Rollup merge of #67467 - matthewjasper:test-slice-patterns, r=oli-obk

Test slice patterns more

Adds tests for const evaluation and some more borrow checking tests.

Fixes some bugs in const eval for subslice patterns.
closes #66934

r? @oli-obk
cc @Centril

src/librustc_mir/interpret/operand.rs

@@ -444,13 +444,27 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             Field(field, _) => self.operand_field(base, field.index() as u64)?,
             Downcast(_, variant) => self.operand_downcast(base, variant)?,
             Deref => self.deref_operand(base)?.into(),
-            Subslice { .. } | ConstantIndex { .. } | Index(_) => if base.layout.is_zst() {
+            ConstantIndex { .. } | Index(_) if base.layout.is_zst() => {
                 OpTy {
                     op: Operand::Immediate(Scalar::zst().into()),
                     // the actual index doesn't matter, so we just pick a convenient one like 0
                     layout: base.layout.field(self, 0)?,
                 }
-            } else {
+            }
+            Subslice { from, to, from_end } if base.layout.is_zst() => {
+                let elem_ty = if let ty::Array(elem_ty, _) = base.layout.ty.kind {
+                    elem_ty
+                } else {
+                    bug!("slices shouldn't be zero-sized");
+                };
+                assert!(!from_end, "arrays shouldn't be subsliced from the end");
+
+                OpTy {
+                    op: Operand::Immediate(Scalar::zst().into()),
+                    layout: self.layout_of(self.tcx.mk_array(elem_ty, (to - from) as u64))?,
+                }
+            }
+            Subslice { .. } | ConstantIndex { .. }  | Index(_) => {
                 // The rest should only occur as mplace, we do not use Immediates for types
                 // allowing such operations.  This matches place_projection forcing an allocation.
                 let mplace = base.assert_mem_place();

src/librustc_mir/interpret/place.rs

@@ -455,7 +455,10 @@ where
     ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
         let len = base.len(self)?; // also asserts that we have a type where this makes sense
         let actual_to = if from_end {
-            assert!(from <= len - to);
+            if from + to > len {
+                // This can only be reached in ConstProp and non-rustc-MIR.
+                throw_ub!(BoundsCheckFailed { len: len as u64, index: from as u64 + to as u64 });
+            }
             len - to
         } else {
             to
@@ -523,7 +526,11 @@ where
                 from_end,
             } => {
                 let n = base.len(self)?;
-                assert!(n >= min_length as u64);
+                if n < min_length as u64 {
+                    // This can only be reached in ConstProp and non-rustc-MIR.
+                    throw_ub!(BoundsCheckFailed { len: min_length as u64, index: n as u64 });
+                }
+                assert!(offset < min_length);
 
                 let index = if from_end {
                     n - u64::from(offset)

