diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 3a92f5806c9ef..b32fc96164a30 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -1349,9 +1349,8 @@ declare_lint! {
/// ### Example
///
/// ```rust
- /// #![feature(box_syntax)]
/// fn main() {
- /// let a = (box [1, 2, 3]).len();
+ /// let a = Box::new([1, 2, 3]).len();
/// }
/// ```
///
@@ -1373,6 +1372,11 @@ impl<'tcx> LateLintPass<'tcx> for UnusedAllocation {
fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
match e.kind {
hir::ExprKind::Box(_) => {}
+ hir::ExprKind::Call(path_expr, [_])
+ if let hir::ExprKind::Path(qpath) = &path_expr.kind
+ && let Some(did) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()
+ && cx.tcx.is_diagnostic_item(sym::box_new, did)
+ => {}
_ => return,
}
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index fb579e4ff772a..a76bf45ec890a 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -429,6 +429,7 @@ symbols! {
borrowck_graphviz_format,
borrowck_graphviz_postflow,
box_free,
+ box_new,
box_patterns,
box_syntax,
bpf_target_feature,
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index 44a37899007f8..241b11c3f5f52 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -214,6 +214,7 @@ impl<T> Box<T> {
#[inline(always)]
#[stable(feature = "rust1", since = "1.0.0")]
#[must_use]
+ #[rustc_diagnostic_item = "box_new"]
pub fn new(x: T) -> Self {
#[rustc_box]
Box::new(x)
diff --git a/library/alloc/src/tests.rs b/library/alloc/src/tests.rs
index 299ed156a5d27..b1d3a9fa8ac90 100644
--- a/library/alloc/src/tests.rs
+++ b/library/alloc/src/tests.rs
@@ -4,7 +4,6 @@ use core::any::Any;
use core::clone::Clone;
use core::convert::TryInto;
use core::ops::Deref;
-use core::result::Result::{Err, Ok};
use std::boxed::Box;
@@ -15,7 +14,7 @@ fn test_owned_clone() {
assert!(a == b);
}
-#[derive(PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq)]
struct Test;
#[test]
@@ -23,24 +22,17 @@ fn any_move() {
let a = Box::new(8) as Box<dyn Any>;
let b = Box::new(Test) as Box<dyn Any>;
- match a.downcast::<i32>() {
- Ok(a) => {
- assert!(a == Box::new(8));
- }
- Err(..) => panic!(),
- }
- match b.downcast::<Test>() {
- Ok(a) => {
- assert!(a == Box::new(Test));
- }
- Err(..) => panic!(),
- }
+ let a: Box<i32> = a.downcast::<i32>().unwrap();
+ assert_eq!(*a, 8);
+
+ let b: Box<Test> = b.downcast::<Test>().unwrap();
+ assert_eq!(*b, Test);
let a = Box::new(8) as Box<dyn Any>;
let b = Box::new(Test) as Box<dyn Any>;
- assert!(a.downcast::<Box<Test>>().is_err());
- assert!(b.downcast::<Box<i32>>().is_err());
+ assert!(a.downcast::<Box<i32>>().is_err());
+ assert!(b.downcast::<Box<Test>>().is_err());
}
#[test]
diff --git a/tests/ui/issues/issue-3029.rs b/tests/ui/issues/issue-3029.rs
index a5d30960a4cdb..43c8a0a23fb5b 100644
--- a/tests/ui/issues/issue-3029.rs
+++ b/tests/ui/issues/issue-3029.rs
@@ -2,9 +2,7 @@
// error-pattern:so long
// ignore-emscripten no processes
-#![allow(unused_allocation)]
#![allow(unreachable_code)]
-#![allow(unused_variables)]
fn main() {
let mut x = Vec::new();
diff --git a/tests/ui/iterators/into-iter-on-arrays-lint.fixed b/tests/ui/iterators/into-iter-on-arrays-lint.fixed
index 6e02a7024b949..5b91aaf9ea554 100644
--- a/tests/ui/iterators/into-iter-on-arrays-lint.fixed
+++ b/tests/ui/iterators/into-iter-on-arrays-lint.fixed
@@ -2,7 +2,7 @@
// run-rustfix
// rustfix-only-machine-applicable
-#[allow(unused_must_use)]
+#[allow(unused_must_use, unused_allocation)]
fn main() {
let small = [1, 2];
let big = [0u8; 33];
diff --git a/tests/ui/iterators/into-iter-on-arrays-lint.rs b/tests/ui/iterators/into-iter-on-arrays-lint.rs
index 582d5cadd0658..25b0cef73d777 100644
--- a/tests/ui/iterators/into-iter-on-arrays-lint.rs
+++ b/tests/ui/iterators/into-iter-on-arrays-lint.rs
@@ -2,7 +2,7 @@
// run-rustfix
// rustfix-only-machine-applicable
-#[allow(unused_must_use)]
+#[allow(unused_must_use, unused_allocation)]
fn main() {
let small = [1, 2];
let big = [0u8; 33];
diff --git a/tests/ui/lint/unused/unused-allocation.rs b/tests/ui/lint/unused/unused-allocation.rs
new file mode 100644
index 0000000000000..c1a6f5ceaf178
--- /dev/null
+++ b/tests/ui/lint/unused/unused-allocation.rs
@@ -0,0 +1,7 @@
+#![feature(rustc_attrs, stmt_expr_attributes)]
+#![deny(unused_allocation)]
+
+fn main() {
