error[E0506]: cannot assign to `vec[..]` because it is borrowed
  --> $DIR/borrowck-vec-pattern-nesting.rs:21:13
   |
LL |         [box ref _a, _, _] => {
   |              ------ borrow of `vec[..]` occurs here
LL |         //~^ borrow of `vec[..]` occurs here
LL |             vec[0] = box 4; //~ ERROR cannot assign
   |             ^^^^^^^^^^^^^^ assignment to borrowed `vec[..]` occurs here

error[E0506]: cannot assign to `vec[..]` because it is borrowed
  --> $DIR/borrowck-vec-pattern-nesting.rs:33:13
   |
LL |         &mut [ref _b..] => {
   |               ------ borrow of `vec[..]` occurs here
LL |         //~^ borrow of `vec[..]` occurs here
LL |             vec[0] = box 4; //~ ERROR cannot assign
   |             ^^^^^^^^^^^^^^ assignment to borrowed `vec[..]` occurs here

error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
  --> $DIR/borrowck-vec-pattern-nesting.rs:43:14
   |
LL |           &mut [_a, //~ ERROR cannot move out
   |                ^-- hint: to prevent move, use `ref _a` or `ref mut _a`
   |  ______________|
   | |
LL | |             //~| cannot move out
LL | |             //~| to prevent move
LL | |             ..
LL | |         ] => {
   | |_________^ cannot move out of here

error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
  --> $DIR/borrowck-vec-pattern-nesting.rs:56:13
   |
LL |     let a = vec[0]; //~ ERROR cannot move out
   |             ^^^^^^
   |             |
   |             cannot move out of here
   |             help: consider using a reference instead: `&vec[0]`

error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
  --> $DIR/borrowck-vec-pattern-nesting.rs:64:14
   |
LL |           &mut [ //~ ERROR cannot move out
   |  ______________^
LL | |         //~^ cannot move out
LL | |          _b] => {}
   | |__________--^ cannot move out of here
   |            |
   |            hint: to prevent move, use `ref _b` or `ref mut _b`

error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
  --> $DIR/borrowck-vec-pattern-nesting.rs:69:13
   |
LL |     let a = vec[0]; //~ ERROR cannot move out
   |             ^^^^^^
   |             |
   |             cannot move out of here
   |             help: consider using a reference instead: `&vec[0]`

error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
  --> $DIR/borrowck-vec-pattern-nesting.rs:77:14
   |
LL |         &mut [_a, _b, _c] => {}  //~ ERROR cannot move out
   |              ^--^^--^^--^
   |              ||   |   |
   |              ||   |   ...and here (use `ref _c` or `ref mut _c`)
   |              ||   ...and here (use `ref _b` or `ref mut _b`)
   |              |hint: to prevent move, use `ref _a` or `ref mut _a`
   |              cannot move out of here

error[E0508]: cannot move out of type `[std::boxed::Box<isize>]`, a non-copy slice
  --> $DIR/borrowck-vec-pattern-nesting.rs:81:13
   |
LL |     let a = vec[0]; //~ ERROR cannot move out
   |             ^^^^^^
   |             |
   |             cannot move out of here
   |             help: consider using a reference instead: `&vec[0]`

error: aborting due to 8 previous errors

You've got a few errors: E0506, E0508
If you want more information on an error, try using "rustc --explain E0506"