Add `rustc_fluent_macro` to decouple fluent from `rustc_macros`

Fluent, with all the icu4x it brings in, takes quite some time to
compile. `fluent_messages!` is only needed in further downstream rustc
crates, but is blocking more upstream crates like `rustc_index`. By
splitting it out, we allow `rustc_macros` to be compiled earlier, which
speeds up `x check compiler` by about 5 seconds (and even more after the
needless dependency on `serde_json` is removed from
`rustc_data_structures`).

1 files changed, 2 insertions, 1 deletions

diff --git a/compiler/rustc_error_messages/src/lib.rs b/compiler/rustc_error_messages/src/lib.rs
index 6f319b96f2f..88d94c93bf5 100644
--- a/compiler/rustc_error_messages/src/lib.rs
+++ b/compiler/rustc_error_messages/src/lib.rs
@@ -12,7 +12,8 @@ use fluent_bundle::FluentResource;
 use fluent_syntax::parser::ParserError;
 use icu_provider_adapters::fallback::{LocaleFallbackProvider, LocaleFallbacker};
 use rustc_data_structures::sync::Lrc;
-use rustc_macros::{fluent_messages, Decodable, Encodable};
+use rustc_fluent_macro::fluent_messages;
+use rustc_macros::{Decodable, Encodable};
 use rustc_span::Span;
 use std::borrow::Cow;
 use std::error::Error;