+ _ = (#[rustc_box] Box::new([1])).len(); //~ error: unnecessary allocation, use `&` instead
+ _ = Box::new([1]).len(); //~ error: unnecessary allocation, use `&` instead
+}
diff --git a/tests/ui/lint/unused/unused-allocation.stderr b/tests/ui/lint/unused/unused-allocation.stderr
new file mode 100644
index 0000000000000..c9ccfbd30e5d4
--- /dev/null
+++ b/tests/ui/lint/unused/unused-allocation.stderr
@@ -0,0 +1,20 @@
+error: unnecessary allocation, use `&` instead
+ --> $DIR/unused-allocation.rs:5:9
+ |
+LL | _ = (#[rustc_box] Box::new([1])).len();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+note: the lint level is defined here
+ --> $DIR/unused-allocation.rs:2:9
+ |
+LL | #![deny(unused_allocation)]
+ | ^^^^^^^^^^^^^^^^^
+
+error: unnecessary allocation, use `&` instead
+ --> $DIR/unused-allocation.rs:6:9
+ |
+LL | _ = Box::new([1]).len();
+ | ^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
diff --git a/tests/ui/self/arbitrary_self_types_trait.rs b/tests/ui/self/arbitrary_self_types_trait.rs
index 973c7cae85a94..c4651ec717787 100644
--- a/tests/ui/self/arbitrary_self_types_trait.rs
+++ b/tests/ui/self/arbitrary_self_types_trait.rs
@@ -1,4 +1,5 @@
// run-pass
+#![allow(unused_allocation)]
use std::rc::Rc;
@@ -13,7 +14,7 @@ impl Trait for Vec<i32> {
}
fn main() {
- let v = vec![1,2,3];
+ let v = vec![1, 2, 3];
- assert_eq!(&[1,2,3], Box::new(Rc::new(v)).trait_method());
+ assert_eq!(&[1, 2, 3], Box::new(Rc::new(v)).trait_method());
}
diff --git a/tests/ui/structs-enums/align-struct.rs b/tests/ui/structs-enums/align-struct.rs
index f5418e754b239..54092542f98fa 100644
--- a/tests/ui/structs-enums/align-struct.rs
+++ b/tests/ui/structs-enums/align-struct.rs
@@ -1,5 +1,5 @@
// run-pass
-#![allow(dead_code)]
+#![allow(dead_code, unused_allocation)]
use std::mem;
@@ -20,7 +20,6 @@ struct AlignMany(i32);
// Raising alignment may not alter size.
#[repr(align(8))]
-#[allow(dead_code)]
struct Align8Many {
a: i32,
b: i32,
@@ -29,9 +28,8 @@ struct Align8Many {
}
enum Enum {
- #[allow(dead_code)]
A(i32),
- B(Align16)
+ B(Align16),
}
// Nested alignment - use `#[repr(C)]` to suppress field reordering for sizeof test
@@ -73,7 +71,7 @@ struct AlignLarge {
union UnionContainsAlign {
a: Align16,
- b: f32
+ b: f32,
}
impl Align16 {
@@ -158,7 +156,7 @@ pub fn main() {
// Note that the size of Nested may change if struct field re-ordering is enabled
assert_eq!(mem::align_of::<Nested>(), 16);
assert_eq!(mem::size_of::<Nested>(), 48);
- let a = Nested{ a: 1, b: 2, c: Align16(3), d: 4};
+ let a = Nested { a: 1, b: 2, c: Align16(3), d: 4 };
assert_eq!(mem::align_of_val(&a), 16);
assert_eq!(mem::align_of_val(&a.b), 4);
assert_eq!(mem::align_of_val(&a.c), 16);
@@ -179,8 +177,8 @@ pub fn main() {
assert_eq!(a.0, 15);
assert_eq!(mem::align_of_val(a), 16);
assert_eq!(mem::size_of_val(a), 16);
- },
- _ => ()
+ }
+ _ => (),
}
assert!(is_aligned_to(&e, 16));
@@ -197,8 +195,8 @@ pub fn main() {
}
// arrays of aligned elements should also be aligned
- assert_eq!(mem::align_of::<[Align16;2]>(), 16);
- assert_eq!(mem::size_of::<[Align16;2]>(), 32);
+ assert_eq!(mem::align_of::<[Align16; 2]>(), 16);
+ assert_eq!(mem::size_of::<[Align16; 2]>(), 32);
let a = [Align16(0), Align16(1)];
assert_eq!(mem::align_of_val(&a[0]), 16);
@@ -209,7 +207,7 @@ pub fn main() {
assert_eq!(mem::align_of_val(Box::new(Align16(0)).as_ref()), 16);
// check heap array is aligned
- let a = vec!(Align16(0), Align16(1));
+ let a = vec![Align16(0), Align16(1)];
assert_eq!(mem::align_of_val(&a[0]), 16);
assert_eq!(mem::align_of_val(&a[1]), 16);
@@ -224,16 +222,14 @@ pub fn main() {
assert_eq!(mem::align_of::<AlignContainsPacked4C>(), 16);
assert_eq!(mem::size_of::<AlignContainsPacked4C>(), 32);
- let a = AlignContainsPacked4C { a: Packed4C{ a: 1, b: 2 }, b: 3 };
+ let a = AlignContainsPacked4C { a: Packed4C { a: 1, b: 2 }, b: 3 };
assert_eq!(mem::align_of_val(&a), 16);
assert_eq!(mem::align_of_val(&a.a), 4);
assert_eq!(mem::align_of_val(&a.b), mem::align_of::<u64>());
assert_eq!(mem::size_of_val(&a), 32);
assert!(is_aligned_to(&a, 16));
- let mut large = Box::new(AlignLarge {
- stuff: [0; 0x10000],
- });
+ let mut large = Box::new(AlignLarge { stuff: [0; 0x10000] });
large.stuff[0] = 132;
*large.stuff.last_mut().unwrap() = 102;
assert_eq!(large.stuff[0], 132);