[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[Boaz Brickner via cfe-commits]

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@@ -477,6 +485,100 @@ void DiagnosticsEngine::setSeverityForAll(diag::Flavor Flavor,
       setSeverity(Diag, Map, Loc);
 }
 
+namespace {
+class WarningsSpecialCaseList : public llvm::SpecialCaseList {
+public:
+  static std::unique_ptr<WarningsSpecialCaseList>
+  create(const llvm::MemoryBuffer &MB, std::string &Err) {
+    auto SCL = std::make_unique<WarningsSpecialCaseList>();
+    if (SCL->createInternal(&MB, Err))
+      return SCL;
+    return nullptr;
+  }
+
+  // Section names refer to diagnostic groups, which cover multiple individual
+  // diagnostics. Expand diagnostic groups here to individual diagnostics.
+  // A diagnostic can have multiple diagnostic groups associated with it, we let
+  // the last section take precedence in such cases.
+  void processSections(DiagnosticsEngine &Diags) {
+    // Drop the default section introduced by special case list, we only support
+    // exact diagnostic group names.
+    Sections.erase("*");
+    // Make sure we iterate sections by their line numbers.
+    std::vector<std::pair<unsigned, const llvm::StringMapEntry<Section> *>>
+        LineAndSection;
+    for (const auto &Entry : Sections) {
+      LineAndSection.emplace_back(
+          Entry.second.SectionMatcher->Globs.at(Entry.first()).second, &Entry);
+    }
+    llvm::sort(LineAndSection);
+    static constexpr auto kFlavor = clang::diag::Flavor::WarningOrError;
+    for (const auto &[_, Entry] : LineAndSection) {
+      SmallVector<diag::kind, 256> GroupDiags;
+      if (Diags.getDiagnosticIDs()->getDiagnosticsInGroup(
+              kFlavor, Entry->first(), GroupDiags)) {
+        StringRef Suggestion =
+            DiagnosticIDs::getNearestOption(kFlavor, Entry->first());
+        Diags.Report(diag::warn_unknown_diag_option)
----------------
bricknerb wrote:

Assuming we hide some functions, this is definitely something that should be fixed.
Also, if the API of the new class, because it inherits from the base class, is wider than necessary, it's also a good reason to refactor.

https://github.com/llvm/llvm-project/pull/112517