src/test/ui/array-slice-vec/subslice-patterns-const-eval-match.rs

@@ -0,0 +1,97 @@
+// Test that slice subslice patterns are correctly handled in const evaluation.
+
+// run-pass
+
+#![feature(slice_patterns, const_fn, const_if_match)]
+#[derive(PartialEq, Debug, Clone)]
+struct N(u8);
+
+#[derive(PartialEq, Debug, Clone)]
+struct Z;
+
+macro_rules! n {
+    ($($e:expr),* $(,)?) => {
+        [$(N($e)),*]
+    }
+}
+
+// This macro has an unused variable so that it can be repeated base on the
+// number of times a repeated variable (`$e` in `z`) occurs.
+macro_rules! zed {
+    ($e:expr) => { Z }
+}
+
+macro_rules! z {
+    ($($e:expr),* $(,)?) => {
+        [$(zed!($e)),*]
+    }
+}
+
+// Compare constant evaluation and runtime evaluation of a given expression.
+macro_rules! compare_evaluation_inner {
+    ($e:expr, $t:ty $(,)?) => {{
+        const CONST_EVAL: $t = $e;
+        const fn const_eval() -> $t { $e }
+        static CONST_EVAL2: $t = const_eval();
+        let runtime_eval = $e;
+        assert_eq!(CONST_EVAL, runtime_eval);
+        assert_eq!(CONST_EVAL2, runtime_eval);
+    }}
+}
+
+// Compare the result of matching `$e` against `$p` using both `if let` and
+// `match`.
+macro_rules! compare_evaluation {
+    ($p:pat, $e:expr, $matches:expr, $t:ty $(,)?) => {{
+        compare_evaluation_inner!(if let $p = $e as &[_] { $matches } else { None }, $t);
+        compare_evaluation_inner!(match $e as &[_] { $p => $matches, _ => None }, $t);
+    }}
+}
+
+// Repeat `$test`, substituting the given macro variables with the given
+// identifiers.
+//
+// For example:
+//
+// repeat! {
+//     ($name); X; Y:
+//     struct $name;
+// }
+//
+// Expands to:
+//
+// struct X; struct Y;
+//
+// This is used to repeat the tests using both the `N` and `Z`
+// types.
+macro_rules! repeat {
+    (($($dollar:tt $placeholder:ident)*); $($($values:ident),+);*: $($test:tt)*) => {
+        macro_rules! single {
+            ($($dollar $placeholder:ident),*) => { $($test)* }
+        }
+        $(single!($($values),+);)*
+    }
+}
+
+fn main() {
+    repeat! {
+        ($arr $Ty); n, N; z, Z:
+        compare_evaluation!([_, x @ .., _], &$arr!(1, 2, 3, 4), Some(x), Option<&'static [$Ty]>);
+        compare_evaluation!([x, .., _], &$arr!(1, 2, 3, 4), Some(x), Option<&'static $Ty>);
+        compare_evaluation!([_, .., x], &$arr!(1, 2, 3, 4), Some(x), Option<&'static $Ty>);
+
+        compare_evaluation!([_, x @ .., _], &$arr!(1, 2), Some(x), Option<&'static [$Ty]>);
+        compare_evaluation!([x, .., _], &$arr!(1, 2), Some(x), Option<&'static $Ty>);
+        compare_evaluation!([_, .., x], &$arr!(1, 2), Some(x), Option<&'static $Ty>);
+
+        compare_evaluation!([_, x @ .., _], &$arr!(1), Some(x), Option<&'static [$Ty]>);
+        compare_evaluation!([x, .., _], &$arr!(1), Some(x), Option<&'static $Ty>);
+        compare_evaluation!([_, .., x], &$arr!(1), Some(x), Option<&'static $Ty>);
+    }
+
+    compare_evaluation!([N(x), .., _], &n!(1, 2, 3, 4), Some(x), Option<&'static u8>);
+    compare_evaluation!([_, .., N(x)], &n!(1, 2, 3, 4), Some(x), Option<&'static u8>);
+
+    compare_evaluation!([N(x), .., _], &n!(1, 2), Some(x), Option<&'static u8>);
+    compare_evaluation!([_, .., N(x)], &n!(1, 2), Some(x), Option<&'static u8>);
+}

