what's your rust version?

Same on solus too.

   Compiling bytes v0.5.0
   Compiling percent-encoding v2.1.0
error: `core::slice::<impl [T]>::len` is not yet stable as a const fn
   --> /home/build/.cargo/registry/src/github.com-1ecc6299db9ec823/bytes-0.5.0/src/bytes.rs:121:18
    |
121 |             len: bytes.len(),
    |                  ^^^^^^^^^^^

error: aborting due to previous error

error: Could not compile `bytes`.

using rust, version: 1.38.0

what's your rust version?

I am using 1.40.0.
rustc 1.40.0 (73528e339 2019-12-16)

[T]::len as const fn was stabilized in 1.39.0 (2019-11-07), see changelog and github issue.

@plu9in are you sure you don't have a toolchain override with more precedence? See here. The only case I can think of is either an outdated nightly or not using the version installed by rustup (so the one from the distro).

Fix here #35

Thanks a lot @chobeat, @ebroto, @beamop. I have built bandwhich now.

I had cargo <= 1.39.0 installed in my PATH with more precedence than my home directory. That's why.
What is strange is that when I did cargo -V I had a right version (>= 1.39.0).

1. What package allows one to run rustup update?
2. I think this problem should be mentioned in the ReadMe.

@LinuxOnTheDesktop you can find installation instructions here.

I will add a note to the README as you suggest.