From 57948c63e0ea76b12cf7c41f16ba6564f47497f0 Mon Sep 17 00:00:00 2001
From: Jon Ross-Perkins <jperkins@google.com>
Date: Fri, 9 Feb 2024 12:57:19 -0800
Subject: [PATCH] Small cleanup for DiagnosticType (#3697)

I was thinking about #3695 a little further after comments; this is a
small cleanup.
---
 toolchain/diagnostics/diagnostic_emitter.h | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/toolchain/diagnostics/diagnostic_emitter.h b/toolchain/diagnostics/diagnostic_emitter.h
index 3ddd64b69bac0..65246c5fd493a 100644
--- a/toolchain/diagnostics/diagnostic_emitter.h
+++ b/toolchain/diagnostics/diagnostic_emitter.h
@@ -180,21 +180,14 @@ concept HasDiagnosticType =
     requires { std::type_identity<typename Arg::DiagnosticType>(); };
 
 // The default implementation with no translation.
-template <typename Arg, typename X = int>
-struct DiagnosticTypeForArg {
-  using StorageType = Arg;
-  static constexpr DiagnosticTypeTranslation Translation =
-      DiagnosticTypeTranslation::None;
-};
+template <typename Arg, typename /*Unused*/ = void>
+struct DiagnosticTypeForArg
+    : public DiagnosticTypeInfo<Arg, DiagnosticTypeTranslation::None> {};
 
 // Exposes a custom translation for an argument type.
 template <typename Arg>
   requires HasDiagnosticType<Arg>
-struct DiagnosticTypeForArg<Arg> {
-  using StorageType = Arg::DiagnosticType::StorageType;
-  static constexpr DiagnosticTypeTranslation Translation =
-      Arg::DiagnosticType::Translation;
-};
+struct DiagnosticTypeForArg<Arg> : public Arg::DiagnosticType {};
 
 // Use the DIAGNOSTIC macro to instantiate this.
 // This stores static information about a diagnostic category.