src/test/ui/array-slice-vec/subslice-patterns-const-eval.rs

@@ -0,0 +1,97 @@
+// Test that array subslice patterns are correctly handled in const evaluation.
+
+// run-pass
+
+#![feature(slice_patterns)]
+
+#[derive(PartialEq, Debug, Clone)]
+struct N(u8);
+
+#[derive(PartialEq, Debug, Clone)]
+struct Z;
+
+macro_rules! n {
+    ($($e:expr),* $(,)?) => {
+        [$(N($e)),*]
+    }
+}
+
+// This macro has an unused variable so that it can be repeated base on the
+// number of times a repeated variable (`$e` in `z`) occurs.
+macro_rules! zed {
+    ($e:expr) => { Z }
+}
+
+macro_rules! z {
+    ($($e:expr),* $(,)?) => {
+        [$(zed!($e)),*]
+    }
+}
+
+// Compare constant evaluation and runtime evaluation of a given expression.
+macro_rules! compare_evaluation {
+    ($e:expr, $t:ty $(,)?) => {{
+        const CONST_EVAL: $t = $e;
+        const fn const_eval() -> $t { $e }
+        static CONST_EVAL2: $t = const_eval();
+        let runtime_eval = $e;
+        assert_eq!(CONST_EVAL, runtime_eval);
+        assert_eq!(CONST_EVAL2, runtime_eval);
+    }}
+}
+
+// Repeat `$test`, substituting the given macro variables with the given
+// identifiers.
+//
+// For example:
+//
+// repeat! {
+//     ($name); X; Y:
+//     struct $name;
+// }
+//
+// Expands to:
+//
+// struct X; struct Y;
+//
+// This is used to repeat the tests using both the `N` and `Z`
+// types.
+macro_rules! repeat {
+    (($($dollar:tt $placeholder:ident)*); $($($values:ident),+);*: $($test:tt)*) => {
+        macro_rules! single {
+            ($($dollar $placeholder:ident),*) => { $($test)* }
+        }
+        $(single!($($values),+);)*
+    }
+}
+
+fn main() {
+    repeat! {
+        ($arr $Ty); n, N; z, Z:
+        compare_evaluation!({ let [_, x @ .., _] = $arr!(1, 2, 3, 4); x }, [$Ty; 2]);
+        compare_evaluation!({ let [_, ref x @ .., _] = $arr!(1, 2, 3, 4); x }, &'static [$Ty; 2]);
+        compare_evaluation!({ let [_, x @ .., _] = &$arr!(1, 2, 3, 4); x }, &'static [$Ty; 2]);
+
+        compare_evaluation!({ let [_, _, x @ .., _, _] = $arr!(1, 2, 3, 4); x }, [$Ty; 0]);
+        compare_evaluation!(
+            { let [_, _, ref x @ .., _, _] = $arr!(1, 2, 3, 4); x },
+            &'static [$Ty; 0],
+        );
+        compare_evaluation!(
+            { let [_, _, x @ .., _, _] = &$arr!(1, 2, 3, 4); x },
+            &'static [$Ty; 0],
+        );
+
+        compare_evaluation!({ let [_, .., x] = $arr!(1, 2, 3, 4); x }, $Ty);
+        compare_evaluation!({ let [_, .., ref x] = $arr!(1, 2, 3, 4); x }, &'static $Ty);
+        compare_evaluation!({ let [_, _y @ .., x] = &$arr!(1, 2, 3, 4); x }, &'static $Ty);
+    }
+
+    compare_evaluation!({ let [_, .., N(x)] = n!(1, 2, 3, 4); x }, u8);
+    compare_evaluation!({ let [_, .., N(ref x)] = n!(1, 2, 3, 4); x }, &'static u8);
+    compare_evaluation!({ let [_, .., N(x)] = &n!(1, 2, 3, 4); x }, &'static u8);
+
+    compare_evaluation!({ let [N(x), .., _] = n!(1, 2, 3, 4); x }, u8);
+    compare_evaluation!({ let [N(ref x), .., _] = n!(1, 2, 3, 4); x }, &'static u8);
+    compare_evaluation!({ let [N(x), .., _] = &n!(1, 2, 3, 4); x }, &'static u8);
+}

