Auto merge of #119606 - nnethercote:consuming-emit, r=oli-obk

Consuming `emit`

This PR makes `DiagnosticBuilder::emit` consuming, i.e. take `self` instead of `&mut self`. This is good because it doesn't make sense to emit a diagnostic twice.

This requires some changes to `DiagnosticBuilder` method changing -- every existing non-consuming chaining method gets a new consuming partner with a `_mv` suffix -- but permits a host of beneficial follow-up changes: more concise code through more chaining, removal of redundant diagnostic construction API methods, and removal of machinery to track the possibility of a diagnostic being emitted multiple times.

r? `@compiler-errors`

src/tools/clippy/clippy_config/src/msrvs.rs

@@ -109,7 +109,7 @@ impl Msrv {
             if let Some(duplicate) = msrv_attrs.last() {
                 sess.dcx()
                     .struct_span_err(duplicate.span, "`clippy::msrv` is defined multiple times")
-                    .span_note(msrv_attr.span, "first definition found here")
+                    .span_note_mv(msrv_attr.span, "first definition found here")
                     .emit();
             }
 

src/tools/clippy/clippy_utils/src/attrs.rs

@@ -136,7 +136,7 @@ pub fn get_unique_attr<'a>(
         if let Some(duplicate) = unique_attr {
             sess.dcx()
                 .struct_span_err(attr.span, format!("`{name}` is defined multiple times"))
-                .span_note(duplicate.span, "first definition found here")
+                .span_note_mv(duplicate.span, "first definition found here")
                 .emit();
         } else {
             unique_attr = Some(attr);

src/tools/rustfmt/src/parse/parser.rs

@@ -114,7 +114,7 @@ impl<'a> Parser<'a> {
             let mut parser = new_parser_from_file(sess.inner(), path, Some(span));
             match parser.parse_mod(&TokenKind::Eof) {
                 Ok((a, i, spans)) => Some((a, i, spans.inner_span)),
-                Err(mut e) => {
+                Err(e) => {
                     e.emit();
                     if sess.can_reset_errors() {
                         sess.reset_errors();
@@ -165,7 +165,7 @@ impl<'a> Parser<'a> {
 
         match catch_unwind(move || parser.parse_crate_mod()) {
             Ok(Ok(k)) => Ok(k),
-            Ok(Err(mut db)) => {
+            Ok(Err(db)) => {
                 db.emit();
                 Err(ParserError::ParseError)
             }