Reenable const_let feature gate

src/test/ui/error-codes/E0010-teach.rs

@@ -14,6 +14,5 @@
 #![allow(warnings)]
 
 const CON : Box<i32> = box 0; //~ ERROR E0010
-//~^ ERROR contains unimplemented expression type
 
 fn main() {}

src/test/ui/error-codes/E0010-teach.stderr

@@ -6,16 +6,6 @@ LL | const CON : Box<i32> = box 0; //~ ERROR E0010
    |
    = 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:16:28
-   |
-LL | const CON : Box<i32> = box 0; //~ ERROR E0010
-   |                            ^
-   |
-   = 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 previous error
 
-error: aborting due to 2 previous errors
-
-Some errors occurred: E0010, E0019.
-For more information about an error, try `rustc --explain E0010`.
+For more information about this error, try `rustc --explain E0010`.

src/test/ui/error-codes/E0010.rs

@@ -12,6 +12,5 @@
 #![allow(warnings)]
 
 const CON : Box<i32> = box 0; //~ ERROR E0010
-//~^ ERROR contains unimplemented expression type
 
 fn main() {}

src/test/ui/error-codes/E0010.stderr

@@ -4,13 +4,6 @@ error[E0010]: allocations are not allowed in constants
 LL | const CON : Box<i32> = box 0; //~ ERROR E0010
    |                        ^^^^^ allocation not allowed in constants
 
-error[E0019]: constant contains unimplemented expression type
-  --> $DIR/E0010.rs:14:28
-   |
-LL | const CON : Box<i32> = box 0; //~ ERROR E0010
-   |                            ^
+error: aborting due to previous error
 
-error: aborting due to 2 previous errors
-
-Some errors occurred: E0010, E0019.
-For more information about an error, try `rustc --explain E0010`.
+For more information about this error, try `rustc --explain E0010`.