src/test/ui/borrowck/borrowck-closures-slice-patterns-ok.rs

@@ -0,0 +1,118 @@
+// Check that closure captures for slice patterns are inferred correctly
+
+#![feature(slice_patterns)]
+#![allow(unused_variables)]
+
+// run-pass
+
+fn arr_by_ref(x: [String; 3]) {
+    let r = &x;
+    let f = || {
+        let [ref y, ref z @ ..] = x;
+    };
+    f();
+    f();
+    // Ensure `x` was borrowed
+    drop(r);
+    // Ensure that `x` wasn't moved from.
+    drop(x);
+}
+
+fn arr_by_mut(mut x: [String; 3]) {
+    let mut f = || {
+        let [ref mut y, ref mut z @ ..] = x;
+    };
+    f();
+    f();
+    drop(x);
+}
+
+fn arr_by_move(x: [String; 3]) {
+    let f = || {
+        let [y, z @ ..] = x;
+    };
+    f();
+}
+
+fn arr_ref_by_ref(x: &[String; 3]) {
+    let r = &x;
+    let f = || {
+        let [ref y, ref z @ ..] = *x;
+    };
+    let g = || {
+        let [y, z @ ..] = x;
+    };
+    f();
+    g();
+    f();
+    g();
+    drop(r);
+    drop(x);
+}
+
+fn arr_ref_by_mut(x: &mut [String; 3]) {
+    let mut f = || {
+        let [ref mut y, ref mut z @ ..] = *x;
+    };
+    f();
+    f();
+    let mut g = || {
+        let [y, z @ ..] = x;
+        // Ensure binding mode was chosen correctly:
+        std::mem::swap(y, &mut z[0]);
+    };
+    g();
+    g();
+    drop(x);
+}
+
+fn arr_box_by_move(x: Box<[String; 3]>) {
+    let f = || {
+        let [y, z @ ..] = *x;
+    };
+    f();
+}
+
+fn slice_by_ref(x: &[String]) {
+    let r = &x;
+    let f = || {
+        if let [ref y, ref z @ ..] = *x {}
+    };
+    let g = || {
+        if let [y, z @ ..] = x {}
+    };
+    f();
+    g();
+    f();
+    g();
+    drop(r);
+    drop(x);
+}
+
+fn slice_by_mut(x: &mut [String]) {
+    let mut f = || {
+        if let [ref mut y, ref mut z @ ..] = *x {}
+    };
+    f();
+    f();
+    let mut g = || {
+        if let [y, z @ ..] = x {
+            // Ensure binding mode was chosen correctly:
+            std::mem::swap(y, &mut z[0]);
+        }
+    };
+    g();
+    g();
+    drop(x);
+}
+
+fn main() {
+    arr_by_ref(Default::default());
+    arr_by_mut(Default::default());
+    arr_by_move(Default::default());
+    arr_ref_by_ref(&Default::default());
+    arr_ref_by_mut(&mut Default::default());
+    arr_box_by_move(Default::default());
+    slice_by_ref(&<[_; 3]>::default());
+    slice_by_mut(&mut <[_; 3]>::default());
+}

src/test/ui/borrowck/borrowck-closures-slice-patterns.rs

@@ -0,0 +1,84 @@
+// Check that closure captures for slice patterns are inferred correctly
+
+#![feature(slice_patterns)]
+
+fn arr_by_ref(mut x: [String; 3]) {
+    let f = || {
+        let [ref y, ref z @ ..] = x;
+    };
+    let r = &mut x;
+    //~^ ERROR cannot borrow
+    f();
+}
+
+fn arr_by_mut(mut x: [String; 3]) {
+    let mut f = || {
+        let [ref mut y, ref mut z @ ..] = x;
+    };
+    let r = &x;
+    //~^ ERROR cannot borrow
+    f();
+}
+
+fn arr_by_move(x: [String; 3]) {
+    let f = || {
+        let [y, z @ ..] = x;
+    };
+    &x;
+    //~^ ERROR borrow of moved value
+}
+
+fn arr_ref_by_ref(x: &mut [String; 3]) {
+    let f = || {
+        let [ref y, ref z @ ..] = *x;
+    };
+    let r = &mut *x;
+    //~^ ERROR cannot borrow
+    f();
+}
+
+fn arr_ref_by_uniq(x: &mut [String; 3]) {
+    let mut f = || {
+        let [ref mut y, ref mut z @ ..] = *x;
+    };
+    let r = &x;
+    //~^ ERROR cannot borrow
+    f();
+}
+
+fn arr_box_by_move(x: Box<[String; 3]>) {
+    let f = || {
+        let [y, z @ ..] = *x;
+    };
+    &x;
+    //~^ ERROR borrow of moved value
+}
+
+fn slice_by_ref(x: &mut [String]) {
+    let f = || {
+        if let [ref y, ref z @ ..] = *x {}
+    };
+    let r = &mut *x;
+    //~^ ERROR cannot borrow
+    f();
+}
+
+fn slice_by_uniq(x: &mut [String]) {
+    let mut f = || {
+        if let [ref mut y, ref mut z @ ..] = *x {}
+    };
+    let r = &x;
+    //~^ ERROR cannot borrow
+    f();
+}
+
+fn main() {
+    arr_by_ref(Default::default());
+    arr_by_mut(Default::default());
+    arr_by_move(Default::default());
+    arr_ref_by_ref(&mut Default::default());
+    arr_ref_by_uniq(&mut Default::default());
+    arr_box_by_move(Default::default());
+    slice_by_ref(&mut <[_; 3]>::default());
+    slice_by_uniq(&mut <[_; 3]>::default());
+}

