1 files changed, 94 insertions, 0 deletions
diff --git a/src/tools/clippy/tests/ui/uninit_vec.rs b/src/tools/clippy/tests/ui/uninit_vec.rs
new file mode 100644
index 00000000000..dc150cf28f2
--- /dev/null
+++ b/src/tools/clippy/tests/ui/uninit_vec.rs
@@ -0,0 +1,94 @@
+#![warn(clippy::uninit_vec)]
+
+use std::mem::MaybeUninit;
+
+#[derive(Default)]
+struct MyVec {
+    vec: Vec<u8>,
+}
+
+fn main() {
+    // with_capacity() -> set_len() should be detected
+    let mut vec: Vec<u8> = Vec::with_capacity(1000);
+    unsafe {
+        vec.set_len(200);
+    }
+
+    // reserve() -> set_len() should be detected
+    vec.reserve(1000);
+    unsafe {
+        vec.set_len(200);
+    }
+
+    // new() -> set_len() should be detected
+    let mut vec: Vec<u8> = Vec::new();
+    unsafe {
+        vec.set_len(200);
+    }
+
+    // default() -> set_len() should be detected
+    let mut vec: Vec<u8> = Default::default();
+    unsafe {
+        vec.set_len(200);
+    }
+
+    let mut vec: Vec<u8> = Vec::default();
+    unsafe {
+        vec.set_len(200);
+    }
+
+    // test when both calls are enclosed in the same unsafe block
+    unsafe {
+        let mut vec: Vec<u8> = Vec::with_capacity(1000);
+        vec.set_len(200);
+
+        vec.reserve(1000);
+        vec.set_len(200);
+    }
+
+    let mut vec: Vec<u8> = Vec::with_capacity(1000);
+    unsafe {
+        // test the case where there are other statements in the following unsafe block
+        vec.set_len(200);
+        assert!(vec.len() == 200);
+    }
+
+    // handle vec stored in the field of a struct
+    let mut my_vec = MyVec::default();
+    my_vec.vec.reserve(1000);
+    unsafe {
+        my_vec.vec.set_len(200);
+    }
+
+    my_vec.vec = Vec::with_capacity(1000);
+    unsafe {
+        my_vec.vec.set_len(200);
+    }
+
+    // Test `#[allow(...)]` attributes on inner unsafe block (shouldn't trigger)
+    let mut vec: Vec<u8> = Vec::with_capacity(1000);
+    #[allow(clippy::uninit_vec)]
+    unsafe {
+        vec.set_len(200);
+    }
+
+    // MaybeUninit-wrapped types should not be detected
+    unsafe {
+        let mut vec: Vec<MaybeUninit<u8>> = Vec::with_capacity(1000);
+        vec.set_len(200);
+
+        let mut vec: Vec<(MaybeUninit<u8>, MaybeUninit<bool>)> = Vec::with_capacity(1000);
+        vec.set_len(200);
+
+        let mut vec: Vec<(MaybeUninit<u8>, [MaybeUninit<bool>; 2])> = Vec::with_capacity(1000);
+        vec.set_len(200);
+    }
+
+    // known false negative
+    let mut vec1: Vec<u8> = Vec::with_capacity(1000);
+    let mut vec2: Vec<u8> = Vec::with_capacity(1000);
+    unsafe {
+        vec1.set_len(200);
+        vec2.set_len(200);
+    }
+}