Sema: use a select to clarify access-level import logic

Exportability issues from access-level imports are reported by
both access-level checks and the exportability checker.
We prevent duplicating diagnostics with some logic that is getting
progressively more complex. Let's simplify it using a select statement.

Author: xymus

lib/Sema/ResilienceDiagnostics.cpp

@@ -279,12 +279,19 @@ static bool diagnoseValueDeclRefExportability(SourceLoc loc, const ValueDecl *D,
   // Except for extensions and protocol conformances, we report them here.
   if (originKind == DisallowedOriginKind::InternalOrLessImport ||
       originKind == DisallowedOriginKind::PackageImport) {
-    bool reportHere =
-      reason == ExportabilityReason::ExtensionWithPublicMembers ||
-      reason == ExportabilityReason::ExtensionWithPackageMembers ||
-      reason == ExportabilityReason::ExtensionWithConditionalConformances ||
-      reason == ExportabilityReason::ExtensionWithPackageConditionalConformances ||
-      (reason == ExportabilityReason::Inheritance && isa<ProtocolDecl>(D));
+    bool reportHere = [&] {
+      switch (*reason) {
+        case ExportabilityReason::ExtensionWithPublicMembers:
+        case ExportabilityReason::ExtensionWithPackageMembers:
+        case ExportabilityReason::ExtensionWithConditionalConformances:
+        case ExportabilityReason::ExtensionWithPackageConditionalConformances:
+          return true;
+        case ExportabilityReason::Inheritance:
+          return isa<ProtocolDecl>(D);
+        default:
+          return false;
+      }
+    }();
     if (!reportHere)
       return false;
   }