src/test/ui/borrowck/borrowck-closures-slice-patterns.stderr

@@ -0,0 +1,114 @@
+error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
+  --> $DIR/borrowck-closures-slice-patterns.rs:9:13
+   |
+LL |     let f = || {
+   |             -- immutable borrow occurs here
+LL |         let [ref y, ref z @ ..] = x;
+   |                                   - first borrow occurs due to use of `x` in closure
+LL |     };
+LL |     let r = &mut x;
+   |             ^^^^^^ mutable borrow occurs here
+LL |
+LL |     f();
+   |     - immutable borrow later used here
+
+error[E0502]: cannot borrow `x` as immutable because it is also borrowed as mutable
+  --> $DIR/borrowck-closures-slice-patterns.rs:18:13
+   |
+LL |     let mut f = || {
+   |                 -- mutable borrow occurs here
+LL |         let [ref mut y, ref mut z @ ..] = x;
+   |                                           - first borrow occurs due to use of `x` in closure
+LL |     };
+LL |     let r = &x;
+   |             ^^ immutable borrow occurs here
+LL |
+LL |     f();
+   |     - mutable borrow later used here
+
+error[E0382]: borrow of moved value: `x`
+  --> $DIR/borrowck-closures-slice-patterns.rs:27:5
+   |
+LL | fn arr_by_move(x: [String; 3]) {
+   |                - move occurs because `x` has type `[std::string::String; 3]`, which does not implement the `Copy` trait
+LL |     let f = || {
+   |             -- value moved into closure here
+LL |         let [y, z @ ..] = x;
+   |                           - variable moved due to use in closure
+LL |     };
+LL |     &x;
+   |     ^^ value borrowed here after move
+
+error[E0502]: cannot borrow `*x` as mutable because it is also borrowed as immutable
+  --> $DIR/borrowck-closures-slice-patterns.rs:35:13
+   |
+LL |     let f = || {
+   |             -- immutable borrow occurs here
+LL |         let [ref y, ref z @ ..] = *x;
+   |                                    - first borrow occurs due to use of `x` in closure
+LL |     };
+LL |     let r = &mut *x;
+   |             ^^^^^^^ mutable borrow occurs here
+LL |
+LL |     f();
+   |     - immutable borrow later used here
+
+error[E0501]: cannot borrow `x` as immutable because previous closure requires unique access
+  --> $DIR/borrowck-closures-slice-patterns.rs:44:13
+   |
+LL |     let mut f = || {
+   |                 -- closure construction occurs here
+LL |         let [ref mut y, ref mut z @ ..] = *x;
+   |                                            - first borrow occurs due to use of `x` in closure
+LL |     };
+LL |     let r = &x;
+   |             ^^ second borrow occurs here
+LL |
+LL |     f();
+   |     - first borrow later used here
+
+error[E0382]: borrow of moved value: `x`
+  --> $DIR/borrowck-closures-slice-patterns.rs:53:5
+   |
+LL | fn arr_box_by_move(x: Box<[String; 3]>) {
+   |                    - move occurs because `x` has type `std::boxed::Box<[std::string::String; 3]>`, which does not implement the `Copy` trait
+LL |     let f = || {
+   |             -- value moved into closure here
+LL |         let [y, z @ ..] = *x;
+   |                            - variable moved due to use in closure
+LL |     };
+LL |     &x;
+   |     ^^ value borrowed here after move
+
+error[E0502]: cannot borrow `*x` as mutable because it is also borrowed as immutable
+  --> $DIR/borrowck-closures-slice-patterns.rs:61:13
+   |
+LL |     let f = || {
+   |             -- immutable borrow occurs here
+LL |         if let [ref y, ref z @ ..] = *x {}
+   |                                       - first borrow occurs due to use of `x` in closure
+LL |     };
+LL |     let r = &mut *x;
+   |             ^^^^^^^ mutable borrow occurs here
+LL |
+LL |     f();
+   |     - immutable borrow later used here
+
+error[E0501]: cannot borrow `x` as immutable because previous closure requires unique access
+  --> $DIR/borrowck-closures-slice-patterns.rs:70:13
+   |
+LL |     let mut f = || {
+   |                 -- closure construction occurs here
+LL |         if let [ref mut y, ref mut z @ ..] = *x {}
+   |                                               - first borrow occurs due to use of `x` in closure
+LL |     };
+LL |     let r = &x;
+   |             ^^ second borrow occurs here
+LL |
+LL |     f();
+   |     - first borrow later used here
+
+error: aborting due to 8 previous errors
+
+Some errors have detailed explanations: E0382, E0501, E0502.
+For more information about an error, try `rustc --explain E0382`.

