Temporarily reinstate LangOptions::EnableBareSlashRegexLiterals for LLDB

Author: DougGregor

include/swift/Basic/LangOptions.h

@@ -354,6 +354,9 @@ namespace swift {
     /// The set of features that have been enabled.
     llvm::SmallSet<Feature, 2> Features;
 
+    /// Temporary flag to support LLDB's transition to using \c Features.
+    bool EnableBareSlashRegexLiterals = false;
+
     /// Use Clang function types for computing canonical types.
     /// If this option is false, the clang function types will still be computed
     /// but will not be used for checking type equality.

lib/Basic/LangOptions.cpp

@@ -229,6 +229,10 @@ bool LangOptions::hasFeature(Feature feature) const {
   if (Features.contains(feature))
     return true;
 
+  if (feature == Feature::BareSlashRegexLiterals &&
+      EnableBareSlashRegexLiterals)
+    return true;
+
   if (auto version = getFeatureLanguageVersion(feature))
     return isSwiftVersionAtLeast(*version);