Bad unreachable pattern error if an enum branch doesn't exist.

[ptal]

The code presented next reports:

$rustc test.rs 
test.rs:19:5: 19:15 error: unreachable pattern [E0001]
test.rs:19     LitBool(_) => PLitBool
               ^~~~~~~~~~
test.rs:19:5: 19:15 help: pass `--explain E0001` to see a detailed explanation
error: aborting due to previous error

But this is wrong, the error is because LitNil doesn't exist anymore. I guess the compiler should check that enum variants used in patterns exist before checking if they can be reached. The test.rs file code is:

#![feature(globs)]
extern crate syntax;
use syntax::ast::Lit_;
use syntax::ast::Lit_::*;
use LitTypePrinter::*;

pub fn lit_to_lit_printer(lit: &Lit_) -> LitTypePrinter
{
  match *lit {
    LitStr(_, _) => PLitStr,
    LitBinary(_) => PLitBinary,
    LitByte(_) => PLitByte,
    LitChar(_) => PLitChar,
    LitInt(_, _) => PLitInt,
    LitFloat(_, _) => PLitFloat,
    LitFloatUnsuffixed(_) => PLitFloatUnsuffixed,
    LitNil => PLitNil,
    LitBool(_) => PLitBool
  }
}

pub enum LitTypePrinter
{
  PLitStr,
  PLitBinary,
  PLitByte,
  PLitChar,
  PLitInt,
  PLitFloat,
  PLitFloatUnsuffixed,
  PLitNil,
  PLitBool
}

fn main() {
  lit_to_lit_printer(&LitChar('a'));
}

[ghost]

I'm going to close this. As of master, this will indeed still fail but also produce a warning that is more informative. See #19115. Thanks!