[clang] [Clang] [NFC] Move diagnostics emitting code from `DiagnosticIDs` into `DiagnosticsEngine` (PR #143517)

[Mariya Podchishchaeva via cfe-commits]

================
@@ -658,13 +658,97 @@ void DiagnosticsEngine::Report(const StoredDiagnostic &storedDiag) {
   Level DiagLevel = storedDiag.getLevel();
   Diagnostic Info(this, storedDiag.getLocation(), storedDiag.getID(),
                   DiagStorage, storedDiag.getMessage());
+  Report(DiagLevel, Info);
+}
+
+void DiagnosticsEngine::Report(Level DiagLevel, const Diagnostic &Info) {
+  assert(DiagLevel != Ignored && "Cannot emit ignored diagnostics!");
   Client->HandleDiagnostic(DiagLevel, Info);
   if (Client->IncludeInDiagnosticCounts()) {
-    if (DiagLevel == DiagnosticsEngine::Warning)
+    if (DiagLevel == Warning)
       ++NumWarnings;
   }
 }
 
+/// ProcessDiag - This is the method used to report a diagnostic that is
+/// finally fully formed.
+bool DiagnosticsEngine::ProcessDiag(const DiagnosticBuilder &DiagBuilder) {
+  Diagnostic Info(this, DiagBuilder);
+
+  assert(getClient() && "DiagnosticClient not set!");
+
+  // Figure out the diagnostic level of this message.
+  unsigned DiagID = Info.getID();
+  Level DiagLevel = getDiagnosticLevel(DiagID, Info.getLocation());
+
+  // Update counts for DiagnosticErrorTrap even if a fatal error occurred
+  // or diagnostics are suppressed.
+  if (DiagLevel >= Error) {
+    ++TrapNumErrorsOccurred;
+    if (Diags->isUnrecoverable(DiagID))
+      ++TrapNumUnrecoverableErrorsOccurred;
+  }
+
+  if (SuppressAllDiagnostics)
+    return false;
+
+  if (DiagLevel != Note) {
+    // Record that a fatal error occurred only when we see a second
+    // non-note diagnostic. This allows notes to be attached to the
+    // fatal error, but suppresses any diagnostics that follow those
+    // notes.
+    if (LastDiagLevel == Fatal)
+      FatalErrorOccurred = true;
+
+    LastDiagLevel = DiagLevel;
+  }
+
+  // If a fatal error has already been emitted, silence all subsequent
+  // diagnostics.
+  if (FatalErrorOccurred) {
+    if (DiagLevel >= Error && Client->IncludeInDiagnosticCounts()) {
+      ++NumErrors;
+    }
----------------
Fznamznon wrote:

```suggestion
    if (DiagLevel >= Error && Client->IncludeInDiagnosticCounts())
      ++NumErrors;
```

https://github.com/llvm/llvm-project/pull/143517