Auto merge of #95149 - cjgillot:once-diag, r=estebank

Remove `Session::one_time_diagnostic`

This is untracked mutable state, which modified the behaviour of queries.
It was used for 2 things: some full-blown errors, but mostly for lint declaration notes ("the lint level is defined here" notes).

It is replaced by the diagnostic deduplication infra which already exists in the diagnostic emitter.
A new diagnostic level `OnceNote` is introduced specifically for lint notes, to deduplicate subdiagnostics.

As a drive-by, diagnostic emission takes a `&mut` to allow dropping the `SubDiagnostic`s.

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index a3e66464fbc..0ce86a764f4 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -49,8 +49,8 @@ macro_rules! panictry_buffer {
         match $e {
             Ok(e) => e,
             Err(errs) => {
-                for e in errs {
-                    $handler.emit_diagnostic(&e);
+                for mut e in errs {
+                    $handler.emit_diagnostic(&mut e);
                 }
                 FatalError.raise()
             }
@@ -167,8 +167,8 @@ fn try_file_to_source_file(
 fn file_to_source_file(sess: &ParseSess, path: &Path, spanopt: Option<Span>) -> Lrc<SourceFile> {
     match try_file_to_source_file(sess, path, spanopt) {
         Ok(source_file) => source_file,
-        Err(d) => {
-            sess.span_diagnostic.emit_diagnostic(&d);
+        Err(mut d) => {
+            sess.span_diagnostic.emit_diagnostic(&mut d);
             FatalError.raise();
         }
     }