error: expected item after attributes using Rust 1.41

[galich]

Our app fails to compile because of the following error given by rustc 1.41.0 (5e1a79984 2020-01-27)

error: expected item after attributes
   --> C:\Users\serg\.cargo\registry\src\github.1485827954.workers.dev-1ecc6299db9ec823\futures-0.3.1\src\lib.rs:529:19
    |
529 |     #[macro_export]
    |                   ^

[Nemo157]

This appears to be an incompatibility introduced with futures-util 0.3.2, probably related to #1891 #1976. Easy fix is to update to 0.3.2 of futures as well or downgrade futures-util back to 0.3.1.

@cramertj worth yanking 0.3.2 (maybe just -util) and publishing a fix as 0.3.3? Seems like a difficult situation to get into unless you're pinning the version of futures but not pinning the underlying libraries.

[Nemo157]

Tested with

> cargo download -x futures==0.3.1
INFO: cargo-download v0.1.2
INFO: Crate `futures==0.3.1` downloaded successfully
INFO: Crate content extracted to ./futures-0.3.1/
> cd futures-0.3.1
> cargo +1.41.0 build
   Compiling proc-macro2 v1.0.8
   Compiling unicode-xid v0.2.0
   Compiling syn v1.0.14
   Compiling proc-macro-nested v0.1.3
   Compiling memchr v2.3.0
   Compiling futures-sink v0.3.2
   Compiling futures-core v0.3.2
   Compiling slab v0.4.2
   Compiling futures-io v0.3.2
   Compiling futures-task v0.3.2
   Compiling pin-utils v0.1.0-alpha.4
   Compiling futures-channel v0.3.2
   Compiling quote v1.0.2
   Compiling proc-macro-hack v0.5.11
   Compiling futures-macro v0.3.2
   Compiling futures-util v0.3.2
   Compiling futures-executor v0.3.2
   Compiling futures v0.3.1 (/private/var/folders/0p/5yvmrvhj5w3_vy1y8x7dvk7m0000gn/T/tmp.hJzVLqqR/futures-0.3.1)
error: expected item after attributes
   --> src/lib.rs:529:19
    |
529 |     #[macro_export]
    |                   ^

error: aborting due to previous error

error: could not compile `futures`.

To learn more, run the command again with --verbose.
> cargo update -p futures-util -p futures-executor --precise 0.3.1
    Updating crates.io index
    Updating futures-executor v0.3.2 -> v0.3.1
    Updating futures-util v0.3.2 -> v0.3.1
> cargo +1.41.0 build
   Compiling futures-util v0.3.1
   Compiling futures-executor v0.3.1
   Compiling futures v0.3.1 (/private/var/folders/0p/5yvmrvhj5w3_vy1y8x7dvk7m0000gn/T/tmp.hJzVLqqR/futures-0.3.1)
    Finished dev [unoptimized + debuginfo] target(s) in 5.53s

[cramertj]

Sure, I'll publish 0.3.3 once #2062 is in. In general, though, using old futures facades with new versions of futures-util is a pretty odd usecase that we won't be testing against, and I'd advise against pinning the futures facade without pinning the inner crates-- I can't think of any reason why you'd want that behavior.

[galich]

Good catch, we do actually pin in the app. But we can't do that for 3rd party crates obviously. May be it's time to re-evalutate Cargo.lock for pinning.

[galich]

thanks for the update, it works perfectly