[NFC] Rework DiagnosticEngine::ignoreDiagnostic()

This feature was implemented with a per-diagnostic table of override DiagnosticBehaviors. That table was able to represent not only that a diagnostic should be ignored, but also many other states that were difficult to integrate with a feature I’m trying to introduce. Simplify the implementation so it can only represent ignoring a diagnostic, which has a much cleaner interaction with the new feature.

Author: beccadax

include/swift/AST/DiagnosticEngine.h

@@ -23,6 +23,7 @@
 #include "swift/AST/DiagnosticConsumer.h"
 #include "swift/AST/TypeLoc.h"
 #include "swift/Localization/LocalizationFormat.h"
+#include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/Allocator.h"
@@ -627,8 +628,8 @@ namespace swift {
     /// Track the previous emitted Behavior, useful for notes
     DiagnosticBehavior previousBehavior = DiagnosticBehavior::Unspecified;
 
-    /// Track settable, per-diagnostic state that we store
-    std::vector<DiagnosticBehavior> perDiagnosticBehavior;
+    /// Track which diagnostics should be ignored.
+    llvm::BitVector ignoredDiagnostics;
 
   public:
     DiagnosticState();
@@ -660,9 +661,9 @@ namespace swift {
       fatalErrorOccurred = false;
     }
 
-    /// Set per-diagnostic behavior
-    void setDiagnosticBehavior(DiagID id, DiagnosticBehavior behavior) {
-      perDiagnosticBehavior[(unsigned)id] = behavior;
+    /// Set whether a diagnostic should be ignored.
+    void setIgnoredDiagnostic(DiagID id, bool ignored) {
+      ignoredDiagnostics[(unsigned)id] = ignored;
     }
 
   private:
@@ -808,7 +809,7 @@ namespace swift {
     }
 
     void ignoreDiagnostic(DiagID id) {
-      state.setDiagnosticBehavior(id, DiagnosticBehavior::Ignore);
+      state.setIgnoredDiagnostic(id, true);
     }
 
     void resetHadAnyError() {

lib/AST/DiagnosticEngine.cpp

@@ -136,9 +136,8 @@ static constexpr EducationalNotes<LocalDiagID::NumDiags> _EducationalNotes = Edu
 static constexpr auto educationalNotes = _EducationalNotes.value;
 
 DiagnosticState::DiagnosticState() {
-  // Initialize our per-diagnostic state to default
-  perDiagnosticBehavior.resize(LocalDiagID::NumDiags,
-                               DiagnosticBehavior::Unspecified);
+  // Initialize our ignored diagnostics to default
+  ignoredDiagnostics.resize(LocalDiagID::NumDiags);
 }
 
 static CharSourceRange toCharSourceRange(SourceManager &SM, SourceRange SR) {
@@ -826,8 +825,7 @@ DiagnosticBehavior DiagnosticState::determineBehavior(DiagID id) {
 
   // We determine how to handle a diagnostic based on the following rules
   //   1) If current state dictates a certain behavior, follow that
-  //   2) If the user provided a behavior for this specific diagnostic, follow
-  //      that
+  //   2) If the user ignored this specific diagnostic, follow that
   //   3) If the user provided a behavior for this diagnostic's kind, follow
   //      that
   //   4) Otherwise remap the diagnostic kind
@@ -846,11 +844,9 @@ DiagnosticBehavior DiagnosticState::determineBehavior(DiagID id) {
     if (!showDiagnosticsAfterFatalError && !isNote)
       return set(DiagnosticBehavior::Ignore);
 
-  //   2) If the user provided a behavior for this specific diagnostic, follow
-  //      that
-
-  if (perDiagnosticBehavior[(unsigned)id] != DiagnosticBehavior::Unspecified)
-    return set(perDiagnosticBehavior[(unsigned)id]);
+  //   2) If the user ignored this specific diagnostic, follow that
+  if (ignoredDiagnostics[(unsigned)diag.getID()])
+    return set(DiagnosticBehavior::Ignore);
 
   //   3) If the user provided a behavior for this diagnostic's kind, follow
   //      that