Rollup merge of rust-lang#119601 - nnethercote:Emitter-cleanups, r=oli-obk

`Emitter` cleanups

Some improvements I found while looking at this code.

r? `@oli-obk`

Author: compiler-errors

src/parse/session.rs

@@ -2,7 +2,7 @@ use std::path::Path;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 use rustc_data_structures::sync::{IntoDynSyncSend, Lrc};
-use rustc_errors::emitter::{DynEmitter, Emitter, EmitterWriter};
+use rustc_errors::emitter::{DynEmitter, Emitter, HumanEmitter};
 use rustc_errors::translation::Translate;
 use rustc_errors::{ColorConfig, DiagCtxt, Diagnostic, Level as DiagnosticLevel};
 use rustc_session::parse::ParseSess as RawParseSess;
@@ -139,7 +139,7 @@ fn default_dcx(
             rustc_driver::DEFAULT_LOCALE_RESOURCES.to_vec(),
             false,
         );
-        Box::new(EmitterWriter::stderr(emit_color, fallback_bundle).sm(Some(source_map.clone())))
+        Box::new(HumanEmitter::stderr(emit_color, fallback_bundle).sm(Some(source_map.clone())))
     };
     DiagCtxt::with_emitter(Box::new(SilentOnIgnoredFilesEmitter {
         has_non_ignorable_parser_errors: false,