {
+        // Things that cannot even be zero.
+        let _val: ! = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: ! = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: (i32, !) = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: (i32, !) = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Void = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: Void = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: &'static i32 = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: &'static i32 = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Ref = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: Ref = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: fn() = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: fn() = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Wrap<fn()> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: Wrap<fn()> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: WrapEnum<fn()> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: WrapEnum<fn()> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Wrap<(RefPair, i32)> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: Wrap<(RefPair, i32)> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: NonNull<i32> = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: NonNull<i32> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: (NonZeroU32, i32) = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: (NonZeroU32, i32) = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: *const dyn Send = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: *const dyn Send = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: [fn(); 2] = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: [fn(); 2] = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: TwoUninhabited = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: TwoUninhabited = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: OneFruitNonZero = mem::zeroed(); //~ ERROR: does not permit zero-initialization
+        let _val: OneFruitNonZero = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        // Things that can be zero, but not uninit.
+        let _val: bool = mem::zeroed();
+        let _val: bool = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Wrap<char> = mem::zeroed();
+        let _val: Wrap<char> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: NonBig = mem::zeroed();
+        let _val: NonBig = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: Fruit = mem::zeroed();
+        let _val: Fruit = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: [bool; 2] = mem::zeroed();
+        let _val: [bool; 2] = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: i32 = mem::zeroed();
+        let _val: i32 = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: f32 = mem::zeroed();
+        let _val: f32 = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: *const () = mem::zeroed();
+        let _val: *const () = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: *const [()] = mem::zeroed();
+        let _val: *const [()] = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        let _val: WrapAroundRange = mem::zeroed();
+        let _val: WrapAroundRange = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        // Things where 0 is okay due to rustc implementation details,
+        // but that are not guaranteed to keep working.
+        let _val: Result<i32, i32> = mem::zeroed();
+        let _val: Result<i32, i32> = mem::uninitialized(); //~ ERROR: does not permit being left uninitialized
+
+        // Some things that happen to be UB-free due to rustc implementation details,
+        // but are not guaranteed to keep working.
+        let _val: OneFruit = mem::zeroed();
+        let _val: OneFruit = mem::uninitialized();
+
+        // Transmute-from-0
+        let _val: &'static i32 = mem::transmute(0usize); //~ ERROR: does not permit zero-initialization
+        let _val: &'static [i32] = mem::transmute((0usize, 0usize)); //~ ERROR: does not permit zero-initialization
+        let _val: NonZeroU32 = mem::transmute(0); //~ ERROR: does not permit zero-initialization
+
+        // `MaybeUninit` cases
+        let _val: NonNull<i32> = MaybeUninit::zeroed().assume_init(); //~ ERROR: does not permit zero-initialization
+        let _val: NonNull<i32> = MaybeUninit::uninit().assume_init(); //~ ERROR: does not permit being left uninitialized
+        let _val: bool = MaybeUninit::uninit().assume_init(); //~ ERROR: does not permit being left uninitialized
+
+        // Some more types that should work just fine.
+        let _val: Option<&'static i32> = mem::zeroed();
+        let _val: Option<fn()> = mem::zeroed();
+        let _val: MaybeUninit<&'static i32> = mem::zeroed();
+        let _val: bool = MaybeUninit::zeroed().assume_init();
+        let _val: [bool; 0] = MaybeUninit::uninit().assume_init();
+        let _val: [!; 0] = MaybeUninit::zeroed().assume_init();
+    }
+}