DiagnosticEngine: support StringRef as diagnostic argument

Author: eeckstein

SwiftCompilerSources/Sources/Basic/Utils.swift

@@ -80,7 +80,7 @@ public extension NoReflectionChildren {
 //===----------------------------------------------------------------------===//
 
 public struct StringRef : CustomStringConvertible, NoReflectionChildren {
-  let _bridged: BridgedStringRef
+  public let _bridged: BridgedStringRef
 
   public init(bridged: BridgedStringRef) { self._bridged = bridged }
 

SwiftCompilerSources/Sources/Optimizer/Utilities/DiagnosticEngine.swift

@@ -25,6 +25,11 @@ extension String: DiagnosticArgument {
     _withBridgedStringRef { fn(BridgedDiagnosticArgument($0)) }
   }
 }
+extension StringRef: DiagnosticArgument {
+  func _withBridgedDiagnosticArgument(_ fn: (BridgedDiagnosticArgument) -> Void) {
+    fn(BridgedDiagnosticArgument(_bridged))
+  }
+}
 extension Int: DiagnosticArgument {
   func _withBridgedDiagnosticArgument(_ fn: (BridgedDiagnosticArgument) -> Void) {
     fn(BridgedDiagnosticArgument(self))