Update upstream source from tag 'upstream/1.52.1+dfsg1'

[rustc.git] / src / tools / clippy / tests / ui / repl_uninit.rs

diff --git a/src/tools/clippy/tests/ui/repl_uninit.rs b/src/tools/clippy/tests/ui/repl_uninit.rs
new file mode 100644 (file)
index 0000000..ad5b8e4
--- /dev/null
+++ b/src/tools/clippy/tests/ui/repl_uninit.rs
@@ -0,0 +1,41 @@
+#![allow(deprecated, invalid_value)]
+#![warn(clippy::all)]
+
+use std::mem;
+
+fn might_panic<X>(x: X) -> X {
+    // in practice this would be a possibly-panicky operation
+    x
+}
+
+fn main() {
+    let mut v = vec![0i32; 4];
+    // the following is UB if `might_panic` panics
+    unsafe {
+        let taken_v = mem::replace(&mut v, mem::uninitialized());
+        let new_v = might_panic(taken_v);
+        std::mem::forget(mem::replace(&mut v, new_v));
+    }
+
+    unsafe {
+        let taken_v = mem::replace(&mut v, mem::MaybeUninit::uninit().assume_init());
+        let new_v = might_panic(taken_v);
+        std::mem::forget(mem::replace(&mut v, new_v));
+    }
+
+    unsafe {
+        let taken_v = mem::replace(&mut v, mem::zeroed());
+        let new_v = might_panic(taken_v);
+        std::mem::forget(mem::replace(&mut v, new_v));
+    }
+
+    // this is silly but OK, because usize is a primitive type
+    let mut u: usize = 42;
+    let uref = &mut u;
+    let taken_u = unsafe { mem::replace(uref, mem::zeroed()) };
+    *uref = taken_u + 1;
+
+    // this is still not OK, because uninit
+    let taken_u = unsafe { mem::replace(uref, mem::uninitialized()) };
+    *uref = taken_u + 1;
+}