src/test/ui/moves/move-out-of-array-ref.rs

@@ -0,0 +1,36 @@
+// Ensure that we cannot move out of a reference to a fixed-size array
+
+#![feature(slice_patterns)]
+
+struct D { _x: u8 }
+
+impl Drop for D { fn drop(&mut self) { } }
+
+fn move_elem(a: &[D; 4]) -> D {
+    let [_, e, _, _] = *a;              //~ ERROR cannot move
+    e
+}
+
+fn move_subarr(a: &[D; 4]) -> [D; 2] {
+    let [_, s @ .. , _] = *a;           //~ ERROR cannot move
+    s
+}
+
+fn move_elem_mut(a: &mut [D; 4]) -> D {
+    let [_, e, _, _] = *a;              //~ ERROR cannot move
+    e
+}
+
+fn move_subarr_mut(a: &mut [D; 4]) -> [D; 2] {
+    let [_, s @ .. , _] = *a;           //~ ERROR cannot move
+    s
+}
+
+fn main() {
+    fn d() -> D { D { _x: 0 } }
+
+    move_elem(&[d(), d(), d(), d()]);
+    move_subarr(&[d(), d(), d(), d()]);
+    move_elem_mut(&mut [d(), d(), d(), d()]);
+    move_subarr_mut(&mut [d(), d(), d(), d()]);
+}

