Make it possible to use indoc with explicit use indoc::indoc;

[RReverser]

Currently indoc works only with #[macro_use] attribute but it would be nice to be able to use it with Rust 2018 style of explicit use statements. E.g. this fails:

extern crate indoc;
use indoc::indoc;
...
indoc!("test");

with

error: cannot find derive macro `indoc_impl` in this scope
   --> ffi/src/lib.rs:336:9
    |
336 |         indoc!("test");
    |         ^^^^^^^^^^^^^^^
    |
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: cannot find macro `proc_macro_call!` in this scope
   --> ffi/src/lib.rs:336:9
    |
336 |         indoc!("test");
    |         ^^^^^^^^^^^^^^^
    |
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

[RReverser]

Looks like use indoc::{indoc, indoc_impl}; works, but that shouldn't be necessary as the second one is an implementation detail.

[dtolnay]

Thanks! I believe this would be fixed by updating to proc-macro-hack 0.5.

[dtolnay]

Fixed in 0.3.0.

[RReverser]

Hmm after upgrading fails with a hard compilation error:

error: unexpected end of macro invocation
   --> /Users/rreverser/.cargo/registry/src/github.com-1ecc6299db9ec823/proc-macro-hack-0.5.2/src/lib.rs:247:60
    |
247 |     proc_macro::TokenStream::from(match parse_macro_input!(input) {
    |                                                            ^^^^^

error: aborting due to previous error

error: Could not compile `proc-macro-hack`.

[RReverser]

Recalled I had a similar issue with quote in the past, and indeed force-upgrading syn helped:

$ cargo update -p syn:0.15.4
    Updating crates.io index
    Updating syn v0.15.4 -> v0.15.22

It feels like dependencies of syn should be stricter regarding minimal version to help Cargo resolve, e.g. here https://github.com/dtolnay/proc-macro-hack/blob/master/Cargo.toml#L17 would be nice to set to some minimal version that is actually known to work.

[dtolnay]

Thanks for letting me know. Should be fixed in 0.3.1.

[RReverser]

Thanks!