Warning on u8 -> char casts; warning: can't cast this type, #[warn(const_err)]

[bluss]

This is a new warning in recent nightlies, for u8 -> char casts.

src/bin.rs:71:13: 71:25 warning: can't cast this type, #[warn(const_err)] on by default
src/bin.rs:71     if c >= 33u8 as char && c < 128u8 as char {
                          ^~~~~~~~~~~~

[klingtnet]

I can confirm this:

   Compiling rosc v0.1.4 (file:///home/andreas/personal/dev/rust/rosc)
src/decoder.rs:110:28: 110:39 warning: can't cast this type, #[warn(const_err)] on by default
src/decoder.rs:110             s.trim_matches(0u8 as char)