src/test/ui/moves/move-out-of-array-ref.stderr

@@ -0,0 +1,47 @@
+error[E0508]: cannot move out of type `[D; 4]`, a non-copy array
+  --> $DIR/move-out-of-array-ref.rs:10:24
+   |
+LL |     let [_, e, _, _] = *a;
+   |             -          ^^
+   |             |          |
+   |             |          cannot move out of here
+   |             |          help: consider borrowing here: `&*a`
+   |             data moved here
+   |             move occurs because `e` has type `D`, which does not implement the `Copy` trait
+
+error[E0508]: cannot move out of type `[D; 4]`, a non-copy array
+  --> $DIR/move-out-of-array-ref.rs:15:27
+   |
+LL |     let [_, s @ .. , _] = *a;
+   |             ------        ^^
+   |             |             |
+   |             |             cannot move out of here
+   |             |             help: consider borrowing here: `&*a`
+   |             data moved here
+   |             move occurs because `s` has type `[D; 2]`, which does not implement the `Copy` trait
+
+error[E0508]: cannot move out of type `[D; 4]`, a non-copy array
+  --> $DIR/move-out-of-array-ref.rs:20:24
+   |
+LL |     let [_, e, _, _] = *a;
+   |             -          ^^
+   |             |          |
+   |             |          cannot move out of here
+   |             |          help: consider borrowing here: `&*a`
+   |             data moved here
+   |             move occurs because `e` has type `D`, which does not implement the `Copy` trait
+
+error[E0508]: cannot move out of type `[D; 4]`, a non-copy array
+  --> $DIR/move-out-of-array-ref.rs:25:27
+   |
+LL |     let [_, s @ .. , _] = *a;
+   |             ------        ^^
+   |             |             |
+   |             |             cannot move out of here
+   |             |             help: consider borrowing here: `&*a`
+   |             data moved here
+   |             move occurs because `s` has type `[D; 2]`, which does not implement the `Copy` trait
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0508`.

src/test/ui/moves/move-out-of-slice-2.rs

@@ -0,0 +1,34 @@
+#![feature(slice_patterns, unsized_locals)]
+
+struct A;
+#[derive(Clone, Copy)]
+struct C;
+
+fn main() {
+    let a: Box<[A]> = Box::new([A]);
+    match *a {
+        //~^ ERROR cannot move out of type `[A]`, a non-copy slice
+        [a @ ..] => {},
+        _ => {}
+    }
+    let b: Box<[A]> = Box::new([A, A, A]);
+    match *b {
+        //~^ ERROR cannot move out of type `[A]`, a non-copy slice
+        [_, _, b @ .., _] => {},
+        _ => {}
+    }
+
+    // `[C]` isn't `Copy`, even if `C` is.
+    let c: Box<[C]> = Box::new([C]);
+    match *c {
+        //~^ ERROR cannot move out of type `[C]`, a non-copy slice
+        [c @ ..] => {},
+        _ => {}
+    }
+    let d: Box<[C]> = Box::new([C, C, C]);
+    match *d {
+        //~^ ERROR cannot move out of type `[C]`, a non-copy slice
+        [_, _, d @ .., _] => {},
+        _ => {}
+    }
+}

src/test/ui/moves/move-out-of-slice-2.stderr

@@ -0,0 +1,51 @@
+error[E0508]: cannot move out of type `[A]`, a non-copy slice
+  --> $DIR/move-out-of-slice-2.rs:9:11
+   |
+LL |     match *a {
+   |           ^^ cannot move out of here
+LL |
+LL |         [a @ ..] => {},
+   |          ------
+   |          |
+   |          data moved here
+   |          move occurs because `a` has type `[A]`, which does not implement the `Copy` trait
+
+error[E0508]: cannot move out of type `[A]`, a non-copy slice
+  --> $DIR/move-out-of-slice-2.rs:15:11
+   |
+LL |     match *b {
+   |           ^^ cannot move out of here
+LL |
+LL |         [_, _, b @ .., _] => {},
+   |                ------
+   |                |
+   |                data moved here
+   |                move occurs because `b` has type `[A]`, which does not implement the `Copy` trait
+
+error[E0508]: cannot move out of type `[C]`, a non-copy slice
+  --> $DIR/move-out-of-slice-2.rs:23:11
+   |
+LL |     match *c {
+   |           ^^ cannot move out of here
+LL |
+LL |         [c @ ..] => {},
+   |          ------
+   |          |
+   |          data moved here
+   |          move occurs because `c` has type `[C]`, which does not implement the `Copy` trait
+
+error[E0508]: cannot move out of type `[C]`, a non-copy slice
+  --> $DIR/move-out-of-slice-2.rs:29:11
+   |
+LL |     match *d {
+   |           ^^ cannot move out of here
+LL |
+LL |         [_, _, d @ .., _] => {},
+   |                ------
+   |                |
+   |                data moved here
+   |                move occurs because `d` has type `[C]`, which does not implement the `Copy` trait
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0508`.