Rollup merge of #119841 - nnethercote:rm-DiagnosticBuilder-buffer, r=oli-obk

Remove `DiagnosticBuilder::buffer`

`DiagnosticBuilder::buffer` doesn't do much, and part of what it does (for `-Ztreat-err-as-bug`) it shouldn't.

This PR strips it back, replaces its uses, and finally removes it, making a few cleanups in the vicinity along the way.

r? ``@oli-obk``

2 files changed, 14 insertions, 43 deletions

diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index a02909f29c4..bd7c58d904e 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -255,35 +255,13 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     /// Stashes diagnostic for possible later improvement in a different,
     /// later stage of the compiler. The diagnostic can be accessed with
     /// the provided `span` and `key` through [`DiagCtxt::steal_diagnostic()`].
-    ///
-    /// As with `buffer`, this is unless the dcx has disabled such buffering.
     pub fn stash(self, span: Span, key: StashKey) {
-        if let Some((diag, dcx)) = self.into_diagnostic() {
-            dcx.stash_diagnostic(span, key, diag);
-        }
-    }
-
-    /// Converts the builder to a `Diagnostic` for later emission,
-    /// unless dcx has disabled such buffering.
-    fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a DiagCtxt)> {
-        if self.dcx.inner.lock().flags.treat_err_as_bug.is_some() {
-            self.emit();
-            return None;
-        }
-
-        let diag = self.take_diag();
-
-        // Logging here is useful to help track down where in logs an error was
-        // actually emitted.
-        debug!("buffer: diag={:?}", diag);
-
-        Some((diag, self.dcx))
+        self.dcx.stash_diagnostic(span, key, self.into_diagnostic());
     }
 
-    /// Buffers the diagnostic for later emission,
-    /// unless dcx has disabled such buffering.
-    pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {
-        buffered_diagnostics.extend(self.into_diagnostic().map(|(diag, _)| diag));
+    /// Converts the builder to a `Diagnostic` for later emission.
+    pub fn into_diagnostic(mut self) -> Diagnostic {
+        self.take_diag()
     }
 
     /// Delay emission of this diagnostic as a bug.
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 8fb539fc358..404c89ea01b 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -981,6 +981,10 @@ impl DiagCtxt {
 
         inner.emit_stashed_diagnostics();
 
+        if inner.treat_err_as_bug() {
+            return;
+        }
+
         let warnings = match inner.deduplicated_warn_count {
             0 => Cow::from(""),
             1 => Cow::from("1 warning emitted"),
@@ -991,9 +995,6 @@ impl DiagCtxt {
             1 => Cow::from("aborting due to 1 previous error"),
             count => Cow::from(format!("aborting due to {count} previous errors")),
         };
-        if inner.treat_err_as_bug() {
-            return;
-        }
 
         match (errors.len(), warnings.len()) {
             (0, 0) => return,
@@ -1168,7 +1169,8 @@ impl DiagCtxt {
         let mut inner = self.inner.borrow_mut();
 
         if loud && lint_level.is_error() {
-            inner.bump_err_count();
+            inner.err_count += 1;
+            inner.panic_if_treat_err_as_bug();
         }
 
         inner.emitter.emit_unused_externs(lint_level, unused_externs)
@@ -1255,7 +1257,7 @@ impl DiagCtxtInner {
     }
 
     fn emit_diagnostic(&mut self, mut diagnostic: Diagnostic) -> Option<ErrorGuaranteed> {
-        if matches!(diagnostic.level, Error | Fatal) && self.treat_err_as_bug() {
+        if matches!(diagnostic.level, Error | Fatal) && self.treat_next_err_as_bug() {
             diagnostic.level = Bug;
         }
 
@@ -1353,10 +1355,11 @@ impl DiagCtxtInner {
             }
             if diagnostic.is_error() {
                 if diagnostic.is_lint {
-                    self.bump_lint_err_count();
+                    self.lint_err_count += 1;
                 } else {
-                    self.bump_err_count();
+                    self.err_count += 1;
                 }
+                self.panic_if_treat_err_as_bug();
 
                 #[allow(deprecated)]
                 {
@@ -1447,16 +1450,6 @@ impl DiagCtxtInner {
         panic::panic_any(DelayedBugPanic);
     }
 
-    fn bump_lint_err_count(&mut self) {
-        self.lint_err_count += 1;
-        self.panic_if_treat_err_as_bug();
-    }
-
-    fn bump_err_count(&mut self) {
-        self.err_count += 1;
-        self.panic_if_treat_err_as_bug();
-    }
-
     fn panic_if_treat_err_as_bug(&self) {
         if self.treat_err_as_bug() {
             match (