Change DiagnosticBehavior into a struct enum so we can put methods on it.

The reason why I am making this change is because I want to put a merge
operation on DiagnosticBehavior. This merge operation allows for
DiagnosticBehavior to work like a lattice. When one merges, one moves
potentially from fatal, error to things like note, ignore.

Author: gottesmm

include/swift/AST/DiagnosticEngine.h

@@ -428,14 +428,29 @@ namespace swift {
 
   /// Describes the current behavior to take with a diagnostic.
   /// Ordered from most severe to least.
-  enum class DiagnosticBehavior : uint8_t {
-    Unspecified = 0,
-    Fatal,
-    Error,
-    Warning,
-    Remark,
-    Note,
-    Ignore,
+  struct DiagnosticBehavior {
+    enum Kind : uint8_t {
+      Unspecified = 0,
+      Fatal,
+      Error,
+      Warning,
+      Remark,
+      Note,
+      Ignore,
+    };
+
+    Kind kind;
+
+    DiagnosticBehavior() : kind(Unspecified) {}
+    DiagnosticBehavior(Kind kind) : kind(kind) {}
+    operator Kind() const { return kind; }
+
+    /// Move up the lattice returning the max value.
+    DiagnosticBehavior merge(DiagnosticBehavior other) const {
+      auto value = std::max(std::underlying_type<Kind>::type(*this),
+                            std::underlying_type<Kind>::type(other));
+      return Kind(value);
+    }
   };
 
   struct DiagnosticFormatOptions {

include/swift/Basic/LangOptions.h

@@ -45,12 +45,12 @@
 
 namespace swift {
 
-  enum class DiagnosticBehavior : uint8_t;
+  struct DiagnosticBehavior;
 
   /// Kind of implicit platform conditions.
   enum class PlatformConditionKind {
-#define PLATFORM_CONDITION(LABEL, IDENTIFIER) LABEL,
-#include "swift/AST/PlatformConditionKinds.def"
+  #define PLATFORM_CONDITION(LABEL, IDENTIFIER) LABEL,
+  #include "swift/AST/PlatformConditionKinds.def"
   };
 
   /// Describes how strict concurrency checking should be.

include/swift/Sema/Concurrency.h

@@ -29,7 +29,7 @@ class SourceFile;
 class NominalTypeDecl;
 class VarDecl;
 
-enum class DiagnosticBehavior: uint8_t;
+struct DiagnosticBehavior;
 
 /// If any of the imports in this source file was @preconcurrency but there were
 /// no diagnostics downgraded or suppressed due to that @preconcurrency, suggest

lib/SILOptimizer/Mandatory/TransferNonSendable.cpp

@@ -122,16 +122,12 @@ getDiagnosticBehaviorLimitForCapturedValue(CapturedValue value) {
 static std::optional<DiagnosticBehavior>
 getDiagnosticBehaviorLimitForCapturedValues(
     ArrayRef<CapturedValue> capturedValues) {
-  using UnderlyingType = std::underlying_type<DiagnosticBehavior>::type;
-
   std::optional<DiagnosticBehavior> diagnosticBehavior;
   for (auto value : capturedValues) {
-    auto lhs = UnderlyingType(
-        diagnosticBehavior.value_or(DiagnosticBehavior::Unspecified));
-    auto rhs = UnderlyingType(
-        getDiagnosticBehaviorLimitForCapturedValue(value).value_or(
-            DiagnosticBehavior::Unspecified));
-    auto result = DiagnosticBehavior(std::max(lhs, rhs));
+    auto lhs = diagnosticBehavior.value_or(DiagnosticBehavior::Unspecified);
+    auto rhs = getDiagnosticBehaviorLimitForCapturedValue(value).value_or(
+        DiagnosticBehavior::Unspecified);
+    auto result = lhs.merge(rhs);
     if (result != DiagnosticBehavior::Unspecified)
       diagnosticBehavior = result;
   }