error[E0010]: allocations are not allowed in constants
  --> $DIR/E0010-teach.rs:6:24
   |
LL | const CON : Box<i32> = box 0;
   |                        ^^^^^ allocation not allowed in constants
   |
   = note: The value of statics and constants must be known at compile time, and they live for the entire lifetime of a program. Creating a boxed value allocates memory on the heap at runtime, and therefore cannot be done at compile time.

error[E0019]: constant contains unimplemented expression type
  --> $DIR/E0010-teach.rs:6:28
   |
LL | const CON : Box<i32> = box 0;
   |                            ^
   |
   = note: A function call isn't allowed in the const's initialization expression because the expression's value must be known at compile-time.
   = note: Remember: you can't use a function call inside a const's initialization expression! However, you can use it anywhere else.

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0010, E0019.
For more information about an error, try `rustc --explain E0010`.