Remove a redundant field

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -536,7 +536,9 @@ pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a Handler)> {
             }
         };
 
-        if handler.flags.dont_buffer_diagnostics || handler.flags.treat_err_as_bug.is_some() {
+        if handler.inner.lock().flags.dont_buffer_diagnostics
+            || handler.inner.lock().flags.treat_err_as_bug.is_some()
+        {
             self.emit();
             return None;
         }

compiler/rustc_errors/src/lib.rs

@@ -391,7 +391,6 @@ fn push_trailing(
 /// Certain errors (fatal, bug, unimpl) may cause immediate exit,
 /// others log errors for later reporting.
 pub struct Handler {
-    flags: HandlerFlags,
     inner: Lock<HandlerInner>,
 }
 
@@ -589,7 +588,6 @@ pub fn with_emitter_and_flags(
         ice_file: Option<PathBuf>,
     ) -> Self {
         Self {
-            flags,
             inner: Lock::new(HandlerInner {
                 flags,
                 lint_err_count: 0,
@@ -637,7 +635,7 @@ pub fn eagerly_translate_to_string<'a>(
     // This is here to not allow mutation of flags;
     // as of this writing it's only used in tests in librustc_middle.
     pub fn can_emit_warnings(&self) -> bool {
-        self.flags.can_emit_warnings
+        self.inner.lock().flags.can_emit_warnings
     }
 
     /// Resets the diagnostic error count as well as the cached emitted diagnostics.