Auto merge of #100810 - matthiaskrgr:rollup-xep778s, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #97963 (net listen backlog set to negative on Linux.)
 - #99935 (Reenable disabled early syntax gates as future-incompatibility lints)
 - #100129 (add miri-test-libstd support to libstd)
 - #100500 (Ban references to `Self` in trait object substs for projection predicates too.)
 - #100636 (Revert "Revert "Allow dynamic linking for iOS/tvOS targets."")
 - #100718 ([rustdoc] Fix item info display)
 - #100769 (Suggest adding a reference to a trait assoc item)
 - #100777 (elaborate how revisions work with FileCheck stuff in src/test/codegen)
 - #100796 (Refactor: remove unnecessary string searchings)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 63 insertions, 12 deletions

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 6555b93ac0b..18e84b70b1b 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -459,6 +459,7 @@ struct HandlerInner {
 pub enum StashKey {
     ItemNoType,
     UnderscoreForArrayLengths,
+    EarlySyntaxWarning,
 }
 
 fn default_track_diagnostic(_: &Diagnostic) {}
@@ -626,19 +627,13 @@ impl Handler {
     /// Stash a given diagnostic with the given `Span` and `StashKey` as the key for later stealing.
     pub fn stash_diagnostic(&self, span: Span, key: StashKey, diag: Diagnostic) {
         let mut inner = self.inner.borrow_mut();
-        // FIXME(Centril, #69537): Consider reintroducing panic on overwriting a stashed diagnostic
-        // if/when we have a more robust macro-friendly replacement for `(span, key)` as a key.
-        // See the PR for a discussion.
-        inner.stashed_diagnostics.insert((span, key), diag);
+        inner.stash((span, key), diag);
     }
 
     /// Steal a previously stashed diagnostic with the given `Span` and `StashKey` as the key.
     pub fn steal_diagnostic(&self, span: Span, key: StashKey) -> Option<DiagnosticBuilder<'_, ()>> {
-        self.inner
-            .borrow_mut()
-            .stashed_diagnostics
-            .remove(&(span, key))
-            .map(|diag| DiagnosticBuilder::new_diagnostic(self, diag))
+        let mut inner = self.inner.borrow_mut();
+        inner.steal((span, key)).map(|diag| DiagnosticBuilder::new_diagnostic(self, diag))
     }
 
     /// Emit all stashed diagnostics.
@@ -1106,13 +1101,31 @@ impl HandlerInner {
 
     /// Emit all stashed diagnostics.
     fn emit_stashed_diagnostics(&mut self) -> Option<ErrorGuaranteed> {
+        let has_errors = self.has_errors();
         let diags = self.stashed_diagnostics.drain(..).map(|x| x.1).collect::<Vec<_>>();
         let mut reported = None;
         for mut diag in diags {
+            // Decrement the count tracking the stash; emitting will increment it.
             if diag.is_error() {
-                reported = Some(ErrorGuaranteed(()));
+                if matches!(diag.level, Level::Error { lint: true }) {
+                    self.lint_err_count -= 1;
+                } else {
+                    self.err_count -= 1;
+                }
+            } else {
+                if diag.is_force_warn() {
+                    self.warn_count -= 1;
+                } else {
+                    // Unless they're forced, don't flush stashed warnings when
+                    // there are errors, to avoid causing warning overload. The
+                    // stash would've been stolen already if it were important.
+                    if has_errors {
+                        continue;
+                    }
+                }
             }
-            self.emit_diagnostic(&mut diag);
+            let reported_this = self.emit_diagnostic(&mut diag);
+            reported = reported.or(reported_this);
         }
         reported
     }
@@ -1302,9 +1315,47 @@ impl HandlerInner {
         }
     }
 
+    fn stash(&mut self, key: (Span, StashKey), diagnostic: Diagnostic) {
+        // Track the diagnostic for counts, but don't panic-if-treat-err-as-bug
+        // yet; that happens when we actually emit the diagnostic.
+        if diagnostic.is_error() {
+            if matches!(diagnostic.level, Level::Error { lint: true }) {
+                self.lint_err_count += 1;
+            } else {
+                self.err_count += 1;
+            }
+        } else {
+            // Warnings are only automatically flushed if they're forced.
+            if diagnostic.is_force_warn() {
+                self.warn_count += 1;
+            }
+        }
+
+        // FIXME(Centril, #69537): Consider reintroducing panic on overwriting a stashed diagnostic
+        // if/when we have a more robust macro-friendly replacement for `(span, key)` as a key.
+        // See the PR for a discussion.
+        self.stashed_diagnostics.insert(key, diagnostic);
+    }
+
+    fn steal(&mut self, key: (Span, StashKey)) -> Option<Diagnostic> {
+        let diagnostic = self.stashed_diagnostics.remove(&key)?;
+        if diagnostic.is_error() {
+            if matches!(diagnostic.level, Level::Error { lint: true }) {
+                self.lint_err_count -= 1;
+            } else {
+                self.err_count -= 1;
+            }
+        } else {
+            if diagnostic.is_force_warn() {
+                self.warn_count -= 1;
+            }
+        }
+        Some(diagnostic)
+    }
+
     #[inline]
     fn err_count(&self) -> usize {
-        self.err_count + self.stashed_diagnostics.len()
+        self.err_count
     }
 
     fn has_errors(&self) -> bool {