Add testcases

clippy_utils/src/higher.rs

@@ -658,18 +658,18 @@ pub fn get_vec_init_kind<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -
             {
                 if name.ident.name == sym::new {
                     return Some(VecInitKind::New);
+                } else if name.ident.name.as_str() == "default" {
+                    return Some(VecInitKind::Default);
                 } else if name.ident.name.as_str() == "with_capacity" {
-                    return args.get(0).and_then(|arg| {
-                        if_chain! {
-                            if let ExprKind::Lit(lit) = &arg.kind;
-                            if let LitKind::Int(num, _) = lit.node;
-                            then {
-                                Some(VecInitKind::WithLiteralCapacity(num.try_into().ok()?))
-                            } else {
-                                Some(VecInitKind::WithExprCapacity(arg.hir_id))
-                            }
+                    let arg = args.get(0)?;
+                    if_chain! {
+                        if let ExprKind::Lit(lit) = &arg.kind;
+                        if let LitKind::Int(num, _) = lit.node;
+                        then {
+                            return Some(VecInitKind::WithLiteralCapacity(num.try_into().ok()?))
                         }
-                    });
+                    }
+                    return Some(VecInitKind::WithExprCapacity(arg.hir_id));
                 }
             }
             ExprKind::Path(QPath::Resolved(_, path))

tests/ui/uninit_vec.rs

@@ -20,6 +20,23 @@ fn main() {
         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);

tests/ui/uninit_vec.stderr

@@ -22,7 +22,40 @@ LL |         vec.set_len(200);
    = help: initialize the buffer or wrap the content in `MaybeUninit`
 
 error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
-  --> $DIR/uninit_vec.rs:32:5
+  --> $DIR/uninit_vec.rs:24:5
+   |
+LL |     let mut vec: Vec<u8> = Vec::new();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     unsafe {
+LL |         vec.set_len(200);
+   |         ^^^^^^^^^^^^^^^^
+   |
+   = help: initialize the buffer or wrap the content in `MaybeUninit`
+
+error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
+  --> $DIR/uninit_vec.rs:30:5
+   |
+LL |     let mut vec: Vec<u8> = Default::default();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     unsafe {
+LL |         vec.set_len(200);
+   |         ^^^^^^^^^^^^^^^^
+   |
+   = help: initialize the buffer or wrap the content in `MaybeUninit`
+
+error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
+  --> $DIR/uninit_vec.rs:35:5
+   |
+LL |     let mut vec: Vec<u8> = Vec::default();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     unsafe {
+LL |         vec.set_len(200);
+   |         ^^^^^^^^^^^^^^^^
+   |
+   = help: initialize the buffer or wrap the content in `MaybeUninit`
+
+error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
+  --> $DIR/uninit_vec.rs:49:5
    |
 LL |     let mut vec: Vec<u8> = Vec::with_capacity(1000);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -33,7 +66,7 @@ LL |         vec.set_len(200);
    = help: initialize the buffer or wrap the content in `MaybeUninit`
 
 error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
-  --> $DIR/uninit_vec.rs:41:5
+  --> $DIR/uninit_vec.rs:58:5
    |
 LL |     my_vec.vec.reserve(1000);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -44,7 +77,7 @@ LL |         my_vec.vec.set_len(200);
    = help: initialize the buffer or wrap the content in `MaybeUninit`
 
 error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
-  --> $DIR/uninit_vec.rs:46:5
+  --> $DIR/uninit_vec.rs:63:5
    |
 LL |     my_vec.vec = Vec::with_capacity(1000);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -55,7 +88,7 @@ LL |         my_vec.vec.set_len(200);
    = help: initialize the buffer or wrap the content in `MaybeUninit`
 
 error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
-  --> $DIR/uninit_vec.rs:25:9
+  --> $DIR/uninit_vec.rs:42:9
    |
 LL |         let mut vec: Vec<u8> = Vec::with_capacity(1000);
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -65,7 +98,7 @@ LL |         vec.set_len(200);
    = help: initialize the buffer or wrap the content in `MaybeUninit`
 
 error: calling `set_len()` immediately after reserving a buffer creates uninitialized values
-  --> $DIR/uninit_vec.rs:28:9
+  --> $DIR/uninit_vec.rs:45:9
    |
 LL |         vec.reserve(1000);
    |         ^^^^^^^^^^^^^^^^^^
@@ -74,5 +107,5 @@ LL |         vec.set_len(200);
    |
    = help: initialize the buffer or wrap the content in `MaybeUninit`
 
-error: aborting due to 7 previous errors
+error: aborting due to 10 previous errors