Comparing chars in constant expression produces incorrect warning

[matthewjasper]

The following code

const X: bool = 'A' == 'B';

produces a warning (playground)

warning: constant evaluation error: bad operands for binary. This will become a HARD ERROR in the future
 --> <anon>:4:21
  |
4 |     const X: bool = 'A' == 'B';
  |                     ^^^^^^^^^^
  |
  = note: #[warn(const_err)] on by default

but X appears to be correctly set to false.