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, 0 insertions, 2 deletions

diff --git a/compiler/rustc_macros/src/diagnostics/mod.rs b/compiler/rustc_macros/src/diagnostics/mod.rs
index 78df0cd1d34..bd84681cbb4 100644
--- a/compiler/rustc_macros/src/diagnostics/mod.rs
+++ b/compiler/rustc_macros/src/diagnostics/mod.rs
@@ -1,12 +1,10 @@
 mod diagnostic;
 mod diagnostic_builder;
 mod error;
-mod fluent;
 mod subdiagnostic;
 mod utils;
 
 use diagnostic::{DiagnosticDerive, LintDiagnosticDerive};
-pub(crate) use fluent::fluent_messages;
 use proc_macro2::TokenStream;
 use quote::format_ident;
 use subdiagnostic::SubdiagnosticDeriveBuilder;