Refactor emit_diagnostic.

- Combine two different blocks involving
  `diagnostic.level.get_expectation_id()` into one.
- Combine several `if`s involving `diagnostic.level` into a single
  `match`.

This requires reordering some of the operations, but this has no
functional effect.

compiler/rustc_errors/src/lib.rs

@@ -1248,24 +1248,36 @@ impl DiagCtxtInner {
  }
 
  fn emit_diagnostic(&mut self, mut diagnostic: Diagnostic) -> Option<ErrorGuaranteed> {
- // The `LintExpectationId` can be stable or unstable depending on when it was created.
- // Diagnostics created before the definition of `HirId`s are unstable and can not yet
- // be stored. Instead, they are buffered until the `LintExpectationId` is replaced by
- // a stable one by the `LintLevelsBuilder`.
- if let Some(LintExpectationId::Unstable { .. }) = diagnostic.level.get_expectation_id() {
- self.unstable_expect_diagnostics.push(diagnostic.clone());
- return None;
+ if let Some(expectation_id) = diagnostic.level.get_expectation_id() {
+ // The `LintExpectationId` can be stable or unstable depending on when it was created.
+ // Diagnostics created before the definition of `HirId`s are unstable and can not yet
+ // be stored. Instead, they are buffered until the `LintExpectationId` is replaced by
+ // a stable one by the `LintLevelsBuilder`.
+ if let LintExpectationId::Unstable { .. } = expectation_id {
+ self.unstable_expect_diagnostics.push(diagnostic.clone());
+ return None;
+ }
+ self.fulfilled_expectations.insert(expectation_id.normalize());
+ }
+
+ if diagnostic.has_future_breakage() {
+ self.future_breakage_diagnostics.push(diagnostic.clone());
+ }
+
+ if matches!(diagnostic.level, DelayedBug(_)) && self.flags.eagerly_emit_delayed_bugs {
+ diagnostic.level = Error;
  }
 
- // FIXME(eddyb) this should check for `has_errors` and stop pushing
- // once *any* errors were emitted (and truncate `span_delayed_bugs`
- // when an error is first emitted, also), but maybe there's a case
- // in which that's not sound? otherwise this is really inefficient.
  match diagnostic.level {
- DelayedBug(_) if self.flags.eagerly_emit_delayed_bugs => {
- diagnostic.level = Error;
+ // This must come after the possible promotion of `DelayedBug` to `Error` above.
+ Fatal | Error if self.treat_next_err_as_bug() => {
+ diagnostic.level = Bug;
  }
  DelayedBug(DelayedBugKind::Normal) => {
+ // FIXME(eddyb) this should check for `has_errors` and stop pushing
+ // once *any* errors were emitted (and truncate `span_delayed_bugs`
+ // when an error is first emitted, also), but maybe there's a case
+ // in which that's not sound? otherwise this is really inefficient.
  let backtrace = std::backtrace::Backtrace::capture();
  self.span_delayed_bugs
  .push(DelayedDiagnostic::with_backtrace(diagnostic.clone(), backtrace));
@@ -1280,39 +1292,22 @@ impl DiagCtxtInner {
 
  return None;
  }
- _ => {}
- }
-
- // This must come after the possible promotion of `DelayedBug` to
- // `Error` above.
- if matches!(diagnostic.level, Error | Fatal) && self.treat_next_err_as_bug() {
- diagnostic.level = Bug;
- }
-
- if diagnostic.has_future_breakage() {
- self.future_breakage_diagnostics.push(diagnostic.clone());
- }
-
- if let Some(expectation_id) = diagnostic.level.get_expectation_id() {
- self.fulfilled_expectations.insert(expectation_id.normalize());
- }
-
- if diagnostic.level == Warning && !self.flags.can_emit_warnings {
- if diagnostic.has_future_breakage() {
+ Warning if !self.flags.can_emit_warnings => {
+ if diagnostic.has_future_breakage() {
+ (*TRACK_DIAGNOSTIC)(diagnostic, &mut |_| {});
+ }
+ return None;
+ }
+ Allow => {
  (*TRACK_DIAGNOSTIC)(diagnostic, &mut |_| {});
+ return None;
  }
- return None;
- }
-
- if matches!(diagnostic.level, Expect(_)) {
- self.suppressed_expected_diag = true;
- (*TRACK_DIAGNOSTIC)(diagnostic, &mut |_| {});
- return None;
- }
-
- if matches!(diagnostic.level, Allow) {
- (*TRACK_DIAGNOSTIC)(diagnostic, &mut |_| {});
- return None;
+ Expect(_) => {
+ self.suppressed_expected_diag = true;
+ (*TRACK_DIAGNOSTIC)(diagnostic, &mut |_| {});
+ return None;
+ }
+ _ => {}
  }
 
  let mut guaranteed = None;