rustc_errors: take self by value in DiagnosticBuilder::cancel.

src/modules.rs

@@ -439,7 +439,7 @@ fn find_external_module(
                 }
             }
             Err(mod_err) if !mods_outside_ast.is_empty() => {
-                if let ModError::ParserError(mut e) = mod_err {
+                if let ModError::ParserError(e) = mod_err {
                     e.cancel();
                 }
                 Ok(Some(SubModKind::MultiExternal(mods_outside_ast)))

src/parse/macros/cfg_if.rs

@@ -57,7 +57,7 @@ fn parse_cfg_if_inner<'a>(
             let item = match parser.parse_item(ForceCollect::No) {
                 Ok(Some(item_ptr)) => item_ptr.into_inner(),
                 Ok(None) => continue,
-                Err(mut err) => {
+                Err(err) => {
                     err.cancel();
                     parser.sess.span_diagnostic.reset_err_count();
                     return Err(

src/parse/macros/lazy_static.rs

@@ -23,7 +23,7 @@ macro_rules! parse_or {
                         val
                     }
                 }
-                Err(mut err) => {
+                Err(err) => {
                     err.cancel();
                     parser.sess.span_diagnostic.reset_err_count();
                     return None;

src/parse/macros/mod.rs

@@ -36,7 +36,7 @@ macro_rules! parse_macro_arg {
                         return Some(MacroArg::$macro_arg($f(x)?));
                     }
                 }
-                Err(mut e) => {
+                Err(e) => {
                     e.cancel();
                     parser.sess.span_diagnostic.reset_err_count();
                 }

src/parse/parser.rs

@@ -115,7 +115,7 @@ pub(crate) fn parse_file_as_module(
             match parser.parse_mod(&TokenKind::Eof) {
                 Ok(result) => Some(result),
                 Err(mut e) => {
-                    sess.emit_or_cancel_diagnostic(&mut e);
+                    e.emit();
                     if sess.can_reset_errors() {
                         sess.reset_errors();
                     }

src/parse/session.rs

@@ -230,17 +230,6 @@ pub(super) fn emit_diagnostics(&self, diagnostics: Vec<Diagnostic>) {
         }
     }
 
-    pub(crate) fn emit_or_cancel_diagnostic(&self, diagnostic: &mut Diagnostic) {
-        self.parse_sess.span_diagnostic.emit_diagnostic(diagnostic);
-        // The Handler will check whether the diagnostic should be emitted
-        // based on the user's rustfmt configuration and the originating file
-        // that caused the parser error. If the Handler determined it should skip
-        // emission then we need to ensure the diagnostic is cancelled.
-        if !diagnostic.cancelled() {
-            diagnostic.cancel();
-        }
-    }
-
     pub(super) fn can_reset_errors(&self) -> bool {
         self.can_reset_errors.load(Ordering::Acquire)
     }