errors: simplify referring to fluent attributes

To render the message of a Fluent attribute, the identifier of the
Fluent message must be known. `DiagnosticMessage::FluentIdentifier`
contains both the message's identifier and optionally the identifier of
an attribute. Generated constants for each attribute would therefore
need to be named uniquely (amongst all error messages) or be able to
refer to only the attribute identifier which will be combined with a
message identifier later. In this commit, the latter strategy is
implemented as part of the `Diagnostic` type's functions for adding
subdiagnostics of various kinds.

Signed-off-by: David Wood <david.wood@huawei.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 5b9b65da343..fb02f1d68eb 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -32,7 +32,8 @@ use rustc_data_structures::sync::{self, Lock, Lrc};
 use rustc_data_structures::AtomicRef;
 pub use rustc_error_messages::{
     fallback_fluent_bundle, fluent, fluent_bundle, DiagnosticMessage, FluentBundle,
-    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, DEFAULT_LOCALE_RESOURCES,
+    LanguageIdentifier, LazyFallbackBundle, MultiSpan, SpanLabel, SubdiagnosticMessage,
+    DEFAULT_LOCALE_RESOURCES,
 };
 pub use rustc_lint_defs::{pluralize, Applicability};
 use rustc_span::source_map::SourceMap;